Hannes Reinecke [Tue, 29 Jul 2025 06:46:36 +0000 (08:46 +0200)]
drivers/base: move memory_block_add_nid() into the caller
Now the node id only needs to be set for early memory, so move
memory_block_add_nid() into the caller and rename it into
memory_block_add_nid_early(). This allows us to further simplify the code
by dropping the 'context' argument to
do_register_memory_block_under_node().
Link: https://lkml.kernel.org/r/20250729064637.51662-4-hare@kernel.org Suggested-by: David Hildenbrand <david@redhat.com> Signed-off-by: Hannes Reinecke <hare@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Donet Tom <donettom@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hannes Reinecke [Tue, 29 Jul 2025 06:46:35 +0000 (08:46 +0200)]
mm/memory_hotplug: activate node before adding new memory blocks
The sysfs attributes for memory blocks require the node ID to be set and
initialized, so move the node activation before adding new memory blocks.
This also has the nice side effect that the BUG_ON() can be converted into
a WARN_ON() as we now can handle registration errors.
Link: https://lkml.kernel.org/r/20250729064637.51662-3-hare@kernel.org Fixes: b9ff036082cd ("mm/memory_hotplug.c: make add_memory_resource use __try_online_node") Signed-off-by: Hannes Reinecke <hare@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Donet Tom <donettom@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hannes Reinecke [Tue, 29 Jul 2025 06:46:34 +0000 (08:46 +0200)]
drivers/base/memory: add node id parameter to add_memory_block()
We have some udev rules trying to read the sysfs attribute 'valid_zones'
during an memory 'add' event, causing a crash in zone_for_pfn_range().
Debugging found that mem->nid was set to NUMA_NO_NODE, which crashed in
NODE_DATA(nid). Further analysis revealed that we're running into a race
with udev event processing: add_memory_resource() has this function calls:
Why do we try to online the node in 1), but only register the node in 4)
_after_ we have created the memory blocks in 3) ? And why do we set the
'nid' value in 5), when the uevent (which might need to see the correct
'nid' value) is sent out in 3) ? There must be a reason, I'm sure ...
So here's a small patchset to fixup uevent ordering. The first patch adds
a 'nid' parameter to add_memory_blocks() (to avoid mem->nid being
initialized with NUMA_NO_NODE), and the second patch reshuffles the code
in add_memory_resource() to fully initialize the node prior to calling
create_memory_block_devices() so that the node is valid at that time and
uevent processing will see correct values in sysfs.
This patch (of 3):
Add a 'nid' parameter to add_memory_block() to initialize the memory block
with the correct node id.
Quanmin Yan [Wed, 10 Sep 2025 11:32:21 +0000 (19:32 +0800)]
mm/damon/reclaim: support addr_unit for DAMON_RECLAIM
Implement a sysfs file to expose addr_unit for DAMON_RECLAIM users.
During parameter application, use the configured addr_unit parameter to
perform the necessary initialization. Similar to the core layer, prevent
setting addr_unit to zero.
It is worth noting that when monitor_region_start and monitor_region_end
are unset (i.e., 0), their values will later be set to biggest_system_ram.
At that point, addr_unit may not be the default value 1. Although we
could divide the biggest_system_ram value by addr_unit, changing addr_unit
without setting monitor_region_start/end should be considered a user
misoperation. And biggest_system_ram is only within the 0~ULONG_MAX
range, system can clearly work correctly with addr_unit=1. Therefore, if
monitor_region_start/end are unset, always silently reset addr_unit to 1.
Link: https://lkml.kernel.org/r/20250910113221.1065764-3-yanquanmin1@huawei.com Signed-off-by: Quanmin Yan <yanquanmin1@huawei.com> Reviewed-by: SeongJae Park <sj@kernel.org> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: ze zuo <zuoze1@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Quanmin Yan [Wed, 10 Sep 2025 11:32:20 +0000 (19:32 +0800)]
mm/damon/lru_sort: support addr_unit for DAMON_LRU_SORT
Patch series "mm/damon: add addr_unit for DAMON_LRU_SORT and
DAMON_RECLAIM".
In DAMON_LRU_SORT and DAMON_RECLAIM, damon_ctx is independent of the core.
Add addr_unit to these modules to support systems like ARM32 with LPAE.
This patch (of 2):
Implement a sysfs file to expose addr_unit for DAMON_LRU_SORT users.
During parameter application, use the configured addr_unit parameter to
perform the necessary initialization. Similar to the core layer, prevent
setting addr_unit to zero.
It is worth noting that when monitor_region_start and monitor_region_end
are unset (i.e., 0), their values will later be set to biggest_system_ram.
At that point, addr_unit may not be the default value 1. Although we
could divide the biggest_system_ram value by addr_unit, changing addr_unit
without setting monitor_region_start/end should be considered a user
misoperation. And biggest_system_ram is only within the 0~ULONG_MAX
range, system can clearly work correctly with addr_unit=1. Therefore, if
monitor_region_start/end are unset, always silently reset addr_unit to 1.
Wei Yang [Wed, 10 Sep 2025 09:22:40 +0000 (09:22 +0000)]
mm/compaction: fix low_pfn advance on isolating hugetlb
Commit 56ae0bb349b4 ("mm: compaction: convert to use a folio in
isolate_migratepages_block()") converts api from page to folio. But the
low_pfn advance for hugetlb page seems wrong when low_pfn doesn't point to
head page.
Originally, if page is a hugetlb tail page, compound_nr() return 1, which
means low_pfn only advance one in next iteration. After the change,
low_pfn would advance more than the hugetlb range, since folio_nr_pages()
always return total number of the large page. This results in skipping
some range to isolate and then to migrate.
The worst case for alloc_contig is it does all the isolation and
migration, but finally find some range is still not isolated. And then
undo all the work and try a new range.
Advance low_pfn to the end of hugetlb.
Link: https://lkml.kernel.org/r/20250910092240.3981-1-richard.weiyang@gmail.com Fixes: 56ae0bb349b4 ("mm: compaction: convert to use a folio in isolate_migratepages_block()") Signed-off-by: Wei Yang <richard.weiyang@gmail.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Brendan Jackman <jackmanb@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
David Hildenbrand [Wed, 10 Sep 2025 09:30:51 +0000 (11:30 +0200)]
selftests/mm: gup_tests: option to GUP all pages in a single call
We recently missed detecting an issue during early testing because the
default (!all) tests would not trigger it and even when running "all"
tests it only would happen sometimes because of races.
So let's allow for an easy way to specify "GUP all pages in a single
call", extend the test matrix and extend our default (!all) tests.
By GUP'ing all pages in a single call, with the default size of 128MiB
we'll cover multiple leaf page tables / PMDs on architectures with sane
THP sizes.
Link: https://lkml.kernel.org/r/20250910093051.1693097-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We already use page->private for storing the order of a page while it's in
the buddy allocator system; extend that to also storing the order while
it's in the pcp_llist.
Link: https://lkml.kernel.org/r/20250910142923.2465470-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm: remove redundant test in validate_page_before_insert()
The page_has_type() call would have included slab since commit 46df8e73a4a3 and now we don't even get that far because slab pages have a
zero refcount since commit 9aec2fb0fd5e.
Link: https://lkml.kernel.org/r/20250910142923.2465470-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
These small cleanups can be applied now to reduce conflicts during the
next merge window. They're all from various efforts to split struct page
from other memdescs. Thanks to Vlastimil for the suggestion.
This patch (of 3):
These functions do not modify their arguments. Telling the compiler this
may improve code generation, and allows us to pass const arguments from
other functions.
Aristeu Rozanski [Tue, 26 Aug 2025 15:37:21 +0000 (11:37 -0400)]
mm: make folio page count functions return unsigned
As raised by Andrew [1], a folio/compound page never spans a negative
number of pages. Consequently, let's use "unsigned long" instead of
"long" consistently for folio_nr_pages(), folio_large_nr_pages() and
compound_nr().
Using "unsigned long" as return value is fine, because even
"(long)-folio_nr_pages()" will keep on working as expected. Using
"unsigned int" instead would actually break these use cases.
This patch takes the first step changing these to return unsigned long
(and making drm_gem_get_pages() use the new types instead of replacing
min()).
In the future, we might want to make more callers of these functions to
consistently use "unsigned long".
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:11 +0000 (21:22 +0100)]
kcov: update kcov to use mmap_prepare
We can use the mmap insert pages functionality provided for use in
mmap_prepare to insert the kcov pages as required.
This does necessitate an allocation, but since it's in the mmap path this
doesn't seem egregious. The allocation/freeing of the pages array is
handled automatically by vma_desc_set_mixedmap_pages() and the mapping
logic.
Link: https://lkml.kernel.org/r/5b1ab8ef7065093884fc9af15364b48c0a02599a.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:10 +0000 (21:22 +0100)]
fs/proc: update vmcore to use .proc_mmap_prepare
Now we have the ability to specify a custom hook we can handle even very
customised behaviour.
As part of this change, we must also update remap_vmalloc_range_partial()
to optionally not update VMA flags. Other than then remap_vmalloc_range()
wrapper, vmcore is the only user of this function so we can simply go
ahead and add a parameter.
Link: https://lkml.kernel.org/r/163fba3d7ec775ec3eb9a13bd641d3255e8ec96c.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:08 +0000 (21:22 +0100)]
mm: update cramfs to use mmap_prepare
cramfs uses either a PFN remap or a mixedmap insertion, we are able to
determine this at the point of mmap_prepare and to select the appropriate
action to perform using the vm_area_desc.
Note that there appears to have been a bug in this code, with the physical
address being specified as the PFN (!!) to vmf_insert_mixed(). This patch
fixes this issue.
Finally, we trivially have to update the pr_debug() message indicating
what's happening to occur before the remap/mixedmap occurs.
Link: https://lkml.kernel.org/r/0b1cefb4e4021e95902d08c7a43a3033d1e3a4d9.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:07 +0000 (21:22 +0100)]
mm: update resctl to use mmap_prepare
Make use of the ability to specify a remap action within mmap_prepare to
update the resctl pseudo-lock to use mmap_prepare in favour of the
deprecated mmap hook.
Link: https://lkml.kernel.org/r/f0bfba7672f5fb39dffeeed65c64900d65ba0124.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: Reinette Chatre <reinette.chatre@intel.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:06 +0000 (21:22 +0100)]
mm: update mem char driver to use mmap_prepare
Update the mem char driver (backing /dev/mem and /dev/zero) to use
f_op->mmap_prepare hook rather than the deprecated f_op->mmap.
The /dev/zero implementation has a very unique and rather concerning
characteristic in that it converts MAP_PRIVATE mmap() mappings anonymous
when they are, in fact, not.
The new f_op->mmap_prepare() can support this, but rather than introducing
a helper function to perform this hack (and risk introducing other users),
simply set desc->vm_op to NULL here and add a comment describing what's
going on.
We also introduce shmem_zero_setup_desc() to allow for the shared mapping
case via an f_op->mmap_prepare() hook, and generalise the code between
this and shmem_zero_setup().
We also use the desc->action_error_hook to filter the remap error to
-EAGAIN to keep behaviour consistent.
Link: https://lkml.kernel.org/r/aeee6a4896304d6dc7515e79d74f8bc5ec424415.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:05 +0000 (21:22 +0100)]
mm/hugetlbfs: update hugetlbfs to use mmap_prepare
Since we can now perform actions after the VMA is established via
mmap_prepare, use desc->action_success_hook to set up the hugetlb lock
once the VMA is setup.
We also make changes throughout hugetlbfs to make this possible.
Link: https://lkml.kernel.org/r/ed2cf936858c0fa14adbbd71e7638be489357df8.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:04 +0000 (21:22 +0100)]
doc: update porting, vfs documentation for mmap_prepare actions
Now we have introduced the ability to specify that actions should be taken
after a VMA is established via the vm_area_desc->action field as specified
in mmap_prepare, update both the VFS documentation and the porting guide
to describe this.
Link: https://lkml.kernel.org/r/e50e91a6f6173f81addb838c5049bed2833f7b0d.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:03 +0000 (21:22 +0100)]
mm: add ability to take further action in vm_area_desc
Some drivers/filesystems need to perform additional tasks after the VMA is
set up. This is typically in the form of pre-population.
The forms of pre-population most likely to be performed are a PFN remap or
insertion of a mixed map, so we provide this functionality, ensuring that
we perform the appropriate actions at the appropriate time - that is
setting flags at the point of .mmap_prepare, and performing the actual
remap at the point at which the VMA is fully established.
This prevents the driver from doing anything too crazy with a VMA at any
stage, and we retain complete control over how the mm functionality is
applied.
Unfortunately callers still do often require some kind of custom action,
so we add an optional success/error _hook to allow the caller to do
something after the action has succeeded or failed.
This is done at the point when the VMA has already been established, so
the harm that can be done is limited.
The error hook can be used to filter errors if necessary.
We implement actions as abstracted from the vm_area_desc, so we provide
the ability for custom hooks to invoke actions distinct from the vma
descriptor.
If any error arises on these final actions, we simply unmap the VMA
altogether.
Also update the stacked filesystem compatibility layer to utilise the
action behaviour, and update the VMA tests accordingly.
For drivers which perform truly custom logic, we provide a custom action
hook which is invoked at the point of action execution.
This can then, in turn, update the desc object and perform other actions,
such as partially remapping ranges for instance. We export
vma_desc_action_prepare() and vma_desc_action_complete() for drivers to do
this.
This is performed at a stage where the VMA is already established,
immediately prior to mapping completion, so it is considerably less
problematic than a general mmap hook.
Note that at the point of the action being taken, the VMA is visible via
the rmap, only the VMA write lock is held, so if anything needs to access
the VMA, it is able to.
Essentially the action is taken as if it were performed after the mapping,
but is kept atomic with VMA state.
Link: https://lkml.kernel.org/r/d85cc08dd7c5f0a4d5a3c5a5a1b75556461392a1.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We need the ability to split PFN remap between updating the VMA and
performing the actual remap, in order to do away with the legacy
f_op->mmap hook.
To do so, update the PFN remap code to provide shared logic, and also make
remap_pfn_range_notrack() static, as its one user, io_mapping_map_user()
was removed in commit 9a4f90e24661 ("mm: remove mm/io-mapping.c").
Then, introduce remap_pfn_range_prepare(), which accepts VMA descriptor
and PFN parameters, and remap_pfn_range_complete() which accepts the same
parameters as remap_pfn_rangte().
remap_pfn_range_prepare() will set the cow vma->vm_pgoff if necessary, so
it must be supplied with a correct PFN to do so. If the caller must hold
locks to be able to do this, those locks should be held across the
operation, and mmap_abort() should be provided to revoke the lock should
an error arise.
While we're here, also clean up the duplicated #ifdef
__HAVE_PFNMAP_TRACKING check and put into a single #ifdef/#else block.
We would prefer to define these functions in mm/internal.h, however we
will do the same for io_remap*() and these have arch defines that require
access to the remap functions.
Link: https://lkml.kernel.org/r/b84a0d7259be8c56dec258665ea98da1e3cbda54.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:22:00 +0000 (21:22 +0100)]
mm/vma: rename __mmap_prepare() function to avoid confusion
Now we have the f_op->mmap_prepare() hook, having a static function called
__mmap_prepare() that has nothing to do with it is confusing, so rename
the function to __mmap_setup().
Link: https://lkml.kernel.org/r/9c9f9f9eaa7ae48cc585e4789117747d90f15c74.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:21:58 +0000 (21:21 +0100)]
mm: add vma_desc_size(), vma_desc_pages() helpers
It's useful to be able to determine the size of a VMA descriptor range
used on f_op->mmap_prepare, expressed both in bytes and pages, so add
helpers for both and update code that could make use of it to do so.
Link: https://lkml.kernel.org/r/5ac75e5ac627c06e62401dfda8c908eadac8dfec.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lorenzo Stoakes [Wed, 10 Sep 2025 20:21:56 +0000 (21:21 +0100)]
mm/shmem: update shmem to use mmap_prepare
Patch series "expand mmap_prepare functionality, port more users", v2.
Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
callback"), The f_op->mmap hook has been deprecated in favour of
f_op->mmap_prepare.
This was introduced in order to make it possible for us to eventually
eliminate the f_op->mmap hook which is highly problematic as it allows
drivers and filesystems raw access to a VMA which is not yet correctly
initialised.
This hook also introduced complexity for the memory mapping operation, as
we must correctly unwind what we do should an error arises.
Overall this interface being so open has caused significant problems for
us, including security issues, it is important for us to simply eliminate
this as a source of problems.
Therefore this series continues what was established by extending the
functionality further to permit more drivers and filesystems to use
mmap_prepare.
We start by udpating some existing users who can use the mmap_prepare
functionality as-is.
We then introduce the concept of an mmap 'action', which a user, on
mmap_prepare, can request to be performed upon the VMA:
* Nothing - default, we're done
* Remap PFN - perform PFN remap with specified parameters
* Insert mixed - Insert a linear PFN range as a mixed map
* Insert mixed pages - Insert a set of specific pages as a mixed map
* Custom action - Should rarely be used, for operations that are truly
custom. A hook is invoked.
By setting the action in mmap_prepare, this alows us to dynamically decide
what to do next, so if a driver/filesystem needs to determine whether to
e.g. remap or use a mixed map, it can do so then change which is done.
This significantly expands the capabilities of the mmap_prepare hook,
while maintaining as much control as possible in the mm logic.
In the custom hook case, which unfortunately we have to provide for the
obstinate drivers which insist on doing 'interesting' things, we make it
possible for them to invoke mmap actions themselves via
mmap_action_prepare() (to be called in mmap_prepare as necessary) and
mmap_action_complete() (to be called in the custom hook).
This way, we keep as much logic in generic code as possible even in the
custom case.
The point at which the VMA is accessible it is safe for it to be
manipulated as it will already be fully established in the maple tree and
error handling can be simplified to unmapping the VMA.
We split remap_pfn_range*() functions which allow for PFN remap (a typical
mapping prepopulation operation) split between a prepare/complete step, as
well as io_mremap_pfn_range_prepare, complete for a similar purpose.
From there we update various mm-adjacent logic to use this functionality
as a first set of changes, as well as resctl and cramfs filesystems to
round off the non-stacked filesystem instances.
We also add success and error hooks for post-action processing for e.g.
output debug log on success and filtering error codes.
This patch (of 16):
This simply assigns the vm_ops so is easily updated - do so.
Link: https://lkml.kernel.org/r/cover.1757534913.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/c328d14480808cb0e136db8090f2a203ade72233.1757534913.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baoquan He <bhe@redhat.com> Cc: Chatre, Reinette <reinette.chatre@intel.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Dave Martin <dave.martin@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guo Ren <guoren@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: James Morse <james.morse@arm.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Oscar Salvador <osalvador@suse.de> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/oom_kill: the OOM reaper traverses the VMA maple tree in reverse order
Although the oom_reaper is delayed and it gives the oom victim chance to
clean up its address space this might take a while especially for
processes with a large address space footprint. In those cases oom_reaper
might start racing with the dying task and compete for shared resources -
e.g. page table lock contention has been observed.
Reduce those races by reaping the oom victim from the other end of the
address space.
It is also a significant improvement for process_mrelease(). When a
process is killed, process_mrelease is used to reap the killed process and
often runs concurrently with the dying task. The test data shows that
after applying the patch, lock contention is greatly reduced during the
procedure of reaping the killed process.
selftests/mm: remove PROT_EXEC req from file-collapse tests
As of v6.8 commit 7fbb5e188248 ("mm: remove VM_EXEC requirement for THP
eligibility") thp collapse no longer requires file-backed mappings be
created with PROT_EXEC.
Remove the overly-strict dependency from thp collapse tests so we test the
least-strict requirement for success.
Link: https://lkml.kernel.org/r/20250909190534.512801-1-zokeefe@google.com Signed-off-by: Zach O'Keefe <zokeefe@google.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Dev Jain <dev.jain@arm.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Brian Norris [Tue, 9 Sep 2025 20:13:57 +0000 (13:13 -0700)]
mm: vm_event_item: explicit #include for THREAD_SIZE
This header uses THREAD_SIZE, which is provided by the thread_info.h
header but is not included in this header. Depending on the #include
ordering in other files, this can produce preprocessor errors.
Link: https://lkml.kernel.org/r/20250909201419.827638-1-briannorris@chromium.org Signed-off-by: Brian Norris <briannorris@chromium.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
alloc_tag: avoid warnings when freeing non-compound "tail" pages
When freeing "tail" pages of a non-compount high-order page, we properly
subtract the allocation tag counters, however later when these pages are
released, alloc_tag_sub() will issue warnings because tags for these pages
are NULL.
This issue was originally anticipated by Vlastimil in his review [1] and
then recently reported by David. Prevent warnings by marking the tags
empty.
Link: https://lkml.kernel.org/r/20250909233409.1013367-4-surenb@google.com Link: https://lore.kernel.org/all/6db0f0c8-81cb-4d04-9560-ba73d63db4b8@suse.cz/ Signed-off-by: Suren Baghdasaryan <surenb@google.com> Suggested-by: David Wang <00107082@163.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Cc: Brendan Jackman <jackmanb@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Michal Hocko <mhocko@suse.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Sourav Panda <souravpanda@google.com> Cc: Usama Arif <usamaarif642@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
alloc_tag: prevent enabling memory profiling if it was shut down
Memory profiling can be shut down due to reasons like a failure during
initialization. When this happens, the user should not be able to
re-enable it. Current sysctrl interface does not handle this properly and
will allow re-enabling memory profiling. Fix this by checking for this
condition during sysctrl write operation.
Link: https://lkml.kernel.org/r/20250909233409.1013367-3-surenb@google.com Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Usama Arif <usamaarif642@gmail.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Cc: Brendan Jackman <jackmanb@google.com> Cc: David Wang <00107082@163.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Michal Hocko <mhocko@suse.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Sourav Panda <souravpanda@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
gpu/drm/nouveau: enable THP support for GPU memory migration
Enable MIGRATE_VMA_SELECT_COMPOUND support in nouveau driver to take
advantage of THP zone device migration capabilities.
Update migration and eviction code paths to handle compound page sizes
appropriately, improving memory bandwidth utilization and reducing
migration overhead for large GPU memory allocations.
Link: https://lkml.kernel.org/r/20250908000448.180088-16-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
lib/test_hmm: add large page allocation failure testing
Add HMM_DMIRROR_FLAG_FAIL_ALLOC flag to simulate large page allocation
failures, enabling testing of split migration code paths.
This test flag allows validation of the fallback behavior when destination
device cannot allocate compound pages. This is useful for testing the
split migration functionality.
Link: https://lkml.kernel.org/r/20250908000448.180088-12-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/migrate_device: add THP splitting during migration
Implement migrate_vma_split_pages() to handle THP splitting during the
migration process when destination cannot allocate compound pages.
This addresses the common scenario where migrate_vma_setup() succeeds with
MIGRATE_PFN_COMPOUND pages, but the destination device cannot allocate
large pages during the migration phase.
Key changes:
- migrate_vma_split_pages(): Split already-isolated pages during migration
- Enhanced folio_split() and __split_unmapped_folio() with isolated
parameter to avoid redundant unmap/remap operations
This provides a fallback mechansim to ensure migration succeeds even when
large page allocation fails at the destination.
Link: https://lkml.kernel.org/r/20250908000448.180088-11-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/memremap: add driver callback support for folio splitting
When a zone device page is split (via huge pmd folio split). The driver
callback for folio_split is invoked to let the device driver know that the
folio size has been split into a smaller order.
Provide a default implementation for drivers that do not provide this
callback that copies the pgmap and mapping fields for the split folios.
Update the HMM test driver to handle the split.
Link: https://lkml.kernel.org/r/20250908000448.180088-10-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
lib/test_hmm: add zone device private THP test infrastructure
Enhance the hmm test driver (lib/test_hmm) with support for THP pages.
A new pool of free_folios() has now been added to the dmirror device,
which can be allocated when a request for a THP zone device private page
is made.
Add compound page awareness to the allocation function during normal
migration and fault based migration. These routines also copy
folio_nr_pages() when moving data between system memory and device memory.
args.src and args.dst used to hold migration entries are now dynamically
allocated (as they need to hold HPAGE_PMD_NR entries or more).
Split and migrate support will be added in future patches in this series.
Link: https://lkml.kernel.org/r/20250908000448.180088-9-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/memory/fault: add THP fault handling for zone device private pages
Implement CPU fault handling for zone device THP entries through
do_huge_pmd_device_private(), enabling transparent migration of
device-private large pages back to system memory on CPU access.
When the CPU accesses a zone device THP entry, the fault handler calls the
device driver's migrate_to_ram() callback to migrate the entire large page
back to system memory.
Link: https://lkml.kernel.org/r/20250908000448.180088-8-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/migrate_device: implement THP migration of zone device pages
MIGRATE_VMA_SELECT_COMPOUND will be used to select THP pages during
migrate_vma_setup() and MIGRATE_PFN_COMPOUND will make migrating device
pages as compound pages during device pfn migration.
migrate_device code paths go through the collect, setup and finalize
phases of migration.
The entries in src and dst arrays passed to these functions still remain
at a PAGE_SIZE granularity. When a compound page is passed, the first
entry has the PFN along with MIGRATE_PFN_COMPOUND and other flags set
(MIGRATE_PFN_MIGRATE, MIGRATE_PFN_VALID), the remaining entries
(HPAGE_PMD_NR - 1) are filled with 0's. This representation allows for
the compound page to be split into smaller page sizes.
migrate_vma_collect_hole(), migrate_vma_collect_pmd() are now THP page
aware. Two new helper functions migrate_vma_collect_huge_pmd() and
migrate_vma_insert_huge_pmd_page() have been added.
migrate_vma_collect_huge_pmd() can collect THP pages, but if for some
reason this fails, there is fallback support to split the folio and
migrate it.
migrate_vma_insert_huge_pmd_page() closely follows the logic of
migrate_vma_insert_page()
Support for splitting pages as needed for migration will follow in later
patches in this series.
Link: https://lkml.kernel.org/r/20250908000448.180088-7-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/migrate_device: handle partially mapped folios during collection
Extend migrate_vma_collect_pmd() to handle partially mapped large folios
that require splitting before migration can proceed.
During PTE walk in the collection phase, if a large folio is only
partially mapped in the migration range, it must be split to ensure the
folio is correctly migrated.
Link: https://lkml.kernel.org/r/8e1ef390-ab28-4294-8528-c57453e3acc1@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add support for splitting device-private THP folios, enabling fallback
to smaller page sizes when large page allocation or migration fails.
Key changes:
- split_huge_pmd(): Handle device-private PMD entries during splitting
- Preserve RMAP_EXCLUSIVE semantics for anonymous exclusive folios
- Skip RMP_USE_SHARED_ZEROPAGE for device-private entries as they
don't support shared zero page semantics
Link: https://lkml.kernel.org/r/20250908000448.180088-5-balbirs@nvidia.com Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/huge_memory: add device-private THP support to PMD operations
Extend core huge page management functions to handle device-private THP
entries. This enables proper handling of large device-private folios in
fundamental MM operations.
The following functions have been updated:
- copy_huge_pmd(): Handle device-private entries during fork/clone
- zap_huge_pmd(): Properly free device-private THP during munmap
- change_huge_pmd(): Support protection changes on device-private THP
- __pte_offset_map(): Add device-private entry awareness
Link: https://lkml.kernel.org/r/20250908000448.180088-3-balbirs@nvidia.com Signed-off-by: Matthew Brost <matthew.brost@intel.com> Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/zone_device: support large zone device private folios
Patch series "mm: support device-private THP", v5.
This series introduces support for Transparent Huge Page (THP) migration
in zone device-private memory. The implementation enables efficient
migration of large folios between system memory and device-private memory
Background
Current zone device-private memory implementation only supports PAGE_SIZE
granularity, leading to:
- Increased TLB pressure
- Inefficient migration between CPU and GPU memory
This series extends the existing zone device-private infrastructure to
support THP, leading to:
- Reduced page table overhead
- Improved memory bandwidth utilization
- Seamless fallback to base pages when needed
In my local testing (using lib/test_hmm) and a throughput test, the series
shows a 350% improvement in data transfer throughput and a 80% improvement
in latency
These patches build on the earlier posts by Ralph Campbell [1]
Two new flags are added in vma_migration to select and mark compound
pages. migrate_vma_setup(), migrate_vma_pages() and
migrate_vma_finalize() support migration of these pages when
MIGRATE_VMA_SELECT_COMPOUND is passed in as arguments.
The series also adds zone device awareness to (m)THP pages along with
fault handling of large zone device private pages. page vma walk and the
rmap code is also zone device aware. Support has also been added for
folios that might need to be split in the middle of migration (when the
src and dst do not agree on MIGRATE_PFN_COMPOUND), that occurs when src
side of the migration can migrate large pages, but the destination has not
been able to allocate large pages. The code supported and used
folio_split() when migrating THP pages, this is used when
MIGRATE_VMA_SELECT_COMPOUND is not passed as an argument to
migrate_vma_setup().
The test infrastructure lib/test_hmm.c has been enhanced to support THP
migration. A new ioctl to emulate failure of large page allocations has
been added to test the folio split code path. hmm-tests.c has new test
cases for huge page migration and to test the folio split path. A new
throughput test has been added as well.
The nouveau dmem code has been enhanced to use the new THP migration
capability.
mTHP support:
The patches hard code, HPAGE_PMD_NR in a few places, but the code has been
kept generic to support various order sizes. With additional refactoring
of the code support of different order sizes should be possible.
The future plan is to post enhancements to support mTHP with a rough
design as follows:
1. Add the notion of allowable thp orders to the HMM based test driver
2. For non PMD based THP paths in migrate_device.c, check to see if
a suitable order is found and supported by the driver
3. Iterate across orders to check the highest supported order for migration
4. Migrate and finalize
The mTHP patches can be built on top of this series, the key design
elements that need to be worked out are infrastructure and driver support
for multiple ordered pages and their migration.
This patch (of 15):
Add routines to support allocation of large order zone device folios
and helper functions for zone device folios, to check if a folio is
device private and helpers for setting zone device data.
When large folios are used, the existing page_free() callback in
pgmap is called when the folio is freed, this is true for both
PAGE_SIZE and higher order pages.
Zone device private large folios do not support deferred split and
scan like normal THP folios.
Link: https://lkml.kernel.org/r/20250908000448.180088-1-balbirs@nvidia.com Link: https://lkml.kernel.org/r/20250908000448.180088-2-balbirs@nvidia.com Link: https://lore.kernel.org/linux-mm/20201106005147.20113-1-rcampbell@nvidia.com/ Signed-off-by: Balbir Singh <balbirs@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: Ying Huang <ying.huang@linux.alibaba.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Nico Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Lyude Paul <lyude@redhat.com> Cc: Danilo Krummrich <dakr@kernel.org> Cc: David Airlie <airlied@gmail.com> Cc: Simona Vetter <simona@ffwll.ch> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Francois Dugast <francois.dugast@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This happens because demotion was enabled, when the memcg's memory limit
was exceeded, memory from the DRAM NUMA node was first migrated to the CXL
NUMA node. After that, a memory reclaim was performed, which was
unnecessary.
When a memory cgroup exceeds its memory limit, the system reclaims its
cold memory.However, if /sys/kernel/mm/numa/demotion_enabled is set to 1,
memory on fast memory nodes will also be demoted to slow memory nodes.
This demotion contradicts the goal of reclaiming cold memory within the
memcg.At this point, demoting cold memory from fast to slow nodes is
pointless;it doesn't reduce the memcg's memory usage. Therefore, we
should set no_demotion when reclaiming memory in a memcg.
Link: https://lkml.kernel.org/r/20250909012141.1467-1-cuishw@inspur.com Signed-off-by: cuishiwei <cuishw@inspur.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Wei Xu <weixugc@google.com> Cc: Yuanchu Xie <yuanchu@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Jackie Liu [Mon, 8 Sep 2025 06:26:14 +0000 (14:26 +0800)]
mm/shmem: remove unused entry_order after large swapin rework
After commit 93c0476e7057 ("mm/shmem, swap: rework swap entry and index
calculation for large swapin"), xas_get_order() will never return a
non-zero value for `entry_order` in shmem_split_large_entry(). As a
result, the local variable `entry_order` is effectively unused.
Clean up the code by removing `entry_order` and directly using
`cur_order`. This change is purely a refactor and has no functional
impact.
No functional change intended.
Link: https://lkml.kernel.org/r/20250908062614.89880-1-liu.yun@linux.dev Signed-off-by: Jackie Liu <liuyun01@kylinos.cn> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kairui Song <kasong@tencent.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kevin Brodsky [Mon, 8 Sep 2025 07:39:30 +0000 (08:39 +0100)]
sparc/mm: support nested lazy_mmu sections
The lazy_mmu API now allows nested sections to be handled by arch code:
enter() can return a flag if called inside another lazy_mmu section, so
that the matching call to leave() leaves any optimisation enabled.
This patch implements that new logic for sparc: if there is an active
batch, then enter() returns LAZY_MMU_NESTED and the matching leave()
leaves batch->active set. The preempt_{enable,disable} calls are left
untouched as they already handle nesting themselves.
TLB flushing is still done in leave() regardless of the nesting level, as
the caller may rely on it whether nesting is occurring or not.
Link: https://lkml.kernel.org/r/20250908073931.4159362-7-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Juegren Gross <jgross@suse.com> Cc: levi.yun <yeoreum.yun@arm.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport (Microsoft) <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kevin Brodsky [Mon, 8 Sep 2025 07:39:29 +0000 (08:39 +0100)]
powerpc/mm: support nested lazy_mmu sections
The lazy_mmu API now allows nested sections to be handled by arch code:
enter() can return a flag if called inside another lazy_mmu section, so
that the matching call to leave() leaves any optimisation enabled.
This patch implements that new logic for powerpc: if there is an active
batch, then enter() returns LAZY_MMU_NESTED and the matching leave()
leaves batch->active set. The preempt_{enable,disable} calls are left
untouched as they already handle nesting themselves.
TLB flushing is still done in leave() regardless of the nesting level, as
the caller may rely on it whether nesting is occurring or not.
Link: https://lkml.kernel.org/r/20250908073931.4159362-6-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Juegren Gross <jgross@suse.com> Cc: levi.yun <yeoreum.yun@arm.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport (Microsoft) <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kevin Brodsky [Mon, 8 Sep 2025 07:39:28 +0000 (08:39 +0100)]
x86/xen: support nested lazy_mmu sections (again)
Commit 49147beb0ccb ("x86/xen: allow nesting of same lazy mode")
originally introduced support for nested lazy sections (LAZY_MMU and
LAZY_CPU). It later got reverted by commit c36549ff8d84 as its
implementation turned out to be intolerant to preemption.
Now that the lazy_mmu API allows enter() to pass through a state to the
matching leave() call, we can support nesting again for the LAZY_MMU mode
in a preemption-safe manner. If xen_enter_lazy_mmu() is called inside an
active lazy_mmu section, xen_lazy_mode will already be set to XEN_LAZY_MMU
and we can then return LAZY_MMU_NESTED to instruct the matching
xen_leave_lazy_mmu() call to leave xen_lazy_mode unchanged.
The only effect of this patch is to ensure that xen_lazy_mode remains set
to XEN_LAZY_MMU until the outermost lazy_mmu section ends.
xen_leave_lazy_mmu() still calls xen_mc_flush() unconditionally.
Link: https://lkml.kernel.org/r/20250908073931.4159362-5-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Juegren Gross <jgross@suse.com> Cc: levi.yun <yeoreum.yun@arm.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport (Microsoft) <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kevin Brodsky [Mon, 8 Sep 2025 07:39:27 +0000 (08:39 +0100)]
arm64: mm: fully support nested lazy_mmu sections
Despite recent efforts to prevent lazy_mmu sections from nesting, it
remains difficult to ensure that it never occurs - and in fact it does
occur on arm64 in certain situations (CONFIG_DEBUG_PAGEALLOC). Commit 1ef3095b1405 ("arm64/mm: Permit lazy_mmu_mode to be nested") made nesting
tolerable on arm64, but without truly supporting it: the inner leave()
call clears TIF_LAZY_MMU, disabling the batching optimisation before the
outer section ends.
Now that the lazy_mmu API allows enter() to pass through a state to the
matching leave() call, we can actually support nesting. If enter() is
called inside an active lazy_mmu section, TIF_LAZY_MMU will already be
set, and we can then return LAZY_MMU_NESTED to instruct the matching
leave() call not to clear TIF_LAZY_MMU.
The only effect of this patch is to ensure that TIF_LAZY_MMU (and
therefore the batching optimisation) remains set until the outermost
lazy_mmu section ends. leave() still emits barriers if needed, regardless
of the nesting level, as the caller may expect any page table changes to
become visible when leave() returns.
Link: https://lkml.kernel.org/r/20250908073931.4159362-4-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Juegren Gross <jgross@suse.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport (Microsoft) <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kevin Brodsky [Mon, 8 Sep 2025 07:39:26 +0000 (08:39 +0100)]
mm: introduce local state for lazy_mmu sections
arch_{enter,leave}_lazy_mmu_mode() currently have a stateless API (taking
and returning no value). This is proving problematic in situations where
leave() needs to restore some context back to its original state (before
enter() was called). In particular, this makes it difficult to support
the nesting of lazy_mmu sections - leave() does not know whether the
matching enter() call occurred while lazy_mmu was already enabled, and
whether to disable it or not.
This patch gives all architectures the chance to store local state while
inside a lazy_mmu section by making enter() return some value, storing it
in a local variable, and having leave() take that value. That value is
typed lazy_mmu_state_t - each architecture defining
__HAVE_ARCH_ENTER_LAZY_MMU_MODE is free to define it as it sees fit. For
now we define it as int everywhere, which is sufficient to support
nesting.
The diff is unfortunately rather large as all the API changes need to be
done atomically. Main parts:
* Changing the prototypes of arch_{enter,leave}_lazy_mmu_mode()
in generic and arch code, and introducing lazy_mmu_state_t.
* Introducing LAZY_MMU_{DEFAULT,NESTED} for future support of
nesting. enter() always returns LAZY_MMU_DEFAULT for now.
(linux/mm_types.h is not the most natural location for defining
those constants, but there is no other obvious header that is
accessible where arch's implement the helpers.)
* Changing all lazy_mmu sections to introduce a lazy_mmu_state
local variable, having enter() set it and leave() take it. Most of
these changes were generated using the following Coccinelle script:
* In a few cases (e.g. xen_flush_lazy_mmu()), a function knows that
lazy_mmu is already enabled, and it temporarily disables it by
calling leave() and then enter() again. Here we want to ensure
that any operation between the leave() and enter() calls is
completed immediately; for that reason we pass LAZY_MMU_DEFAULT to
leave() to fully disable lazy_mmu. enter() will then re-enable it
- this achieves the expected behaviour, whether nesting occurred
before that function was called or not.
Note: it is difficult to provide a default definition of lazy_mmu_state_t
for architectures implementing lazy_mmu, because that definition would
need to be available in arch/x86/include/asm/paravirt_types.h and adding a
new generic #include there is very tricky due to the existing header soup.
Link: https://lkml.kernel.org/r/20250908073931.4159362-3-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com> Reviewed-by: Juergen Gross <jgross@suse.com> # arch/x86 Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: David Hildenbrand <david@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It seems fair to say that nested calls to
arch_{enter,leave}_lazy_mmu_mode() were not expected, and most
architectures never explicitly supported it.
Ryan Roberts' series from March [1] attempted to prevent nesting from ever
occurring, and mostly succeeded. Unfortunately, a corner case
(DEBUG_PAGEALLOC) may still cause nesting to occur on arm64. Ryan
proposed [2] to address that corner case at the generic level but this
approach received pushback; [3] then attempted to solve the issue on arm64
only, but it was deemed too fragile.
It feels generally fragile to rely on lazy_mmu sections not to nest,
because callers of various standard mm functions do not know if the
function uses lazy_mmu itself. This series therefore performs a U-turn
and adds support for nested lazy_mmu sections, on all architectures.
The main change enabling nesting is patch 2, following the approach
suggested by Catalin Marinas [4]: have enter() return some state and the
matching leave() take that state. In this series, the state is only used
to handle nesting, but it could be used for other purposes such as
restoring context modified by enter(); the proposed kpkeys framework would
be an immediate user [5].
This patch (of 7):
This function has only ever been used in arch/x86, so there is no need for
other architectures to implement it. Remove it from linux/pgtable.h and
all architectures besides x86.
The arm64 implementation is not empty but it is only called from
arch_leave_lazy_mmu_mode(), so we can simply fold it there.
Dev Jain [Mon, 8 Sep 2025 07:50:27 +0000 (13:20 +0530)]
mm: enable khugepaged anonymous collapse on non-writable regions
Patch series "Expand scope of khugepaged anonymous collapse", v2.
Currently khugepaged does not collapse an anonymous region which does not
have a single writable pte. This is wasteful since a region mapped with
non-writable ptes, for example, non-writable VMAs mapped by the
application, won't benefit from THP collapse.
An additional consequence of this constraint is that MADV_COLLAPSE does
not perform a collapse on a non-writable VMA, and this restriction is
nowhere to be found on the manpage - the restriction itself sounds wrong
to me since the user knows the protection of the memory it has mapped, so
collapsing read-only memory via madvise() should be a choice of the user
which shouldn't be overridden by the kernel.
Therefore, remove this constraint.
On an arm64 bare metal machine, comparing with vanilla 6.17-rc2, an
average of 5% improvement is seen on some mmtests benchmarks, particularly
hackbench, with a maximum improvement of 12%. In the following table, (I)
denotes statistically significant improvement, (R) denotes statistically
significant regression.
Currently khugepaged does not collapse an anonymous region which does not
have a single writable pte. This is wasteful since a region mapped with
non-writable ptes, for example, non-writable VMAs mapped by the
application, won't benefit from THP collapse.
An additional consequence of this constraint is that MADV_COLLAPSE does
not perform a collapse on a non-writable VMA, and this restriction is
nowhere to be found on the manpage - the restriction itself sounds wrong
to me since the user knows the protection of the memory it has mapped, so
collapsing read-only memory via madvise() should be a choice of the user
which shouldn't be overridden by the kernel.
Therefore, remove this restriction by not honouring SCAN_PAGE_RO.
Link: https://lkml.kernel.org/r/20250908075028.38431-1-dev.jain@arm.com Link: https://lkml.kernel.org/r/20250908075028.38431-2-dev.jain@arm.com Signed-off-by: Dev Jain <dev.jain@arm.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Wei Yang <richard.weiyang@gmail.com> Reviewed-by: Kiryl Shutsemau <kas@kernel.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Zach O'Keefe <zokeefe@google.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Mariano Pache <npache@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Lance Yang [Mon, 8 Sep 2025 09:07:41 +0000 (17:07 +0800)]
mm: skip mlocked THPs that are underused early in deferred_split_scan()
When we stumble over a fully-mapped mlocked THP in the deferred shrinker,
it does not make sense to try to detect whether it is underused, because
try_to_map_unused_to_zeropage(), called while splitting the folio, will
not actually replace any zeroed pages by the shared zeropage.
Splitting the folio in that case does not make any sense, so let's not
even scan to check if the folio is underused.
Link: https://lkml.kernel.org/r/20250908090741.61519-1-lance.yang@linux.dev Signed-off-by: Lance Yang <lance.yang@linux.dev> Suggested-by: David Hildenbrand <david@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Usama Arif <usamaarif642@gmail.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Barry Song <baohua@kernel.org> Cc: Dev Jain <dev.jain@arm.com> Cc: Lance Yang <lance.yang@linux.dev> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Mariano Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Kiryl Shutsemau <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Once support for THP migration of zone device pages is enabled, device
private swap entries will be found during the walk not only for PTEs but
also for PMDs.
Therefore, it is necessary to extend to PMDs the special handling which is
already in place for PTEs when device private pages are owned by the
caller: instead of faulting or skipping the range, the correct behavior is
to use the swap entry to populate HMM PFNs.
This change is a prerequisite to make use of device-private THP in drivers
using drivers/gpu/drm/drm_pagemap, such as xe.
Even though subsequent PFNs can be inferred when handling large order
PFNs, the PFN list is still fully populated because this is currently
expected by HMM users. In case this changes in the future, that is all
HMM users support a sparsely populated PFN list, the for() loop can be
made to skip remaining PFNs for the current order. A quick test shows the
loop takes about 10 ns, roughly 20 times faster than without this
optimization.
Link: https://lkml.kernel.org/r/20250908091052.612303-1-francois.dugast@intel.com Signed-off-by: Francois Dugast <francois.dugast@intel.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Leon Romanovsky <leonro@nvidia.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Balbir Singh <balbirs@nvidia.com> Cc: David Airlie <airlied@gmail.com> Cc: Christian König <christian.koenig@amd.com> Cc: Mika Penttilä <mpenttil@redhat.com> Cc: Thomas Hellstrom <thomas.hellstrom@linux.intel.com> Cc: Matthew Brost <matthew.brost@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
David Hildenbrand [Mon, 8 Sep 2025 09:45:17 +0000 (11:45 +0200)]
mm/gup: fix handling of errors from arch_make_folio_accessible() in follow_page_pte()
In case we call arch_make_folio_accessible() and it fails, we would
incorrectly return a value that is "!= 0" to the caller, indicating that
we pinned all requested pages and that the caller can keep going.
follow_page_pte() is not supposed to return error values, but instead "0"
on failure and "1" on success -- we'll clean that up separately.
In case we return "!= 0", the caller will just keep going pinning more
pages. If we happen to pin a page afterwards, we're in trouble, because
we essentially skipped some pages in the requested range.
Staring at the arch_make_folio_accessible() implementation on s390x, I
assume it should actually never really fail unless something unexpected
happens (BUG?). So let's not CC stable and just fix common code to do the
right thing.
Clean up the code a bit now that there is no reason to store the return
value of arch_make_folio_accessible().
Link: https://lkml.kernel.org/r/20250908094517.303409-1-david@redhat.com Fixes: f28d43636d6f ("mm/gup/writeback: add callbacks for inaccessible pages") Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chanwon Park [Mon, 8 Sep 2025 10:04:10 +0000 (19:04 +0900)]
mm: re-enable kswapd when memory pressure subsides or demotion is toggled
If kswapd fails to reclaim pages from a node MAX_RECLAIM_RETRIES in a
row, kswapd on that node gets disabled. That is, the system won't wakeup
kswapd for that node until page reclamation is observed at least once.
That reclamation is mostly done by direct reclaim, which in turn enables
kswapd back.
However, on systems with CXL memory nodes, workloads with high anon page
usage can disable kswapd indefinitely, without triggering direct
reclaim. This can be reproduced with following steps:
numa node 0 (32GB memory, 48 CPUs)
numa node 2~5 (512GB CXL memory, 128GB each)
(numa node 1 is disabled)
swap space 8GB
1) Set /sys/kernel/mm/demotion_enabled to 0.
2) Set /proc/sys/kernel/numa_balancing to 0.
3) Run a process that allocates and random accesses 500GB of anon
pages.
4) Let the process exit normally.
During 3), free memory on node 0 gets lower than low watermark, and
kswapd runs and depletes swap space. Then, kswapd fails consecutively
and gets disabled. Allocation afterwards happens on CXL memory, so node
0 never gains more memory pressure to trigger direct reclaim.
After 4), kswapd on node 0 remains disabled, and tasks running on that
node are unable to swap. If you turn on NUMA_BALANCING_MEMORY_TIERING
and demotion now, it won't work properly since kswapd is disabled.
To mitigate this problem, reset kswapd_failures to 0 on following
conditions:
a) ZONE_BELOW_HIGH bit of a zone in hopeless node with a fallback
memory node gets cleared.
b) demotion_enabled is changed from false to true.
Rationale for a):
ZONE_BELOW_HIGH bit being cleared might be a sign that the node may
be reclaimable afterwards. This won't help much if the memory-hungry
process keeps running without freeing anything, but at least the node
will go back to reclaimable state when the process exits.
Rationale for b):
When demotion_enabled is false, kswapd can only reclaim anon pages by
swapping them out to swap space. If demotion_enabled is turned on,
kswapd can demote anon pages to another node for reclaiming. So, the
original failure count for determining reclaimability is no longer
valid.
Since kswapd_failures resets may be missed by ++ operation, it is
changed from int to atomic_t.
Link: https://lkml.kernel.org/r/aL6qGi69jWXfPc4D@pcw-MS-7D22 Signed-off-by: Chanwon Park <flyinrm@gmail.com> Cc: Brendan Jackman <jackmanb@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Vernon Yang [Mon, 8 Sep 2025 12:31:28 +0000 (20:31 +0800)]
mm: shmem: fix too little space for tmpfs only fallback 4KB
When the system memory is sufficient, allocating memory is always
successful, but when tmpfs size is low (e.g. 1MB), it falls back directly
from 2MB to 4KB, and other small granularity (8KB ~ 1024KB) will not be
tried.
Therefore add check whether the remaining space of tmpfs is sufficient for
allocation. If there is too little space left, try smaller large folio.
Link: https://lkml.kernel.org/r/20250908123128.900254-1-vernon2gm@gmail.com Fixes: acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs") Signed-off-by: Vernon Yang <yanglincheng@kylinos.cn> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Daniel Gomez <da.gomez@samsung.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chunyu Hu [Mon, 8 Sep 2025 12:47:39 +0000 (20:47 +0800)]
selftests/mm: fix va_high_addr_switch.sh failure on x86_64
The test will fail as below on x86_64 with cpu la57 support (will skip if
no la57 support). Note, the test requries nr_hugepages to be set first.
# running bash ./va_high_addr_switch.sh
# -------------------------------------
# mmap(addr_switch_hint - pagesize, pagesize): 0x7f55b60fa000 - OK
# mmap(addr_switch_hint - pagesize, (2 * pagesize)): 0x7f55b60f9000 - OK
# mmap(addr_switch_hint, pagesize): 0x800000000000 - OK
# mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0x800000000000 - OK
# mmap(NULL): 0x7f55b60f9000 - OK
# mmap(low_addr): 0x40000000 - OK
# mmap(high_addr): 0x1000000000000 - OK
# mmap(high_addr) again: 0xffff55b6136000 - OK
# mmap(high_addr, MAP_FIXED): 0x1000000000000 - OK
# mmap(-1): 0xffff55b6134000 - OK
# mmap(-1) again: 0xffff55b6132000 - OK
# mmap(addr_switch_hint - pagesize, pagesize): 0x7f55b60fa000 - OK
# mmap(addr_switch_hint - pagesize, 2 * pagesize): 0x7f55b60f9000 - OK
# mmap(addr_switch_hint - pagesize/2 , 2 * pagesize): 0x7f55b60f7000 - OK
# mmap(addr_switch_hint, pagesize): 0x800000000000 - OK
# mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0x800000000000 - OK
# mmap(NULL, MAP_HUGETLB): 0x7f55b5c00000 - OK
# mmap(low_addr, MAP_HUGETLB): 0x40000000 - OK
# mmap(high_addr, MAP_HUGETLB): 0x1000000000000 - OK
# mmap(high_addr, MAP_HUGETLB) again: 0xffff55b5e00000 - OK
# mmap(high_addr, MAP_FIXED | MAP_HUGETLB): 0x1000000000000 - OK
# mmap(-1, MAP_HUGETLB): 0x7f55b5c00000 - OK
# mmap(-1, MAP_HUGETLB) again: 0x7f55b5a00000 - OK
# mmap(addr_switch_hint - pagesize, 2*hugepagesize, MAP_HUGETLB): 0x800000000000 - FAILED
# mmap(addr_switch_hint , 2*hugepagesize, MAP_FIXED | MAP_HUGETLB): 0x800000000000 - OK
# [FAIL]
addr_switch_hint is defined as DFEFAULT_MAP_WINDOW in the failed test (for
x86_64, DFEFAULT_MAP_WINDOW is defined as (1UL<<47) - pagesize) in 64 bit.
Before commit cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*}
functions"), for x86_64 hugetlb_get_unmapped_area() is handled in arch
code arch/x86/mm/hugetlbpage.c and addr is checked with
map_address_hint_valid() after align with 'addr &= huge_page_mask(h)'
which is a round down way, and it will fail the check because the addr is
within the DEFAULT_MAP_WINDOW but (addr + len) is above the
DFEFAULT_MAP_WINDOW. So it wil go through the
hugetlb_get_unmmaped_area_top_down() to find an area within the
DFEFAULT_MAP_WINDOW.
After commit cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*}
functions"). The addr hint for hugetlb_get_unmmaped_area() will be
rounded up and aligned to hugepage size with ALIGN() for all arches. And
after the align, the addr will be above the default MAP_DEFAULT_WINDOW,
and the map_addresshint_valid() check will pass because both aligned addr
(addr0) and (addr + len) are above the DEFAULT_MAP_WINDOW, and the aligned
hint address (0x800000000000) is returned as an suitable gap is found
there, in arch_get_unmapped_area_topdown().
To still cover the case that addr is within the DEFAULT_MAP_WINDOW, and
addr + len is above the DFEFAULT_MAP_WINDOW, make the addr hint one
hugepage lower, so that after the align it's still within
DEFAULT_MAP_WINDOW, and the addr + len (2 hugepages) will be above
DEFAULT_MAP_WINDOW.
Link: https://lkml.kernel.org/r/20250908124740.2946005-4-chuhu@redhat.com Fixes: cc92882ee218 ("mm: drop hugetlb_get_unmapped_area{_*} functions") Signed-off-by: Chunyu Hu <chuhu@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chunyu Hu [Mon, 8 Sep 2025 12:47:38 +0000 (20:47 +0800)]
selftests/mm: alloc hugepages in va_high_addr_switch test
Alloc hugepages in the test internally, so we don't fully rely on the
run_vmtests.sh. If run_vmtests.sh does that great, free hugepages is
enough for being used to run the test, leave it as it is, otherwise setup
the hugepages in the test.
Save the original nr_hugepages value and restore it after test finish, so
leave a stable test envronment.
Link: https://lkml.kernel.org/r/20250908124740.2946005-3-chuhu@redhat.com Signed-off-by: Chunyu Hu <chuhu@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chunyu Hu [Mon, 8 Sep 2025 12:47:37 +0000 (20:47 +0800)]
selftests/mm: fix hugepages cleanup too early
Patch series "Fix va_high_addr_switch.sh test failure", v2.
These three patches fix a va_high_addr_switch.sh test failure on x86_64.
This patch (of 3):
The nr_hugepgs variable is used to keep the original nr_hugepages at the
hugepage setup step at test beginning. After userfaultfd test, a cleaup
is executed, both /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages and
/proc/sys//vm/nr_hugepages are reset to 'original' value before
userfaultfd test starts.
Issue here is the value used to restore /proc/sys/vm/nr_hugepages is
nr_hugepgs which is the initial value before the vm_runtests.sh runs, not
the value before userfaultfd test starts. 'va_high_addr_swith.sh' tests
runs after that will possibly see no hugepages available for test, and got
EINVAL when mmap(HUGETLB), making the result invalid.
And before pkey tests, nr_hugepgs is changed to be used as a temp variable
to save nr_hugepages before pkey test, and restore it after pkey tests
finish. The original nr_hugepages value is not tracked anymore, so no way
to restore it after all tests finish.
Add a new variable orig_nr_hugepgs to save the original nr_hugepages, and
and restore it to nr_hugepages after all tests finish. And change to use
the nr_hugepgs variable to save the /proc/sys/vm/nr_hugeages after
hugepage setup, it's also the value before userfaultfd test starts, and
the correct value to be restored after userfaultfd finishes. The
va_high_addr_switch.sh broken will be resolved.
Link: https://lkml.kernel.org/r/20250908124740.2946005-1-chuhu@redhat.com Link: https://lkml.kernel.org/r/20250908124740.2946005-2-chuhu@redhat.com Signed-off-by: Chunyu Hu <chuhu@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
That's because scripts/decodecode doesn't preserve the alignment. No need
to modify it, it is enough to give only the "Code: (...)" part to this
script, and print the prefix without modifications.
With lines having a symbol to decode, the script was only trying to
preserve the alignment for the timestamps, but not the rest, nor when the
caller was set (CONFIG_PRINTK_CALLER=y).
A few patches slightly improving the output generated by
decode_stacktrace.sh.
This patch (of 3):
Lines having a symbol to decode might not always have info after this
symbol. It means ${info_str} might not be set, but it will always be
printed after a space, causing trailing whitespaces.
That's a detail, but when the output is opened with an editor marking
these trailing whitespaces, that's a bit disturbing. It is easy to remove
them by printing this variable with a space only if it is set.
While at it, do the same with ${module} and print everything in one line.
ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor()
In preparation for splitting struct ptdesc from struct page and struct
folio, remove mentions of struct folio from these functions. Introduce
ptdesc_nr_pages() to avoid using lruvec_stat_add/sub_folio()
Link: https://lkml.kernel.org/r/20250908171104.2409217-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The first two patches here are preparation for splitting struct ptdesc
from struct page and struct folio. I think their only dependency is on
the memdesc_flags_t patches from August which is in mm-new. The third
patch is just something I noticed while working on the code.
This patch (of 3):
Use the new memdesc_flags_t type to show that these are the same bits as
page/folio/slab and thesefore have the zone/node/section information in
them. Remove a use of ptdesc_folio() by converting
pagetable_is_reserved() to use test_bit() directly.
Alice Ryhl [Tue, 2 Sep 2025 08:36:11 +0000 (08:36 +0000)]
maple_tree: remove lockdep_map_p typedef
Having the ma_external_lock field exist when CONFIG_LOCKDEP=n isn't used
anywhere, so just get rid of it. This also avoids generating a typedef
called lockdep_map_p that could overlap with typedefs in other header
files.
Stanislav Fort [Fri, 5 Sep 2025 09:38:51 +0000 (12:38 +0300)]
mm/memcg: v1: account event registrations and drop world-writable cgroup.event_control
In cgroup v1, the legacy cgroup.event_control file is world-writable and
allows unprivileged users to register unbounded events and thresholds.
Each registration allocates kernel memory without capping or memcg
charging, which can be abused to exhaust kernel memory in affected
configurations.
Make the following minimal changes:
- Account allocations with __GFP_ACCOUNT in event and threshold registration.
- Remove CFTYPE_WORLD_WRITABLE from cgroup.event_control to make it
owner-writable.
This does not affect cgroup v2. Allocations are still subject to kmem
accounting being enabled, but this reduces unbounded global growth.
Link: https://lkml.kernel.org/r/20250905093851.80596-1-disclosure@aisle.com Signed-off-by: Stanislav Fort <disclosure@aisle.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:33 +0000 (00:08 +0800)]
mm, swap: use a single page for swap table when the size fits
We have a cluster size of 512 slots. Each slot consumes 8 bytes in swap
table so the swap table size of each cluster is exactly one page (4K).
If that condition is true, allocate one page direct and disable the slab
cache to reduce the memory usage of swap table and avoid fragmentation.
Link: https://lkml.kernel.org/r/20250910160833.3464-16-ryncsn@gmail.com Co-developed-by: Chris Li <chrisl@kernel.org> Signed-off-by: Chris Li <chrisl@kernel.org> Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:32 +0000 (00:08 +0800)]
mm, swap: implement dynamic allocation of swap table
Now swap table is cluster based, which means free clusters can free its
table since no one should modify it.
There could be speculative readers, like swap cache look up, protect them
by making them RCU protected. All swap table should be filled with null
entries before free, so such readers will either see a NULL pointer or a
null filled table being lazy freed.
On allocation, allocate the table when a cluster is used by any order.
This way, we can reduce the memory usage of large swap device
significantly.
This idea to dynamically release unused swap cluster data was initially
suggested by Chris Li while proposing the cluster swap allocator and it
suits the swap table idea very well.
Link: https://lkml.kernel.org/r/20250910160833.3464-15-ryncsn@gmail.com Co-developed-by: Chris Li <chrisl@kernel.org> Signed-off-by: Chris Li <chrisl@kernel.org> Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:31 +0000 (00:08 +0800)]
mm, swap: remove contention workaround for swap cache
Swap cluster setup will try to shuffle the clusters on initialization. It
was helpful to avoid contention for the swap cache space. The cluster
size (2M) was much smaller than each swap cache space (64M), so shuffling
the cluster means the allocator will try to allocate swap slots that are
in different swap cache spaces for each CPU, reducing the chance of two
CPUs using the same swap cache space, and hence reducing the contention.
Now, swap cache is managed by swap clusters, this shuffle is pointless.
Just remove it, and clean up related macros.
This also improves the HDD swap performance as shuffling IO is a bad idea
for HDD, and now the shuffling is gone. Test have shown a ~40%
performance gain for HDD [1]:
Doing sequential swap in of 8G data using 8 processes with usemem, average
of 3 test runs:
Before: 1270.91 KB/s per process
After: 1849.54 KB/s per process
Link: https://lore.kernel.org/linux-mm/CAMgjq7AdauQ8=X0zeih2r21QoV=-WWj1hyBxLWRzq74n-C=-Ng@mail.gmail.com/ Link: https://lkml.kernel.org/r/20250910160833.3464-14-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202504241621.f27743ec-lkp@intel.com Acked-by: Chris Li <chrisl@kernel.org> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:30 +0000 (00:08 +0800)]
mm, swap: mark swap address space ro and add context debug check
Swap cache is now backed by swap table, and the address space is not
holding any mutable data anymore. And swap cache is now protected by the
swap cluster lock, instead of the XArray lock. All access to swap cache
are wrapped by swap cache helpers. Locking is mostly handled internally
by swap cache helpers, only a few __swap_cache_* helpers require the
caller to lock the cluster by themselves.
Worth noting that, unlike XArray, the cluster lock is not IRQ safe. The
swap cache was very different compared to filemap, and now it's completely
separated from filemap. Nothing wants to mark or change anything or do a
writeback callback in IRQ.
So explicitly document this and add a debug check to avoid further
potential misuse. And mark the swap cache space as read-only to avoid any
user wrongly mixing unexpected filemap helpers with swap cache.
Link: https://lkml.kernel.org/r/20250910160833.3464-13-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:29 +0000 (00:08 +0800)]
mm, swap: use the swap table for the swap cache and switch API
Introduce basic swap table infrastructures, which are now just a
fixed-sized flat array inside each swap cluster, with access wrappers.
Each cluster contains a swap table of 512 entries. Each table entry is an
opaque atomic long. It could be in 3 types: a shadow type (XA_VALUE), a
folio type (pointer), or NULL.
In this first step, it only supports storing a folio or shadow, and it is
a drop-in replacement for the current swap cache. Convert all swap cache
users to use the new sets of APIs. Chris Li has been suggesting using a
new infrastructure for swap cache for better performance, and that idea
combined well with the swap table as the new backing structure. Now the
lock contention range is reduced to 2M clusters, which is much smaller
than the 64M address_space. And we can also drop the multiple
address_space design.
All the internal works are done with swap_cache_get_* helpers. Swap cache
lookup is still lock-less like before, and the helper's contexts are same
with original swap cache helpers. They still require a pin on the swap
device to prevent the backing data from being freed.
Swap cache updates are now protected by the swap cluster lock instead of
the Xarray lock. This is mostly handled internally, but new
__swap_cache_* helpers require the caller to lock the cluster. So, a few
new cluster access and locking helpers are also introduced.
A fully cluster-based unified swap table can be implemented on top of this
to take care of all count tracking and synchronization work, with dynamic
allocation. It should reduce the memory usage while making the
performance even better.
Link: https://lkml.kernel.org/r/20250910160833.3464-12-ryncsn@gmail.com Co-developed-by: Chris Li <chrisl@kernel.org> Signed-off-by: Chris Li <chrisl@kernel.org> Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:28 +0000 (00:08 +0800)]
mm, swap: wrap swap cache replacement with a helper
There are currently three swap cache users that are trying to replace an
existing folio with a new one: huge memory splitting, migration, and shmem
replacement. What they are doing is quite similar.
Introduce a common helper for this. In later commits, this can be easily
switched to use the swap table by updating this helper.
The newly added helper also makes the swap cache API better defined, and
make debugging easier by adding a few more debug checks.
Migration and shmem replace are meant to clone the folio, including
content, swap entry value, and flags. And splitting will adjust each sub
folio's swap entry according to order, which could be non-uniform in the
future. So document it clearly that it's the caller's responsibility to
set up the new folio's swap entries and flags before calling the helper.
The helper will just follow the new folio's entry value.
This also prepares for replacing high-order folios in the swap cache.
Currently, only splitting to order 0 is allowed for swap cache folios.
Using the new helper, we can handle high-order folio splitting better.
Link: https://lkml.kernel.org/r/20250910160833.3464-11-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:27 +0000 (00:08 +0800)]
mm/shmem, swap: remove redundant error handling for replacing folio
Shmem may replace a folio in the swap cache if the cached one doesn't fit
the swapin's GFP zone. When doing so, shmem has already double checked
that the swap cache folio is locked, still has the swap cache flag set,
and contains the wanted swap entry. So it is impossible to fail due to an
XArray mismatch. There is even a comment for that.
Delete the defensive error handling path, and add a WARN_ON instead: if
that happened, something has broken the basic principle of how the swap
cache works, we should catch and fix that.
Link: https://lkml.kernel.org/r/20250910160833.3464-10-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:26 +0000 (00:08 +0800)]
mm, swap: cleanup swap cache API and add kerneldoc
In preparation for replacing the swap cache backend with the swap table,
clean up and add proper kernel doc for all swap cache APIs. Now all swap
cache APIs are well-defined with consistent names.
No feature change, only renaming and documenting.
Link: https://lkml.kernel.org/r/20250910160833.3464-9-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:25 +0000 (00:08 +0800)]
mm, swap: tidy up swap device and cluster info helpers
swp_swap_info is the most commonly used helper for retrieving swap info.
It has an internal check that may lead to a NULL return value, but almost
none of its caller checks the return value, making the internal check
pointless. In fact, most of these callers already ensured the entry is
valid and never expect a NULL value.
Tidy this up and improve the function names. If the caller can make sure
the swap entry/type is valid and the device is pinned, use the new
introduced __swap_entry_to_info/__swap_type_to_info instead. They have
more debug sanity checks and lower overhead as they are inlined.
Callers that may expect a NULL value should use
swap_entry_to_info/swap_type_to_info instead.
No feature change. The rearranged codes should have had no effect, or
they should have been hitting NULL de-ref bugs already. Only some new
sanity checks are added so potential issues may show up in debug build.
The new helpers will be frequently used with swap table later when working
with swap cache folios. A locked swap cache folio ensures the entries are
valid and stable so these helpers are very helpful.
Link: https://lkml.kernel.org/r/20250910160833.3464-8-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:24 +0000 (00:08 +0800)]
mm, swap: rename and move some swap cluster definition and helpers
No feature change, move cluster related definitions and helpers to
mm/swap.h, also tidy up and add a "swap_" prefix for cluster lock/unlock
helpers, so they can be used outside of swap files. And while at it, add
kerneldoc.
Link: https://lkml.kernel.org/r/20250910160833.3464-7-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:23 +0000 (00:08 +0800)]
mm, swap: always lock and check the swap cache folio before use
Swap cache lookup only increases the reference count of the returned
folio. That's not enough to ensure a folio is stable in the swap cache,
so the folio could be removed from the swap cache at any time. The caller
should always lock and check the folio before using it.
We have just documented this in kerneldoc, now introduce a helper for swap
cache folio verification with proper sanity checks.
Also, sanitize a few current users to use this convention and the new
helper for easier debugging. They were not having observable problems
yet, only trivial issues like wasted CPU cycles on swapoff or reclaiming.
They would fail in some other way, but it is still better to always follow
this convention to make things robust and make later commits easier to do.
Link: https://lkml.kernel.org/r/20250910160833.3464-6-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:22 +0000 (00:08 +0800)]
mm, swap: check page poison flag after locking it
Instead of checking the poison flag only in the fast swap cache lookup
path, always check the poison flags after locking a swap cache folio.
There are two reasons to do so.
The folio is unstable and could be removed from the swap cache anytime, so
it's totally possible that the folio is no longer the backing folio of a
swap entry, and could be an irrelevant poisoned folio. We might
mistakenly kill a faulting process.
And it's totally possible or even common for the slow swap in path
(swapin_readahead) to bring in a cached folio. The cache folio could be
poisoned, too. Only checking the poison flag in the fast path will miss
such folios.
The race window is tiny, so it's very unlikely to happen, though. While
at it, also add a unlikely prefix.
Link: https://lkml.kernel.org/r/20250910160833.3464-5-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Acked-by: Chris Li <chrisl@kernel.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:21 +0000 (00:08 +0800)]
mm, swap: fix swap cache index error when retrying reclaim
The allocator will reclaim cached slots while scanning. Currently, it
will try again if reclaim found a folio that is already removed from the
swap cache due to a race. But the following lookup will be using the
wrong index. It won't cause any OOB issue since the swap cache index is
truncated upon lookup, but it may lead to reclaiming of an irrelevant
folio.
This should not cause a measurable issue, but we should fix it.
Link: https://lkml.kernel.org/r/20250910160833.3464-4-ryncsn@gmail.com Fixes: fae859550531 ("mm, swap: avoid reclaiming irrelevant swap cache") Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Acked-by: Nhat Pham <nphamcs@gmail.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kairui Song [Wed, 10 Sep 2025 16:08:20 +0000 (00:08 +0800)]
mm, swap: use unified helper for swap cache look up
The swap cache lookup helper swap_cache_get_folio currently does readahead
updates as well, so callers that are not doing swapin from any VMA or
mapping are forced to reuse filemap helpers instead, and have to access
the swap cache space directly.
So decouple readahead update with swap cache lookup. Move the readahead
update part into a standalone helper. Let the caller call the readahead
update helper if they do readahead. And convert all swap cache lookups to
use swap_cache_get_folio.
After this commit, there are only three special cases for accessing swap
cache space now: huge memory splitting, migration, and shmem replacing,
because they need to lock the XArray. The following commits will wrap
their accesses to the swap cache too, with special helpers.
And worth noting, currently dropbehind is not supported for anon folio,
and we will never see a dropbehind folio in swap cache. The unified
helper can be updated later to handle that.
While at it, add proper kernedoc for touched helpers.
No functional change.
Link: https://lkml.kernel.org/r/20250910160833.3464-3-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Barry Song <baohua@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: Nhat Pham <nphamcs@gmail.com> Cc: Baoquan He <bhe@redhat.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chris Li [Wed, 10 Sep 2025 16:08:19 +0000 (00:08 +0800)]
docs/mm: add document for swap table
Patch series "mm, swap: introduce swap table as swap cache (phase I)", v3.
This is the first phase of the bigger series implementing basic
infrastructures for the Swap Table idea proposed at the LSF/MM/BPF topic
"Integrate swap cache, swap maps with swap allocator" [1]. To give credit
where it is due, this is based on Chris Li's idea and a prototype of using
cluster size atomic arrays to implement swap cache.
This phase I contains 15 patches, introduces the swap table infrastructure
and uses it as the swap cache backend. By doing so, we have up to ~5-20%
performance gain in throughput, RPS or build time for benchmark and
workload tests. The speed up is due to less contention on the swap cache
access and shallower swap cache lookup path. The cluster size is much
finer-grained than the 64M address space split, which is removed in this
phase I. It also unifies and cleans up the swap code base.
Each swap cluster will dynamically allocate the swap table, which is an
atomic array to cover every swap slot in the cluster. It replaces the
swap cache backed by XArray. In phase I, the static allocated swap_map
still co-exists with the swap table. The memory usage is about the same
as the original on average. A few exception test cases show about 1%
higher in memory usage. In the following phases of the series, swap_map
will merge into the swap table without additional memory allocation. It
will result in net memory reduction compared to the original swap cache.
Testing has shown that phase I has a significant performance improvement
from 8c/1G ARM machine to 48c96t/128G x86_64 servers in many practical
workloads.
The full picture with a summary can be found at [2]. An older bigger
series of 28 patches is posted at [3].
vm-scability test:
==================
Test with:
usemem --init-time -O -y -x -n 31 1G (4G memcg, PMEM as swap)
Before: After:
System time: 219.12s 158.16s (-27.82%)
Sum Throughput: 4767.13 MB/s 6128.59 MB/s (+28.55%)
Single process Throughput: 150.21 MB/s 196.52 MB/s (+30.83%)
Free latency: 175047.58 us 131411.87 us (-24.92%)
usemem --init-time -O -y -x -n 32 1536M (16G memory, global pressure,
PMEM as swap)
Before: After:
System time: 356.16s 284.68s (-20.06%)
Sum Throughput: 4648.35 MB/s 5453.52 MB/s (+17.32%)
Single process Throughput: 141.63 MB/s 168.35 MB/s (+18.86%)
Free latency: 499907.71 us 484977.03 us (-2.99%)
This shows an improvement of more than 20% improvement in most readings.
Build kernel test:
==================
The following result matrix is from building kernel with defconfig on
tmpfs with ZSWAP / ZRAM, using different memory pressure and setups.
Measuring sys and real time in seconds, less is better (user time is
almost identical as expected):
-j<NR> / Mem | Sys before / after | Real before / after
Using 16G ZRAM with memcg limit:
6 / 192M | 9686 / 9472 -2.21% | 2130 / 2096 -1.59%
12 / 256M | 6610 / 6451 -2.41% | 827 / 812 -1.81%
24 / 384M | 5938 / 5701 -3.37% | 414 / 405 -2.17%
48 / 768M | 4696 / 4409 -6.11% | 188 / 182 -3.19%
With 64k folio:
24 / 512M | 4222 / 4162 -1.42% | 326 / 321 -1.53%
48 / 1G | 3688 / 3622 -1.79% | 151 / 149 -1.32%
With ZSWAP with 3G memcg (using higher limit due to kmem account):
48 / 3G | 603 / 581 -3.65% | 81 / 80 -1.23%
Testing extremely high global memory and schedule pressure: Using ZSWAP
with 32G NVMEs in a 48c VM that has 4G memory, no memcg limit, system
components take up about 1.5G already, using make -j48 to build defconfig:
Before: sys time: 2069.53s real time: 135.76s
After: sys time: 2021.13s (-2.34%) real time: 134.23s (-1.12%)
On another 48c 4G memory VM, using 16G ZRAM as swap, testing make
-j48 with same config:
Before: sys time: 1756.96s real time: 111.01s
After: sys time: 1715.90s (-2.34%) real time: 109.51s (-1.35%)
All cases are more or less faster, and no regression even under extremely
heavy global memory pressure.
Redis / Valkey bench:
=====================
The test machine is a ARM64 VM with 1536M memory 12 cores, Redis is set to
use 2500M memory, and ZRAM swap size is set to 5G:
With BGSAVE enabled, most Redis memory will have a swap count > 1 so swap
cache is heavily in use. We can see a about 6% performance gain. No
BGSAVE is very slightly slower (<0.1%) due to the higher memory pressure
of the co-existence of swap_map and swap table. This will be optimzed
into a net gain and up to 20% gain in BGSAVE case in the following phases.
HDD swap is also ~40% faster with usemem because we removed an old
contention workaround.
GUP no longer uses get_dev_pagemap(). As it was the only user of the
get_dev_pagemap() pgmap caching feature it can be removed.
Link: https://lkml.kernel.org/r/20250903225926.34702-2-apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Prior to commit aed877c2b425 ("device/dax: properly refcount device dax
pages when mapping") ZONE_DEVICE pages were not fully reference counted
when mapped into user page tables. Instead GUP would take a reference on
the associated pgmap to ensure the results of pfn_to_page() remained
valid.
This is no longer required and most of the code was removed by commit fd2825b0760a ("mm/gup: remove pXX_devmap usage from get_user_pages()").
Finish cleaning this up by removing the dead calls to put_dev_pagemap()
and the temporary context struct.
Link: https://lkml.kernel.org/r/20250903225926.34702-1-apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Wei Yang [Fri, 5 Sep 2025 14:03:58 +0000 (14:03 +0000)]
mm/page_alloc: check the correct buddy if it is a starting block
find_large_buddy() search buddy based on start_pfn, which maybe different
from page's pfn, e.g. when page is not pageblock aligned, because
prep_move_freepages_block() always align start_pfn to pageblock.
This means when we found a starting block at start_pfn, it may check on
the wrong page theoretically. And not split the free page as it is
supposed to, causing a freelist migratetype mismatch.
The good news is the page passed to __move_freepages_block_isolate() has
only two possible cases:
* page is pageblock aligned
* page is __first_valid_page() of this block
So it is safe for the first case, and it won't get a buddy larger than
pageblock for the second case.
To fix the issue, check the returned pfn of find_large_buddy() to decide
whether to split the free page:
1. if it is not a PageBuddy pfn, no split;
2. if it is a PageBuddy pfn but order <= pageblock_order, no split;
3. if it is a PageBuddy pfn with order > pageblock_order, start_pfn is
either in the starting block or tail block, split the PageBuddy at
pageblock_order level.
Link: https://lkml.kernel.org/r/20250905140358.28849-1-richard.weiyang@gmail.com Signed-off-by: Wei Yang <richard.weiyang@gmail.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Miaohe Lin [Thu, 4 Sep 2025 06:22:58 +0000 (14:22 +0800)]
mm/hwpoison: decouple hwpoison_filter from mm/memory-failure.c
mm/memory-failure.c defines and uses hwpoison_filter_* parameters but the
values of those parameters can only be modified via mm/hwpoison-inject.c
from userspace. They have a potentially different life time. Decouple
those parameters from mm/memory-failure.c to fix this broken layering.
Link: https://lkml.kernel.org/r/20250904062258.3336092-1-linmiaohe@huawei.com Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Suggested-by: Michal Hocko <mhocko@suse.com> Cc: David Hildenbrand <david@redhat.com> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
huge_memory: return -EINVAL in folio split functions when THP is disabled
split_huge_page_to_list_[to_order](), split_huge_page() and
try_folio_split() return 0 on success and error codes on failure.
When THP is disabled, these functions return 0 indicating success even
though an error code should be returned as it is not possible to split a
folio when THP is disabled.
Make all these functions return -EINVAL to indicate failure instead of 0.
As large folios depend on CONFIG_THP, issue warning as this function
should not be called without a large folio.
Link: https://lkml.kernel.org/r/20250905150012.93714-1-kernel@pankajraghav.com Signed-off-by: Pankaj Raghav <p.raghav@samsung.com> Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202509051753.riCeG7LC-lkp@intel.com/ Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Zi Yan <ziy@nvidia.com> Acked-by: Kiryl Shutsemau <kas@kernel.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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