mm,thp,shmem: make khugepaged obey tmpfs mount flags

Currently if thp enabled=[madvise], mounting a tmpfs filesystem with
huge=always and mmapping files from that tmpfs does not result in
khugepaged collapsing those mappings, despite the mount flag indicating
that it should.

Fix that by breaking up the blocks of tests in hugepage_vma_check a little
bit, and testing things in the correct order.

Link: https://lkml.kernel.org/r/20201124194925.623931-4-riel@surriel.com
Fixes: c2231020ea7b ("mm: thp: register mm for khugepaged when merging vma for shmem")
Signed-off-by: Rik van Riel <riel@surriel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index c941b73773216fc9a935c94e844254221e2ae390..2fcc01891b474f642fc95243d1664efe66009ae5 100644 (file)
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -3,6 +3,7 @@
 #define _LINUX_KHUGEPAGED_H
 
 #include <linux/sched/coredump.h> /* MMF_VM_HUGEPAGE */
+#include <linux/shmem_fs.h>
 
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -57,6 +58,7 @@ static inline int khugepaged_enter(struct vm_area_struct *vma,
 {
        if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
                if ((khugepaged_always() ||
+                    (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) ||
                     (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
                    !(vm_flags & VM_NOHUGEPAGE) &&
                    !test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 64b4558737110e6492340e1fe4236632369d2955..8369d9620f6d7aafa2d7424492afb072ce1c5d74 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -442,18 +442,28 @@ static inline int khugepaged_test_exit(struct mm_struct *mm)
 static bool hugepage_vma_check(struct vm_area_struct *vma,
                               unsigned long vm_flags)
 {
-       if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
-           (vm_flags & VM_NOHUGEPAGE) ||
+       /* Explicitly disabled through madvise. */
+       if ((vm_flags & VM_NOHUGEPAGE) ||
            test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
                return false;
 
-       if (shmem_file(vma->vm_file) ||
-           (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
-            vma->vm_file &&
-            (vm_flags & VM_DENYWRITE))) {
+       /* Enabled via shmem mount options or sysfs settings. */
+       if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) {
                return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
                                HPAGE_PMD_NR);
        }
+
+       /* THP settings require madvise. */
+       if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
+               return false;
+
+       /* Read-only file mappings need to be aligned for THP to work. */
+       if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file &&
+           (vm_flags & VM_DENYWRITE)) {
+               return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
+                               HPAGE_PMD_NR);
+       }
+
        if (!vma->anon_vma || vma->vm_ops)
                return false;
        if (vma_is_temporary_stack(vma))