From: Lorenzo Stoakes Date: Wed, 10 Sep 2025 20:22:04 +0000 (+0100) Subject: doc: update porting, vfs documentation for mmap_prepare actions X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=280b2f241ec6c50d9396ef74ec320440e5dd9dd2;p=users%2Fjedix%2Flinux-maple.git 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 Reviewed-by: Jan Kara Cc: Alexander Gordeev Cc: Al Viro Cc: Andreas Larsson Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Chatre, Reinette Cc: Christian Borntraeger Cc: Christian Brauner Cc: Dan Williams Cc: Dave Jiang Cc: Dave Martin Cc: Dave Young Cc: David Hildenbrand Cc: David S. Miller Cc: Dmitriy Vyukov Cc: Greg Kroah-Hartman Cc: Guo Ren Cc: Heiko Carstens Cc: Hugh Dickins Cc: James Morse Cc: Jann Horn Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Konstantin Komarov Cc: Liam Howlett Cc: "Luck, Tony" Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Nicolas Pitre Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: "Uladzislau Rezki (Sony)" Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 85f590254f07..6743ed0b9112 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -1285,3 +1285,8 @@ rather than a VMA, as the VMA at this stage is not yet valid. The vm_area_desc provides the minimum required information for a filesystem to initialise state upon memory mapping of a file-backed region, and output parameters for the file system to set this state. + +In nearly all cases, this is all that is required for a filesystem. However, if +a filesystem needs to perform an operation such a pre-population of page tables, +then that action can be specified in the vm_area_desc->action field, which can +be configured using the mmap_action_*() helpers. diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 486a91633474..9e96c46ee10e 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -1236,6 +1236,10 @@ otherwise noted. file-backed memory mapping, most notably establishing relevant private state and VMA callbacks. + If further action such as pre-population of page tables is required, + this can be specified by the vm_area_desc->action field and related + parameters. + Note that the file operations are implemented by the specific filesystem in which the inode resides. When opening a device node (character or block special) most filesystems will call special