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| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2023-08-18 21:23:34 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-08-24 16:20:29 -0700 |
| commit | 40d49a3c9e4a0e5cf7a6fcebc8d4d7d63d1f3f1b (patch) | |
| tree | 3bd5bfde4e95a2bb85c40cf795a8418eef084760 /Documentation/filesystems/locking.rst | |
| parent | 051ddcfeb1bdbae45e660c0db2468d29ca15c6c2 (diff) | |
| download | linux-40d49a3c9e4a0e5cf7a6fcebc8d4d7d63d1f3f1b.tar.gz linux-40d49a3c9e4a0e5cf7a6fcebc8d4d7d63d1f3f1b.tar.bz2 linux-40d49a3c9e4a0e5cf7a6fcebc8d4d7d63d1f3f1b.zip | |
mm: allow ->huge_fault() to be called without the mmap_lock held
Remove the checks for the VMA lock being held, allowing the page fault
path to call into the filesystem instead of retrying with the mmap_lock
held. This will improve scalability for DAX page faults. Also update the
documentation to match (and fix some other changes that have happened
recently).
Link: https://lkml.kernel.org/r/20230818202335.2739663-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems/locking.rst')
| -rw-r--r-- | Documentation/filesystems/locking.rst | 36 |
1 files changed, 23 insertions, 13 deletions
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 211a03053992..1a2cb60b2499 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -628,26 +628,29 @@ vm_operations_struct prototypes:: - void (*open)(struct vm_area_struct*); - void (*close)(struct vm_area_struct*); - vm_fault_t (*fault)(struct vm_area_struct*, struct vm_fault *); + void (*open)(struct vm_area_struct *); + void (*close)(struct vm_area_struct *); + vm_fault_t (*fault)(struct vm_fault *); + vm_fault_t (*huge_fault)(struct vm_fault *, unsigned int order); + vm_fault_t (*map_pages)(struct vm_fault *, pgoff_t start, pgoff_t end); vm_fault_t (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *); vm_fault_t (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *); int (*access)(struct vm_area_struct *, unsigned long, void*, int, int); locking rules: -============= ========= =========================== +============= ========== =========================== ops mmap_lock PageLocked(page) -============= ========= =========================== -open: yes -close: yes -fault: yes can return with page locked -map_pages: read -page_mkwrite: yes can return with page locked -pfn_mkwrite: yes -access: yes -============= ========= =========================== +============= ========== =========================== +open: write +close: read/write +fault: read can return with page locked +huge_fault: maybe-read +map_pages: maybe-read +page_mkwrite: read can return with page locked +pfn_mkwrite: read +access: read +============= ========== =========================== ->fault() is called when a previously not present pte is about to be faulted in. The filesystem must find and return the page associated with the passed in @@ -657,6 +660,13 @@ then ensure the page is not already truncated (invalidate_lock will block subsequent truncate), and then return with VM_FAULT_LOCKED, and the page locked. The VM will unlock the page. +->huge_fault() is called when there is no PUD or PMD entry present. This +gives the filesystem the opportunity to install a PUD or PMD sized page. +Filesystems can also use the ->fault method to return a PMD sized page, +so implementing this function may not be necessary. In particular, +filesystems should not call filemap_fault() from ->huge_fault(). +The mmap_lock may not be held when this method is called. + ->map_pages() is called when VM asks to map easy accessible pages. Filesystem should find and map pages associated with offsets from "start_pgoff" till "end_pgoff". ->map_pages() is called with the RCU lock held and must |