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author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2009-05-08 18:29:27 -0700 |
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committer | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2009-05-08 18:29:27 -0700 |
commit | d585a021c0b10b0477d6b608c53e1feb8cde0507 (patch) | |
tree | 5ca059da1db7f15d4b29427644ad9c08270c885c /Documentation/filesystems/Locking | |
parent | 84e5b0d00f8f84c4ae226be131d4bebbcee88bd3 (diff) | |
parent | 091bf7624d1c90cec9e578a18529f615213ff847 (diff) |
Merge commit 'v2.6.30-rc5' into next
Diffstat (limited to 'Documentation/filesystems/Locking')
-rw-r--r-- | Documentation/filesystems/Locking | 33 |
1 files changed, 22 insertions, 11 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index ec6a9392a17..3120f8dd2c3 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -437,8 +437,11 @@ grab BKL for cases when we close a file that had been opened r/w, but that can and should be done using the internal locking with smaller critical areas). Current worst offender is ext2_get_block()... -->fasync() is a mess. This area needs a big cleanup and that will probably -affect locking. +->fasync() is called without BKL protection, and is responsible for +maintaining the FASYNC bit in filp->f_flags. Most instances call +fasync_helper(), which does that maintenance, so it's not normally +something one needs to worry about. Return values > 0 will be mapped to +zero in the VFS layer. ->readdir() and ->ioctl() on directories must be changed. Ideally we would move ->readdir() to inode_operations and use a separate method for directory @@ -502,23 +505,31 @@ prototypes: void (*open)(struct vm_area_struct*); void (*close)(struct vm_area_struct*); int (*fault)(struct vm_area_struct*, struct vm_fault *); - int (*page_mkwrite)(struct vm_area_struct *, struct page *); + int (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *); int (*access)(struct vm_area_struct *, unsigned long, void*, int, int); locking rules: BKL mmap_sem PageLocked(page) open: no yes close: no yes -fault: no yes -page_mkwrite: no yes no +fault: no yes can return with page locked +page_mkwrite: no yes can return with page locked access: no yes - ->page_mkwrite() is called when a previously read-only page is -about to become writeable. The file system is responsible for -protecting against truncate races. Once appropriate action has been -taking to lock out truncate, the page range should be verified to be -within i_size. The page mapping should also be checked that it is not -NULL. + ->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 "pgoff" in the vm_fault structure. If it is possible that +the page may be truncated and/or invalidated, then the filesystem must lock +the page, then ensure it is not already truncated (the page lock will block +subsequent truncate), and then return with VM_FAULT_LOCKED, and the page +locked. The VM will unlock the page. + + ->page_mkwrite() is called when a previously read-only pte is +about to become writeable. The filesystem again must ensure that there are +no truncate/invalidate races, and then return with the page locked. If +the page has been truncated, the filesystem should not look up a new page +like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which +will cause the VM to retry the fault. ->access() is called when get_user_pages() fails in acces_process_vm(), typically used to debug a process through |