diff options
Diffstat (limited to 'Documentation/filesystems/locking.rst')
| -rw-r--r-- | Documentation/filesystems/locking.rst | 91 |
1 files changed, 24 insertions, 67 deletions
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 2fd01b9aaced..77704fde9845 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -17,7 +17,8 @@ dentry_operations prototypes:: - int (*d_revalidate)(struct dentry *, unsigned int); + int (*d_revalidate)(struct inode *, const struct qstr *, + struct dentry *, unsigned int); int (*d_weak_revalidate)(struct dentry *, unsigned int); int (*d_hash)(const struct dentry *, struct qstr *); int (*d_compare)(const struct dentry *, @@ -29,7 +30,9 @@ prototypes:: char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen); struct vfsmount *(*d_automount)(struct path *path); int (*d_manage)(const struct path *, bool); - struct dentry *(*d_real)(struct dentry *, const struct inode *); + struct dentry *(*d_real)(struct dentry *, enum d_real_type type); + bool (*d_unalias_trylock)(const struct dentry *); + void (*d_unalias_unlock)(const struct dentry *); locking rules: @@ -49,6 +52,8 @@ d_dname: no no no no d_automount: no no yes no d_manage: no no yes (ref-walk) maybe d_real no no yes no +d_unalias_trylock yes no no no +d_unalias_unlock yes no no no ================== =========== ======== ============== ======== inode_operations @@ -61,7 +66,7 @@ prototypes:: int (*link) (struct dentry *,struct inode *,struct dentry *); int (*unlink) (struct inode *,struct dentry *); int (*symlink) (struct mnt_idmap *, struct inode *,struct dentry *,const char *); - int (*mkdir) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t); + struct dentry *(*mkdir) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t); int (*rmdir) (struct inode *,struct dentry *); int (*mknod) (struct mnt_idmap *, struct inode *,struct dentry *,umode_t,dev_t); int (*rename) (struct mnt_idmap *, struct inode *, struct dentry *, @@ -82,8 +87,8 @@ prototypes:: int (*tmpfile) (struct mnt_idmap *, struct inode *, struct file *, umode_t); int (*fileattr_set)(struct mnt_idmap *idmap, - struct dentry *dentry, struct fileattr *fa); - int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); + struct dentry *dentry, struct file_kattr *fa); + int (*fileattr_get)(struct dentry *dentry, struct file_kattr *fa); struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int); struct offset_ctx *(*get_offset_ctx)(struct inode *inode); @@ -101,7 +106,7 @@ symlink: exclusive mkdir: exclusive unlink: exclusive (both) rmdir: exclusive (both)(see below) -rename: exclusive (all) (see below) +rename: exclusive (both parents, some children) (see below) readlink: no get_link: no setattr: exclusive @@ -123,6 +128,9 @@ get_offset_ctx no Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem exclusive on victim. cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. + ->unlink() and ->rename() have ->i_rwsem exclusive on all non-directories + involved. + ->rename() has ->i_rwsem exclusive on any subdirectory that changes parent. See Documentation/filesystems/directory-locking.rst for more detailed discussion of the locking scheme for directory operations. @@ -241,17 +249,16 @@ address_space_operations ======================== prototypes:: - int (*writepage)(struct page *page, struct writeback_control *wbc); int (*read_folio)(struct file *, struct folio *); int (*writepages)(struct address_space *, struct writeback_control *); bool (*dirty_folio)(struct address_space *, struct folio *folio); void (*readahead)(struct readahead_control *); - int (*write_begin)(struct file *, struct address_space *mapping, + int (*write_begin)(const struct kiocb *, struct address_space *mapping, loff_t pos, unsigned len, - struct page **pagep, void **fsdata); - int (*write_end)(struct file *, struct address_space *mapping, + struct folio **foliop, void **fsdata); + int (*write_end)(const struct kiocb *, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, - struct page *page, void *fsdata); + struct folio *folio, void *fsdata); sector_t (*bmap)(struct address_space *, sector_t); void (*invalidate_folio) (struct folio *, size_t start, size_t len); bool (*release_folio)(struct folio *, gfp_t); @@ -261,7 +268,7 @@ prototypes:: struct folio *src, enum migrate_mode); int (*launder_folio)(struct folio *); bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count); - int (*error_remove_page)(struct address_space *, struct page *); + int (*error_remove_folio)(struct address_space *, struct folio *); int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span) int (*swap_deactivate)(struct file *); int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter); @@ -272,12 +279,11 @@ locking rules: ====================== ======================== ========= =============== ops folio locked i_rwsem invalidate_lock ====================== ======================== ========= =============== -writepage: yes, unlocks (see below) read_folio: yes, unlocks shared writepages: dirty_folio: maybe readahead: yes, unlocks shared -write_begin: locks the page exclusive +write_begin: locks the folio exclusive write_end: yes, unlocks exclusive bmap: invalidate_folio: yes exclusive @@ -287,7 +293,7 @@ direct_IO: migrate_folio: yes (both) launder_folio: yes is_partially_uptodate: yes -error_remove_page: yes +error_remove_folio: yes swap_activate: no swap_deactivate: no swap_rw: yes, unlocks @@ -301,54 +307,6 @@ completion. ->readahead() unlocks the folios that I/O is attempted on like ->read_folio(). -->writepage() is used for two purposes: for "memory cleansing" and for -"sync". These are quite different operations and the behaviour may differ -depending upon the mode. - -If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then -it *must* start I/O against the page, even if that would involve -blocking on in-progress I/O. - -If writepage is called for memory cleansing (sync_mode == -WBC_SYNC_NONE) then its role is to get as much writeout underway as -possible. So writepage should try to avoid blocking against -currently-in-progress I/O. - -If the filesystem is not called for "sync" and it determines that it -would need to block against in-progress I/O to be able to start new I/O -against the page the filesystem should redirty the page with -redirty_page_for_writepage(), then unlock the page and return zero. -This may also be done to avoid internal deadlocks, but rarely. - -If the filesystem is called for sync then it must wait on any -in-progress I/O and then start new I/O. - -The filesystem should unlock the page synchronously, before returning to the -caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE -value. WRITEPAGE_ACTIVATE means that page cannot really be written out -currently, and VM should stop calling ->writepage() on this page for some -time. VM does this by moving page to the head of the active list, hence the -name. - -Unless the filesystem is going to redirty_page_for_writepage(), unlock the page -and return zero, writepage *must* run set_page_writeback() against the page, -followed by unlocking it. Once set_page_writeback() has been run against the -page, write I/O can be submitted and the write I/O completion handler must run -end_page_writeback() once the I/O is complete. If no I/O is submitted, the -filesystem must run end_page_writeback() against the page before returning from -writepage. - -That is: after 2.5.12, pages which are under writeout are *not* locked. Note, -if the filesystem needs the page to be locked during writeout, that is ok, too, -the page is allowed to be unlocked at any point in time between the calls to -set_page_writeback() and end_page_writeback(). - -Note, failure to run either redirty_page_for_writepage() or the combination of -set_page_writeback()/end_page_writeback() on a page submitted to writepage -will leave the page itself marked clean but it will be tagged as dirty in the -radix tree. This incoherency can lead to all sorts of hard-to-debug problems -in the filesystem like having dirty inodes at umount and losing written data. - ->writepages() is used for periodic writeback and for syscall-initiated sync operations. The address_space should start I/O against at least ``*nr_to_write`` pages. ``*nr_to_write`` must be decremented for each page @@ -356,8 +314,8 @@ which is written. The address_space implementation may write more (or less) pages than ``*nr_to_write`` asks for, but it should try to be reasonably close. If nr_to_write is NULL, all dirty pages must be written. -writepages should _only_ write pages which are present on -mapping->io_pages. +writepages should _only_ write pages which are present in +mapping->i_pages. ->dirty_folio() is called from various places in the kernel when the target folio is marked as needing writeback. The folio cannot be @@ -485,7 +443,7 @@ prototypes:: int (*direct_access) (struct block_device *, sector_t, void **, unsigned long *); void (*unlock_native_capacity) (struct gendisk *); - int (*getgeo)(struct block_device *, struct hd_geometry *); + int (*getgeo)(struct gendisk *, struct hd_geometry *); void (*swap_slot_free_notify) (struct block_device *, unsigned long); locking rules: @@ -518,7 +476,6 @@ prototypes:: ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); int (*iopoll) (struct kiocb *kiocb, bool spin); - int (*iterate) (struct file *, struct dir_context *); int (*iterate_shared) (struct file *, struct dir_context *); __poll_t (*poll) (struct file *, struct poll_table_struct *); long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); |