diff options
Diffstat (limited to 'Documentation/filesystems/vfs.rst')
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 55 |
1 files changed, 37 insertions, 18 deletions
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index eebcc0f9e2bc..31eea688609a 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -810,7 +810,7 @@ cache in your filesystem. The following members are defined: struct page **pagep, void **fsdata); int (*write_end)(struct file *, 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); @@ -913,8 +913,7 @@ cache in your filesystem. The following members are defined: stop attempting I/O, it can simply return. The caller will remove the remaining pages from the address space, unlock them and decrement the page refcount. Set PageUptodate if the I/O - completes successfully. Setting PageError on any page will be - ignored; simply unlock the page if an I/O error occurs. + completes successfully. ``write_begin`` Called by the generic buffered write code to ask the filesystem @@ -926,12 +925,12 @@ cache in your filesystem. The following members are defined: (if they haven't been read already) so that the updated blocks can be written out properly. - The filesystem must return the locked pagecache page for the - specified offset, in ``*pagep``, for the caller to write into. + The filesystem must return the locked pagecache folio for the + specified offset, in ``*foliop``, for the caller to write into. It must be able to cope with short writes (where the length passed to write_begin is greater than the number of bytes copied - into the page). + into the folio). A void * may be returned in fsdata, which then gets passed into write_end. @@ -944,8 +943,8 @@ cache in your filesystem. The following members are defined: called. len is the original len passed to write_begin, and copied is the amount that was able to be copied. - The filesystem must take care of unlocking the page and - releasing it refcount, and updating i_size. + The filesystem must take care of unlocking the folio, + decrementing its refcount, and updating i_size. Returns < 0 on failure, otherwise the number of bytes (<= 'copied') that were able to be copied into pagecache. @@ -1252,7 +1251,8 @@ defined: .. code-block:: c struct dentry_operations { - 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 *, @@ -1264,7 +1264,9 @@ defined: char *(*d_dname)(struct dentry *, char *, int); struct vfsmount *(*d_automount)(struct 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 *); }; ``d_revalidate`` @@ -1419,16 +1421,33 @@ defined: the dentry being transited from. ``d_real`` - overlay/union type filesystems implement this method to return - one of the underlying dentries hidden by the overlay. It is - used in two different modes: + overlay/union type filesystems implement this method to return one + of the underlying dentries of a regular file hidden by the overlay. - Called from file_dentry() it returns the real dentry matching - the inode argument. The real dentry may be from a lower layer - already copied up, but still referenced from the file. This - mode is selected with a non-NULL inode argument. + The 'type' argument takes the values D_REAL_DATA or D_REAL_METADATA + for returning the real underlying dentry that refers to the inode + hosting the file's data or metadata respectively. + + For non-regular files, the 'dentry' argument is returned. + +``d_unalias_trylock`` + if present, will be called by d_splice_alias() before moving a + preexisting attached alias. Returning false prevents __d_move(), + making d_splice_alias() fail with -ESTALE. + + Rationale: setting FS_RENAME_DOES_D_MOVE will prevent d_move() + and d_exchange() calls from the outside of filesystem methods; + however, it does not guarantee that attached dentries won't + be renamed or moved by d_splice_alias() finding a preexisting + alias for a directory inode. Normally we would not care; + however, something that wants to stabilize the entire path to + root over a blocking operation might need that. See 9p for one + (and hopefully only) example. + +``d_unalias_unlock`` + should be paired with ``d_unalias_trylock``; that one is called after + __d_move() call in __d_unalias(). - With NULL inode the topmost real underlying dentry is returned. Each dentry has a pointer to its parent dentry, as well as a hash list of child dentries. Child dentries are basically like files in a |