diff options
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 64 |
1 files changed, 44 insertions, 20 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index c61a223ef..9ace359d6 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -364,7 +364,6 @@ struct inode_operations { int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode, int *opened); int (*tmpfile) (struct inode *, struct dentry *, umode_t); - int (*dentry_open)(struct dentry *, struct file *, const struct cred *); }; Again, all methods are called without any locks being held, unless @@ -534,9 +533,7 @@ __sync_single_inode) to check if ->writepages has been successful in writing out the whole address_space. The Writeback tag is used by filemap*wait* and sync_page* functions, -via filemap_fdatawait_range, to wait for all writeback to -complete. While waiting ->sync_page (if defined) will be called on -each page that is found to require writeback. +via filemap_fdatawait_range, to wait for all writeback to complete. An address_space handler may attach extra information to a page, typically using the 'private' field in the 'struct page'. If such @@ -554,8 +551,8 @@ address_space has finer control of write sizes. The read process essentially only requires 'readpage'. The write process is more complicated and uses write_begin/write_end or -set_page_dirty to write data into the address_space, and writepage, -sync_page, and writepages to writeback data to storage. +set_page_dirty to write data into the address_space, and writepage +and writepages to writeback data to storage. Adding and removing pages to/from an address_space is protected by the inode's i_mutex. @@ -592,9 +589,14 @@ struct address_space_operations { int (*releasepage) (struct page *, int); void (*freepage)(struct page *); ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter); + /* isolate a page for migration */ + bool (*isolate_page) (struct page *, isolate_mode_t); /* migrate the contents of a page to the specified target */ int (*migratepage) (struct page *, struct page *); + /* put migration-failed page back to right list */ + void (*putback_page) (struct page *); int (*launder_page) (struct page *); + int (*is_partially_uptodate) (struct page *, unsigned long, unsigned long); void (*is_dirty_writeback) (struct page *, bool *, bool *); @@ -696,13 +698,6 @@ struct address_space_operations { but instead uses bmap to find out where the blocks in the file are and uses those addresses directly. - dentry_open: *WARNING: probably going away soon, do not use!* This is an - alternative to f_op->open(), the difference is that this method may open - a file not necessarily originating from the same filesystem as the one - i_op->open() was called on. It may be useful for stacking filesystems - which want to allow native I/O directly on underlying files. - - invalidatepage: If a page has PagePrivate set, then invalidatepage will be called when part or all of the page is to be removed from the address space. This generally corresponds to either a @@ -747,6 +742,10 @@ struct address_space_operations { and transfer data directly between the storage and the application's address space. + isolate_page: Called by the VM when isolating a movable non-lru page. + If page is successfully isolated, VM marks the page as PG_isolated + via __SetPageIsolated. + migrate_page: This is used to compact the physical memory usage. If the VM wants to relocate a page (maybe off a memory card that is signalling imminent failure) it will pass a new page @@ -754,6 +753,8 @@ struct address_space_operations { transfer any private data across and update any references that it has to the page. + putback_page: Called by the VM when isolated page's migration fails. + launder_page: Called before freeing a page - it writes back the dirty page. To prevent redirtying the page, it is kept locked during the whole operation. @@ -930,14 +931,17 @@ struct dentry_operations { int (*d_revalidate)(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 *, const struct dentry *, + int (*d_compare)(const struct dentry *, unsigned int, const char *, const struct qstr *); int (*d_delete)(const struct dentry *); + int (*d_init)(struct dentry *); void (*d_release)(struct dentry *); void (*d_iput)(struct dentry *, struct inode *); char *(*d_dname)(struct dentry *, char *, int); struct vfsmount *(*d_automount)(struct path *); int (*d_manage)(struct dentry *, bool); + struct dentry *(*d_real)(struct dentry *, const struct inode *, + unsigned int); }; d_revalidate: called when the VFS needs to revalidate a dentry. This @@ -1003,6 +1007,8 @@ struct dentry_operations { always cache a reachable dentry. d_delete must be constant and idempotent. + d_init: called when a dentry is allocated + d_release: called when a dentry is really deallocated d_iput: called when a dentry loses its inode (just prior to its @@ -1022,6 +1028,14 @@ struct dentry_operations { at the end of the buffer, and returns a pointer to the first char. dynamic_dname() helper function is provided to take care of this. + Example : + + static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen) + { + return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", + dentry->d_inode->i_ino); + } + d_automount: called when an automount dentry is to be traversed (optional). This should create a new VFS mount record and return the record to the caller. The caller is supplied with a path parameter giving the @@ -1060,13 +1074,23 @@ struct dentry_operations { This function is only used if DCACHE_MANAGE_TRANSIT is set on the dentry being transited from. -Example : + d_real: overlay/union type filesystems implement this method to return one of + the underlying dentries hidden by the overlay. It is used in three + different modes: -static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen) -{ - return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]", - dentry->d_inode->i_ino); -} + Called from open it may need to copy-up the file depending on the + supplied open flags. This mode is selected with a non-zero flags + argument. In this mode the d_real method can return an error. + + 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. This will always succeed. + + With NULL inode and zero flags the topmost real underlying dentry is + returned. This will always succeed. + + This method is never called with both non-NULL inode and non-zero flags. 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 |