6 New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(),
7 sb_set_blocksize() and sb_min_blocksize().
11 (sb_find_get_block() replaces 2.4's get_hash_table())
16 New methods: ->alloc_inode() and ->destroy_inode().
18 Remove inode->u.foo_inode_i
20 struct foo_inode_info {
21 /* fs-private stuff */
22 struct inode vfs_inode;
24 static inline struct foo_inode_info *FOO_I(struct inode *inode)
26 return list_entry(inode, struct foo_inode_info, vfs_inode);
29 Use FOO_I(inode) instead of &inode->u.foo_inode_i;
31 Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate
32 foo_inode_info and return the address of ->vfs_inode, the latter should free
33 FOO_I(inode) (see in-tree filesystems for examples).
35 Make them ->alloc_inode and ->destroy_inode in your super_operations.
37 Keep in mind that now you need explicit initialization of private data
38 typically between calling iget_locked() and unlocking the inode.
40 At some point that will become mandatory.
45 Change of file_system_type method (->read_super to ->get_sb)
47 ->read_super() is no more. Ditto for DECLARE_FSTYPE and DECLARE_FSTYPE_DEV.
49 Turn your foo_read_super() into a function that would return 0 in case of
50 success and negative number in case of error (-EINVAL unless you have more
51 informative error value to report). Call it foo_fill_super(). Now declare
53 int foo_get_sb(struct file_system_type *fs_type,
54 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
56 return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super,
60 (or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of
63 Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as
69 Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames.
70 Most likely there is no need to change anything, but if you relied on
71 global exclusion between renames for some internal purpose - you need to
72 change your internal locking. Otherwise exclusion warranties remain the
73 same (i.e. parents and victim are locked, etc.).
78 Now we have the exclusion between ->lookup() and directory removal (by
79 ->rmdir() and ->rename()). If you used to need that exclusion and do
80 it by internal locking (most of filesystems couldn't care less) - you
81 can relax your locking.
86 ->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(),
87 ->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename()
88 and ->readdir() are called without BKL now. Grab it on entry, drop upon return
89 - that will guarantee the same locking you used to have. If your method or its
90 parts do not need BKL - better yet, now you can shift lock_kernel() and
91 unlock_kernel() so that they would protect exactly what needs to be
97 BKL is also moved from around sb operations. BKL should have been shifted into
98 individual fs sb_op functions. If you don't need it, remove it.
103 check for ->link() target not being a directory is done by callers. Feel
109 ->link() callers hold ->i_mutex on the object we are linking to. Some of your
110 problems might be over...
115 new file_system_type method - kill_sb(superblock). If you are converting
116 an existing filesystem, set it according to ->fs_flags:
117 FS_REQUIRES_DEV - kill_block_super
118 FS_LITTER - kill_litter_super
119 neither - kill_anon_super
120 FS_LITTER is gone - just remove it from fs_flags.
125 FS_SINGLE is gone (actually, that had happened back when ->get_sb()
126 went in - and hadn't been documented ;-/). Just remove it from fs_flags
127 (and see ->get_sb() entry for other actions).
132 ->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so
133 watch for ->i_mutex-grabbing code that might be used by your ->setattr().
134 Callers of notify_change() need ->i_mutex now.
139 New super_block field "struct export_operations *s_export_op" for
140 explicit support for exporting, e.g. via NFS. The structure is fully
141 documented at its declaration in include/linux/fs.h, and in
142 Documentation/filesystems/nfs/Exporting.
144 Briefly it allows for the definition of decode_fh and encode_fh operations
145 to encode and decode filehandles, and allows the filesystem to use
146 a standard helper function for decode_fh, and provide file-system specific
147 support for this helper, particularly get_parent.
149 It is planned that this will be required for exporting once the code
154 s_export_op is now required for exporting a filesystem.
155 isofs, ext2, ext3, resierfs, fat
156 can be used as examples of very different filesystems.
161 iget4() and the read_inode2 callback have been superseded by iget5_locked()
162 which has the following prototype,
164 struct inode *iget5_locked(struct super_block *sb, unsigned long ino,
165 int (*test)(struct inode *, void *),
166 int (*set)(struct inode *, void *),
169 'test' is an additional function that can be used when the inode
170 number is not sufficient to identify the actual file object. 'set'
171 should be a non-blocking function that initializes those parts of a
172 newly created inode to allow the test function to succeed. 'data' is
173 passed as an opaque value to both test and set functions.
175 When the inode has been created by iget5_locked(), it will be returned with the
176 I_NEW flag set and will still be locked. The filesystem then needs to finalize
177 the initialization. Once the inode is initialized it must be unlocked by
178 calling unlock_new_inode().
180 The filesystem is responsible for setting (and possibly testing) i_ino
181 when appropriate. There is also a simpler iget_locked function that
182 just takes the superblock and inode number as arguments and does the
183 test and set for you.
186 inode = iget_locked(sb, ino);
187 if (inode->i_state & I_NEW) {
188 err = read_inode_from_disk(inode);
193 unlock_new_inode(inode);
196 Note that if the process of setting up a new inode fails, then iget_failed()
197 should be called on the inode to render it dead, and an appropriate error
198 should be passed back to the caller.
203 ->getattr() finally getting used. See instances in nfs, minix, etc.
208 ->revalidate() is gone. If your filesystem had it - provide ->getattr()
209 and let it call whatever you had as ->revlidate() + (for symlinks that
210 had ->revalidate()) add calls in ->follow_link()/->readlink().
215 ->d_parent changes are not protected by BKL anymore. Read access is safe
216 if at least one of the following is true:
217 * filesystem has no cross-directory rename()
218 * we know that parent had been locked (e.g. we are looking at
219 ->d_parent of ->lookup() argument).
220 * we are called from ->rename().
221 * the child's ->d_lock is held
222 Audit your code and add locking if needed. Notice that any place that is
223 not protected by the conditions above is risky even in the old tree - you
224 had been relying on BKL and that's prone to screwups. Old tree had quite
225 a few holes of that kind - unprotected access to ->d_parent leading to
226 anything from oops to silent memory corruption.
231 FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags
232 (see rootfs for one kind of solution and bdev/socket/pipe for another).
237 Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter
238 is still alive, but only because of the mess in drivers/s390/block/dasd.c.
239 As soon as it gets fixed is_read_only() will die.
244 ->permission() is called without BKL now. Grab it on entry, drop upon
245 return - that will guarantee the same locking you used to have. If
246 your method or its parts do not need BKL - better yet, now you can
247 shift lock_kernel() and unlock_kernel() so that they would protect
248 exactly what needs to be protected.
253 ->statfs() is now called without BKL held. BKL should have been
254 shifted into individual fs sb_op functions where it's not clear that
255 it's safe to remove it. If you don't need it, remove it.
260 is_read_only() is gone; use bdev_read_only() instead.
265 destroy_buffers() is gone; use invalidate_bdev().
270 fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is
271 deliberate; as soon as struct block_device * is propagated in a reasonable
272 way by that code fixing will become trivial; until then nothing can be
277 block truncatation on error exit from ->write_begin, and ->direct_IO
278 moved from generic methods (block_write_begin, cont_write_begin,
279 nobh_write_begin, blockdev_direct_IO*) to callers. Take a look at
280 ext2_write_failed and callers for an example.
284 ->truncate is gone. The whole truncate sequence needs to be
285 implemented in ->setattr, which is now mandatory for filesystems
286 implementing on-disk size changes. Start with a copy of the old inode_setattr
287 and vmtruncate, and the reorder the vmtruncate + foofs_vmtruncate sequence to
288 be in order of zeroing blocks using block_truncate_page or similar helpers,
289 size update and on finally on-disk truncation which should not fail.
290 inode_change_ok now includes the size checks for ATTR_SIZE and must be called
291 in the beginning of ->setattr unconditionally.
295 ->clear_inode() and ->delete_inode() are gone; ->evict_inode() should
296 be used instead. It gets called whenever the inode is evicted, whether it has
297 remaining links or not. Caller does *not* evict the pagecache or inode-associated
298 metadata buffers; the method has to use truncate_inode_pages_final() to get rid
299 of those. Caller makes sure async writeback cannot be running for the inode while
300 (or after) ->evict_inode() is called.
302 ->drop_inode() returns int now; it's called on final iput() with
303 inode->i_lock held and it returns true if filesystems wants the inode to be
304 dropped. As before, generic_drop_inode() is still the default and it's been
305 updated appropriately. generic_delete_inode() is also alive and it consists
306 simply of return 1. Note that all actual eviction work is done by caller after
307 ->drop_inode() returns.
309 As before, clear_inode() must be called exactly once on each call of
310 ->evict_inode() (as it used to be for each call of ->delete_inode()). Unlike
311 before, if you are using inode-associated metadata buffers (i.e.
312 mark_buffer_dirty_inode()), it's your responsibility to call
313 invalidate_inode_buffers() before clear_inode().
315 NOTE: checking i_nlink in the beginning of ->write_inode() and bailing out
316 if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput()
317 may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly
318 free the on-disk inode, you may end up doing that while ->write_inode() is writing
324 .d_delete() now only advises the dcache as to whether or not to cache
325 unreferenced dentries, and is now only called when the dentry refcount goes to
326 0. Even on 0 refcount transition, it must be able to tolerate being called 0,
327 1, or more times (eg. constant, idempotent).
332 .d_compare() calling convention and locking rules are significantly
333 changed. Read updated documentation in Documentation/filesystems/vfs.txt (and
334 look at examples of other filesystems) for guidance.
339 .d_hash() calling convention and locking rules are significantly
340 changed. Read updated documentation in Documentation/filesystems/vfs.txt (and
341 look at examples of other filesystems) for guidance.
345 dcache_lock is gone, replaced by fine grained locks. See fs/dcache.c
346 for details of what locks to replace dcache_lock with in order to protect
347 particular things. Most of the time, a filesystem only needs ->d_lock, which
348 protects *all* the dcache state of a given dentry.
353 Filesystems must RCU-free their inodes, if they can have been accessed
354 via rcu-walk path walk (basically, if the file can have had a path name in the
357 Even though i_dentry and i_rcu share storage in a union, we will
358 initialize the former in inode_init_always(), so just leave it alone in
359 the callback. It used to be necessary to clean it there, but not anymore
364 vfs now tries to do path walking in "rcu-walk mode", which avoids
365 atomic operations and scalability hazards on dentries and inodes (see
366 Documentation/filesystems/path-lookup.txt). d_hash and d_compare changes
367 (above) are examples of the changes required to support this. For more complex
368 filesystem callbacks, the vfs drops out of rcu-walk mode before the fs call, so
369 no changes are required to the filesystem. However, this is costly and loses
370 the benefits of rcu-walk mode. We will begin to add filesystem callbacks that
371 are rcu-walk aware, shown below. Filesystems should take advantage of this
376 d_revalidate is a callback that is made on every path element (if
377 the filesystem provides it), which requires dropping out of rcu-walk mode. This
378 may now be called in rcu-walk mode (nd->flags & LOOKUP_RCU). -ECHILD should be
379 returned if the filesystem cannot handle rcu-walk. See
380 Documentation/filesystems/vfs.txt for more details.
382 permission is an inode permission check that is called on many or all
383 directory inodes on the way down a path walk (to check for exec permission). It
384 must now be rcu-walk aware (mask & MAY_NOT_BLOCK). See
385 Documentation/filesystems/vfs.txt for more details.
389 In ->fallocate() you must check the mode option passed in. If your
390 filesystem does not support hole punching (deallocating space in the middle of a
391 file) you must return -EOPNOTSUPP if FALLOC_FL_PUNCH_HOLE is set in mode.
392 Currently you can only have FALLOC_FL_PUNCH_HOLE with FALLOC_FL_KEEP_SIZE set,
393 so the i_size should not change when hole punching, even when puching the end of
398 ->get_sb() is gone. Switch to use of ->mount(). Typically it's just
399 a matter of switching from calling get_sb_... to mount_... and changing the
400 function type. If you were doing it manually, just switch from setting ->mnt_root
401 to some pointer to returning that pointer. On errors return ERR_PTR(...).
405 ->permission() and generic_permission()have lost flags
406 argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask.
407 generic_permission() has also lost the check_acl argument; ACL checking
408 has been taken to VFS and filesystems need to provide a non-NULL ->i_op->get_acl
409 to read an ACL from disk.
413 If you implement your own ->llseek() you must handle SEEK_HOLE and
414 SEEK_DATA. You can hanle this by returning -EINVAL, but it would be nicer to
415 support it in some way. The generic handler assumes that the entire file is
416 data and there is a virtual hole at the end of the file. So if the provided
417 offset is less than i_size and SEEK_DATA is specified, return the same offset.
418 If the above is true for the offset and you are given SEEK_HOLE, return the end
419 of the file. If the offset is i_size or greater return -ENXIO in either case.
422 If you have your own ->fsync() you must make sure to call
423 filemap_write_and_wait_range() so that all dirty pages are synced out properly.
424 You must also keep in mind that ->fsync() is not called with i_mutex held
425 anymore, so if you require i_mutex locking you must make sure to take it and
430 d_alloc_root() is gone, along with a lot of bugs caused by code
431 misusing it. Replacement: d_make_root(inode). The difference is,
432 d_make_root() drops the reference to inode if dentry allocation fails.
436 The witch is dead! Well, 2/3 of it, anyway. ->d_revalidate() and
437 ->lookup() do *not* take struct nameidata anymore; just the flags.
440 ->create() doesn't take struct nameidata *; unlike the previous
441 two, it gets "is it an O_EXCL or equivalent?" boolean argument. Note that
442 local filesystems can ignore tha argument - they are guaranteed that the
443 object doesn't exist. It's remote/distributed ones that might care...
446 FS_REVAL_DOT is gone; if you used to have it, add ->d_weak_revalidate()
447 in your dentry operations instead.
450 vfs_readdir() is gone; switch to iterate_dir() instead
453 ->readdir() is gone now; switch to ->iterate()
455 vfs_follow_link has been removed. Filesystems must use nd_set_link
456 from ->follow_link for normal symlinks, or nd_jump_link for magic
457 /proc/<pid> style links.
460 iget5_locked()/ilookup5()/ilookup5_nowait() test() callback used to be
461 called with both ->i_lock and inode_hash_lock held; the former is *not*
462 taken anymore, so verify that your callbacks do not rely on it (none
463 of the in-tree instances did). inode_hash_lock is still held,
464 of course, so they are still serialized wrt removal from inode hash,
465 as well as wrt set() callback of iget5_locked().
468 d_materialise_unique() is gone; d_splice_alias() does everything you
469 need now. Remember that they have opposite orders of arguments ;-/
472 f_dentry is gone; use f_path.dentry, or, better yet, see if you can avoid
476 never call ->read() and ->write() directly; use __vfs_{read,write} or
477 wrappers; instead of checking for ->write or ->read being NULL, look for
478 FMODE_CAN_{WRITE,READ} in file->f_mode.
481 do _not_ use new_sync_{read,write} for ->read/->write; leave it NULL
485 ->aio_read/->aio_write are gone. Use ->read_iter/->write_iter.
488 for embedded ("fast") symlinks just set inode->i_link to wherever the
489 symlink body is and use simple_follow_link() as ->follow_link().
492 calling conventions for ->follow_link() have changed. Instead of returning
493 cookie and using nd_set_link() to store the body to traverse, we return
494 the body to traverse and store the cookie using explicit void ** argument.
495 nameidata isn't passed at all - nd_jump_link() doesn't need it and
496 nd_[gs]et_link() is gone.
499 calling conventions for ->put_link() have changed. It gets inode instead of
500 dentry, it does not get nameidata at all and it gets called only when cookie
501 is non-NULL. Note that link body isn't available anymore, so if you need it,
505 __fd_install() & fd_install() can now sleep. Callers should not
506 hold a spinlock or other resources that do not allow a schedule.
509 any symlink that might use page_follow_link_light/page_put_link() must
510 have inode_nohighmem(inode) called before anything might start playing with