1 ====================
2 Changes since 2.5.0:
3 ====================
4
5 ---
6
7 **recommended**
8
9 New helpers: sb_bread(), sb_getblk(), sb_find_
10 sb_set_blocksize() and sb_min_blocksize().
11
12 Use them.
13
14 (sb_find_get_block() replaces 2.4's get_hash_t
15
16 ---
17
18 **recommended**
19
20 New methods: ->alloc_inode() and ->destroy_ino
21
22 Remove inode->u.foo_inode_i
23
24 Declare::
25
26 struct foo_inode_info {
27 /* fs-private stuff */
28 struct inode vfs_inode;
29 };
30 static inline struct foo_inode_info *F
31 {
32 return list_entry(inode, struc
33 }
34
35 Use FOO_I(inode) instead of &inode->u.foo_inod
36
37 Add foo_alloc_inode() and foo_destroy_inode()
38 foo_inode_info and return the address of ->vfs
39 FOO_I(inode) (see in-tree filesystems for exam
40
41 Make them ->alloc_inode and ->destroy_inode in
42
43 Keep in mind that now you need explicit initia
44 typically between calling iget_locked() and un
45
46 At some point that will become mandatory.
47
48 **mandatory**
49
50 The foo_inode_info should always be allocated
51 than kmem_cache_alloc() or kmalloc() related t
52 correctly.
53
54 ---
55
56 **mandatory**
57
58 Change of file_system_type method (->read_supe
59
60 ->read_super() is no more. Ditto for DECLARE_
61
62 Turn your foo_read_super() into a function tha
63 success and negative number in case of error (
64 informative error value to report). Call it f
65
66 int foo_get_sb(struct file_system_type *fs_t
67 int flags, const char *dev_name, void
68 {
69 return get_sb_bdev(fs_type, flags, dev
70 mnt);
71 }
72
73 (or similar with s/bdev/nodev/ or s/bdev/singl
74 filesystem).
75
76 Replace DECLARE_FSTYPE... with explicit initia
77 foo_get_sb.
78
79 ---
80
81 **mandatory**
82
83 Locking change: ->s_vfs_rename_sem is taken on
84 Most likely there is no need to change anythin
85 global exclusion between renames for some inte
86 change your internal locking. Otherwise exclu
87 same (i.e. parents and victim are locked, etc.
88
89 ---
90
91 **informational**
92
93 Now we have the exclusion between ->lookup() a
94 ->rmdir() and ->rename()). If you used to nee
95 it by internal locking (most of filesystems co
96 can relax your locking.
97
98 ---
99
100 **mandatory**
101
102 ->lookup(), ->truncate(), ->create(), ->unlink
103 ->rmdir(), ->link(), ->lseek(), ->symlink(), -
104 and ->readdir() are called without BKL now. G
105 - that will guarantee the same locking you use
106 parts do not need BKL - better yet, now you ca
107 unlock_kernel() so that they would protect exa
108 protected.
109
110 ---
111
112 **mandatory**
113
114 BKL is also moved from around sb operations. B
115 individual fs sb_op functions. If you don't n
116
117 ---
118
119 **informational**
120
121 check for ->link() target not being a director
122 free to drop it...
123
124 ---
125
126 **informational**
127
128 ->link() callers hold ->i_mutex on the object
129 problems might be over...
130
131 ---
132
133 **mandatory**
134
135 new file_system_type method - kill_sb(superblo
136 an existing filesystem, set it according to ->
137
138 FS_REQUIRES_DEV - kill_b
139 FS_LITTER - kill_l
140 neither - kill_a
141
142 FS_LITTER is gone - just remove it from fs_fla
143
144 ---
145
146 **mandatory**
147
148 FS_SINGLE is gone (actually, that had happened
149 went in - and hadn't been documented ;-/). Ju
150 (and see ->get_sb() entry for other actions).
151
152 ---
153
154 **mandatory**
155
156 ->setattr() is called without BKL now. Caller
157 watch for ->i_mutex-grabbing code that might b
158 Callers of notify_change() need ->i_mutex now.
159
160 ---
161
162 **recommended**
163
164 New super_block field ``struct export_operatio
165 explicit support for exporting, e.g. via NFS.
166 documented at its declaration in include/linux
167 Documentation/filesystems/nfs/exporting.rst.
168
169 Briefly it allows for the definition of decode
170 to encode and decode filehandles, and allows t
171 a standard helper function for decode_fh, and
172 support for this helper, particularly get_pare
173
174 It is planned that this will be required for e
175 settles down a bit.
176
177 **mandatory**
178
179 s_export_op is now required for exporting a fi
180 isofs, ext2, ext3, reiserfs, fat
181 can be used as examples of very different file
182
183 ---
184
185 **mandatory**
186
187 iget4() and the read_inode2 callback have been
188 which has the following prototype::
189
190 struct inode *iget5_locked(struct super_bl
191 int (*test)(st
192 int (*set)(str
193 void *data);
194
195 'test' is an additional function that can be u
196 number is not sufficient to identify the actua
197 should be a non-blocking function that initial
198 newly created inode to allow the test function
199 passed as an opaque value to both test and set
200
201 When the inode has been created by iget5_locke
202 I_NEW flag set and will still be locked. The
203 the initialization. Once the inode is initiali
204 calling unlock_new_inode().
205
206 The filesystem is responsible for setting (and
207 when appropriate. There is also a simpler iget
208 just takes the superblock and inode number as
209 test and set for you.
210
211 e.g.::
212
213 inode = iget_locked(sb, ino);
214 if (inode->i_state & I_NEW) {
215 err = read_inode_from_disk(ino
216 if (err < 0) {
217 iget_failed(inode);
218 return err;
219 }
220 unlock_new_inode(inode);
221 }
222
223 Note that if the process of setting up a new i
224 should be called on the inode to render it dea
225 should be passed back to the caller.
226
227 ---
228
229 **recommended**
230
231 ->getattr() finally getting used. See instanc
232
233 ---
234
235 **mandatory**
236
237 ->revalidate() is gone. If your filesystem ha
238 and let it call whatever you had as ->revlidat
239 had ->revalidate()) add calls in ->follow_link
240
241 ---
242
243 **mandatory**
244
245 ->d_parent changes are not protected by BKL an
246 if at least one of the following is true:
247
248 * filesystem has no cross-directory re
249 * we know that parent had been locked
250 ->d_parent of ->lookup() argument).
251 * we are called from ->rename().
252 * the child's ->d_lock is held
253
254 Audit your code and add locking if needed. No
255 not protected by the conditions above is risky
256 had been relying on BKL and that's prone to sc
257 a few holes of that kind - unprotected access
258 anything from oops to silent memory corruption
259
260 ---
261
262 **mandatory**
263
264 FS_NOMOUNT is gone. If you use it - just set
265 (see rootfs for one kind of solution and bdev/
266
267 ---
268
269 **recommended**
270
271 Use bdev_read_only(bdev) instead of is_read_on
272 is still alive, but only because of the mess i
273 As soon as it gets fixed is_read_only() will d
274
275 ---
276
277 **mandatory**
278
279 ->permission() is called without BKL now. Grab
280 return - that will guarantee the same locking
281 your method or its parts do not need BKL - bet
282 shift lock_kernel() and unlock_kernel() so tha
283 exactly what needs to be protected.
284
285 ---
286
287 **mandatory**
288
289 ->statfs() is now called without BKL held. BK
290 shifted into individual fs sb_op functions whe
291 it's safe to remove it. If you don't need it,
292
293 ---
294
295 **mandatory**
296
297 is_read_only() is gone; use bdev_read_only() i
298
299 ---
300
301 **mandatory**
302
303 destroy_buffers() is gone; use invalidate_bdev
304
305 ---
306
307 **mandatory**
308
309 fsync_dev() is gone; use fsync_bdev(). NOTE:
310 deliberate; as soon as struct block_device * i
311 way by that code fixing will become trivial; u
312 done.
313
314 **mandatory**
315
316 block truncatation on error exit from ->write_
317 moved from generic methods (block_write_begin,
318 nobh_write_begin, blockdev_direct_IO*) to call
319 ext2_write_failed and callers for an example.
320
321 **mandatory**
322
323 ->truncate is gone. The whole truncate sequen
324 implemented in ->setattr, which is now mandato
325 implementing on-disk size changes. Start with
326 and vmtruncate, and the reorder the vmtruncate
327 be in order of zeroing blocks using block_trun
328 size update and on finally on-disk truncation
329 setattr_prepare (which used to be inode_change
330 for ATTR_SIZE and must be called in the beginn
331
332 **mandatory**
333
334 ->clear_inode() and ->delete_inode() are gone;
335 be used instead. It gets called whenever the
336 remaining links or not. Caller does *not* evi
337 metadata buffers; the method has to use trunca
338 of those. Caller makes sure async writeback ca
339 (or after) ->evict_inode() is called.
340
341 ->drop_inode() returns int now; it's called on
342 inode->i_lock held and it returns true if file
343 dropped. As before, generic_drop_inode() is s
344 updated appropriately. generic_delete_inode()
345 simply of return 1. Note that all actual evic
346 ->drop_inode() returns.
347
348 As before, clear_inode() must be called exactl
349 ->evict_inode() (as it used to be for each cal
350 before, if you are using inode-associated meta
351 mark_buffer_dirty_inode()), it's your responsi
352 invalidate_inode_buffers() before clear_inode(
353
354 NOTE: checking i_nlink in the beginning of ->w
355 if it's zero is not *and* *never* *had* *been*
356 may happen while the inode is in the middle of
357 free the on-disk inode, you may end up doing t
358 to it.
359
360 ---
361
362 **mandatory**
363
364 .d_delete() now only advises the dcache as to
365 unreferenced dentries, and is now only called
366 0. Even on 0 refcount transition, it must be a
367 1, or more times (eg. constant, idempotent).
368
369 ---
370
371 **mandatory**
372
373 .d_compare() calling convention and locking ru
374 changed. Read updated documentation in Documen
375 look at examples of other filesystems) for gui
376
377 ---
378
379 **mandatory**
380
381 .d_hash() calling convention and locking rules
382 changed. Read updated documentation in Documen
383 look at examples of other filesystems) for gui
384
385 ---
386
387 **mandatory**
388
389 dcache_lock is gone, replaced by fine grained
390 for details of what locks to replace dcache_lo
391 particular things. Most of the time, a filesys
392 protects *all* the dcache state of a given den
393
394 ---
395
396 **mandatory**
397
398 Filesystems must RCU-free their inodes, if the
399 via rcu-walk path walk (basically, if the file
400 vfs namespace).
401
402 Even though i_dentry and i_rcu share storage i
403 initialize the former in inode_init_always(),
404 the callback. It used to be necessary to clea
405 (starting at 3.2).
406
407 ---
408
409 **recommended**
410
411 vfs now tries to do path walking in "rcu-walk
412 atomic operations and scalability hazards on d
413 Documentation/filesystems/path-lookup.txt). d_
414 (above) are examples of the changes required t
415 filesystem callbacks, the vfs drops out of rcu
416 no changes are required to the filesystem. How
417 the benefits of rcu-walk mode. We will begin t
418 are rcu-walk aware, shown below. Filesystems s
419 where possible.
420
421 ---
422
423 **mandatory**
424
425 d_revalidate is a callback that is made on eve
426 the filesystem provides it), which requires dr
427 may now be called in rcu-walk mode (nd->flags
428 returned if the filesystem cannot handle rcu-w
429 Documentation/filesystems/vfs.rst for more det
430
431 permission is an inode permission check that i
432 directory inodes on the way down a path walk (
433 must now be rcu-walk aware (mask & MAY_NOT_BLO
434 Documentation/filesystems/vfs.rst for more det
435
436 ---
437
438 **mandatory**
439
440 In ->fallocate() you must check the mode optio
441 filesystem does not support hole punching (dea
442 file) you must return -EOPNOTSUPP if FALLOC_FL
443 Currently you can only have FALLOC_FL_PUNCH_HO
444 so the i_size should not change when hole punc
445 a file off.
446
447 ---
448
449 **mandatory**
450
451 ->get_sb() is gone. Switch to use of ->mount(
452 a matter of switching from calling ``get_sb_``
453 the function type. If you were doing it manua
454 ->mnt_root to some pointer to returning that p
455 ERR_PTR(...).
456
457 ---
458
459 **mandatory**
460
461 ->permission() and generic_permission()have lo
462 argument; instead of passing IPERM_FLAG_RCU we
463
464 generic_permission() has also lost the check_a
465 has been taken to VFS and filesystems need to
466 ->i_op->get_inode_acl to read an ACL from disk
467
468 ---
469
470 **mandatory**
471
472 If you implement your own ->llseek() you must
473 SEEK_DATA. You can handle this by returning -
474 support it in some way. The generic handler a
475 data and there is a virtual hole at the end of
476 offset is less than i_size and SEEK_DATA is sp
477 If the above is true for the offset and you ar
478 of the file. If the offset is i_size or great
479
480 **mandatory**
481
482 If you have your own ->fsync() you must make s
483 filemap_write_and_wait_range() so that all dir
484 You must also keep in mind that ->fsync() is n
485 anymore, so if you require i_mutex locking you
486 release it yourself.
487
488 ---
489
490 **mandatory**
491
492 d_alloc_root() is gone, along with a lot of bu
493 misusing it. Replacement: d_make_root(inode).
494 allocates and returns a new dentry instantiate
495 On failure NULL is returned and the passed in
496 to inode is consumed in all cases and failure
497 for the inode. If d_make_root(inode) is passe
498 and also requires no further error handling. T
499
500 inode = foofs_new_inode(....);
501 s->s_root = d_make_root(inode);
502 if (!s->s_root)
503 /* Nothing needed for the inod
504 return -ENOMEM;
505 ...
506
507 ---
508
509 **mandatory**
510
511 The witch is dead! Well, 2/3 of it, anyway.
512 ->lookup() do *not* take struct nameidata anym
513
514 ---
515
516 **mandatory**
517
518 ->create() doesn't take ``struct nameidata *``
519 two, it gets "is it an O_EXCL or equivalent?"
520 local filesystems can ignore this argument - t
521 object doesn't exist. It's remote/distributed
522
523 ---
524
525 **mandatory**
526
527 FS_REVAL_DOT is gone; if you used to have it,
528 in your dentry operations instead.
529
530 ---
531
532 **mandatory**
533
534 vfs_readdir() is gone; switch to iterate_dir()
535
536 ---
537
538 **mandatory**
539
540 ->readdir() is gone now; switch to ->iterate_s
541
542 **mandatory**
543
544 vfs_follow_link has been removed. Filesystems
545 from ->follow_link for normal symlinks, or nd_
546 /proc/<pid> style links.
547
548 ---
549
550 **mandatory**
551
552 iget5_locked()/ilookup5()/ilookup5_nowait() te
553 called with both ->i_lock and inode_hash_lock
554 taken anymore, so verify that your callbacks d
555 of the in-tree instances did). inode_hash_loc
556 of course, so they are still serialized wrt re
557 as well as wrt set() callback of iget5_locked(
558
559 ---
560
561 **mandatory**
562
563 d_materialise_unique() is gone; d_splice_alias
564 need now. Remember that they have opposite or
565
566 ---
567
568 **mandatory**
569
570 f_dentry is gone; use f_path.dentry, or, bette
571 it entirely.
572
573 ---
574
575 **mandatory**
576
577 never call ->read() and ->write() directly; us
578 wrappers; instead of checking for ->write or -
579 FMODE_CAN_{WRITE,READ} in file->f_mode.
580
581 ---
582
583 **mandatory**
584
585 do _not_ use new_sync_{read,write} for ->read/
586 instead.
587
588 ---
589
590 **mandatory**
591 ->aio_read/->aio_write are gone. Use
592
593 ---
594
595 **recommended**
596
597 for embedded ("fast") symlinks just set inode-
598 symlink body is and use simple_follow_link() a
599
600 ---
601
602 **mandatory**
603
604 calling conventions for ->follow_link() have c
605 cookie and using nd_set_link() to store the bo
606 the body to traverse and store the cookie usin
607 nameidata isn't passed at all - nd_jump_link()
608 nd_[gs]et_link() is gone.
609
610 ---
611
612 **mandatory**
613
614 calling conventions for ->put_link() have chan
615 dentry, it does not get nameidata at all and
616 is non-NULL. Note that link body isn't availa
617 store it as cookie.
618
619 ---
620
621 **mandatory**
622
623 any symlink that might use page_follow_link_li
624 have inode_nohighmem(inode) called before anyt
625 its pagecache. No highmem pages should end up
626 symlinks. That includes any preseeding that m
627 creation. page_symlink() will honour the mapp
628 you've done inode_nohighmem() it's safe to use
629 insert the page manually, make sure to use the
630
631 ---
632
633 **mandatory**
634
635 ->follow_link() is replaced with ->get_link();
636
637 * ->get_link() gets inode as a separat
638 * ->get_link() may be called in RCU mo
639 dentry is passed
640
641 ---
642
643 **mandatory**
644
645 ->get_link() gets struct delayed_call ``*done`
646 set_delayed_call() where it used to set ``*coo
647
648 ->put_link() is gone - just give the destructo
649 in ->get_link().
650
651 ---
652
653 **mandatory**
654
655 ->getxattr() and xattr_handler.get() get dentr
656 dentry might be yet to be attached to inode, s
657 in the instances. Rationale: !@#!@# security_
658 called before we attach dentry to inode.
659
660 ---
661
662 **mandatory**
663
664 symlinks are no longer the only inodes that do
665 i_pipe/i_link union zeroed out at inode evicti
666 assume that non-NULL value in ->i_nlink at ->d
667 it's a symlink. Checking ->i_mode is really n
668 to fix shmem_destroy_callback() that used to t
669 watch out, since that shortcut is no longer va
670
671 ---
672
673 **mandatory**
674
675 ->i_mutex is replaced with ->i_rwsem now. ino
676 they used to - they just take it exclusive. H
677 called with parent locked shared. Its instanc
678
679 * use d_instantiate) and d_rehash() se
680 d_splice_alias() instead.
681 * use d_rehash() alone - call d_add(ne
682 * in the unlikely case when (read-only
683 data structures needs exclusion for
684 yourself. None of the in-tree files
685 * rely on ->d_parent and ->d_name not
686 been fed to d_add() or d_splice_alia
687 in-tree instances relied upon that.
688
689 We are guaranteed that lookups of the same nam
690 will not happen in parallel ("same" in the sen
691 Lookups on different names in the same directo
692 parallel now.
693
694 ---
695
696 **mandatory**
697
698 ->iterate_shared() is added.
699 Exclusion on struct file level is still provid
700 between it and lseek on the same struct file),
701 has been opened several times, you can get the
702 Exclusion between that method and all director
703 still provided, of course.
704
705 If you have any per-inode or per-dentry in-cor
706 by ->iterate_shared(), you might need somethin
707 to them. If you do dcache pre-seeding, you'll
708 d_alloc_parallel() for that; look for in-tree
709
710 ---
711
712 **mandatory**
713
714 ->atomic_open() calls without O_CREAT may happ
715
716 ---
717
718 **mandatory**
719
720 ->setxattr() and xattr_handler.set() get dentr
721 The xattr_handler.set() gets passed the user n
722 is seen from so filesystems can idmap the i_ui
723 dentry might be yet to be attached to inode, s
724 in the instances. Rationale: !@#!@# security_
725 called before we attach dentry to inode and !@
726 ->d_instantiate() uses not just ->getxattr() b
727
728 ---
729
730 **mandatory**
731
732 ->d_compare() doesn't get parent as a separate
733 used it for finding the struct super_block inv
734 work just as well; if it's something more comp
735 Just be careful not to assume that fetching it
736 the same value - in RCU mode it could change u
737
738 ---
739
740 **mandatory**
741
742 ->rename() has an added flags argument. Any f
743 filesystem should result in EINVAL being retur
744
745 ---
746
747
748 **recommended**
749
750 ->readlink is optional for symlinks. Don't se
751 to fake something for readlink(2).
752
753 ---
754
755 **mandatory**
756
757 ->getattr() is now passed a struct path rather
758 dentry separately, and it now has request_mask
759 to specify the fields and sync type requested
760 supporting any statx-specific features may ign
761
762 ---
763
764 **mandatory**
765
766 ->atomic_open() calling conventions have chang
767 along with FILE_OPENED/FILE_CREATED. In place
768 FMODE_OPENED/FMODE_CREATED, set in file->f_mod
769 value for 'called finish_no_open(), open it yo
770 0, not 1. Since finish_no_open() itself is re
771 does not need any changes in ->atomic_open() i
772
773 ---
774
775 **mandatory**
776
777 alloc_file() has become static now; two wrappe
778 alloc_file_pseudo(inode, vfsmount, name, flags
779 when dentry needs to be created; that's the ma
780 users. Calling conventions: on success a refe
781 is returned and callers reference to inode is
782 failure, ERR_PTR() is returned and no caller's
783 so the caller needs to drop the inode referenc
784 alloc_file_clone(file, flags, ops) does not af
785 On success you get a new struct file sharing t
786 original, on failure - ERR_PTR().
787
788 ---
789
790 **mandatory**
791
792 ->clone_file_range() and ->dedupe_file_range h
793 ->remap_file_range(). See Documentation/files
794 information.
795
796 ---
797
798 **recommended**
799
800 ->lookup() instances doing an equivalent of::
801
802 if (IS_ERR(inode))
803 return ERR_CAST(inode);
804 return d_splice_alias(inode, dentry);
805
806 don't need to bother with the check - d_splice
807 right thing when given ERR_PTR(...) as inode.
808 inode to d_splice_alias() will also do the rig
809 d_add(dentry, NULL); return NULL;), so that ki
810 also doesn't need a separate treatment.
811
812 ---
813
814 **strongly recommended**
815
816 take the RCU-delayed parts of ->destroy_inode(
817 ->free_inode(). If ->destroy_inode() becomes
818 just get rid of it. Synchronous work (e.g. th
819 be done from an RCU callback, or any WARN_ON()
820 stack trace) *might* be movable to ->evict_ino
821 that goes only for the things that are not nee
822 done by ->alloc_inode(). IOW, if it's cleanin
823 might have accumulated over the life of in-cor
824 might be a fit.
825
826 Rules for inode destruction:
827
828 * if ->destroy_inode() is non-NULL, it
829 * if ->free_inode() is non-NULL, it ge
830 * combination of NULL ->destroy_inode
831 treated as NULL/free_inode_nonrcu, t
832
833 Note that the callback (be it via ->free_inode
834 in ->destroy_inode()) is *NOT* ordered wrt sup
835 as the matter of fact, the superblock and all
836 might be already gone. The filesystem driver
837 there, but that's it. Freeing memory in the c
838 more than that is possible, but requires a lot
839 avoided.
840
841 ---
842
843 **mandatory**
844
845 DCACHE_RCUACCESS is gone; having an RCU delay
846 default. DCACHE_NORCU opts out, and only d_al
847 business doing so.
848
849 ---
850
851 **mandatory**
852
853 d_alloc_pseudo() is internal-only; uses outsid
854 very suspect (and won't work in modules). Suc
855 be misspelled d_alloc_anon().
856
857 ---
858
859 **mandatory**
860
861 [should've been added in 2016] stale comment i
862 failure exits in ->atomic_open() instances sho
863 no matter what. Everything is handled by the
864
865 ---
866
867 **mandatory**
868
869 clone_private_mount() returns a longterm mount
870 its result is kern_unmount() or kern_unmount_a
871
872 ---
873
874 **mandatory**
875
876 zero-length bvec segments are disallowed, they
877 passed on to an iterator.
878
879 ---
880
881 **mandatory**
882
883 For bvec based itererators bio_iov_iter_get_pa
884 uses the one provided. Anyone issuing kiocb-I/
885 page references stay until I/O has completed,
886 been called or returned with non -EIOCBQUEUED
887
888 ---
889
890 **mandatory**
891
892 mnt_want_write_file() can now only be paired w
893 whereas previously it could be paired with mnt
894
895 ---
896
897 **mandatory**
898
899 iov_iter_copy_from_user_atomic() is gone; use
900 The difference is copy_page_from_iter_atomic()
901 you don't need iov_iter_advance() after it. H
902 only a part of obtained data, you should do io
903
904 ---
905
906 **mandatory**
907
908 Calling conventions for file_open_root() chang
909 instead of passing mount and dentry separately
910 pass <mnt, mnt->mnt_root> pair (i.e. the root
911 is provided - file_open_root_mnt(). In-tree u
912
913 ---
914
915 **mandatory**
916
917 no_llseek is gone; don't set .llseek to that -
918 Checks for "does that file have llseek(2), or
919 should be done by looking at FMODE_LSEEK in fi
920
921 ---
922
923 *mandatory*
924
925 filldir_t (readdir callbacks) calling conventi
926 returning 0 or -E... it returns bool now. fal
927 to) and true - "keep going" (as 0 in old calli
928 callers never looked at specific -E... values
929 instances require no changes at all, all filld
930 converted.
931
932 ---
933
934 **mandatory**
935
936 Calling conventions for ->tmpfile() have chang
937 file pointer instead of struct dentry pointer.
938 changed to simplify callers. The passed file
939 success must be opened before returning (e.g.
940 finish_open_simple()).
941
942 ---
943
944 **mandatory**
945
946 Calling convention for ->huge_fault has change
947 order instead of an enum page_entry_size, and
948 mmap_lock held. All in-tree users have been a
949 depend on the mmap_lock being held, but out of
950 for themselves. If they do need it, they can
951 be called with the mmap_lock held.
952
953 ---
954
955 **mandatory**
956
957 The order of opening block devices and matchin
958 changed.
959
960 The old logic opened block devices first and t
961 suitable superblock to reuse based on the bloc
962
963 The new logic tries to find a suitable superbl
964 number, and opening the block device afterward
965
966 Since opening block devices cannot happen unde
967 ordering requirements s_umount is now dropped
968 reacquired before calling fill_super().
969
970 In the old logic concurrent mounters would fin
971 superblocks for the filesystem type. Since the
972 would hold s_umount they would wait until the
973 was discarded due to initialization failure.
974
975 Since the new logic drops s_umount concurrent
976 would spin. Instead they are now made to wait
977 mechanism without having to hold s_umount.
978
979 ---
980
981 **mandatory**
982
983 The holder of a block device is now the superb
984
985 The holder of a block device used to be the fi
986 particularly useful. It wasn't possible to go
987 superblock without matching on the device poin
988 This mechanism would only work for a single de
989 find the owning superblock of any additional d
990
991 In the old mechanism reusing or creating a sup
992 umount(2) relied on the file_system_type as th
993 underdocumented however:
994
995 (1) Any concurrent mounter that managed to gra
996 existing superblock was made to wait until
997 ready or until the superblock was removed
998 the filesystem type. If the superblock is
999 reuse it.
1000
1001 (2) If the mounter came after deactivate_lock
1002 the superblock had been removed from the
1003 filesystem type the mounter would wait un
1004 reuse the block device and allocate a new
1005
1006 (3) If the mounter came after deactivate_lock
1007 the superblock had been removed from the
1008 filesystem type the mounter would reuse t
1009 superblock (the bd_holder point may still
1010
1011 Because the holder of the block device was th
1012 mounter could open the block devices of any s
1013 file_system_type without risking seeing EBUSY
1014 still in use by another superblock.
1015
1016 Making the superblock the owner of the block
1017 is now a unique superblock and thus block dev
1018 reused by concurrent mounters. So a concurren
1019 see EBUSY when trying to open a block device
1020 superblock.
1021
1022 The new logic thus waits until the superblock
1023 ->kill_sb(). Removal of the superblock from t
1024 filesystem type is now moved to a later point
1025
1026 (1) Any concurrent mounter managing to grab a
1027 superblock is made to wait until the supe
1028 the superblock and all devices are shutdo
1029 superblock is ready the caller will simpl
1030
1031 (2) If the mounter comes after deactivate_loc
1032 the superblock has been removed from the
1033 filesystem type the mounter is made to wa
1034 devices are shut down in ->kill_sb() and
1035 list of superblocks of the filesystem typ
1036 superblock and grab ownership of the bloc
1037 the block device will be set to the newly
1038
1039 (3) This case is now collapsed into (2) as th
1040 of superblocks of the filesystem type unt
1041 ->kill_sb(). In other words, if the super
1042 superblock of the filesystem type anymore
1043 all associated block devices (the bd_hold
1044
1045 As this is a VFS level change it has no pract
1046 other than that all of them must use one of t
1047 kill_anon_super(), or kill_block_super() help
1048
1049 ---
1050
1051 **mandatory**
1052
1053 Lock ordering has been changed so that s_umou
1054 All places where s_umount was taken under ope
1055
1056 ---
1057
1058 **mandatory**
1059
1060 export_operations ->encode_fh() no longer has
1061 encode FILEID_INO32_GEN* file handles.
1062 Filesystems that used the default implementat
1063 generic_encode_ino32_fh() explicitly.
1064
1065 ---
1066
1067 **mandatory**
1068
1069 If ->rename() update of .. on cross-directory
1070 directory modifications, do *not* lock the su
1071 ->rename() - it's done by the caller now [tha
1072 28eceeda130f "fs: Lock moved directories"].
1073
1074 ---
1075
1076 **mandatory**
1077
1078 On same-directory ->rename() the (tautologica
1079 by any locks; just don't do it if the old par
1080 We really can't lock two subdirectories in sa
1081 deadlocks.
1082
1083 ---
1084
1085 **mandatory**
1086
1087 lock_rename() and lock_rename_child() may fai
1088 their arguments do not have a common ancestor
1089 is returned, with no locks taken. In-tree us
1090 would need to do so.
1091
1092 ---
1093
1094 **mandatory**
1095
1096 The list of children anchored in parent dentr
1097 Field names got changed (->d_children/->d_sib
1098 for anchor/entries resp.), so any affected pl
1099 by compiler.
1100
1101 ---
1102
1103 **mandatory**
1104
1105 ->d_delete() instances are now called for den
1106 and refcount equal to 0. They are not permit
1107 None of in-tree instances did anything of tha
1108
1109 ---
1110
1111 **mandatory**
1112
1113 ->d_prune() instances are now called without
1114 ->d_lock on dentry itself is still held; if y
1115 of the in-tree instances did), use your own s
1116
1117 ->d_iput() and ->d_release() are called with
1118 list of parent's children. It is still unhas
1119 removed from parent's ->d_children yet.
1120
1121 Anyone iterating through the list of children
1122 half-killed dentries that might be seen there
1123 see them negative, unhashed and with negative
1124 of the in-kernel users would've done the righ
1125
1126 ---
1127
1128 **recommended**
1129
1130 Block device freezing and thawing have been m
1131
1132 Before this change, get_active_super() would
1133 superblock of the main block device, i.e., th
1134 device freezing now works for any block devic
1135 just the main block device. The get_active_su
1136 pointer are gone.
1137
1138 ---
1139
1140 **mandatory**
1141
1142 set_blocksize() takes opened struct file inst
1143 and it *must* be opened exclusive.
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