blob: 37c10cba717725f599ec999eb0a0a4ff6b1fc483 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001 The text below describes the locking rules for VFS-related methods.
2It is (believed to be) up-to-date. *Please*, if you change anything in
3prototypes or locking protocols - update this file. And update the relevant
4instances in the tree, don't leave that to maintainers of filesystems/devices/
5etc. At the very least, put the list of dubious cases in the end of this file.
6Don't turn it into log - maintainers of out-of-the-tree code are supposed to
7be able to use diff(1).
8 Thing currently missing here: socket operations. Alexey?
9
10--------------------------- dentry_operations --------------------------
11prototypes:
12 int (*d_revalidate)(struct dentry *, int);
13 int (*d_hash) (struct dentry *, struct qstr *);
14 int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
15 int (*d_delete)(struct dentry *);
16 void (*d_release)(struct dentry *);
17 void (*d_iput)(struct dentry *, struct inode *);
Eric Dumazetc23fbb62007-05-08 00:26:18 -070018 char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
Linus Torvalds1da177e2005-04-16 15:20:36 -070019
20locking rules:
21 none have BKL
22 dcache_lock rename_lock ->d_lock may block
23d_revalidate: no no no yes
24d_hash no no no yes
25d_compare: no yes no no
26d_delete: yes no yes no
27d_release: no no no yes
28d_iput: no no no yes
Eric Dumazetc23fbb62007-05-08 00:26:18 -070029d_dname: no no no no
Linus Torvalds1da177e2005-04-16 15:20:36 -070030
31--------------------------- inode_operations ---------------------------
32prototypes:
33 int (*create) (struct inode *,struct dentry *,int, struct nameidata *);
34 struct dentry * (*lookup) (struct inode *,struct dentry *, struct nameid
35ata *);
36 int (*link) (struct dentry *,struct inode *,struct dentry *);
37 int (*unlink) (struct inode *,struct dentry *);
38 int (*symlink) (struct inode *,struct dentry *,const char *);
39 int (*mkdir) (struct inode *,struct dentry *,int);
40 int (*rmdir) (struct inode *,struct dentry *);
41 int (*mknod) (struct inode *,struct dentry *,int,dev_t);
42 int (*rename) (struct inode *, struct dentry *,
43 struct inode *, struct dentry *);
44 int (*readlink) (struct dentry *, char __user *,int);
45 int (*follow_link) (struct dentry *, struct nameidata *);
46 void (*truncate) (struct inode *);
47 int (*permission) (struct inode *, int, struct nameidata *);
48 int (*setattr) (struct dentry *, struct iattr *);
49 int (*getattr) (struct vfsmount *, struct dentry *, struct kstat *);
50 int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);
51 ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
52 ssize_t (*listxattr) (struct dentry *, char *, size_t);
53 int (*removexattr) (struct dentry *, const char *);
54
55locking rules:
56 all may block, none have BKL
Artem Bityutskiya7bc02f2007-05-09 07:53:16 +020057 i_mutex(inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -070058lookup: yes
59create: yes
60link: yes (both)
61mknod: yes
62symlink: yes
63mkdir: yes
64unlink: yes (both)
65rmdir: yes (both) (see below)
66rename: yes (all) (see below)
67readlink: no
68follow_link: no
69truncate: yes (see below)
70setattr: yes
71permission: no
72getattr: no
73setxattr: yes
74getxattr: no
75listxattr: no
76removexattr: yes
Artem Bityutskiya7bc02f2007-05-09 07:53:16 +020077 Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
Linus Torvalds1da177e2005-04-16 15:20:36 -070078victim.
79 cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
80 ->truncate() is never called directly - it's a callback, not a
81method. It's called by vmtruncate() - library function normally used by
82->setattr(). Locking information above applies to that call (i.e. is
83inherited from ->setattr() - vmtruncate() is used when ATTR_SIZE had been
84passed).
85
86See Documentation/filesystems/directory-locking for more detailed discussion
87of the locking scheme for directory operations.
88
89--------------------------- super_operations ---------------------------
90prototypes:
91 struct inode *(*alloc_inode)(struct super_block *sb);
92 void (*destroy_inode)(struct inode *);
93 void (*read_inode) (struct inode *);
94 void (*dirty_inode) (struct inode *);
95 int (*write_inode) (struct inode *, int);
96 void (*put_inode) (struct inode *);
97 void (*drop_inode) (struct inode *);
98 void (*delete_inode) (struct inode *);
99 void (*put_super) (struct super_block *);
100 void (*write_super) (struct super_block *);
101 int (*sync_fs)(struct super_block *sb, int wait);
102 void (*write_super_lockfs) (struct super_block *);
103 void (*unlockfs) (struct super_block *);
David Howells726c3342006-06-23 02:02:58 -0700104 int (*statfs) (struct dentry *, struct kstatfs *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 int (*remount_fs) (struct super_block *, int *, char *);
106 void (*clear_inode) (struct inode *);
107 void (*umount_begin) (struct super_block *);
108 int (*show_options)(struct seq_file *, struct vfsmount *);
109 ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
110 ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
111
112locking rules:
113 All may block.
114 BKL s_lock s_umount
115alloc_inode: no no no
116destroy_inode: no
117read_inode: no (see below)
118dirty_inode: no (must not sleep)
119write_inode: no
120put_inode: no
121drop_inode: no !!!inode_lock!!!
122delete_inode: no
123put_super: yes yes no
124write_super: no yes read
125sync_fs: no no read
126write_super_lockfs: ?
127unlockfs: ?
128statfs: no no no
Vasily Averin70888bd2006-12-06 20:37:23 -0800129remount_fs: yes yes maybe (see below)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130clear_inode: no
131umount_begin: yes no no
132show_options: no (vfsmount->sem)
133quota_read: no no no (see below)
134quota_write: no no no (see below)
135
136->read_inode() is not a method - it's a callback used in iget().
137->remount_fs() will have the s_umount lock if it's already mounted.
138When called from get_sb_single, it does NOT have the s_umount lock.
139->quota_read() and ->quota_write() functions are both guaranteed to
140be the only ones operating on the quota file by the quota code (via
141dqio_sem) (unless an admin really wants to screw up something and
142writes to quota files with quotas on). For other details about locking
143see also dquot_operations section.
144
145--------------------------- file_system_type ---------------------------
146prototypes:
Jonathan Corbet5d8b2eb2006-07-10 04:44:07 -0700147 int (*get_sb) (struct file_system_type *, int,
148 const char *, void *, struct vfsmount *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 void (*kill_sb) (struct super_block *);
150locking rules:
151 may block BKL
152get_sb yes yes
153kill_sb yes yes
154
David Howells454e2392006-06-23 02:02:57 -0700155->get_sb() returns error or 0 with locked superblock attached to the vfsmount
156(exclusive on ->s_umount).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157->kill_sb() takes a write-locked superblock, does all shutdown work on it,
158unlocks and drops the reference.
159
160--------------------------- address_space_operations --------------------------
161prototypes:
162 int (*writepage)(struct page *page, struct writeback_control *wbc);
163 int (*readpage)(struct file *, struct page *);
164 int (*sync_page)(struct page *);
165 int (*writepages)(struct address_space *, struct writeback_control *);
166 int (*set_page_dirty)(struct page *page);
167 int (*readpages)(struct file *filp, struct address_space *mapping,
168 struct list_head *pages, unsigned nr_pages);
169 int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
170 int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
171 sector_t (*bmap)(struct address_space *, sector_t);
172 int (*invalidatepage) (struct page *, unsigned long);
173 int (*releasepage) (struct page *, int);
174 int (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
175 loff_t offset, unsigned long nr_segs);
Trond Myklebuste3db7692007-01-10 23:15:39 -0800176 int (*launder_page) (struct page *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177
178locking rules:
179 All except set_page_dirty may block
180
Nick Pigginafddba42007-10-16 01:25:01 -0700181 BKL PageLocked(page) i_sem
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182writepage: no yes, unlocks (see below)
183readpage: no yes, unlocks
184sync_page: no maybe
185writepages: no
186set_page_dirty no no
187readpages: no
Nick Pigginafddba42007-10-16 01:25:01 -0700188prepare_write: no yes yes
189commit_write: no yes yes
190write_begin: no locks the page yes
191write_end: no yes, unlocks yes
192perform_write: no n/a yes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193bmap: yes
194invalidatepage: no yes
195releasepage: no yes
196direct_IO: no
Trond Myklebuste3db7692007-01-10 23:15:39 -0800197launder_page: no yes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
199 ->prepare_write(), ->commit_write(), ->sync_page() and ->readpage()
200may be called from the request handler (/dev/loop).
201
202 ->readpage() unlocks the page, either synchronously or via I/O
203completion.
204
205 ->readpages() populates the pagecache with the passed pages and starts
206I/O against them. They come unlocked upon I/O completion.
207
208 ->writepage() is used for two purposes: for "memory cleansing" and for
209"sync". These are quite different operations and the behaviour may differ
210depending upon the mode.
211
212If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then
213it *must* start I/O against the page, even if that would involve
214blocking on in-progress I/O.
215
216If writepage is called for memory cleansing (sync_mode ==
217WBC_SYNC_NONE) then its role is to get as much writeout underway as
218possible. So writepage should try to avoid blocking against
219currently-in-progress I/O.
220
221If the filesystem is not called for "sync" and it determines that it
222would need to block against in-progress I/O to be able to start new I/O
223against the page the filesystem should redirty the page with
224redirty_page_for_writepage(), then unlock the page and return zero.
225This may also be done to avoid internal deadlocks, but rarely.
226
Robert P. J. Day3a4fa0a2007-10-19 23:10:43 +0200227If the filesystem is called for sync then it must wait on any
Linus Torvalds1da177e2005-04-16 15:20:36 -0700228in-progress I/O and then start new I/O.
229
Nikita Danilov20546062005-05-01 08:58:37 -0700230The filesystem should unlock the page synchronously, before returning to the
231caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE
232value. WRITEPAGE_ACTIVATE means that page cannot really be written out
233currently, and VM should stop calling ->writepage() on this page for some
234time. VM does this by moving page to the head of the active list, hence the
235name.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236
237Unless the filesystem is going to redirty_page_for_writepage(), unlock the page
238and return zero, writepage *must* run set_page_writeback() against the page,
239followed by unlocking it. Once set_page_writeback() has been run against the
240page, write I/O can be submitted and the write I/O completion handler must run
241end_page_writeback() once the I/O is complete. If no I/O is submitted, the
242filesystem must run end_page_writeback() against the page before returning from
243writepage.
244
245That is: after 2.5.12, pages which are under writeout are *not* locked. Note,
246if the filesystem needs the page to be locked during writeout, that is ok, too,
247the page is allowed to be unlocked at any point in time between the calls to
248set_page_writeback() and end_page_writeback().
249
250Note, failure to run either redirty_page_for_writepage() or the combination of
251set_page_writeback()/end_page_writeback() on a page submitted to writepage
252will leave the page itself marked clean but it will be tagged as dirty in the
253radix tree. This incoherency can lead to all sorts of hard-to-debug problems
254in the filesystem like having dirty inodes at umount and losing written data.
255
256 ->sync_page() locking rules are not well-defined - usually it is called
257with lock on page, but that is not guaranteed. Considering the currently
258existing instances of this method ->sync_page() itself doesn't look
259well-defined...
260
261 ->writepages() is used for periodic writeback and for syscall-initiated
262sync operations. The address_space should start I/O against at least
263*nr_to_write pages. *nr_to_write must be decremented for each page which is
264written. The address_space implementation may write more (or less) pages
265than *nr_to_write asks for, but it should try to be reasonably close. If
266nr_to_write is NULL, all dirty pages must be written.
267
268writepages should _only_ write pages which are present on
269mapping->io_pages.
270
271 ->set_page_dirty() is called from various places in the kernel
272when the target page is marked as needing writeback. It may be called
273under spinlock (it cannot block) and is sometimes called with the page
274not locked.
275
276 ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some
277filesystems and by the swapper. The latter will eventually go away. All
278instances do not actually need the BKL. Please, keep it that way and don't
279breed new callers.
280
281 ->invalidatepage() is called when the filesystem must attempt to drop
282some or all of the buffers from the page when it is being truncated. It
283returns zero on success. If ->invalidatepage is zero, the kernel uses
284block_invalidatepage() instead.
285
286 ->releasepage() is called when the kernel is about to try to drop the
287buffers from the page in preparation for freeing it. It returns zero to
288indicate that the buffers are (or may be) freeable. If ->releasepage is zero,
289the kernel assumes that the fs has no private interest in the buffers.
290
Trond Myklebuste3db7692007-01-10 23:15:39 -0800291 ->launder_page() may be called prior to releasing a page if
292it is still found to be dirty. It returns zero if the page was successfully
293cleaned, or an error value if not. Note that in order to prevent the page
294getting mapped back in and redirtied, it needs to be kept locked
295across the entire operation.
296
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 Note: currently almost all instances of address_space methods are
298using BKL for internal serialization and that's one of the worst sources
299of contention. Normally they are calling library functions (in fs/buffer.c)
300and pass foo_get_block() as a callback (on local block-based filesystems,
301indeed). BKL is not needed for library stuff and is usually taken by
302foo_get_block(). It's an overkill, since block bitmaps can be protected by
303internal fs locking and real critical areas are much smaller than the areas
304filesystems protect now.
305
306----------------------- file_lock_operations ------------------------------
307prototypes:
308 void (*fl_insert)(struct file_lock *); /* lock insertion callback */
309 void (*fl_remove)(struct file_lock *); /* lock removal callback */
310 void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
311 void (*fl_release_private)(struct file_lock *);
312
313
314locking rules:
315 BKL may block
316fl_insert: yes no
317fl_remove: yes no
318fl_copy_lock: yes no
319fl_release_private: yes yes
320
321----------------------- lock_manager_operations ---------------------------
322prototypes:
323 int (*fl_compare_owner)(struct file_lock *, struct file_lock *);
324 void (*fl_notify)(struct file_lock *); /* unblock callback */
325 void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
326 void (*fl_release_private)(struct file_lock *);
327 void (*fl_break)(struct file_lock *); /* break_lease callback */
328
329locking rules:
330 BKL may block
331fl_compare_owner: yes no
332fl_notify: yes no
333fl_copy_lock: yes no
334fl_release_private: yes yes
335fl_break: yes no
336
337 Currently only NFSD and NLM provide instances of this class. None of the
338them block. If you have out-of-tree instances - please, show up. Locking
339in that area will change.
340--------------------------- buffer_head -----------------------------------
341prototypes:
342 void (*b_end_io)(struct buffer_head *bh, int uptodate);
343
344locking rules:
345 called from interrupts. In other words, extreme care is needed here.
346bh is locked, but that's all warranties we have here. Currently only RAID1,
347highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices
348call this method upon the IO completion.
349
350--------------------------- block_device_operations -----------------------
351prototypes:
352 int (*open) (struct inode *, struct file *);
353 int (*release) (struct inode *, struct file *);
354 int (*ioctl) (struct inode *, struct file *, unsigned, unsigned long);
355 int (*media_changed) (struct gendisk *);
356 int (*revalidate_disk) (struct gendisk *);
357
358locking rules:
359 BKL bd_sem
360open: yes yes
361release: yes yes
362ioctl: yes no
363media_changed: no no
364revalidate_disk: no no
365
366The last two are called only from check_disk_change().
367
368--------------------------- file_operations -------------------------------
369prototypes:
370 loff_t (*llseek) (struct file *, loff_t, int);
371 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
Badari Pulavarty027445c2006-09-30 23:28:46 -0700373 ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
374 ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 int (*readdir) (struct file *, void *, filldir_t);
376 unsigned int (*poll) (struct file *, struct poll_table_struct *);
377 int (*ioctl) (struct inode *, struct file *, unsigned int,
378 unsigned long);
379 long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
380 long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
381 int (*mmap) (struct file *, struct vm_area_struct *);
382 int (*open) (struct inode *, struct file *);
383 int (*flush) (struct file *);
384 int (*release) (struct inode *, struct file *);
385 int (*fsync) (struct file *, struct dentry *, int datasync);
386 int (*aio_fsync) (struct kiocb *, int datasync);
387 int (*fasync) (int, struct file *, int);
388 int (*lock) (struct file *, int, struct file_lock *);
389 ssize_t (*readv) (struct file *, const struct iovec *, unsigned long,
390 loff_t *);
391 ssize_t (*writev) (struct file *, const struct iovec *, unsigned long,
392 loff_t *);
393 ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t,
394 void __user *);
395 ssize_t (*sendpage) (struct file *, struct page *, int, size_t,
396 loff_t *, int);
397 unsigned long (*get_unmapped_area)(struct file *, unsigned long,
398 unsigned long, unsigned long, unsigned long);
399 int (*check_flags)(int);
400 int (*dir_notify)(struct file *, unsigned long);
401};
402
403locking rules:
404 All except ->poll() may block.
405 BKL
406llseek: no (see below)
407read: no
408aio_read: no
409write: no
410aio_write: no
411readdir: no
412poll: no
413ioctl: yes (see below)
414unlocked_ioctl: no (see below)
415compat_ioctl: no
416mmap: no
417open: maybe (see below)
418flush: no
419release: no
420fsync: no (see below)
421aio_fsync: no
422fasync: yes (see below)
423lock: yes
424readv: no
425writev: no
426sendfile: no
427sendpage: no
428get_unmapped_area: no
429check_flags: no
430dir_notify: no
431
432->llseek() locking has moved from llseek to the individual llseek
433implementations. If your fs is not using generic_file_llseek, you
434need to acquire and release the appropriate locks in your ->llseek().
435For many filesystems, it is probably safe to acquire the inode
436semaphore. Note some filesystems (i.e. remote ones) provide no
437protection for i_size so you will need to use the BKL.
438
439->open() locking is in-transit: big lock partially moved into the methods.
440The only exception is ->open() in the instances of file_operations that never
441end up in ->i_fop/->proc_fops, i.e. ones that belong to character devices
442(chrdev_open() takes lock before replacing ->f_op and calling the secondary
443method. As soon as we fix the handling of module reference counters all
444instances of ->open() will be called without the BKL.
445
446Note: ext2_release() was *the* source of contention on fs-intensive
447loads and dropping BKL on ->release() helps to get rid of that (we still
448grab BKL for cases when we close a file that had been opened r/w, but that
449can and should be done using the internal locking with smaller critical areas).
450Current worst offender is ext2_get_block()...
451
452->fasync() is a mess. This area needs a big cleanup and that will probably
453affect locking.
454
455->readdir() and ->ioctl() on directories must be changed. Ideally we would
456move ->readdir() to inode_operations and use a separate method for directory
457->ioctl() or kill the latter completely. One of the problems is that for
458anything that resembles union-mount we won't have a struct file for all
459components. And there are other reasons why the current interface is a mess...
460
461->ioctl() on regular files is superceded by the ->unlocked_ioctl() that
462doesn't take the BKL.
463
464->read on directories probably must go away - we should just enforce -EISDIR
465in sys_read() and friends.
466
Artem Bityutskiya7bc02f2007-05-09 07:53:16 +0200467->fsync() has i_mutex on inode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468
469--------------------------- dquot_operations -------------------------------
470prototypes:
471 int (*initialize) (struct inode *, int);
472 int (*drop) (struct inode *);
473 int (*alloc_space) (struct inode *, qsize_t, int);
474 int (*alloc_inode) (const struct inode *, unsigned long);
475 int (*free_space) (struct inode *, qsize_t);
476 int (*free_inode) (const struct inode *, unsigned long);
477 int (*transfer) (struct inode *, struct iattr *);
478 int (*write_dquot) (struct dquot *);
479 int (*acquire_dquot) (struct dquot *);
480 int (*release_dquot) (struct dquot *);
481 int (*mark_dirty) (struct dquot *);
482 int (*write_info) (struct super_block *, int);
483
484These operations are intended to be more or less wrapping functions that ensure
485a proper locking wrt the filesystem and call the generic quota operations.
486
487What filesystem should expect from the generic quota functions:
488
489 FS recursion Held locks when called
490initialize: yes maybe dqonoff_sem
491drop: yes -
492alloc_space: ->mark_dirty() -
493alloc_inode: ->mark_dirty() -
494free_space: ->mark_dirty() -
495free_inode: ->mark_dirty() -
496transfer: yes -
497write_dquot: yes dqonoff_sem or dqptr_sem
498acquire_dquot: yes dqonoff_sem or dqptr_sem
499release_dquot: yes dqonoff_sem or dqptr_sem
500mark_dirty: no -
501write_info: yes dqonoff_sem
502
503FS recursion means calling ->quota_read() and ->quota_write() from superblock
504operations.
505
506->alloc_space(), ->alloc_inode(), ->free_space(), ->free_inode() are called
507only directly by the filesystem and do not call any fs functions only
508the ->mark_dirty() operation.
509
510More details about quota locking can be found in fs/dquot.c.
511
512--------------------------- vm_operations_struct -----------------------------
513prototypes:
514 void (*open)(struct vm_area_struct*);
515 void (*close)(struct vm_area_struct*);
Nick Piggind0217ac2007-07-19 01:47:03 -0700516 int (*fault)(struct vm_area_struct*, struct vm_fault *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 struct page *(*nopage)(struct vm_area_struct*, unsigned long, int *);
Mark Fashehed2f2f92007-07-19 01:47:01 -0700518 int (*page_mkwrite)(struct vm_area_struct *, struct page *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519
520locking rules:
Mark Fashehed2f2f92007-07-19 01:47:01 -0700521 BKL mmap_sem PageLocked(page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522open: no yes
523close: no yes
Nick Piggin54cb8822007-07-19 01:46:59 -0700524fault: no yes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525nopage: no yes
Mark Fashehed2f2f92007-07-19 01:47:01 -0700526page_mkwrite: no yes no
527
528 ->page_mkwrite() is called when a previously read-only page is
529about to become writeable. The file system is responsible for
530protecting against truncate races. Once appropriate action has been
531taking to lock out truncate, the page range should be verified to be
532within i_size. The page mapping should also be checked that it is not
533NULL.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534
535================================================================================
536 Dubious stuff
537
538(if you break something or notice that it is broken and do not fix it yourself
539- at least put it here)
540
541ipc/shm.c::shm_delete() - may need BKL.
542->read() and ->write() in many drivers are (probably) missing BKL.
543drivers/sgi/char/graphics.c::sgi_graphics_nopage() - may need BKL.