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1da177e4 LT |
1 | The text below describes the locking rules for VFS-related methods. |
2 | It is (believed to be) up-to-date. *Please*, if you change anything in | |
3 | prototypes or locking protocols - update this file. And update the relevant | |
4 | instances in the tree, don't leave that to maintainers of filesystems/devices/ | |
5 | etc. At the very least, put the list of dubious cases in the end of this file. | |
6 | Don't turn it into log - maintainers of out-of-the-tree code are supposed to | |
7 | be able to use diff(1). | |
8 | Thing currently missing here: socket operations. Alexey? | |
9 | ||
10 | --------------------------- dentry_operations -------------------------- | |
11 | prototypes: | |
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 *); | |
18 | ||
19 | locking rules: | |
20 | none have BKL | |
21 | dcache_lock rename_lock ->d_lock may block | |
22 | d_revalidate: no no no yes | |
23 | d_hash no no no yes | |
24 | d_compare: no yes no no | |
25 | d_delete: yes no yes no | |
26 | d_release: no no no yes | |
27 | d_iput: no no no yes | |
28 | ||
29 | --------------------------- inode_operations --------------------------- | |
30 | prototypes: | |
31 | int (*create) (struct inode *,struct dentry *,int, struct nameidata *); | |
32 | struct dentry * (*lookup) (struct inode *,struct dentry *, struct nameid | |
33 | ata *); | |
34 | int (*link) (struct dentry *,struct inode *,struct dentry *); | |
35 | int (*unlink) (struct inode *,struct dentry *); | |
36 | int (*symlink) (struct inode *,struct dentry *,const char *); | |
37 | int (*mkdir) (struct inode *,struct dentry *,int); | |
38 | int (*rmdir) (struct inode *,struct dentry *); | |
39 | int (*mknod) (struct inode *,struct dentry *,int,dev_t); | |
40 | int (*rename) (struct inode *, struct dentry *, | |
41 | struct inode *, struct dentry *); | |
42 | int (*readlink) (struct dentry *, char __user *,int); | |
43 | int (*follow_link) (struct dentry *, struct nameidata *); | |
44 | void (*truncate) (struct inode *); | |
45 | int (*permission) (struct inode *, int, struct nameidata *); | |
46 | int (*setattr) (struct dentry *, struct iattr *); | |
47 | int (*getattr) (struct vfsmount *, struct dentry *, struct kstat *); | |
48 | int (*setxattr) (struct dentry *, const char *,const void *,size_t,int); | |
49 | ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t); | |
50 | ssize_t (*listxattr) (struct dentry *, char *, size_t); | |
51 | int (*removexattr) (struct dentry *, const char *); | |
52 | ||
53 | locking rules: | |
54 | all may block, none have BKL | |
55 | i_sem(inode) | |
56 | lookup: yes | |
57 | create: yes | |
58 | link: yes (both) | |
59 | mknod: yes | |
60 | symlink: yes | |
61 | mkdir: yes | |
62 | unlink: yes (both) | |
63 | rmdir: yes (both) (see below) | |
64 | rename: yes (all) (see below) | |
65 | readlink: no | |
66 | follow_link: no | |
67 | truncate: yes (see below) | |
68 | setattr: yes | |
69 | permission: no | |
70 | getattr: no | |
71 | setxattr: yes | |
72 | getxattr: no | |
73 | listxattr: no | |
74 | removexattr: yes | |
75 | Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_sem on | |
76 | victim. | |
77 | cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. | |
78 | ->truncate() is never called directly - it's a callback, not a | |
79 | method. It's called by vmtruncate() - library function normally used by | |
80 | ->setattr(). Locking information above applies to that call (i.e. is | |
81 | inherited from ->setattr() - vmtruncate() is used when ATTR_SIZE had been | |
82 | passed). | |
83 | ||
84 | See Documentation/filesystems/directory-locking for more detailed discussion | |
85 | of the locking scheme for directory operations. | |
86 | ||
87 | --------------------------- super_operations --------------------------- | |
88 | prototypes: | |
89 | struct inode *(*alloc_inode)(struct super_block *sb); | |
90 | void (*destroy_inode)(struct inode *); | |
91 | void (*read_inode) (struct inode *); | |
92 | void (*dirty_inode) (struct inode *); | |
93 | int (*write_inode) (struct inode *, int); | |
94 | void (*put_inode) (struct inode *); | |
95 | void (*drop_inode) (struct inode *); | |
96 | void (*delete_inode) (struct inode *); | |
97 | void (*put_super) (struct super_block *); | |
98 | void (*write_super) (struct super_block *); | |
99 | int (*sync_fs)(struct super_block *sb, int wait); | |
100 | void (*write_super_lockfs) (struct super_block *); | |
101 | void (*unlockfs) (struct super_block *); | |
102 | int (*statfs) (struct super_block *, struct kstatfs *); | |
103 | int (*remount_fs) (struct super_block *, int *, char *); | |
104 | void (*clear_inode) (struct inode *); | |
105 | void (*umount_begin) (struct super_block *); | |
106 | int (*show_options)(struct seq_file *, struct vfsmount *); | |
107 | ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t); | |
108 | ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t); | |
109 | ||
110 | locking rules: | |
111 | All may block. | |
112 | BKL s_lock s_umount | |
113 | alloc_inode: no no no | |
114 | destroy_inode: no | |
115 | read_inode: no (see below) | |
116 | dirty_inode: no (must not sleep) | |
117 | write_inode: no | |
118 | put_inode: no | |
119 | drop_inode: no !!!inode_lock!!! | |
120 | delete_inode: no | |
121 | put_super: yes yes no | |
122 | write_super: no yes read | |
123 | sync_fs: no no read | |
124 | write_super_lockfs: ? | |
125 | unlockfs: ? | |
126 | statfs: no no no | |
127 | remount_fs: no yes maybe (see below) | |
128 | clear_inode: no | |
129 | umount_begin: yes no no | |
130 | show_options: no (vfsmount->sem) | |
131 | quota_read: no no no (see below) | |
132 | quota_write: no no no (see below) | |
133 | ||
134 | ->read_inode() is not a method - it's a callback used in iget(). | |
135 | ->remount_fs() will have the s_umount lock if it's already mounted. | |
136 | When called from get_sb_single, it does NOT have the s_umount lock. | |
137 | ->quota_read() and ->quota_write() functions are both guaranteed to | |
138 | be the only ones operating on the quota file by the quota code (via | |
139 | dqio_sem) (unless an admin really wants to screw up something and | |
140 | writes to quota files with quotas on). For other details about locking | |
141 | see also dquot_operations section. | |
142 | ||
143 | --------------------------- file_system_type --------------------------- | |
144 | prototypes: | |
145 | struct super_block *(*get_sb) (struct file_system_type *, int, | |
146 | const char *, void *); | |
147 | void (*kill_sb) (struct super_block *); | |
148 | locking rules: | |
149 | may block BKL | |
150 | get_sb yes yes | |
151 | kill_sb yes yes | |
152 | ||
153 | ->get_sb() returns error or a locked superblock (exclusive on ->s_umount). | |
154 | ->kill_sb() takes a write-locked superblock, does all shutdown work on it, | |
155 | unlocks and drops the reference. | |
156 | ||
157 | --------------------------- address_space_operations -------------------------- | |
158 | prototypes: | |
159 | int (*writepage)(struct page *page, struct writeback_control *wbc); | |
160 | int (*readpage)(struct file *, struct page *); | |
161 | int (*sync_page)(struct page *); | |
162 | int (*writepages)(struct address_space *, struct writeback_control *); | |
163 | int (*set_page_dirty)(struct page *page); | |
164 | int (*readpages)(struct file *filp, struct address_space *mapping, | |
165 | struct list_head *pages, unsigned nr_pages); | |
166 | int (*prepare_write)(struct file *, struct page *, unsigned, unsigned); | |
167 | int (*commit_write)(struct file *, struct page *, unsigned, unsigned); | |
168 | sector_t (*bmap)(struct address_space *, sector_t); | |
169 | int (*invalidatepage) (struct page *, unsigned long); | |
170 | int (*releasepage) (struct page *, int); | |
171 | int (*direct_IO)(int, struct kiocb *, const struct iovec *iov, | |
172 | loff_t offset, unsigned long nr_segs); | |
173 | ||
174 | locking rules: | |
175 | All except set_page_dirty may block | |
176 | ||
177 | BKL PageLocked(page) | |
178 | writepage: no yes, unlocks (see below) | |
179 | readpage: no yes, unlocks | |
180 | sync_page: no maybe | |
181 | writepages: no | |
182 | set_page_dirty no no | |
183 | readpages: no | |
184 | prepare_write: no yes | |
185 | commit_write: no yes | |
186 | bmap: yes | |
187 | invalidatepage: no yes | |
188 | releasepage: no yes | |
189 | direct_IO: no | |
190 | ||
191 | ->prepare_write(), ->commit_write(), ->sync_page() and ->readpage() | |
192 | may be called from the request handler (/dev/loop). | |
193 | ||
194 | ->readpage() unlocks the page, either synchronously or via I/O | |
195 | completion. | |
196 | ||
197 | ->readpages() populates the pagecache with the passed pages and starts | |
198 | I/O against them. They come unlocked upon I/O completion. | |
199 | ||
200 | ->writepage() is used for two purposes: for "memory cleansing" and for | |
201 | "sync". These are quite different operations and the behaviour may differ | |
202 | depending upon the mode. | |
203 | ||
204 | If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then | |
205 | it *must* start I/O against the page, even if that would involve | |
206 | blocking on in-progress I/O. | |
207 | ||
208 | If writepage is called for memory cleansing (sync_mode == | |
209 | WBC_SYNC_NONE) then its role is to get as much writeout underway as | |
210 | possible. So writepage should try to avoid blocking against | |
211 | currently-in-progress I/O. | |
212 | ||
213 | If the filesystem is not called for "sync" and it determines that it | |
214 | would need to block against in-progress I/O to be able to start new I/O | |
215 | against the page the filesystem should redirty the page with | |
216 | redirty_page_for_writepage(), then unlock the page and return zero. | |
217 | This may also be done to avoid internal deadlocks, but rarely. | |
218 | ||
219 | If the filesytem is called for sync then it must wait on any | |
220 | in-progress I/O and then start new I/O. | |
221 | ||
2054606a ND |
222 | The filesystem should unlock the page synchronously, before returning to the |
223 | caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE | |
224 | value. WRITEPAGE_ACTIVATE means that page cannot really be written out | |
225 | currently, and VM should stop calling ->writepage() on this page for some | |
226 | time. VM does this by moving page to the head of the active list, hence the | |
227 | name. | |
1da177e4 LT |
228 | |
229 | Unless the filesystem is going to redirty_page_for_writepage(), unlock the page | |
230 | and return zero, writepage *must* run set_page_writeback() against the page, | |
231 | followed by unlocking it. Once set_page_writeback() has been run against the | |
232 | page, write I/O can be submitted and the write I/O completion handler must run | |
233 | end_page_writeback() once the I/O is complete. If no I/O is submitted, the | |
234 | filesystem must run end_page_writeback() against the page before returning from | |
235 | writepage. | |
236 | ||
237 | That is: after 2.5.12, pages which are under writeout are *not* locked. Note, | |
238 | if the filesystem needs the page to be locked during writeout, that is ok, too, | |
239 | the page is allowed to be unlocked at any point in time between the calls to | |
240 | set_page_writeback() and end_page_writeback(). | |
241 | ||
242 | Note, failure to run either redirty_page_for_writepage() or the combination of | |
243 | set_page_writeback()/end_page_writeback() on a page submitted to writepage | |
244 | will leave the page itself marked clean but it will be tagged as dirty in the | |
245 | radix tree. This incoherency can lead to all sorts of hard-to-debug problems | |
246 | in the filesystem like having dirty inodes at umount and losing written data. | |
247 | ||
248 | ->sync_page() locking rules are not well-defined - usually it is called | |
249 | with lock on page, but that is not guaranteed. Considering the currently | |
250 | existing instances of this method ->sync_page() itself doesn't look | |
251 | well-defined... | |
252 | ||
253 | ->writepages() is used for periodic writeback and for syscall-initiated | |
254 | sync operations. The address_space should start I/O against at least | |
255 | *nr_to_write pages. *nr_to_write must be decremented for each page which is | |
256 | written. The address_space implementation may write more (or less) pages | |
257 | than *nr_to_write asks for, but it should try to be reasonably close. If | |
258 | nr_to_write is NULL, all dirty pages must be written. | |
259 | ||
260 | writepages should _only_ write pages which are present on | |
261 | mapping->io_pages. | |
262 | ||
263 | ->set_page_dirty() is called from various places in the kernel | |
264 | when the target page is marked as needing writeback. It may be called | |
265 | under spinlock (it cannot block) and is sometimes called with the page | |
266 | not locked. | |
267 | ||
268 | ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some | |
269 | filesystems and by the swapper. The latter will eventually go away. All | |
270 | instances do not actually need the BKL. Please, keep it that way and don't | |
271 | breed new callers. | |
272 | ||
273 | ->invalidatepage() is called when the filesystem must attempt to drop | |
274 | some or all of the buffers from the page when it is being truncated. It | |
275 | returns zero on success. If ->invalidatepage is zero, the kernel uses | |
276 | block_invalidatepage() instead. | |
277 | ||
278 | ->releasepage() is called when the kernel is about to try to drop the | |
279 | buffers from the page in preparation for freeing it. It returns zero to | |
280 | indicate that the buffers are (or may be) freeable. If ->releasepage is zero, | |
281 | the kernel assumes that the fs has no private interest in the buffers. | |
282 | ||
283 | Note: currently almost all instances of address_space methods are | |
284 | using BKL for internal serialization and that's one of the worst sources | |
285 | of contention. Normally they are calling library functions (in fs/buffer.c) | |
286 | and pass foo_get_block() as a callback (on local block-based filesystems, | |
287 | indeed). BKL is not needed for library stuff and is usually taken by | |
288 | foo_get_block(). It's an overkill, since block bitmaps can be protected by | |
289 | internal fs locking and real critical areas are much smaller than the areas | |
290 | filesystems protect now. | |
291 | ||
292 | ----------------------- file_lock_operations ------------------------------ | |
293 | prototypes: | |
294 | void (*fl_insert)(struct file_lock *); /* lock insertion callback */ | |
295 | void (*fl_remove)(struct file_lock *); /* lock removal callback */ | |
296 | void (*fl_copy_lock)(struct file_lock *, struct file_lock *); | |
297 | void (*fl_release_private)(struct file_lock *); | |
298 | ||
299 | ||
300 | locking rules: | |
301 | BKL may block | |
302 | fl_insert: yes no | |
303 | fl_remove: yes no | |
304 | fl_copy_lock: yes no | |
305 | fl_release_private: yes yes | |
306 | ||
307 | ----------------------- lock_manager_operations --------------------------- | |
308 | prototypes: | |
309 | int (*fl_compare_owner)(struct file_lock *, struct file_lock *); | |
310 | void (*fl_notify)(struct file_lock *); /* unblock callback */ | |
311 | void (*fl_copy_lock)(struct file_lock *, struct file_lock *); | |
312 | void (*fl_release_private)(struct file_lock *); | |
313 | void (*fl_break)(struct file_lock *); /* break_lease callback */ | |
314 | ||
315 | locking rules: | |
316 | BKL may block | |
317 | fl_compare_owner: yes no | |
318 | fl_notify: yes no | |
319 | fl_copy_lock: yes no | |
320 | fl_release_private: yes yes | |
321 | fl_break: yes no | |
322 | ||
323 | Currently only NFSD and NLM provide instances of this class. None of the | |
324 | them block. If you have out-of-tree instances - please, show up. Locking | |
325 | in that area will change. | |
326 | --------------------------- buffer_head ----------------------------------- | |
327 | prototypes: | |
328 | void (*b_end_io)(struct buffer_head *bh, int uptodate); | |
329 | ||
330 | locking rules: | |
331 | called from interrupts. In other words, extreme care is needed here. | |
332 | bh is locked, but that's all warranties we have here. Currently only RAID1, | |
333 | highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices | |
334 | call this method upon the IO completion. | |
335 | ||
336 | --------------------------- block_device_operations ----------------------- | |
337 | prototypes: | |
338 | int (*open) (struct inode *, struct file *); | |
339 | int (*release) (struct inode *, struct file *); | |
340 | int (*ioctl) (struct inode *, struct file *, unsigned, unsigned long); | |
341 | int (*media_changed) (struct gendisk *); | |
342 | int (*revalidate_disk) (struct gendisk *); | |
343 | ||
344 | locking rules: | |
345 | BKL bd_sem | |
346 | open: yes yes | |
347 | release: yes yes | |
348 | ioctl: yes no | |
349 | media_changed: no no | |
350 | revalidate_disk: no no | |
351 | ||
352 | The last two are called only from check_disk_change(). | |
353 | ||
354 | --------------------------- file_operations ------------------------------- | |
355 | prototypes: | |
356 | loff_t (*llseek) (struct file *, loff_t, int); | |
357 | ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); | |
358 | ssize_t (*aio_read) (struct kiocb *, char __user *, size_t, loff_t); | |
359 | ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); | |
360 | ssize_t (*aio_write) (struct kiocb *, const char __user *, size_t, | |
361 | loff_t); | |
362 | int (*readdir) (struct file *, void *, filldir_t); | |
363 | unsigned int (*poll) (struct file *, struct poll_table_struct *); | |
364 | int (*ioctl) (struct inode *, struct file *, unsigned int, | |
365 | unsigned long); | |
366 | long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); | |
367 | long (*compat_ioctl) (struct file *, unsigned int, unsigned long); | |
368 | int (*mmap) (struct file *, struct vm_area_struct *); | |
369 | int (*open) (struct inode *, struct file *); | |
370 | int (*flush) (struct file *); | |
371 | int (*release) (struct inode *, struct file *); | |
372 | int (*fsync) (struct file *, struct dentry *, int datasync); | |
373 | int (*aio_fsync) (struct kiocb *, int datasync); | |
374 | int (*fasync) (int, struct file *, int); | |
375 | int (*lock) (struct file *, int, struct file_lock *); | |
376 | ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, | |
377 | loff_t *); | |
378 | ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, | |
379 | loff_t *); | |
380 | ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t, | |
381 | void __user *); | |
382 | ssize_t (*sendpage) (struct file *, struct page *, int, size_t, | |
383 | loff_t *, int); | |
384 | unsigned long (*get_unmapped_area)(struct file *, unsigned long, | |
385 | unsigned long, unsigned long, unsigned long); | |
386 | int (*check_flags)(int); | |
387 | int (*dir_notify)(struct file *, unsigned long); | |
388 | }; | |
389 | ||
390 | locking rules: | |
391 | All except ->poll() may block. | |
392 | BKL | |
393 | llseek: no (see below) | |
394 | read: no | |
395 | aio_read: no | |
396 | write: no | |
397 | aio_write: no | |
398 | readdir: no | |
399 | poll: no | |
400 | ioctl: yes (see below) | |
401 | unlocked_ioctl: no (see below) | |
402 | compat_ioctl: no | |
403 | mmap: no | |
404 | open: maybe (see below) | |
405 | flush: no | |
406 | release: no | |
407 | fsync: no (see below) | |
408 | aio_fsync: no | |
409 | fasync: yes (see below) | |
410 | lock: yes | |
411 | readv: no | |
412 | writev: no | |
413 | sendfile: no | |
414 | sendpage: no | |
415 | get_unmapped_area: no | |
416 | check_flags: no | |
417 | dir_notify: no | |
418 | ||
419 | ->llseek() locking has moved from llseek to the individual llseek | |
420 | implementations. If your fs is not using generic_file_llseek, you | |
421 | need to acquire and release the appropriate locks in your ->llseek(). | |
422 | For many filesystems, it is probably safe to acquire the inode | |
423 | semaphore. Note some filesystems (i.e. remote ones) provide no | |
424 | protection for i_size so you will need to use the BKL. | |
425 | ||
426 | ->open() locking is in-transit: big lock partially moved into the methods. | |
427 | The only exception is ->open() in the instances of file_operations that never | |
428 | end up in ->i_fop/->proc_fops, i.e. ones that belong to character devices | |
429 | (chrdev_open() takes lock before replacing ->f_op and calling the secondary | |
430 | method. As soon as we fix the handling of module reference counters all | |
431 | instances of ->open() will be called without the BKL. | |
432 | ||
433 | Note: ext2_release() was *the* source of contention on fs-intensive | |
434 | loads and dropping BKL on ->release() helps to get rid of that (we still | |
435 | grab BKL for cases when we close a file that had been opened r/w, but that | |
436 | can and should be done using the internal locking with smaller critical areas). | |
437 | Current worst offender is ext2_get_block()... | |
438 | ||
439 | ->fasync() is a mess. This area needs a big cleanup and that will probably | |
440 | affect locking. | |
441 | ||
442 | ->readdir() and ->ioctl() on directories must be changed. Ideally we would | |
443 | move ->readdir() to inode_operations and use a separate method for directory | |
444 | ->ioctl() or kill the latter completely. One of the problems is that for | |
445 | anything that resembles union-mount we won't have a struct file for all | |
446 | components. And there are other reasons why the current interface is a mess... | |
447 | ||
448 | ->ioctl() on regular files is superceded by the ->unlocked_ioctl() that | |
449 | doesn't take the BKL. | |
450 | ||
451 | ->read on directories probably must go away - we should just enforce -EISDIR | |
452 | in sys_read() and friends. | |
453 | ||
454 | ->fsync() has i_sem on inode. | |
455 | ||
456 | --------------------------- dquot_operations ------------------------------- | |
457 | prototypes: | |
458 | int (*initialize) (struct inode *, int); | |
459 | int (*drop) (struct inode *); | |
460 | int (*alloc_space) (struct inode *, qsize_t, int); | |
461 | int (*alloc_inode) (const struct inode *, unsigned long); | |
462 | int (*free_space) (struct inode *, qsize_t); | |
463 | int (*free_inode) (const struct inode *, unsigned long); | |
464 | int (*transfer) (struct inode *, struct iattr *); | |
465 | int (*write_dquot) (struct dquot *); | |
466 | int (*acquire_dquot) (struct dquot *); | |
467 | int (*release_dquot) (struct dquot *); | |
468 | int (*mark_dirty) (struct dquot *); | |
469 | int (*write_info) (struct super_block *, int); | |
470 | ||
471 | These operations are intended to be more or less wrapping functions that ensure | |
472 | a proper locking wrt the filesystem and call the generic quota operations. | |
473 | ||
474 | What filesystem should expect from the generic quota functions: | |
475 | ||
476 | FS recursion Held locks when called | |
477 | initialize: yes maybe dqonoff_sem | |
478 | drop: yes - | |
479 | alloc_space: ->mark_dirty() - | |
480 | alloc_inode: ->mark_dirty() - | |
481 | free_space: ->mark_dirty() - | |
482 | free_inode: ->mark_dirty() - | |
483 | transfer: yes - | |
484 | write_dquot: yes dqonoff_sem or dqptr_sem | |
485 | acquire_dquot: yes dqonoff_sem or dqptr_sem | |
486 | release_dquot: yes dqonoff_sem or dqptr_sem | |
487 | mark_dirty: no - | |
488 | write_info: yes dqonoff_sem | |
489 | ||
490 | FS recursion means calling ->quota_read() and ->quota_write() from superblock | |
491 | operations. | |
492 | ||
493 | ->alloc_space(), ->alloc_inode(), ->free_space(), ->free_inode() are called | |
494 | only directly by the filesystem and do not call any fs functions only | |
495 | the ->mark_dirty() operation. | |
496 | ||
497 | More details about quota locking can be found in fs/dquot.c. | |
498 | ||
499 | --------------------------- vm_operations_struct ----------------------------- | |
500 | prototypes: | |
501 | void (*open)(struct vm_area_struct*); | |
502 | void (*close)(struct vm_area_struct*); | |
503 | struct page *(*nopage)(struct vm_area_struct*, unsigned long, int *); | |
504 | ||
505 | locking rules: | |
506 | BKL mmap_sem | |
507 | open: no yes | |
508 | close: no yes | |
509 | nopage: no yes | |
510 | ||
511 | ================================================================================ | |
512 | Dubious stuff | |
513 | ||
514 | (if you break something or notice that it is broken and do not fix it yourself | |
515 | - at least put it here) | |
516 | ||
517 | ipc/shm.c::shm_delete() - may need BKL. | |
518 | ->read() and ->write() in many drivers are (probably) missing BKL. | |
519 | drivers/sgi/char/graphics.c::sgi_graphics_nopage() - may need BKL. |