]>
Commit | Line | Data |
---|---|---|
ec23eb54 MCC |
1 | ======= |
2 | Locking | |
3 | ======= | |
4 | ||
5 | The text below describes the locking rules for VFS-related methods. | |
1da177e4 LT |
6 | It is (believed to be) up-to-date. *Please*, if you change anything in |
7 | prototypes or locking protocols - update this file. And update the relevant | |
8 | instances in the tree, don't leave that to maintainers of filesystems/devices/ | |
9 | etc. At the very least, put the list of dubious cases in the end of this file. | |
10 | Don't turn it into log - maintainers of out-of-the-tree code are supposed to | |
11 | be able to use diff(1). | |
1da177e4 | 12 | |
ec23eb54 MCC |
13 | Thing currently missing here: socket operations. Alexey? |
14 | ||
15 | dentry_operations | |
16 | ================= | |
17 | ||
18 | prototypes:: | |
19 | ||
0b728e19 | 20 | int (*d_revalidate)(struct dentry *, unsigned int); |
ecf3d1f1 | 21 | int (*d_weak_revalidate)(struct dentry *, unsigned int); |
da53be12 | 22 | int (*d_hash)(const struct dentry *, struct qstr *); |
6fa67e70 | 23 | int (*d_compare)(const struct dentry *, |
621e155a | 24 | unsigned int, const char *, const struct qstr *); |
1da177e4 | 25 | int (*d_delete)(struct dentry *); |
285b102d | 26 | int (*d_init)(struct dentry *); |
1da177e4 LT |
27 | void (*d_release)(struct dentry *); |
28 | void (*d_iput)(struct dentry *, struct inode *); | |
c23fbb6b | 29 | char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen); |
9875cf80 | 30 | struct vfsmount *(*d_automount)(struct path *path); |
fb5f51c7 | 31 | int (*d_manage)(const struct path *, bool); |
fb16043b | 32 | struct dentry *(*d_real)(struct dentry *, const struct inode *); |
1da177e4 LT |
33 | |
34 | locking rules: | |
ec23eb54 MCC |
35 | |
36 | ================== =========== ======== ============== ======== | |
37 | ops rename_lock ->d_lock may block rcu-walk | |
38 | ================== =========== ======== ============== ======== | |
39 | d_revalidate: no no yes (ref-walk) maybe | |
40 | d_weak_revalidate: no no yes no | |
41 | d_hash no no no maybe | |
42 | d_compare: yes no no maybe | |
43 | d_delete: no yes no no | |
44 | d_init: no no yes no | |
45 | d_release: no no yes no | |
46 | d_prune: no yes no no | |
47 | d_iput: no no yes no | |
48 | d_dname: no no no no | |
49 | d_automount: no no yes no | |
50 | d_manage: no no yes (ref-walk) maybe | |
51 | d_real no no yes no | |
52 | ================== =========== ======== ============== ======== | |
53 | ||
54 | inode_operations | |
55 | ================ | |
56 | ||
57 | prototypes:: | |
58 | ||
ebfc3b49 | 59 | int (*create) (struct inode *,struct dentry *,umode_t, bool); |
00cd8dd3 | 60 | struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int); |
1da177e4 LT |
61 | int (*link) (struct dentry *,struct inode *,struct dentry *); |
62 | int (*unlink) (struct inode *,struct dentry *); | |
63 | int (*symlink) (struct inode *,struct dentry *,const char *); | |
18bb1db3 | 64 | int (*mkdir) (struct inode *,struct dentry *,umode_t); |
1da177e4 | 65 | int (*rmdir) (struct inode *,struct dentry *); |
1a67aafb | 66 | int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t); |
1da177e4 | 67 | int (*rename) (struct inode *, struct dentry *, |
520c8b16 | 68 | struct inode *, struct dentry *, unsigned int); |
1da177e4 | 69 | int (*readlink) (struct dentry *, char __user *,int); |
1a6a3165 | 70 | const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *); |
1da177e4 | 71 | void (*truncate) (struct inode *); |
b74c79e9 | 72 | int (*permission) (struct inode *, int, unsigned int); |
4e34e719 | 73 | int (*get_acl)(struct inode *, int); |
1da177e4 | 74 | int (*setattr) (struct dentry *, struct iattr *); |
75dd7e4b | 75 | int (*getattr) (const struct path *, struct kstat *, u32, unsigned int); |
1da177e4 | 76 | ssize_t (*listxattr) (struct dentry *, char *, size_t); |
b83be6f2 | 77 | int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len); |
c3b2da31 | 78 | void (*update_time)(struct inode *, struct timespec *, int); |
d9585277 | 79 | int (*atomic_open)(struct inode *, struct dentry *, |
30d90494 | 80 | struct file *, unsigned open_flag, |
6c9b1de1 | 81 | umode_t create_mode); |
48bde8d3 | 82 | int (*tmpfile) (struct inode *, struct dentry *, umode_t); |
1da177e4 LT |
83 | |
84 | locking rules: | |
b83be6f2 | 85 | all may block |
ec23eb54 MCC |
86 | |
87 | ============ ============================================= | |
88 | ops i_rwsem(inode) | |
89 | ============ ============================================= | |
965de0ec SA |
90 | lookup: shared |
91 | create: exclusive | |
92 | link: exclusive (both) | |
93 | mknod: exclusive | |
94 | symlink: exclusive | |
95 | mkdir: exclusive | |
96 | unlink: exclusive (both) | |
97 | rmdir: exclusive (both)(see below) | |
98 | rename: exclusive (all) (see below) | |
1da177e4 | 99 | readlink: no |
6b255391 | 100 | get_link: no |
965de0ec | 101 | setattr: exclusive |
b74c79e9 | 102 | permission: no (may not block if called in rcu-walk mode) |
4e34e719 | 103 | get_acl: no |
1da177e4 | 104 | getattr: no |
1da177e4 | 105 | listxattr: no |
b83be6f2 | 106 | fiemap: no |
c3b2da31 | 107 | update_time: no |
ff467342 | 108 | atomic_open: shared (exclusive if O_CREAT is set in open flags) |
48bde8d3 | 109 | tmpfile: no |
ec23eb54 | 110 | ============ ============================================= |
c3b2da31 | 111 | |
6c6ef9f2 | 112 | |
965de0ec SA |
113 | Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem |
114 | exclusive on victim. | |
2773bf00 | 115 | cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. |
1da177e4 | 116 | |
ec23eb54 | 117 | See Documentation/filesystems/directory-locking.rst for more detailed discussion |
1da177e4 LT |
118 | of the locking scheme for directory operations. |
119 | ||
ec23eb54 MCC |
120 | xattr_handler operations |
121 | ======================== | |
122 | ||
123 | prototypes:: | |
124 | ||
6c6ef9f2 AG |
125 | bool (*list)(struct dentry *dentry); |
126 | int (*get)(const struct xattr_handler *handler, struct dentry *dentry, | |
127 | struct inode *inode, const char *name, void *buffer, | |
128 | size_t size); | |
129 | int (*set)(const struct xattr_handler *handler, struct dentry *dentry, | |
130 | struct inode *inode, const char *name, const void *buffer, | |
131 | size_t size, int flags); | |
132 | ||
133 | locking rules: | |
134 | all may block | |
ec23eb54 MCC |
135 | |
136 | ===== ============== | |
137 | ops i_rwsem(inode) | |
138 | ===== ============== | |
6c6ef9f2 AG |
139 | list: no |
140 | get: no | |
965de0ec | 141 | set: exclusive |
ec23eb54 MCC |
142 | ===== ============== |
143 | ||
144 | super_operations | |
145 | ================ | |
146 | ||
147 | prototypes:: | |
6c6ef9f2 | 148 | |
1da177e4 | 149 | struct inode *(*alloc_inode)(struct super_block *sb); |
fdb0da89 | 150 | void (*free_inode)(struct inode *); |
1da177e4 | 151 | void (*destroy_inode)(struct inode *); |
aa385729 | 152 | void (*dirty_inode) (struct inode *, int flags); |
b83be6f2 | 153 | int (*write_inode) (struct inode *, struct writeback_control *wbc); |
336fb3b9 AV |
154 | int (*drop_inode) (struct inode *); |
155 | void (*evict_inode) (struct inode *); | |
1da177e4 | 156 | void (*put_super) (struct super_block *); |
1da177e4 | 157 | int (*sync_fs)(struct super_block *sb, int wait); |
c4be0c1d TS |
158 | int (*freeze_fs) (struct super_block *); |
159 | int (*unfreeze_fs) (struct super_block *); | |
726c3342 | 160 | int (*statfs) (struct dentry *, struct kstatfs *); |
1da177e4 | 161 | int (*remount_fs) (struct super_block *, int *, char *); |
1da177e4 | 162 | void (*umount_begin) (struct super_block *); |
34c80b1d | 163 | int (*show_options)(struct seq_file *, struct dentry *); |
1da177e4 LT |
164 | ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t); |
165 | ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t); | |
b83be6f2 | 166 | int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t); |
1da177e4 LT |
167 | |
168 | locking rules: | |
336fb3b9 | 169 | All may block [not true, see below] |
ec23eb54 MCC |
170 | |
171 | ====================== ============ ======================== | |
172 | ops s_umount note | |
173 | ====================== ============ ======================== | |
7e325d3a | 174 | alloc_inode: |
fdb0da89 | 175 | free_inode: called from RCU callback |
7e325d3a | 176 | destroy_inode: |
aa385729 | 177 | dirty_inode: |
7e325d3a | 178 | write_inode: |
f283c86a | 179 | drop_inode: !!!inode->i_lock!!! |
336fb3b9 | 180 | evict_inode: |
7e325d3a | 181 | put_super: write |
7e325d3a | 182 | sync_fs: read |
06fd516c VA |
183 | freeze_fs: write |
184 | unfreeze_fs: write | |
336fb3b9 AV |
185 | statfs: maybe(read) (see below) |
186 | remount_fs: write | |
7e325d3a CH |
187 | umount_begin: no |
188 | show_options: no (namespace_sem) | |
189 | quota_read: no (see below) | |
190 | quota_write: no (see below) | |
b83be6f2 | 191 | bdev_try_to_free_page: no (see below) |
ec23eb54 | 192 | ====================== ============ ======================== |
1da177e4 | 193 | |
336fb3b9 AV |
194 | ->statfs() has s_umount (shared) when called by ustat(2) (native or |
195 | compat), but that's an accident of bad API; s_umount is used to pin | |
196 | the superblock down when we only have dev_t given us by userland to | |
197 | identify the superblock. Everything else (statfs(), fstatfs(), etc.) | |
198 | doesn't hold it when calling ->statfs() - superblock is pinned down | |
199 | by resolving the pathname passed to syscall. | |
ec23eb54 | 200 | |
1da177e4 LT |
201 | ->quota_read() and ->quota_write() functions are both guaranteed to |
202 | be the only ones operating on the quota file by the quota code (via | |
203 | dqio_sem) (unless an admin really wants to screw up something and | |
204 | writes to quota files with quotas on). For other details about locking | |
205 | see also dquot_operations section. | |
ec23eb54 | 206 | |
b83be6f2 CH |
207 | ->bdev_try_to_free_page is called from the ->releasepage handler of |
208 | the block device inode. See there for more details. | |
1da177e4 | 209 | |
ec23eb54 MCC |
210 | file_system_type |
211 | ================ | |
212 | ||
213 | prototypes:: | |
214 | ||
b83be6f2 CH |
215 | struct dentry *(*mount) (struct file_system_type *, int, |
216 | const char *, void *); | |
1da177e4 | 217 | void (*kill_sb) (struct super_block *); |
ec23eb54 | 218 | |
1da177e4 | 219 | locking rules: |
ec23eb54 MCC |
220 | |
221 | ======= ========= | |
222 | ops may block | |
223 | ======= ========= | |
b83be6f2 CH |
224 | mount yes |
225 | kill_sb yes | |
ec23eb54 | 226 | ======= ========= |
1da177e4 | 227 | |
1a102ff9 AV |
228 | ->mount() returns ERR_PTR or the root dentry; its superblock should be locked |
229 | on return. | |
ec23eb54 | 230 | |
1da177e4 LT |
231 | ->kill_sb() takes a write-locked superblock, does all shutdown work on it, |
232 | unlocks and drops the reference. | |
233 | ||
ec23eb54 MCC |
234 | address_space_operations |
235 | ======================== | |
236 | prototypes:: | |
237 | ||
1da177e4 LT |
238 | int (*writepage)(struct page *page, struct writeback_control *wbc); |
239 | int (*readpage)(struct file *, struct page *); | |
1da177e4 LT |
240 | int (*writepages)(struct address_space *, struct writeback_control *); |
241 | int (*set_page_dirty)(struct page *page); | |
242 | int (*readpages)(struct file *filp, struct address_space *mapping, | |
243 | struct list_head *pages, unsigned nr_pages); | |
4e02ed4b NP |
244 | int (*write_begin)(struct file *, struct address_space *mapping, |
245 | loff_t pos, unsigned len, unsigned flags, | |
246 | struct page **pagep, void **fsdata); | |
247 | int (*write_end)(struct file *, struct address_space *mapping, | |
248 | loff_t pos, unsigned len, unsigned copied, | |
249 | struct page *page, void *fsdata); | |
1da177e4 | 250 | sector_t (*bmap)(struct address_space *, sector_t); |
d47992f8 | 251 | void (*invalidatepage) (struct page *, unsigned int, unsigned int); |
1da177e4 | 252 | int (*releasepage) (struct page *, int); |
6072d13c | 253 | void (*freepage)(struct page *); |
c8b8e32d | 254 | int (*direct_IO)(struct kiocb *, struct iov_iter *iter); |
bda807d4 | 255 | bool (*isolate_page) (struct page *, isolate_mode_t); |
b83be6f2 | 256 | int (*migratepage)(struct address_space *, struct page *, struct page *); |
bda807d4 | 257 | void (*putback_page) (struct page *); |
b83be6f2 | 258 | int (*launder_page)(struct page *); |
c186afb4 | 259 | int (*is_partially_uptodate)(struct page *, unsigned long, unsigned long); |
b83be6f2 | 260 | int (*error_remove_page)(struct address_space *, struct page *); |
62c230bc MG |
261 | int (*swap_activate)(struct file *); |
262 | int (*swap_deactivate)(struct file *); | |
1da177e4 LT |
263 | |
264 | locking rules: | |
6072d13c | 265 | All except set_page_dirty and freepage may block |
1da177e4 | 266 | |
ec23eb54 MCC |
267 | ====================== ======================== ========= |
268 | ops PageLocked(page) i_rwsem | |
269 | ====================== ======================== ========= | |
b83be6f2 CH |
270 | writepage: yes, unlocks (see below) |
271 | readpage: yes, unlocks | |
b83be6f2 CH |
272 | writepages: |
273 | set_page_dirty no | |
274 | readpages: | |
ec23eb54 MCC |
275 | write_begin: locks the page exclusive |
276 | write_end: yes, unlocks exclusive | |
b83be6f2 CH |
277 | bmap: |
278 | invalidatepage: yes | |
279 | releasepage: yes | |
280 | freepage: yes | |
281 | direct_IO: | |
bda807d4 | 282 | isolate_page: yes |
b83be6f2 | 283 | migratepage: yes (both) |
bda807d4 | 284 | putback_page: yes |
b83be6f2 CH |
285 | launder_page: yes |
286 | is_partially_uptodate: yes | |
287 | error_remove_page: yes | |
62c230bc MG |
288 | swap_activate: no |
289 | swap_deactivate: no | |
ec23eb54 | 290 | ====================== ======================== ========= |
1da177e4 | 291 | |
ec23eb54 | 292 | ->write_begin(), ->write_end() and ->readpage() may be called from |
f4e6d844 | 293 | the request handler (/dev/loop). |
1da177e4 | 294 | |
ec23eb54 | 295 | ->readpage() unlocks the page, either synchronously or via I/O |
1da177e4 LT |
296 | completion. |
297 | ||
ec23eb54 | 298 | ->readpages() populates the pagecache with the passed pages and starts |
1da177e4 LT |
299 | I/O against them. They come unlocked upon I/O completion. |
300 | ||
ec23eb54 | 301 | ->writepage() is used for two purposes: for "memory cleansing" and for |
1da177e4 LT |
302 | "sync". These are quite different operations and the behaviour may differ |
303 | depending upon the mode. | |
304 | ||
305 | If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then | |
306 | it *must* start I/O against the page, even if that would involve | |
307 | blocking on in-progress I/O. | |
308 | ||
309 | If writepage is called for memory cleansing (sync_mode == | |
310 | WBC_SYNC_NONE) then its role is to get as much writeout underway as | |
311 | possible. So writepage should try to avoid blocking against | |
312 | currently-in-progress I/O. | |
313 | ||
314 | If the filesystem is not called for "sync" and it determines that it | |
315 | would need to block against in-progress I/O to be able to start new I/O | |
316 | against the page the filesystem should redirty the page with | |
317 | redirty_page_for_writepage(), then unlock the page and return zero. | |
318 | This may also be done to avoid internal deadlocks, but rarely. | |
319 | ||
3a4fa0a2 | 320 | If the filesystem is called for sync then it must wait on any |
1da177e4 LT |
321 | in-progress I/O and then start new I/O. |
322 | ||
2054606a ND |
323 | The filesystem should unlock the page synchronously, before returning to the |
324 | caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE | |
325 | value. WRITEPAGE_ACTIVATE means that page cannot really be written out | |
326 | currently, and VM should stop calling ->writepage() on this page for some | |
327 | time. VM does this by moving page to the head of the active list, hence the | |
328 | name. | |
1da177e4 LT |
329 | |
330 | Unless the filesystem is going to redirty_page_for_writepage(), unlock the page | |
331 | and return zero, writepage *must* run set_page_writeback() against the page, | |
332 | followed by unlocking it. Once set_page_writeback() has been run against the | |
333 | page, write I/O can be submitted and the write I/O completion handler must run | |
334 | end_page_writeback() once the I/O is complete. If no I/O is submitted, the | |
335 | filesystem must run end_page_writeback() against the page before returning from | |
336 | writepage. | |
337 | ||
338 | That is: after 2.5.12, pages which are under writeout are *not* locked. Note, | |
339 | if the filesystem needs the page to be locked during writeout, that is ok, too, | |
340 | the page is allowed to be unlocked at any point in time between the calls to | |
341 | set_page_writeback() and end_page_writeback(). | |
342 | ||
343 | Note, failure to run either redirty_page_for_writepage() or the combination of | |
344 | set_page_writeback()/end_page_writeback() on a page submitted to writepage | |
345 | will leave the page itself marked clean but it will be tagged as dirty in the | |
346 | radix tree. This incoherency can lead to all sorts of hard-to-debug problems | |
347 | in the filesystem like having dirty inodes at umount and losing written data. | |
348 | ||
ec23eb54 | 349 | ->writepages() is used for periodic writeback and for syscall-initiated |
1da177e4 | 350 | sync operations. The address_space should start I/O against at least |
ec23eb54 MCC |
351 | ``*nr_to_write`` pages. ``*nr_to_write`` must be decremented for each page |
352 | which is written. The address_space implementation may write more (or less) | |
353 | pages than ``*nr_to_write`` asks for, but it should try to be reasonably close. | |
354 | If nr_to_write is NULL, all dirty pages must be written. | |
1da177e4 LT |
355 | |
356 | writepages should _only_ write pages which are present on | |
357 | mapping->io_pages. | |
358 | ||
ec23eb54 | 359 | ->set_page_dirty() is called from various places in the kernel |
1da177e4 LT |
360 | when the target page is marked as needing writeback. It may be called |
361 | under spinlock (it cannot block) and is sometimes called with the page | |
362 | not locked. | |
363 | ||
ec23eb54 | 364 | ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some |
b83be6f2 CH |
365 | filesystems and by the swapper. The latter will eventually go away. Please, |
366 | keep it that way and don't breed new callers. | |
1da177e4 | 367 | |
ec23eb54 | 368 | ->invalidatepage() is called when the filesystem must attempt to drop |
d47992f8 LC |
369 | some or all of the buffers from the page when it is being truncated. It |
370 | returns zero on success. If ->invalidatepage is zero, the kernel uses | |
1da177e4 LT |
371 | block_invalidatepage() instead. |
372 | ||
ec23eb54 | 373 | ->releasepage() is called when the kernel is about to try to drop the |
1da177e4 LT |
374 | buffers from the page in preparation for freeing it. It returns zero to |
375 | indicate that the buffers are (or may be) freeable. If ->releasepage is zero, | |
376 | the kernel assumes that the fs has no private interest in the buffers. | |
377 | ||
ec23eb54 | 378 | ->freepage() is called when the kernel is done dropping the page |
6072d13c LT |
379 | from the page cache. |
380 | ||
ec23eb54 | 381 | ->launder_page() may be called prior to releasing a page if |
e3db7691 TM |
382 | it is still found to be dirty. It returns zero if the page was successfully |
383 | cleaned, or an error value if not. Note that in order to prevent the page | |
384 | getting mapped back in and redirtied, it needs to be kept locked | |
385 | across the entire operation. | |
386 | ||
ec23eb54 | 387 | ->swap_activate will be called with a non-zero argument on |
62c230bc MG |
388 | files backing (non block device backed) swapfiles. A return value |
389 | of zero indicates success, in which case this file can be used for | |
390 | backing swapspace. The swapspace operations will be proxied to the | |
391 | address space operations. | |
392 | ||
ec23eb54 | 393 | ->swap_deactivate() will be called in the sys_swapoff() |
62c230bc MG |
394 | path after ->swap_activate() returned success. |
395 | ||
ec23eb54 MCC |
396 | file_lock_operations |
397 | ==================== | |
398 | ||
399 | prototypes:: | |
400 | ||
1da177e4 LT |
401 | void (*fl_copy_lock)(struct file_lock *, struct file_lock *); |
402 | void (*fl_release_private)(struct file_lock *); | |
403 | ||
404 | ||
405 | locking rules: | |
ec23eb54 MCC |
406 | |
407 | =================== ============= ========= | |
408 | ops inode->i_lock may block | |
409 | =================== ============= ========= | |
b83be6f2 | 410 | fl_copy_lock: yes no |
ec23eb54 MCC |
411 | fl_release_private: maybe maybe[1]_ |
412 | =================== ============= ========= | |
413 | ||
414 | .. [1]: | |
415 | ->fl_release_private for flock or POSIX locks is currently allowed | |
416 | to block. Leases however can still be freed while the i_lock is held and | |
417 | so fl_release_private called on a lease should not block. | |
2ece173e | 418 | |
ec23eb54 MCC |
419 | lock_manager_operations |
420 | ======================= | |
421 | ||
422 | prototypes:: | |
1da177e4 | 423 | |
8fb47a4f BF |
424 | void (*lm_notify)(struct file_lock *); /* unblock callback */ |
425 | int (*lm_grant)(struct file_lock *, struct file_lock *, int); | |
8fb47a4f BF |
426 | void (*lm_break)(struct file_lock *); /* break_lease callback */ |
427 | int (*lm_change)(struct file_lock **, int); | |
1da177e4 LT |
428 | |
429 | locking rules: | |
1c8c601a | 430 | |
ec23eb54 MCC |
431 | ========== ============= ================= ========= |
432 | ops inode->i_lock blocked_lock_lock may block | |
433 | ========== ============= ================= ========= | |
7b2296af JL |
434 | lm_notify: yes yes no |
435 | lm_grant: no no no | |
436 | lm_break: yes no no | |
437 | lm_change yes no no | |
ec23eb54 MCC |
438 | ========== ============= ================= ========= |
439 | ||
440 | buffer_head | |
441 | =========== | |
442 | ||
443 | prototypes:: | |
1c8c601a | 444 | |
1da177e4 LT |
445 | void (*b_end_io)(struct buffer_head *bh, int uptodate); |
446 | ||
447 | locking rules: | |
ec23eb54 MCC |
448 | |
449 | called from interrupts. In other words, extreme care is needed here. | |
1da177e4 LT |
450 | bh is locked, but that's all warranties we have here. Currently only RAID1, |
451 | highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices | |
452 | call this method upon the IO completion. | |
453 | ||
ec23eb54 MCC |
454 | block_device_operations |
455 | ======================= | |
456 | prototypes:: | |
457 | ||
e1455d1b CH |
458 | int (*open) (struct block_device *, fmode_t); |
459 | int (*release) (struct gendisk *, fmode_t); | |
460 | int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); | |
461 | int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); | |
7a9eb206 | 462 | int (*direct_access) (struct block_device *, sector_t, void **, |
e2e05394 | 463 | unsigned long *); |
1da177e4 | 464 | int (*media_changed) (struct gendisk *); |
e1455d1b | 465 | void (*unlock_native_capacity) (struct gendisk *); |
1da177e4 | 466 | int (*revalidate_disk) (struct gendisk *); |
e1455d1b CH |
467 | int (*getgeo)(struct block_device *, struct hd_geometry *); |
468 | void (*swap_slot_free_notify) (struct block_device *, unsigned long); | |
1da177e4 LT |
469 | |
470 | locking rules: | |
ec23eb54 MCC |
471 | |
472 | ======================= =================== | |
473 | ops bd_mutex | |
474 | ======================= =================== | |
b83be6f2 CH |
475 | open: yes |
476 | release: yes | |
477 | ioctl: no | |
478 | compat_ioctl: no | |
479 | direct_access: no | |
480 | media_changed: no | |
481 | unlock_native_capacity: no | |
482 | revalidate_disk: no | |
483 | getgeo: no | |
484 | swap_slot_free_notify: no (see below) | |
ec23eb54 | 485 | ======================= =================== |
e1455d1b CH |
486 | |
487 | media_changed, unlock_native_capacity and revalidate_disk are called only from | |
488 | check_disk_change(). | |
489 | ||
490 | swap_slot_free_notify is called with swap_lock and sometimes the page lock | |
491 | held. | |
1da177e4 | 492 | |
1da177e4 | 493 | |
ec23eb54 MCC |
494 | file_operations |
495 | =============== | |
496 | ||
497 | prototypes:: | |
498 | ||
1da177e4 LT |
499 | loff_t (*llseek) (struct file *, loff_t, int); |
500 | ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); | |
1da177e4 | 501 | ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); |
293bc982 AV |
502 | ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); |
503 | ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); | |
2233f31a | 504 | int (*iterate) (struct file *, struct dir_context *); |
965de0ec | 505 | int (*iterate_shared) (struct file *, struct dir_context *); |
6e8b704d | 506 | __poll_t (*poll) (struct file *, struct poll_table_struct *); |
1da177e4 LT |
507 | long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); |
508 | long (*compat_ioctl) (struct file *, unsigned int, unsigned long); | |
509 | int (*mmap) (struct file *, struct vm_area_struct *); | |
510 | int (*open) (struct inode *, struct file *); | |
511 | int (*flush) (struct file *); | |
512 | int (*release) (struct inode *, struct file *); | |
02c24a82 | 513 | int (*fsync) (struct file *, loff_t start, loff_t end, int datasync); |
1da177e4 LT |
514 | int (*fasync) (int, struct file *, int); |
515 | int (*lock) (struct file *, int, struct file_lock *); | |
516 | ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, | |
517 | loff_t *); | |
518 | ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, | |
519 | loff_t *); | |
520 | ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t, | |
521 | void __user *); | |
522 | ssize_t (*sendpage) (struct file *, struct page *, int, size_t, | |
523 | loff_t *, int); | |
524 | unsigned long (*get_unmapped_area)(struct file *, unsigned long, | |
525 | unsigned long, unsigned long, unsigned long); | |
526 | int (*check_flags)(int); | |
b83be6f2 CH |
527 | int (*flock) (struct file *, int, struct file_lock *); |
528 | ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, | |
529 | size_t, unsigned int); | |
530 | ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, | |
531 | size_t, unsigned int); | |
e6f5c789 | 532 | int (*setlease)(struct file *, long, struct file_lock **, void **); |
2fe17c10 | 533 | long (*fallocate)(struct file *, int, loff_t, loff_t); |
1da177e4 LT |
534 | |
535 | locking rules: | |
a11e1d43 | 536 | All may block. |
b83be6f2 | 537 | |
1da177e4 LT |
538 | ->llseek() locking has moved from llseek to the individual llseek |
539 | implementations. If your fs is not using generic_file_llseek, you | |
540 | need to acquire and release the appropriate locks in your ->llseek(). | |
541 | For many filesystems, it is probably safe to acquire the inode | |
866707fc JB |
542 | mutex or just to use i_size_read() instead. |
543 | Note: this does not protect the file->f_pos against concurrent modifications | |
544 | since this is something the userspace has to take care about. | |
1da177e4 | 545 | |
965de0ec SA |
546 | ->iterate() is called with i_rwsem exclusive. |
547 | ||
548 | ->iterate_shared() is called with i_rwsem at least shared. | |
549 | ||
b83be6f2 CH |
550 | ->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags. |
551 | Most instances call fasync_helper(), which does that maintenance, so it's | |
552 | not normally something one needs to worry about. Return values > 0 will be | |
553 | mapped to zero in the VFS layer. | |
1da177e4 LT |
554 | |
555 | ->readdir() and ->ioctl() on directories must be changed. Ideally we would | |
556 | move ->readdir() to inode_operations and use a separate method for directory | |
557 | ->ioctl() or kill the latter completely. One of the problems is that for | |
558 | anything that resembles union-mount we won't have a struct file for all | |
559 | components. And there are other reasons why the current interface is a mess... | |
560 | ||
1da177e4 LT |
561 | ->read on directories probably must go away - we should just enforce -EISDIR |
562 | in sys_read() and friends. | |
563 | ||
f82b4b67 JL |
564 | ->setlease operations should call generic_setlease() before or after setting |
565 | the lease within the individual filesystem to record the result of the | |
566 | operation | |
567 | ||
ec23eb54 MCC |
568 | dquot_operations |
569 | ================ | |
570 | ||
571 | prototypes:: | |
572 | ||
1da177e4 LT |
573 | int (*write_dquot) (struct dquot *); |
574 | int (*acquire_dquot) (struct dquot *); | |
575 | int (*release_dquot) (struct dquot *); | |
576 | int (*mark_dirty) (struct dquot *); | |
577 | int (*write_info) (struct super_block *, int); | |
578 | ||
579 | These operations are intended to be more or less wrapping functions that ensure | |
580 | a proper locking wrt the filesystem and call the generic quota operations. | |
581 | ||
582 | What filesystem should expect from the generic quota functions: | |
583 | ||
ec23eb54 MCC |
584 | ============== ============ ========================= |
585 | ops FS recursion Held locks when called | |
586 | ============== ============ ========================= | |
1da177e4 LT |
587 | write_dquot: yes dqonoff_sem or dqptr_sem |
588 | acquire_dquot: yes dqonoff_sem or dqptr_sem | |
589 | release_dquot: yes dqonoff_sem or dqptr_sem | |
590 | mark_dirty: no - | |
591 | write_info: yes dqonoff_sem | |
ec23eb54 | 592 | ============== ============ ========================= |
1da177e4 LT |
593 | |
594 | FS recursion means calling ->quota_read() and ->quota_write() from superblock | |
595 | operations. | |
596 | ||
1da177e4 LT |
597 | More details about quota locking can be found in fs/dquot.c. |
598 | ||
ec23eb54 MCC |
599 | vm_operations_struct |
600 | ==================== | |
601 | ||
602 | prototypes:: | |
603 | ||
1da177e4 LT |
604 | void (*open)(struct vm_area_struct*); |
605 | void (*close)(struct vm_area_struct*); | |
fe3136f4 SJ |
606 | vm_fault_t (*fault)(struct vm_area_struct*, struct vm_fault *); |
607 | vm_fault_t (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *); | |
608 | vm_fault_t (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *); | |
28b2ee20 | 609 | int (*access)(struct vm_area_struct *, unsigned long, void*, int, int); |
1da177e4 LT |
610 | |
611 | locking rules: | |
ec23eb54 MCC |
612 | |
613 | ============= ======== =========================== | |
614 | ops mmap_sem PageLocked(page) | |
615 | ============= ======== =========================== | |
b83be6f2 CH |
616 | open: yes |
617 | close: yes | |
618 | fault: yes can return with page locked | |
8c6e50b0 | 619 | map_pages: yes |
b83be6f2 | 620 | page_mkwrite: yes can return with page locked |
dd906184 | 621 | pfn_mkwrite: yes |
b83be6f2 | 622 | access: yes |
ec23eb54 | 623 | ============= ======== =========================== |
ed2f2f9b | 624 | |
ec23eb54 | 625 | ->fault() is called when a previously not present pte is about |
b827e496 NP |
626 | to be faulted in. The filesystem must find and return the page associated |
627 | with the passed in "pgoff" in the vm_fault structure. If it is possible that | |
628 | the page may be truncated and/or invalidated, then the filesystem must lock | |
629 | the page, then ensure it is not already truncated (the page lock will block | |
630 | subsequent truncate), and then return with VM_FAULT_LOCKED, and the page | |
631 | locked. The VM will unlock the page. | |
632 | ||
ec23eb54 | 633 | ->map_pages() is called when VM asks to map easy accessible pages. |
bae473a4 KS |
634 | Filesystem should find and map pages associated with offsets from "start_pgoff" |
635 | till "end_pgoff". ->map_pages() is called with page table locked and must | |
8c6e50b0 KS |
636 | not block. If it's not possible to reach a page without blocking, |
637 | filesystem should skip it. Filesystem should use do_set_pte() to setup | |
bae473a4 | 638 | page table entry. Pointer to entry associated with the page is passed in |
82b0f8c3 | 639 | "pte" field in vm_fault structure. Pointers to entries for other offsets |
bae473a4 | 640 | should be calculated relative to "pte". |
8c6e50b0 | 641 | |
ec23eb54 | 642 | ->page_mkwrite() is called when a previously read-only pte is |
b827e496 NP |
643 | about to become writeable. The filesystem again must ensure that there are |
644 | no truncate/invalidate races, and then return with the page locked. If | |
645 | the page has been truncated, the filesystem should not look up a new page | |
646 | like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which | |
647 | will cause the VM to retry the fault. | |
1da177e4 | 648 | |
ec23eb54 | 649 | ->pfn_mkwrite() is the same as page_mkwrite but when the pte is |
dd906184 BH |
650 | VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is |
651 | VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior | |
652 | after this call is to make the pte read-write, unless pfn_mkwrite returns | |
653 | an error. | |
654 | ||
ec23eb54 | 655 | ->access() is called when get_user_pages() fails in |
507da6a1 | 656 | access_process_vm(), typically used to debug a process through |
28b2ee20 RR |
657 | /proc/pid/mem or ptrace. This function is needed only for |
658 | VM_IO | VM_PFNMAP VMAs. | |
659 | ||
ec23eb54 MCC |
660 | -------------------------------------------------------------------------------- |
661 | ||
1da177e4 LT |
662 | Dubious stuff |
663 | ||
664 | (if you break something or notice that it is broken and do not fix it yourself | |
665 | - at least put it here) |