Commit | Line | Data |
---|---|---|
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: | |
0b728e19 | 12 | int (*d_revalidate)(struct dentry *, unsigned int); |
ecf3d1f1 | 13 | int (*d_weak_revalidate)(struct dentry *, unsigned int); |
da53be12 | 14 | int (*d_hash)(const struct dentry *, struct qstr *); |
6fa67e70 | 15 | int (*d_compare)(const struct dentry *, |
621e155a | 16 | unsigned int, const char *, const struct qstr *); |
1da177e4 | 17 | int (*d_delete)(struct dentry *); |
285b102d | 18 | int (*d_init)(struct dentry *); |
1da177e4 LT |
19 | void (*d_release)(struct dentry *); |
20 | void (*d_iput)(struct dentry *, struct inode *); | |
c23fbb6b | 21 | char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen); |
9875cf80 | 22 | struct vfsmount *(*d_automount)(struct path *path); |
fb5f51c7 | 23 | int (*d_manage)(const struct path *, bool); |
fb16043b | 24 | struct dentry *(*d_real)(struct dentry *, const struct inode *); |
1da177e4 LT |
25 | |
26 | locking rules: | |
34286d66 NP |
27 | rename_lock ->d_lock may block rcu-walk |
28 | d_revalidate: no no yes (ref-walk) maybe | |
ecf3d1f1 | 29 | d_weak_revalidate:no no yes no |
34286d66 NP |
30 | d_hash no no no maybe |
31 | d_compare: yes no no maybe | |
32 | d_delete: no yes no no | |
285b102d | 33 | d_init: no no yes no |
34286d66 | 34 | d_release: no no yes no |
f0023bc6 | 35 | d_prune: no yes no no |
34286d66 NP |
36 | d_iput: no no yes no |
37 | d_dname: no no no no | |
9875cf80 | 38 | d_automount: no no yes no |
ab90911f | 39 | d_manage: no no yes (ref-walk) maybe |
e698b8a4 | 40 | d_real no no yes no |
1da177e4 LT |
41 | |
42 | --------------------------- inode_operations --------------------------- | |
43 | prototypes: | |
ebfc3b49 | 44 | int (*create) (struct inode *,struct dentry *,umode_t, bool); |
00cd8dd3 | 45 | struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int); |
1da177e4 LT |
46 | int (*link) (struct dentry *,struct inode *,struct dentry *); |
47 | int (*unlink) (struct inode *,struct dentry *); | |
48 | int (*symlink) (struct inode *,struct dentry *,const char *); | |
18bb1db3 | 49 | int (*mkdir) (struct inode *,struct dentry *,umode_t); |
1da177e4 | 50 | int (*rmdir) (struct inode *,struct dentry *); |
1a67aafb | 51 | int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t); |
1da177e4 | 52 | int (*rename) (struct inode *, struct dentry *, |
520c8b16 | 53 | struct inode *, struct dentry *, unsigned int); |
1da177e4 | 54 | int (*readlink) (struct dentry *, char __user *,int); |
1a6a3165 | 55 | const char *(*get_link) (struct dentry *, struct inode *, struct delayed_call *); |
1da177e4 | 56 | void (*truncate) (struct inode *); |
b74c79e9 | 57 | int (*permission) (struct inode *, int, unsigned int); |
4e34e719 | 58 | int (*get_acl)(struct inode *, int); |
1da177e4 | 59 | int (*setattr) (struct dentry *, struct iattr *); |
75dd7e4b | 60 | int (*getattr) (const struct path *, struct kstat *, u32, unsigned int); |
1da177e4 | 61 | ssize_t (*listxattr) (struct dentry *, char *, size_t); |
b83be6f2 | 62 | int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len); |
c3b2da31 | 63 | void (*update_time)(struct inode *, struct timespec *, int); |
d9585277 | 64 | int (*atomic_open)(struct inode *, struct dentry *, |
30d90494 | 65 | struct file *, unsigned open_flag, |
6c9b1de1 | 66 | umode_t create_mode); |
48bde8d3 | 67 | int (*tmpfile) (struct inode *, struct dentry *, umode_t); |
1da177e4 LT |
68 | |
69 | locking rules: | |
b83be6f2 | 70 | all may block |
965de0ec SA |
71 | i_rwsem(inode) |
72 | lookup: shared | |
73 | create: exclusive | |
74 | link: exclusive (both) | |
75 | mknod: exclusive | |
76 | symlink: exclusive | |
77 | mkdir: exclusive | |
78 | unlink: exclusive (both) | |
79 | rmdir: exclusive (both)(see below) | |
80 | rename: exclusive (all) (see below) | |
1da177e4 | 81 | readlink: no |
6b255391 | 82 | get_link: no |
965de0ec | 83 | setattr: exclusive |
b74c79e9 | 84 | permission: no (may not block if called in rcu-walk mode) |
4e34e719 | 85 | get_acl: no |
1da177e4 | 86 | getattr: no |
1da177e4 | 87 | listxattr: no |
b83be6f2 | 88 | fiemap: no |
c3b2da31 | 89 | update_time: no |
965de0ec | 90 | atomic_open: exclusive |
48bde8d3 | 91 | tmpfile: no |
c3b2da31 | 92 | |
6c6ef9f2 | 93 | |
965de0ec SA |
94 | Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem |
95 | exclusive on victim. | |
2773bf00 | 96 | cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. |
1da177e4 LT |
97 | |
98 | See Documentation/filesystems/directory-locking for more detailed discussion | |
99 | of the locking scheme for directory operations. | |
100 | ||
6c6ef9f2 AG |
101 | ----------------------- xattr_handler operations ----------------------- |
102 | prototypes: | |
103 | bool (*list)(struct dentry *dentry); | |
104 | int (*get)(const struct xattr_handler *handler, struct dentry *dentry, | |
105 | struct inode *inode, const char *name, void *buffer, | |
106 | size_t size); | |
107 | int (*set)(const struct xattr_handler *handler, struct dentry *dentry, | |
108 | struct inode *inode, const char *name, const void *buffer, | |
109 | size_t size, int flags); | |
110 | ||
111 | locking rules: | |
112 | all may block | |
965de0ec | 113 | i_rwsem(inode) |
6c6ef9f2 AG |
114 | list: no |
115 | get: no | |
965de0ec | 116 | set: exclusive |
6c6ef9f2 | 117 | |
1da177e4 LT |
118 | --------------------------- super_operations --------------------------- |
119 | prototypes: | |
120 | struct inode *(*alloc_inode)(struct super_block *sb); | |
fdb0da89 | 121 | void (*free_inode)(struct inode *); |
1da177e4 | 122 | void (*destroy_inode)(struct inode *); |
aa385729 | 123 | void (*dirty_inode) (struct inode *, int flags); |
b83be6f2 | 124 | int (*write_inode) (struct inode *, struct writeback_control *wbc); |
336fb3b9 AV |
125 | int (*drop_inode) (struct inode *); |
126 | void (*evict_inode) (struct inode *); | |
1da177e4 | 127 | void (*put_super) (struct super_block *); |
1da177e4 | 128 | int (*sync_fs)(struct super_block *sb, int wait); |
c4be0c1d TS |
129 | int (*freeze_fs) (struct super_block *); |
130 | int (*unfreeze_fs) (struct super_block *); | |
726c3342 | 131 | int (*statfs) (struct dentry *, struct kstatfs *); |
1da177e4 | 132 | int (*remount_fs) (struct super_block *, int *, char *); |
1da177e4 | 133 | void (*umount_begin) (struct super_block *); |
34c80b1d | 134 | int (*show_options)(struct seq_file *, struct dentry *); |
1da177e4 LT |
135 | ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t); |
136 | ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t); | |
b83be6f2 | 137 | int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t); |
1da177e4 LT |
138 | |
139 | locking rules: | |
336fb3b9 | 140 | All may block [not true, see below] |
7e325d3a CH |
141 | s_umount |
142 | alloc_inode: | |
fdb0da89 | 143 | free_inode: called from RCU callback |
7e325d3a | 144 | destroy_inode: |
aa385729 | 145 | dirty_inode: |
7e325d3a | 146 | write_inode: |
f283c86a | 147 | drop_inode: !!!inode->i_lock!!! |
336fb3b9 | 148 | evict_inode: |
7e325d3a | 149 | put_super: write |
7e325d3a | 150 | sync_fs: read |
06fd516c VA |
151 | freeze_fs: write |
152 | unfreeze_fs: write | |
336fb3b9 AV |
153 | statfs: maybe(read) (see below) |
154 | remount_fs: write | |
7e325d3a CH |
155 | umount_begin: no |
156 | show_options: no (namespace_sem) | |
157 | quota_read: no (see below) | |
158 | quota_write: no (see below) | |
b83be6f2 | 159 | bdev_try_to_free_page: no (see below) |
1da177e4 | 160 | |
336fb3b9 AV |
161 | ->statfs() has s_umount (shared) when called by ustat(2) (native or |
162 | compat), but that's an accident of bad API; s_umount is used to pin | |
163 | the superblock down when we only have dev_t given us by userland to | |
164 | identify the superblock. Everything else (statfs(), fstatfs(), etc.) | |
165 | doesn't hold it when calling ->statfs() - superblock is pinned down | |
166 | by resolving the pathname passed to syscall. | |
1da177e4 LT |
167 | ->quota_read() and ->quota_write() functions are both guaranteed to |
168 | be the only ones operating on the quota file by the quota code (via | |
169 | dqio_sem) (unless an admin really wants to screw up something and | |
170 | writes to quota files with quotas on). For other details about locking | |
171 | see also dquot_operations section. | |
b83be6f2 CH |
172 | ->bdev_try_to_free_page is called from the ->releasepage handler of |
173 | the block device inode. See there for more details. | |
1da177e4 LT |
174 | |
175 | --------------------------- file_system_type --------------------------- | |
176 | prototypes: | |
b83be6f2 CH |
177 | struct dentry *(*mount) (struct file_system_type *, int, |
178 | const char *, void *); | |
1da177e4 LT |
179 | void (*kill_sb) (struct super_block *); |
180 | locking rules: | |
b83be6f2 | 181 | may block |
b83be6f2 CH |
182 | mount yes |
183 | kill_sb yes | |
1da177e4 | 184 | |
1a102ff9 AV |
185 | ->mount() returns ERR_PTR or the root dentry; its superblock should be locked |
186 | on return. | |
1da177e4 LT |
187 | ->kill_sb() takes a write-locked superblock, does all shutdown work on it, |
188 | unlocks and drops the reference. | |
189 | ||
190 | --------------------------- address_space_operations -------------------------- | |
191 | prototypes: | |
192 | int (*writepage)(struct page *page, struct writeback_control *wbc); | |
193 | int (*readpage)(struct file *, struct page *); | |
1da177e4 LT |
194 | int (*writepages)(struct address_space *, struct writeback_control *); |
195 | int (*set_page_dirty)(struct page *page); | |
196 | int (*readpages)(struct file *filp, struct address_space *mapping, | |
197 | struct list_head *pages, unsigned nr_pages); | |
4e02ed4b NP |
198 | int (*write_begin)(struct file *, struct address_space *mapping, |
199 | loff_t pos, unsigned len, unsigned flags, | |
200 | struct page **pagep, void **fsdata); | |
201 | int (*write_end)(struct file *, struct address_space *mapping, | |
202 | loff_t pos, unsigned len, unsigned copied, | |
203 | struct page *page, void *fsdata); | |
1da177e4 | 204 | sector_t (*bmap)(struct address_space *, sector_t); |
d47992f8 | 205 | void (*invalidatepage) (struct page *, unsigned int, unsigned int); |
1da177e4 | 206 | int (*releasepage) (struct page *, int); |
6072d13c | 207 | void (*freepage)(struct page *); |
c8b8e32d | 208 | int (*direct_IO)(struct kiocb *, struct iov_iter *iter); |
bda807d4 | 209 | bool (*isolate_page) (struct page *, isolate_mode_t); |
b83be6f2 | 210 | int (*migratepage)(struct address_space *, struct page *, struct page *); |
bda807d4 | 211 | void (*putback_page) (struct page *); |
b83be6f2 | 212 | int (*launder_page)(struct page *); |
c186afb4 | 213 | int (*is_partially_uptodate)(struct page *, unsigned long, unsigned long); |
b83be6f2 | 214 | int (*error_remove_page)(struct address_space *, struct page *); |
62c230bc MG |
215 | int (*swap_activate)(struct file *); |
216 | int (*swap_deactivate)(struct file *); | |
1da177e4 LT |
217 | |
218 | locking rules: | |
6072d13c | 219 | All except set_page_dirty and freepage may block |
1da177e4 | 220 | |
965de0ec | 221 | PageLocked(page) i_rwsem |
b83be6f2 CH |
222 | writepage: yes, unlocks (see below) |
223 | readpage: yes, unlocks | |
b83be6f2 CH |
224 | writepages: |
225 | set_page_dirty no | |
226 | readpages: | |
965de0ec SA |
227 | write_begin: locks the page exclusive |
228 | write_end: yes, unlocks exclusive | |
b83be6f2 CH |
229 | bmap: |
230 | invalidatepage: yes | |
231 | releasepage: yes | |
232 | freepage: yes | |
233 | direct_IO: | |
bda807d4 | 234 | isolate_page: yes |
b83be6f2 | 235 | migratepage: yes (both) |
bda807d4 | 236 | putback_page: yes |
b83be6f2 CH |
237 | launder_page: yes |
238 | is_partially_uptodate: yes | |
239 | error_remove_page: yes | |
62c230bc MG |
240 | swap_activate: no |
241 | swap_deactivate: no | |
1da177e4 | 242 | |
f4e6d844 MW |
243 | ->write_begin(), ->write_end() and ->readpage() may be called from |
244 | the request handler (/dev/loop). | |
1da177e4 LT |
245 | |
246 | ->readpage() unlocks the page, either synchronously or via I/O | |
247 | completion. | |
248 | ||
249 | ->readpages() populates the pagecache with the passed pages and starts | |
250 | I/O against them. They come unlocked upon I/O completion. | |
251 | ||
252 | ->writepage() is used for two purposes: for "memory cleansing" and for | |
253 | "sync". These are quite different operations and the behaviour may differ | |
254 | depending upon the mode. | |
255 | ||
256 | If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then | |
257 | it *must* start I/O against the page, even if that would involve | |
258 | blocking on in-progress I/O. | |
259 | ||
260 | If writepage is called for memory cleansing (sync_mode == | |
261 | WBC_SYNC_NONE) then its role is to get as much writeout underway as | |
262 | possible. So writepage should try to avoid blocking against | |
263 | currently-in-progress I/O. | |
264 | ||
265 | If the filesystem is not called for "sync" and it determines that it | |
266 | would need to block against in-progress I/O to be able to start new I/O | |
267 | against the page the filesystem should redirty the page with | |
268 | redirty_page_for_writepage(), then unlock the page and return zero. | |
269 | This may also be done to avoid internal deadlocks, but rarely. | |
270 | ||
3a4fa0a2 | 271 | If the filesystem is called for sync then it must wait on any |
1da177e4 LT |
272 | in-progress I/O and then start new I/O. |
273 | ||
2054606a ND |
274 | The filesystem should unlock the page synchronously, before returning to the |
275 | caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE | |
276 | value. WRITEPAGE_ACTIVATE means that page cannot really be written out | |
277 | currently, and VM should stop calling ->writepage() on this page for some | |
278 | time. VM does this by moving page to the head of the active list, hence the | |
279 | name. | |
1da177e4 LT |
280 | |
281 | Unless the filesystem is going to redirty_page_for_writepage(), unlock the page | |
282 | and return zero, writepage *must* run set_page_writeback() against the page, | |
283 | followed by unlocking it. Once set_page_writeback() has been run against the | |
284 | page, write I/O can be submitted and the write I/O completion handler must run | |
285 | end_page_writeback() once the I/O is complete. If no I/O is submitted, the | |
286 | filesystem must run end_page_writeback() against the page before returning from | |
287 | writepage. | |
288 | ||
289 | That is: after 2.5.12, pages which are under writeout are *not* locked. Note, | |
290 | if the filesystem needs the page to be locked during writeout, that is ok, too, | |
291 | the page is allowed to be unlocked at any point in time between the calls to | |
292 | set_page_writeback() and end_page_writeback(). | |
293 | ||
294 | Note, failure to run either redirty_page_for_writepage() or the combination of | |
295 | set_page_writeback()/end_page_writeback() on a page submitted to writepage | |
296 | will leave the page itself marked clean but it will be tagged as dirty in the | |
297 | radix tree. This incoherency can lead to all sorts of hard-to-debug problems | |
298 | in the filesystem like having dirty inodes at umount and losing written data. | |
299 | ||
1da177e4 LT |
300 | ->writepages() is used for periodic writeback and for syscall-initiated |
301 | sync operations. The address_space should start I/O against at least | |
302 | *nr_to_write pages. *nr_to_write must be decremented for each page which is | |
303 | written. The address_space implementation may write more (or less) pages | |
304 | than *nr_to_write asks for, but it should try to be reasonably close. If | |
305 | nr_to_write is NULL, all dirty pages must be written. | |
306 | ||
307 | writepages should _only_ write pages which are present on | |
308 | mapping->io_pages. | |
309 | ||
310 | ->set_page_dirty() is called from various places in the kernel | |
311 | when the target page is marked as needing writeback. It may be called | |
312 | under spinlock (it cannot block) and is sometimes called with the page | |
313 | not locked. | |
314 | ||
315 | ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some | |
b83be6f2 CH |
316 | filesystems and by the swapper. The latter will eventually go away. Please, |
317 | keep it that way and don't breed new callers. | |
1da177e4 LT |
318 | |
319 | ->invalidatepage() is called when the filesystem must attempt to drop | |
d47992f8 LC |
320 | some or all of the buffers from the page when it is being truncated. It |
321 | returns zero on success. If ->invalidatepage is zero, the kernel uses | |
1da177e4 LT |
322 | block_invalidatepage() instead. |
323 | ||
324 | ->releasepage() is called when the kernel is about to try to drop the | |
325 | buffers from the page in preparation for freeing it. It returns zero to | |
326 | indicate that the buffers are (or may be) freeable. If ->releasepage is zero, | |
327 | the kernel assumes that the fs has no private interest in the buffers. | |
328 | ||
6072d13c LT |
329 | ->freepage() is called when the kernel is done dropping the page |
330 | from the page cache. | |
331 | ||
e3db7691 TM |
332 | ->launder_page() may be called prior to releasing a page if |
333 | it is still found to be dirty. It returns zero if the page was successfully | |
334 | cleaned, or an error value if not. Note that in order to prevent the page | |
335 | getting mapped back in and redirtied, it needs to be kept locked | |
336 | across the entire operation. | |
337 | ||
62c230bc MG |
338 | ->swap_activate will be called with a non-zero argument on |
339 | files backing (non block device backed) swapfiles. A return value | |
340 | of zero indicates success, in which case this file can be used for | |
341 | backing swapspace. The swapspace operations will be proxied to the | |
342 | address space operations. | |
343 | ||
344 | ->swap_deactivate() will be called in the sys_swapoff() | |
345 | path after ->swap_activate() returned success. | |
346 | ||
1da177e4 LT |
347 | ----------------------- file_lock_operations ------------------------------ |
348 | prototypes: | |
1da177e4 LT |
349 | void (*fl_copy_lock)(struct file_lock *, struct file_lock *); |
350 | void (*fl_release_private)(struct file_lock *); | |
351 | ||
352 | ||
353 | locking rules: | |
1c8c601a | 354 | inode->i_lock may block |
b83be6f2 | 355 | fl_copy_lock: yes no |
2ece173e JL |
356 | fl_release_private: maybe maybe[1] |
357 | ||
358 | [1]: ->fl_release_private for flock or POSIX locks is currently allowed | |
359 | to block. Leases however can still be freed while the i_lock is held and | |
360 | so fl_release_private called on a lease should not block. | |
1da177e4 LT |
361 | |
362 | ----------------------- lock_manager_operations --------------------------- | |
363 | prototypes: | |
8fb47a4f BF |
364 | void (*lm_notify)(struct file_lock *); /* unblock callback */ |
365 | int (*lm_grant)(struct file_lock *, struct file_lock *, int); | |
8fb47a4f BF |
366 | void (*lm_break)(struct file_lock *); /* break_lease callback */ |
367 | int (*lm_change)(struct file_lock **, int); | |
1da177e4 LT |
368 | |
369 | locking rules: | |
1c8c601a | 370 | |
7b2296af | 371 | inode->i_lock blocked_lock_lock may block |
7b2296af JL |
372 | lm_notify: yes yes no |
373 | lm_grant: no no no | |
374 | lm_break: yes no no | |
375 | lm_change yes no no | |
1c8c601a | 376 | |
1da177e4 LT |
377 | --------------------------- buffer_head ----------------------------------- |
378 | prototypes: | |
379 | void (*b_end_io)(struct buffer_head *bh, int uptodate); | |
380 | ||
381 | locking rules: | |
382 | called from interrupts. In other words, extreme care is needed here. | |
383 | bh is locked, but that's all warranties we have here. Currently only RAID1, | |
384 | highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices | |
385 | call this method upon the IO completion. | |
386 | ||
387 | --------------------------- block_device_operations ----------------------- | |
388 | prototypes: | |
e1455d1b CH |
389 | int (*open) (struct block_device *, fmode_t); |
390 | int (*release) (struct gendisk *, fmode_t); | |
391 | int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); | |
392 | int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); | |
7a9eb206 | 393 | int (*direct_access) (struct block_device *, sector_t, void **, |
e2e05394 | 394 | unsigned long *); |
1da177e4 | 395 | int (*media_changed) (struct gendisk *); |
e1455d1b | 396 | void (*unlock_native_capacity) (struct gendisk *); |
1da177e4 | 397 | int (*revalidate_disk) (struct gendisk *); |
e1455d1b CH |
398 | int (*getgeo)(struct block_device *, struct hd_geometry *); |
399 | void (*swap_slot_free_notify) (struct block_device *, unsigned long); | |
1da177e4 LT |
400 | |
401 | locking rules: | |
b83be6f2 CH |
402 | bd_mutex |
403 | open: yes | |
404 | release: yes | |
405 | ioctl: no | |
406 | compat_ioctl: no | |
407 | direct_access: no | |
408 | media_changed: no | |
409 | unlock_native_capacity: no | |
410 | revalidate_disk: no | |
411 | getgeo: no | |
412 | swap_slot_free_notify: no (see below) | |
e1455d1b CH |
413 | |
414 | media_changed, unlock_native_capacity and revalidate_disk are called only from | |
415 | check_disk_change(). | |
416 | ||
417 | swap_slot_free_notify is called with swap_lock and sometimes the page lock | |
418 | held. | |
1da177e4 | 419 | |
1da177e4 LT |
420 | |
421 | --------------------------- file_operations ------------------------------- | |
422 | prototypes: | |
423 | loff_t (*llseek) (struct file *, loff_t, int); | |
424 | ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); | |
1da177e4 | 425 | ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); |
293bc982 AV |
426 | ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); |
427 | ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); | |
2233f31a | 428 | int (*iterate) (struct file *, struct dir_context *); |
965de0ec | 429 | int (*iterate_shared) (struct file *, struct dir_context *); |
6e8b704d | 430 | __poll_t (*poll) (struct file *, struct poll_table_struct *); |
1da177e4 LT |
431 | long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); |
432 | long (*compat_ioctl) (struct file *, unsigned int, unsigned long); | |
433 | int (*mmap) (struct file *, struct vm_area_struct *); | |
434 | int (*open) (struct inode *, struct file *); | |
435 | int (*flush) (struct file *); | |
436 | int (*release) (struct inode *, struct file *); | |
02c24a82 | 437 | int (*fsync) (struct file *, loff_t start, loff_t end, int datasync); |
1da177e4 LT |
438 | int (*fasync) (int, struct file *, int); |
439 | int (*lock) (struct file *, int, struct file_lock *); | |
440 | ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, | |
441 | loff_t *); | |
442 | ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, | |
443 | loff_t *); | |
444 | ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t, | |
445 | void __user *); | |
446 | ssize_t (*sendpage) (struct file *, struct page *, int, size_t, | |
447 | loff_t *, int); | |
448 | unsigned long (*get_unmapped_area)(struct file *, unsigned long, | |
449 | unsigned long, unsigned long, unsigned long); | |
450 | int (*check_flags)(int); | |
b83be6f2 CH |
451 | int (*flock) (struct file *, int, struct file_lock *); |
452 | ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, | |
453 | size_t, unsigned int); | |
454 | ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, | |
455 | size_t, unsigned int); | |
e6f5c789 | 456 | int (*setlease)(struct file *, long, struct file_lock **, void **); |
2fe17c10 | 457 | long (*fallocate)(struct file *, int, loff_t, loff_t); |
1da177e4 LT |
458 | }; |
459 | ||
460 | locking rules: | |
a11e1d43 | 461 | All may block. |
b83be6f2 | 462 | |
1da177e4 LT |
463 | ->llseek() locking has moved from llseek to the individual llseek |
464 | implementations. If your fs is not using generic_file_llseek, you | |
465 | need to acquire and release the appropriate locks in your ->llseek(). | |
466 | For many filesystems, it is probably safe to acquire the inode | |
866707fc JB |
467 | mutex or just to use i_size_read() instead. |
468 | Note: this does not protect the file->f_pos against concurrent modifications | |
469 | since this is something the userspace has to take care about. | |
1da177e4 | 470 | |
965de0ec SA |
471 | ->iterate() is called with i_rwsem exclusive. |
472 | ||
473 | ->iterate_shared() is called with i_rwsem at least shared. | |
474 | ||
b83be6f2 CH |
475 | ->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags. |
476 | Most instances call fasync_helper(), which does that maintenance, so it's | |
477 | not normally something one needs to worry about. Return values > 0 will be | |
478 | mapped to zero in the VFS layer. | |
1da177e4 LT |
479 | |
480 | ->readdir() and ->ioctl() on directories must be changed. Ideally we would | |
481 | move ->readdir() to inode_operations and use a separate method for directory | |
482 | ->ioctl() or kill the latter completely. One of the problems is that for | |
483 | anything that resembles union-mount we won't have a struct file for all | |
484 | components. And there are other reasons why the current interface is a mess... | |
485 | ||
1da177e4 LT |
486 | ->read on directories probably must go away - we should just enforce -EISDIR |
487 | in sys_read() and friends. | |
488 | ||
f82b4b67 JL |
489 | ->setlease operations should call generic_setlease() before or after setting |
490 | the lease within the individual filesystem to record the result of the | |
491 | operation | |
492 | ||
1da177e4 LT |
493 | --------------------------- dquot_operations ------------------------------- |
494 | prototypes: | |
1da177e4 LT |
495 | int (*write_dquot) (struct dquot *); |
496 | int (*acquire_dquot) (struct dquot *); | |
497 | int (*release_dquot) (struct dquot *); | |
498 | int (*mark_dirty) (struct dquot *); | |
499 | int (*write_info) (struct super_block *, int); | |
500 | ||
501 | These operations are intended to be more or less wrapping functions that ensure | |
502 | a proper locking wrt the filesystem and call the generic quota operations. | |
503 | ||
504 | What filesystem should expect from the generic quota functions: | |
505 | ||
506 | FS recursion Held locks when called | |
1da177e4 LT |
507 | write_dquot: yes dqonoff_sem or dqptr_sem |
508 | acquire_dquot: yes dqonoff_sem or dqptr_sem | |
509 | release_dquot: yes dqonoff_sem or dqptr_sem | |
510 | mark_dirty: no - | |
511 | write_info: yes dqonoff_sem | |
512 | ||
513 | FS recursion means calling ->quota_read() and ->quota_write() from superblock | |
514 | operations. | |
515 | ||
1da177e4 LT |
516 | More details about quota locking can be found in fs/dquot.c. |
517 | ||
518 | --------------------------- vm_operations_struct ----------------------------- | |
519 | prototypes: | |
520 | void (*open)(struct vm_area_struct*); | |
521 | void (*close)(struct vm_area_struct*); | |
fe3136f4 SJ |
522 | vm_fault_t (*fault)(struct vm_area_struct*, struct vm_fault *); |
523 | vm_fault_t (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *); | |
524 | vm_fault_t (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *); | |
28b2ee20 | 525 | int (*access)(struct vm_area_struct *, unsigned long, void*, int, int); |
1da177e4 LT |
526 | |
527 | locking rules: | |
b83be6f2 CH |
528 | mmap_sem PageLocked(page) |
529 | open: yes | |
530 | close: yes | |
531 | fault: yes can return with page locked | |
8c6e50b0 | 532 | map_pages: yes |
b83be6f2 | 533 | page_mkwrite: yes can return with page locked |
dd906184 | 534 | pfn_mkwrite: yes |
b83be6f2 | 535 | access: yes |
ed2f2f9b | 536 | |
b827e496 NP |
537 | ->fault() is called when a previously not present pte is about |
538 | to be faulted in. The filesystem must find and return the page associated | |
539 | with the passed in "pgoff" in the vm_fault structure. If it is possible that | |
540 | the page may be truncated and/or invalidated, then the filesystem must lock | |
541 | the page, then ensure it is not already truncated (the page lock will block | |
542 | subsequent truncate), and then return with VM_FAULT_LOCKED, and the page | |
543 | locked. The VM will unlock the page. | |
544 | ||
8c6e50b0 | 545 | ->map_pages() is called when VM asks to map easy accessible pages. |
bae473a4 KS |
546 | Filesystem should find and map pages associated with offsets from "start_pgoff" |
547 | till "end_pgoff". ->map_pages() is called with page table locked and must | |
8c6e50b0 KS |
548 | not block. If it's not possible to reach a page without blocking, |
549 | filesystem should skip it. Filesystem should use do_set_pte() to setup | |
bae473a4 | 550 | page table entry. Pointer to entry associated with the page is passed in |
82b0f8c3 | 551 | "pte" field in vm_fault structure. Pointers to entries for other offsets |
bae473a4 | 552 | should be calculated relative to "pte". |
8c6e50b0 | 553 | |
b827e496 NP |
554 | ->page_mkwrite() is called when a previously read-only pte is |
555 | about to become writeable. The filesystem again must ensure that there are | |
556 | no truncate/invalidate races, and then return with the page locked. If | |
557 | the page has been truncated, the filesystem should not look up a new page | |
558 | like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which | |
559 | will cause the VM to retry the fault. | |
1da177e4 | 560 | |
dd906184 BH |
561 | ->pfn_mkwrite() is the same as page_mkwrite but when the pte is |
562 | VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is | |
563 | VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior | |
564 | after this call is to make the pte read-write, unless pfn_mkwrite returns | |
565 | an error. | |
566 | ||
28b2ee20 | 567 | ->access() is called when get_user_pages() fails in |
507da6a1 | 568 | access_process_vm(), typically used to debug a process through |
28b2ee20 RR |
569 | /proc/pid/mem or ptrace. This function is needed only for |
570 | VM_IO | VM_PFNMAP VMAs. | |
571 | ||
1da177e4 LT |
572 | ================================================================================ |
573 | Dubious stuff | |
574 | ||
575 | (if you break something or notice that it is broken and do not fix it yourself | |
576 | - at least put it here) |