Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * linux/fs/file_table.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu) | |
6 | */ | |
7 | ||
8 | #include <linux/string.h> | |
9 | #include <linux/slab.h> | |
10 | #include <linux/file.h> | |
9f3acc31 | 11 | #include <linux/fdtable.h> |
1da177e4 LT |
12 | #include <linux/init.h> |
13 | #include <linux/module.h> | |
1da177e4 LT |
14 | #include <linux/fs.h> |
15 | #include <linux/security.h> | |
16 | #include <linux/eventpoll.h> | |
ab2af1f5 | 17 | #include <linux/rcupdate.h> |
1da177e4 | 18 | #include <linux/mount.h> |
16f7e0fe | 19 | #include <linux/capability.h> |
1da177e4 | 20 | #include <linux/cdev.h> |
0eeca283 | 21 | #include <linux/fsnotify.h> |
529bf6be | 22 | #include <linux/sysctl.h> |
6416ccb7 | 23 | #include <linux/lglock.h> |
529bf6be | 24 | #include <linux/percpu_counter.h> |
6416ccb7 | 25 | #include <linux/percpu.h> |
0552f879 | 26 | #include <linux/ima.h> |
529bf6be DS |
27 | |
28 | #include <asm/atomic.h> | |
1da177e4 | 29 | |
e81e3f4d EP |
30 | #include "internal.h" |
31 | ||
1da177e4 LT |
32 | /* sysctl tunables... */ |
33 | struct files_stat_struct files_stat = { | |
34 | .max_files = NR_FILE | |
35 | }; | |
36 | ||
6416ccb7 NP |
37 | DECLARE_LGLOCK(files_lglock); |
38 | DEFINE_LGLOCK(files_lglock); | |
1da177e4 | 39 | |
b6b3fdea ED |
40 | /* SLAB cache for file structures */ |
41 | static struct kmem_cache *filp_cachep __read_mostly; | |
42 | ||
529bf6be | 43 | static struct percpu_counter nr_files __cacheline_aligned_in_smp; |
1da177e4 | 44 | |
529bf6be | 45 | static inline void file_free_rcu(struct rcu_head *head) |
1da177e4 | 46 | { |
d76b0d9b DH |
47 | struct file *f = container_of(head, struct file, f_u.fu_rcuhead); |
48 | ||
49 | put_cred(f->f_cred); | |
529bf6be | 50 | kmem_cache_free(filp_cachep, f); |
1da177e4 LT |
51 | } |
52 | ||
529bf6be | 53 | static inline void file_free(struct file *f) |
1da177e4 | 54 | { |
529bf6be | 55 | percpu_counter_dec(&nr_files); |
ad775f5a | 56 | file_check_state(f); |
529bf6be | 57 | call_rcu(&f->f_u.fu_rcuhead, file_free_rcu); |
1da177e4 LT |
58 | } |
59 | ||
529bf6be DS |
60 | /* |
61 | * Return the total number of open files in the system | |
62 | */ | |
63 | static int get_nr_files(void) | |
1da177e4 | 64 | { |
529bf6be | 65 | return percpu_counter_read_positive(&nr_files); |
1da177e4 LT |
66 | } |
67 | ||
529bf6be DS |
68 | /* |
69 | * Return the maximum number of open files in the system | |
70 | */ | |
71 | int get_max_files(void) | |
ab2af1f5 | 72 | { |
529bf6be | 73 | return files_stat.max_files; |
ab2af1f5 | 74 | } |
529bf6be DS |
75 | EXPORT_SYMBOL_GPL(get_max_files); |
76 | ||
77 | /* | |
78 | * Handle nr_files sysctl | |
79 | */ | |
80 | #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) | |
8d65af78 | 81 | int proc_nr_files(ctl_table *table, int write, |
529bf6be DS |
82 | void __user *buffer, size_t *lenp, loff_t *ppos) |
83 | { | |
84 | files_stat.nr_files = get_nr_files(); | |
8d65af78 | 85 | return proc_dointvec(table, write, buffer, lenp, ppos); |
529bf6be DS |
86 | } |
87 | #else | |
8d65af78 | 88 | int proc_nr_files(ctl_table *table, int write, |
529bf6be DS |
89 | void __user *buffer, size_t *lenp, loff_t *ppos) |
90 | { | |
91 | return -ENOSYS; | |
92 | } | |
93 | #endif | |
ab2af1f5 | 94 | |
1da177e4 LT |
95 | /* Find an unused file structure and return a pointer to it. |
96 | * Returns NULL, if there are no more free file structures or | |
97 | * we run out of memory. | |
430e285e DH |
98 | * |
99 | * Be very careful using this. You are responsible for | |
100 | * getting write access to any mount that you might assign | |
101 | * to this filp, if it is opened for write. If this is not | |
102 | * done, you will imbalance int the mount's writer count | |
103 | * and a warning at __fput() time. | |
1da177e4 LT |
104 | */ |
105 | struct file *get_empty_filp(void) | |
106 | { | |
86a264ab | 107 | const struct cred *cred = current_cred(); |
af4d2ecb | 108 | static int old_max; |
1da177e4 LT |
109 | struct file * f; |
110 | ||
111 | /* | |
112 | * Privileged users can go above max_files | |
113 | */ | |
529bf6be DS |
114 | if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) { |
115 | /* | |
116 | * percpu_counters are inaccurate. Do an expensive check before | |
117 | * we go and fail. | |
118 | */ | |
52d9f3b4 | 119 | if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files) |
529bf6be DS |
120 | goto over; |
121 | } | |
af4d2ecb | 122 | |
4975e45f | 123 | f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL); |
af4d2ecb KK |
124 | if (f == NULL) |
125 | goto fail; | |
126 | ||
529bf6be | 127 | percpu_counter_inc(&nr_files); |
af4d2ecb KK |
128 | if (security_file_alloc(f)) |
129 | goto fail_sec; | |
1da177e4 | 130 | |
5a6b7951 | 131 | INIT_LIST_HEAD(&f->f_u.fu_list); |
516e0cc5 | 132 | atomic_long_set(&f->f_count, 1); |
af4d2ecb | 133 | rwlock_init(&f->f_owner.lock); |
d76b0d9b | 134 | f->f_cred = get_cred(cred); |
68499914 | 135 | spin_lock_init(&f->f_lock); |
5a6b7951 | 136 | eventpoll_init_file(f); |
af4d2ecb | 137 | /* f->f_version: 0 */ |
af4d2ecb KK |
138 | return f; |
139 | ||
140 | over: | |
1da177e4 | 141 | /* Ran out of filps - report that */ |
529bf6be | 142 | if (get_nr_files() > old_max) { |
1da177e4 | 143 | printk(KERN_INFO "VFS: file-max limit %d reached\n", |
529bf6be DS |
144 | get_max_files()); |
145 | old_max = get_nr_files(); | |
1da177e4 | 146 | } |
af4d2ecb KK |
147 | goto fail; |
148 | ||
149 | fail_sec: | |
150 | file_free(f); | |
1da177e4 LT |
151 | fail: |
152 | return NULL; | |
153 | } | |
154 | ||
ce8d2cdf DH |
155 | /** |
156 | * alloc_file - allocate and initialize a 'struct file' | |
157 | * @mnt: the vfsmount on which the file will reside | |
158 | * @dentry: the dentry representing the new file | |
159 | * @mode: the mode with which the new file will be opened | |
160 | * @fop: the 'struct file_operations' for the new file | |
161 | * | |
162 | * Use this instead of get_empty_filp() to get a new | |
163 | * 'struct file'. Do so because of the same initialization | |
164 | * pitfalls reasons listed for init_file(). This is a | |
165 | * preferred interface to using init_file(). | |
166 | * | |
167 | * If all the callers of init_file() are eliminated, its | |
168 | * code should be moved into this function. | |
169 | */ | |
2c48b9c4 AV |
170 | struct file *alloc_file(struct path *path, fmode_t mode, |
171 | const struct file_operations *fop) | |
ce8d2cdf DH |
172 | { |
173 | struct file *file; | |
ce8d2cdf DH |
174 | |
175 | file = get_empty_filp(); | |
176 | if (!file) | |
177 | return NULL; | |
178 | ||
2c48b9c4 AV |
179 | file->f_path = *path; |
180 | file->f_mapping = path->dentry->d_inode->i_mapping; | |
ce8d2cdf DH |
181 | file->f_mode = mode; |
182 | file->f_op = fop; | |
4a3fd211 DH |
183 | |
184 | /* | |
185 | * These mounts don't really matter in practice | |
186 | * for r/o bind mounts. They aren't userspace- | |
187 | * visible. We do this for consistency, and so | |
188 | * that we can do debugging checks at __fput() | |
189 | */ | |
2c48b9c4 | 190 | if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) { |
ad775f5a | 191 | file_take_write(file); |
385e3ed4 | 192 | WARN_ON(mnt_clone_write(path->mnt)); |
4a3fd211 | 193 | } |
0552f879 | 194 | ima_counts_get(file); |
3d1e4631 | 195 | return file; |
ce8d2cdf | 196 | } |
73efc468 | 197 | EXPORT_SYMBOL(alloc_file); |
ce8d2cdf | 198 | |
aceaf78d DH |
199 | /** |
200 | * drop_file_write_access - give up ability to write to a file | |
201 | * @file: the file to which we will stop writing | |
202 | * | |
203 | * This is a central place which will give up the ability | |
204 | * to write to @file, along with access to write through | |
205 | * its vfsmount. | |
206 | */ | |
207 | void drop_file_write_access(struct file *file) | |
208 | { | |
4a3fd211 | 209 | struct vfsmount *mnt = file->f_path.mnt; |
aceaf78d DH |
210 | struct dentry *dentry = file->f_path.dentry; |
211 | struct inode *inode = dentry->d_inode; | |
212 | ||
213 | put_write_access(inode); | |
ad775f5a DH |
214 | |
215 | if (special_file(inode->i_mode)) | |
216 | return; | |
217 | if (file_check_writeable(file) != 0) | |
218 | return; | |
219 | mnt_drop_write(mnt); | |
220 | file_release_write(file); | |
aceaf78d DH |
221 | } |
222 | EXPORT_SYMBOL_GPL(drop_file_write_access); | |
223 | ||
d7065da0 | 224 | /* the real guts of fput() - releasing the last reference to file |
1da177e4 | 225 | */ |
d7065da0 | 226 | static void __fput(struct file *file) |
1da177e4 | 227 | { |
0f7fc9e4 JJS |
228 | struct dentry *dentry = file->f_path.dentry; |
229 | struct vfsmount *mnt = file->f_path.mnt; | |
1da177e4 LT |
230 | struct inode *inode = dentry->d_inode; |
231 | ||
232 | might_sleep(); | |
0eeca283 RL |
233 | |
234 | fsnotify_close(file); | |
1da177e4 LT |
235 | /* |
236 | * The function eventpoll_release() should be the first called | |
237 | * in the file cleanup chain. | |
238 | */ | |
239 | eventpoll_release(file); | |
240 | locks_remove_flock(file); | |
241 | ||
233e70f4 AV |
242 | if (unlikely(file->f_flags & FASYNC)) { |
243 | if (file->f_op && file->f_op->fasync) | |
244 | file->f_op->fasync(-1, file, 0); | |
245 | } | |
1da177e4 LT |
246 | if (file->f_op && file->f_op->release) |
247 | file->f_op->release(inode, file); | |
248 | security_file_free(file); | |
89068c57 | 249 | ima_file_free(file); |
577c4eb0 | 250 | if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL)) |
1da177e4 LT |
251 | cdev_put(inode->i_cdev); |
252 | fops_put(file->f_op); | |
609d7fa9 | 253 | put_pid(file->f_owner.pid); |
ee2ffa0d | 254 | file_sb_list_del(file); |
aceaf78d DH |
255 | if (file->f_mode & FMODE_WRITE) |
256 | drop_file_write_access(file); | |
0f7fc9e4 JJS |
257 | file->f_path.dentry = NULL; |
258 | file->f_path.mnt = NULL; | |
1da177e4 LT |
259 | file_free(file); |
260 | dput(dentry); | |
261 | mntput(mnt); | |
262 | } | |
263 | ||
d7065da0 AV |
264 | void fput(struct file *file) |
265 | { | |
266 | if (atomic_long_dec_and_test(&file->f_count)) | |
267 | __fput(file); | |
268 | } | |
269 | ||
270 | EXPORT_SYMBOL(fput); | |
271 | ||
fc9b52cd | 272 | struct file *fget(unsigned int fd) |
1da177e4 LT |
273 | { |
274 | struct file *file; | |
275 | struct files_struct *files = current->files; | |
276 | ||
ab2af1f5 | 277 | rcu_read_lock(); |
1da177e4 | 278 | file = fcheck_files(files, fd); |
ab2af1f5 | 279 | if (file) { |
516e0cc5 | 280 | if (!atomic_long_inc_not_zero(&file->f_count)) { |
ab2af1f5 DS |
281 | /* File object ref couldn't be taken */ |
282 | rcu_read_unlock(); | |
283 | return NULL; | |
284 | } | |
285 | } | |
286 | rcu_read_unlock(); | |
287 | ||
1da177e4 LT |
288 | return file; |
289 | } | |
290 | ||
291 | EXPORT_SYMBOL(fget); | |
292 | ||
293 | /* | |
58939473 TB |
294 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. |
295 | * | |
296 | * You can use this instead of fget if you satisfy all of the following | |
297 | * conditions: | |
298 | * 1) You must call fput_light before exiting the syscall and returning control | |
299 | * to userspace (i.e. you cannot remember the returned struct file * after | |
300 | * returning to userspace). | |
301 | * 2) You must not call filp_close on the returned struct file * in between | |
302 | * calls to fget_light and fput_light. | |
303 | * 3) You must not clone the current task in between the calls to fget_light | |
304 | * and fput_light. | |
305 | * | |
306 | * The fput_needed flag returned by fget_light should be passed to the | |
307 | * corresponding fput_light. | |
1da177e4 | 308 | */ |
fc9b52cd | 309 | struct file *fget_light(unsigned int fd, int *fput_needed) |
1da177e4 LT |
310 | { |
311 | struct file *file; | |
312 | struct files_struct *files = current->files; | |
313 | ||
314 | *fput_needed = 0; | |
315 | if (likely((atomic_read(&files->count) == 1))) { | |
316 | file = fcheck_files(files, fd); | |
317 | } else { | |
ab2af1f5 | 318 | rcu_read_lock(); |
1da177e4 LT |
319 | file = fcheck_files(files, fd); |
320 | if (file) { | |
516e0cc5 | 321 | if (atomic_long_inc_not_zero(&file->f_count)) |
ab2af1f5 DS |
322 | *fput_needed = 1; |
323 | else | |
324 | /* Didn't get the reference, someone's freed */ | |
325 | file = NULL; | |
1da177e4 | 326 | } |
ab2af1f5 | 327 | rcu_read_unlock(); |
1da177e4 | 328 | } |
ab2af1f5 | 329 | |
1da177e4 LT |
330 | return file; |
331 | } | |
332 | ||
1da177e4 LT |
333 | void put_filp(struct file *file) |
334 | { | |
516e0cc5 | 335 | if (atomic_long_dec_and_test(&file->f_count)) { |
1da177e4 | 336 | security_file_free(file); |
ee2ffa0d | 337 | file_sb_list_del(file); |
1da177e4 LT |
338 | file_free(file); |
339 | } | |
340 | } | |
341 | ||
6416ccb7 NP |
342 | static inline int file_list_cpu(struct file *file) |
343 | { | |
344 | #ifdef CONFIG_SMP | |
345 | return file->f_sb_list_cpu; | |
346 | #else | |
347 | return smp_processor_id(); | |
348 | #endif | |
349 | } | |
350 | ||
351 | /* helper for file_sb_list_add to reduce ifdefs */ | |
352 | static inline void __file_sb_list_add(struct file *file, struct super_block *sb) | |
353 | { | |
354 | struct list_head *list; | |
355 | #ifdef CONFIG_SMP | |
356 | int cpu; | |
357 | cpu = smp_processor_id(); | |
358 | file->f_sb_list_cpu = cpu; | |
359 | list = per_cpu_ptr(sb->s_files, cpu); | |
360 | #else | |
361 | list = &sb->s_files; | |
362 | #endif | |
363 | list_add(&file->f_u.fu_list, list); | |
364 | } | |
365 | ||
366 | /** | |
367 | * file_sb_list_add - add a file to the sb's file list | |
368 | * @file: file to add | |
369 | * @sb: sb to add it to | |
370 | * | |
371 | * Use this function to associate a file with the superblock of the inode it | |
372 | * refers to. | |
373 | */ | |
ee2ffa0d | 374 | void file_sb_list_add(struct file *file, struct super_block *sb) |
1da177e4 | 375 | { |
6416ccb7 NP |
376 | lg_local_lock(files_lglock); |
377 | __file_sb_list_add(file, sb); | |
378 | lg_local_unlock(files_lglock); | |
1da177e4 LT |
379 | } |
380 | ||
6416ccb7 NP |
381 | /** |
382 | * file_sb_list_del - remove a file from the sb's file list | |
383 | * @file: file to remove | |
384 | * @sb: sb to remove it from | |
385 | * | |
386 | * Use this function to remove a file from its superblock. | |
387 | */ | |
ee2ffa0d | 388 | void file_sb_list_del(struct file *file) |
1da177e4 | 389 | { |
2f512016 | 390 | if (!list_empty(&file->f_u.fu_list)) { |
6416ccb7 | 391 | lg_local_lock_cpu(files_lglock, file_list_cpu(file)); |
2f512016 | 392 | list_del_init(&file->f_u.fu_list); |
6416ccb7 | 393 | lg_local_unlock_cpu(files_lglock, file_list_cpu(file)); |
1da177e4 LT |
394 | } |
395 | } | |
396 | ||
6416ccb7 NP |
397 | #ifdef CONFIG_SMP |
398 | ||
399 | /* | |
400 | * These macros iterate all files on all CPUs for a given superblock. | |
401 | * files_lglock must be held globally. | |
402 | */ | |
403 | #define do_file_list_for_each_entry(__sb, __file) \ | |
404 | { \ | |
405 | int i; \ | |
406 | for_each_possible_cpu(i) { \ | |
407 | struct list_head *list; \ | |
408 | list = per_cpu_ptr((__sb)->s_files, i); \ | |
409 | list_for_each_entry((__file), list, f_u.fu_list) | |
410 | ||
411 | #define while_file_list_for_each_entry \ | |
412 | } \ | |
413 | } | |
414 | ||
415 | #else | |
416 | ||
417 | #define do_file_list_for_each_entry(__sb, __file) \ | |
418 | { \ | |
419 | struct list_head *list; \ | |
420 | list = &(sb)->s_files; \ | |
421 | list_for_each_entry((__file), list, f_u.fu_list) | |
422 | ||
423 | #define while_file_list_for_each_entry \ | |
424 | } | |
425 | ||
426 | #endif | |
427 | ||
1da177e4 LT |
428 | int fs_may_remount_ro(struct super_block *sb) |
429 | { | |
cfdaf9e5 | 430 | struct file *file; |
1da177e4 | 431 | /* Check that no files are currently opened for writing. */ |
6416ccb7 NP |
432 | lg_global_lock(files_lglock); |
433 | do_file_list_for_each_entry(sb, file) { | |
0f7fc9e4 | 434 | struct inode *inode = file->f_path.dentry->d_inode; |
1da177e4 LT |
435 | |
436 | /* File with pending delete? */ | |
437 | if (inode->i_nlink == 0) | |
438 | goto too_bad; | |
439 | ||
440 | /* Writeable file? */ | |
441 | if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE)) | |
442 | goto too_bad; | |
6416ccb7 NP |
443 | } while_file_list_for_each_entry; |
444 | lg_global_unlock(files_lglock); | |
1da177e4 LT |
445 | return 1; /* Tis' cool bro. */ |
446 | too_bad: | |
6416ccb7 | 447 | lg_global_unlock(files_lglock); |
1da177e4 LT |
448 | return 0; |
449 | } | |
450 | ||
864d7c4c | 451 | /** |
452 | * mark_files_ro - mark all files read-only | |
453 | * @sb: superblock in question | |
454 | * | |
455 | * All files are marked read-only. We don't care about pending | |
456 | * delete files so this should be used in 'force' mode only. | |
457 | */ | |
458 | void mark_files_ro(struct super_block *sb) | |
459 | { | |
460 | struct file *f; | |
461 | ||
462 | retry: | |
6416ccb7 NP |
463 | lg_global_lock(files_lglock); |
464 | do_file_list_for_each_entry(sb, f) { | |
864d7c4c | 465 | struct vfsmount *mnt; |
466 | if (!S_ISREG(f->f_path.dentry->d_inode->i_mode)) | |
467 | continue; | |
468 | if (!file_count(f)) | |
469 | continue; | |
470 | if (!(f->f_mode & FMODE_WRITE)) | |
471 | continue; | |
42e49608 | 472 | spin_lock(&f->f_lock); |
864d7c4c | 473 | f->f_mode &= ~FMODE_WRITE; |
42e49608 | 474 | spin_unlock(&f->f_lock); |
864d7c4c | 475 | if (file_check_writeable(f) != 0) |
476 | continue; | |
477 | file_release_write(f); | |
478 | mnt = mntget(f->f_path.mnt); | |
ee2ffa0d | 479 | /* This can sleep, so we can't hold the spinlock. */ |
6416ccb7 | 480 | lg_global_unlock(files_lglock); |
864d7c4c | 481 | mnt_drop_write(mnt); |
482 | mntput(mnt); | |
483 | goto retry; | |
6416ccb7 NP |
484 | } while_file_list_for_each_entry; |
485 | lg_global_unlock(files_lglock); | |
864d7c4c | 486 | } |
487 | ||
1da177e4 LT |
488 | void __init files_init(unsigned long mempages) |
489 | { | |
490 | int n; | |
b6b3fdea ED |
491 | |
492 | filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, | |
493 | SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
494 | ||
495 | /* | |
496 | * One file with associated inode and dcache is very roughly 1K. | |
1da177e4 LT |
497 | * Per default don't use more than 10% of our memory for files. |
498 | */ | |
499 | ||
500 | n = (mempages * (PAGE_SIZE / 1024)) / 10; | |
501 | files_stat.max_files = n; | |
502 | if (files_stat.max_files < NR_FILE) | |
503 | files_stat.max_files = NR_FILE; | |
ab2af1f5 | 504 | files_defer_init(); |
6416ccb7 | 505 | lg_lock_init(files_lglock); |
0216bfcf | 506 | percpu_counter_init(&nr_files, 0); |
1da177e4 | 507 | } |