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Commit | Line | Data |
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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 DS |
22 | #include <linux/sysctl.h> |
23 | #include <linux/percpu_counter.h> | |
24 | ||
25 | #include <asm/atomic.h> | |
1da177e4 | 26 | |
e81e3f4d EP |
27 | #include "internal.h" |
28 | ||
1da177e4 LT |
29 | /* sysctl tunables... */ |
30 | struct files_stat_struct files_stat = { | |
31 | .max_files = NR_FILE | |
32 | }; | |
33 | ||
1da177e4 | 34 | /* public. Not pretty! */ |
529bf6be | 35 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock); |
1da177e4 | 36 | |
b6b3fdea ED |
37 | /* SLAB cache for file structures */ |
38 | static struct kmem_cache *filp_cachep __read_mostly; | |
39 | ||
529bf6be | 40 | static struct percpu_counter nr_files __cacheline_aligned_in_smp; |
1da177e4 | 41 | |
529bf6be | 42 | static inline void file_free_rcu(struct rcu_head *head) |
1da177e4 | 43 | { |
d76b0d9b DH |
44 | struct file *f = container_of(head, struct file, f_u.fu_rcuhead); |
45 | ||
46 | put_cred(f->f_cred); | |
529bf6be | 47 | kmem_cache_free(filp_cachep, f); |
1da177e4 LT |
48 | } |
49 | ||
529bf6be | 50 | static inline void file_free(struct file *f) |
1da177e4 | 51 | { |
529bf6be | 52 | percpu_counter_dec(&nr_files); |
ad775f5a | 53 | file_check_state(f); |
529bf6be | 54 | call_rcu(&f->f_u.fu_rcuhead, file_free_rcu); |
1da177e4 LT |
55 | } |
56 | ||
529bf6be DS |
57 | /* |
58 | * Return the total number of open files in the system | |
59 | */ | |
60 | static int get_nr_files(void) | |
1da177e4 | 61 | { |
529bf6be | 62 | return percpu_counter_read_positive(&nr_files); |
1da177e4 LT |
63 | } |
64 | ||
529bf6be DS |
65 | /* |
66 | * Return the maximum number of open files in the system | |
67 | */ | |
68 | int get_max_files(void) | |
ab2af1f5 | 69 | { |
529bf6be | 70 | return files_stat.max_files; |
ab2af1f5 | 71 | } |
529bf6be DS |
72 | EXPORT_SYMBOL_GPL(get_max_files); |
73 | ||
74 | /* | |
75 | * Handle nr_files sysctl | |
76 | */ | |
77 | #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) | |
8d65af78 | 78 | int proc_nr_files(ctl_table *table, int write, |
529bf6be DS |
79 | void __user *buffer, size_t *lenp, loff_t *ppos) |
80 | { | |
81 | files_stat.nr_files = get_nr_files(); | |
8d65af78 | 82 | return proc_dointvec(table, write, buffer, lenp, ppos); |
529bf6be DS |
83 | } |
84 | #else | |
8d65af78 | 85 | int proc_nr_files(ctl_table *table, int write, |
529bf6be DS |
86 | void __user *buffer, size_t *lenp, loff_t *ppos) |
87 | { | |
88 | return -ENOSYS; | |
89 | } | |
90 | #endif | |
ab2af1f5 | 91 | |
1da177e4 LT |
92 | /* Find an unused file structure and return a pointer to it. |
93 | * Returns NULL, if there are no more free file structures or | |
94 | * we run out of memory. | |
430e285e DH |
95 | * |
96 | * Be very careful using this. You are responsible for | |
97 | * getting write access to any mount that you might assign | |
98 | * to this filp, if it is opened for write. If this is not | |
99 | * done, you will imbalance int the mount's writer count | |
100 | * and a warning at __fput() time. | |
1da177e4 LT |
101 | */ |
102 | struct file *get_empty_filp(void) | |
103 | { | |
86a264ab | 104 | const struct cred *cred = current_cred(); |
af4d2ecb | 105 | static int old_max; |
1da177e4 LT |
106 | struct file * f; |
107 | ||
108 | /* | |
109 | * Privileged users can go above max_files | |
110 | */ | |
529bf6be DS |
111 | if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) { |
112 | /* | |
113 | * percpu_counters are inaccurate. Do an expensive check before | |
114 | * we go and fail. | |
115 | */ | |
52d9f3b4 | 116 | if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files) |
529bf6be DS |
117 | goto over; |
118 | } | |
af4d2ecb | 119 | |
4975e45f | 120 | f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL); |
af4d2ecb KK |
121 | if (f == NULL) |
122 | goto fail; | |
123 | ||
529bf6be | 124 | percpu_counter_inc(&nr_files); |
af4d2ecb KK |
125 | if (security_file_alloc(f)) |
126 | goto fail_sec; | |
1da177e4 | 127 | |
5a6b7951 | 128 | INIT_LIST_HEAD(&f->f_u.fu_list); |
516e0cc5 | 129 | atomic_long_set(&f->f_count, 1); |
af4d2ecb | 130 | rwlock_init(&f->f_owner.lock); |
d76b0d9b | 131 | f->f_cred = get_cred(cred); |
68499914 | 132 | spin_lock_init(&f->f_lock); |
5a6b7951 | 133 | eventpoll_init_file(f); |
af4d2ecb | 134 | /* f->f_version: 0 */ |
af4d2ecb KK |
135 | return f; |
136 | ||
137 | over: | |
1da177e4 | 138 | /* Ran out of filps - report that */ |
529bf6be | 139 | if (get_nr_files() > old_max) { |
1da177e4 | 140 | printk(KERN_INFO "VFS: file-max limit %d reached\n", |
529bf6be DS |
141 | get_max_files()); |
142 | old_max = get_nr_files(); | |
1da177e4 | 143 | } |
af4d2ecb KK |
144 | goto fail; |
145 | ||
146 | fail_sec: | |
147 | file_free(f); | |
1da177e4 LT |
148 | fail: |
149 | return NULL; | |
150 | } | |
151 | ||
ce8d2cdf DH |
152 | /** |
153 | * alloc_file - allocate and initialize a 'struct file' | |
154 | * @mnt: the vfsmount on which the file will reside | |
155 | * @dentry: the dentry representing the new file | |
156 | * @mode: the mode with which the new file will be opened | |
157 | * @fop: the 'struct file_operations' for the new file | |
158 | * | |
159 | * Use this instead of get_empty_filp() to get a new | |
160 | * 'struct file'. Do so because of the same initialization | |
161 | * pitfalls reasons listed for init_file(). This is a | |
162 | * preferred interface to using init_file(). | |
163 | * | |
164 | * If all the callers of init_file() are eliminated, its | |
165 | * code should be moved into this function. | |
166 | */ | |
2c48b9c4 AV |
167 | struct file *alloc_file(struct path *path, fmode_t mode, |
168 | const struct file_operations *fop) | |
ce8d2cdf DH |
169 | { |
170 | struct file *file; | |
ce8d2cdf DH |
171 | |
172 | file = get_empty_filp(); | |
173 | if (!file) | |
174 | return NULL; | |
175 | ||
2c48b9c4 AV |
176 | file->f_path = *path; |
177 | file->f_mapping = path->dentry->d_inode->i_mapping; | |
ce8d2cdf DH |
178 | file->f_mode = mode; |
179 | file->f_op = fop; | |
4a3fd211 DH |
180 | |
181 | /* | |
182 | * These mounts don't really matter in practice | |
183 | * for r/o bind mounts. They aren't userspace- | |
184 | * visible. We do this for consistency, and so | |
185 | * that we can do debugging checks at __fput() | |
186 | */ | |
2c48b9c4 | 187 | if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) { |
3d1e4631 | 188 | int error = 0; |
ad775f5a | 189 | file_take_write(file); |
2c48b9c4 | 190 | error = mnt_clone_write(path->mnt); |
4a3fd211 DH |
191 | WARN_ON(error); |
192 | } | |
3d1e4631 | 193 | return file; |
ce8d2cdf | 194 | } |
ce8d2cdf | 195 | |
fc9b52cd | 196 | void fput(struct file *file) |
1da177e4 | 197 | { |
516e0cc5 | 198 | if (atomic_long_dec_and_test(&file->f_count)) |
1da177e4 LT |
199 | __fput(file); |
200 | } | |
201 | ||
202 | EXPORT_SYMBOL(fput); | |
203 | ||
aceaf78d DH |
204 | /** |
205 | * drop_file_write_access - give up ability to write to a file | |
206 | * @file: the file to which we will stop writing | |
207 | * | |
208 | * This is a central place which will give up the ability | |
209 | * to write to @file, along with access to write through | |
210 | * its vfsmount. | |
211 | */ | |
212 | void drop_file_write_access(struct file *file) | |
213 | { | |
4a3fd211 | 214 | struct vfsmount *mnt = file->f_path.mnt; |
aceaf78d DH |
215 | struct dentry *dentry = file->f_path.dentry; |
216 | struct inode *inode = dentry->d_inode; | |
217 | ||
218 | put_write_access(inode); | |
ad775f5a DH |
219 | |
220 | if (special_file(inode->i_mode)) | |
221 | return; | |
222 | if (file_check_writeable(file) != 0) | |
223 | return; | |
224 | mnt_drop_write(mnt); | |
225 | file_release_write(file); | |
aceaf78d DH |
226 | } |
227 | EXPORT_SYMBOL_GPL(drop_file_write_access); | |
228 | ||
1da177e4 LT |
229 | /* __fput is called from task context when aio completion releases the last |
230 | * last use of a struct file *. Do not use otherwise. | |
231 | */ | |
fc9b52cd | 232 | void __fput(struct file *file) |
1da177e4 | 233 | { |
0f7fc9e4 JJS |
234 | struct dentry *dentry = file->f_path.dentry; |
235 | struct vfsmount *mnt = file->f_path.mnt; | |
1da177e4 LT |
236 | struct inode *inode = dentry->d_inode; |
237 | ||
238 | might_sleep(); | |
0eeca283 RL |
239 | |
240 | fsnotify_close(file); | |
1da177e4 LT |
241 | /* |
242 | * The function eventpoll_release() should be the first called | |
243 | * in the file cleanup chain. | |
244 | */ | |
245 | eventpoll_release(file); | |
246 | locks_remove_flock(file); | |
247 | ||
233e70f4 AV |
248 | if (unlikely(file->f_flags & FASYNC)) { |
249 | if (file->f_op && file->f_op->fasync) | |
250 | file->f_op->fasync(-1, file, 0); | |
251 | } | |
1da177e4 LT |
252 | if (file->f_op && file->f_op->release) |
253 | file->f_op->release(inode, file); | |
254 | security_file_free(file); | |
577c4eb0 | 255 | if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL)) |
1da177e4 LT |
256 | cdev_put(inode->i_cdev); |
257 | fops_put(file->f_op); | |
609d7fa9 | 258 | put_pid(file->f_owner.pid); |
1da177e4 | 259 | file_kill(file); |
aceaf78d DH |
260 | if (file->f_mode & FMODE_WRITE) |
261 | drop_file_write_access(file); | |
0f7fc9e4 JJS |
262 | file->f_path.dentry = NULL; |
263 | file->f_path.mnt = NULL; | |
1da177e4 LT |
264 | file_free(file); |
265 | dput(dentry); | |
266 | mntput(mnt); | |
267 | } | |
268 | ||
fc9b52cd | 269 | struct file *fget(unsigned int fd) |
1da177e4 LT |
270 | { |
271 | struct file *file; | |
272 | struct files_struct *files = current->files; | |
273 | ||
ab2af1f5 | 274 | rcu_read_lock(); |
1da177e4 | 275 | file = fcheck_files(files, fd); |
ab2af1f5 | 276 | if (file) { |
516e0cc5 | 277 | if (!atomic_long_inc_not_zero(&file->f_count)) { |
ab2af1f5 DS |
278 | /* File object ref couldn't be taken */ |
279 | rcu_read_unlock(); | |
280 | return NULL; | |
281 | } | |
282 | } | |
283 | rcu_read_unlock(); | |
284 | ||
1da177e4 LT |
285 | return file; |
286 | } | |
287 | ||
288 | EXPORT_SYMBOL(fget); | |
289 | ||
290 | /* | |
291 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. | |
292 | * You can use this only if it is guranteed that the current task already | |
293 | * holds a refcnt to that file. That check has to be done at fget() only | |
294 | * and a flag is returned to be passed to the corresponding fput_light(). | |
295 | * There must not be a cloning between an fget_light/fput_light pair. | |
296 | */ | |
fc9b52cd | 297 | struct file *fget_light(unsigned int fd, int *fput_needed) |
1da177e4 LT |
298 | { |
299 | struct file *file; | |
300 | struct files_struct *files = current->files; | |
301 | ||
302 | *fput_needed = 0; | |
303 | if (likely((atomic_read(&files->count) == 1))) { | |
304 | file = fcheck_files(files, fd); | |
305 | } else { | |
ab2af1f5 | 306 | rcu_read_lock(); |
1da177e4 LT |
307 | file = fcheck_files(files, fd); |
308 | if (file) { | |
516e0cc5 | 309 | if (atomic_long_inc_not_zero(&file->f_count)) |
ab2af1f5 DS |
310 | *fput_needed = 1; |
311 | else | |
312 | /* Didn't get the reference, someone's freed */ | |
313 | file = NULL; | |
1da177e4 | 314 | } |
ab2af1f5 | 315 | rcu_read_unlock(); |
1da177e4 | 316 | } |
ab2af1f5 | 317 | |
1da177e4 LT |
318 | return file; |
319 | } | |
320 | ||
321 | ||
322 | void put_filp(struct file *file) | |
323 | { | |
516e0cc5 | 324 | if (atomic_long_dec_and_test(&file->f_count)) { |
1da177e4 LT |
325 | security_file_free(file); |
326 | file_kill(file); | |
327 | file_free(file); | |
328 | } | |
329 | } | |
330 | ||
331 | void file_move(struct file *file, struct list_head *list) | |
332 | { | |
333 | if (!list) | |
334 | return; | |
335 | file_list_lock(); | |
2f512016 | 336 | list_move(&file->f_u.fu_list, list); |
1da177e4 LT |
337 | file_list_unlock(); |
338 | } | |
339 | ||
340 | void file_kill(struct file *file) | |
341 | { | |
2f512016 | 342 | if (!list_empty(&file->f_u.fu_list)) { |
1da177e4 | 343 | file_list_lock(); |
2f512016 | 344 | list_del_init(&file->f_u.fu_list); |
1da177e4 LT |
345 | file_list_unlock(); |
346 | } | |
347 | } | |
348 | ||
349 | int fs_may_remount_ro(struct super_block *sb) | |
350 | { | |
cfdaf9e5 | 351 | struct file *file; |
1da177e4 LT |
352 | |
353 | /* Check that no files are currently opened for writing. */ | |
354 | file_list_lock(); | |
cfdaf9e5 | 355 | list_for_each_entry(file, &sb->s_files, f_u.fu_list) { |
0f7fc9e4 | 356 | struct inode *inode = file->f_path.dentry->d_inode; |
1da177e4 LT |
357 | |
358 | /* File with pending delete? */ | |
359 | if (inode->i_nlink == 0) | |
360 | goto too_bad; | |
361 | ||
362 | /* Writeable file? */ | |
363 | if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE)) | |
364 | goto too_bad; | |
365 | } | |
366 | file_list_unlock(); | |
367 | return 1; /* Tis' cool bro. */ | |
368 | too_bad: | |
369 | file_list_unlock(); | |
370 | return 0; | |
371 | } | |
372 | ||
864d7c4c NP |
373 | /** |
374 | * mark_files_ro - mark all files read-only | |
375 | * @sb: superblock in question | |
376 | * | |
377 | * All files are marked read-only. We don't care about pending | |
378 | * delete files so this should be used in 'force' mode only. | |
379 | */ | |
380 | void mark_files_ro(struct super_block *sb) | |
381 | { | |
382 | struct file *f; | |
383 | ||
384 | retry: | |
385 | file_list_lock(); | |
386 | list_for_each_entry(f, &sb->s_files, f_u.fu_list) { | |
387 | struct vfsmount *mnt; | |
388 | if (!S_ISREG(f->f_path.dentry->d_inode->i_mode)) | |
389 | continue; | |
390 | if (!file_count(f)) | |
391 | continue; | |
392 | if (!(f->f_mode & FMODE_WRITE)) | |
393 | continue; | |
394 | f->f_mode &= ~FMODE_WRITE; | |
395 | if (file_check_writeable(f) != 0) | |
396 | continue; | |
397 | file_release_write(f); | |
398 | mnt = mntget(f->f_path.mnt); | |
399 | file_list_unlock(); | |
400 | /* | |
401 | * This can sleep, so we can't hold | |
402 | * the file_list_lock() spinlock. | |
403 | */ | |
404 | mnt_drop_write(mnt); | |
405 | mntput(mnt); | |
406 | goto retry; | |
407 | } | |
408 | file_list_unlock(); | |
409 | } | |
410 | ||
1da177e4 LT |
411 | void __init files_init(unsigned long mempages) |
412 | { | |
413 | int n; | |
b6b3fdea ED |
414 | |
415 | filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, | |
416 | SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
417 | ||
418 | /* | |
419 | * One file with associated inode and dcache is very roughly 1K. | |
1da177e4 LT |
420 | * Per default don't use more than 10% of our memory for files. |
421 | */ | |
422 | ||
423 | n = (mempages * (PAGE_SIZE / 1024)) / 10; | |
424 | files_stat.max_files = n; | |
425 | if (files_stat.max_files < NR_FILE) | |
426 | files_stat.max_files = NR_FILE; | |
ab2af1f5 | 427 | files_defer_init(); |
0216bfcf | 428 | percpu_counter_init(&nr_files, 0); |
1da177e4 | 429 | } |