2 * linux/fs/file_table.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
8 #include <linux/string.h>
9 #include <linux/slab.h>
10 #include <linux/file.h>
11 #include <linux/fdtable.h>
12 #include <linux/init.h>
13 #include <linux/module.h>
15 #include <linux/security.h>
16 #include <linux/ima.h>
17 #include <linux/eventpoll.h>
18 #include <linux/rcupdate.h>
19 #include <linux/mount.h>
20 #include <linux/capability.h>
21 #include <linux/cdev.h>
22 #include <linux/fsnotify.h>
23 #include <linux/sysctl.h>
24 #include <linux/percpu_counter.h>
26 #include <asm/atomic.h>
28 /* sysctl tunables... */
29 struct files_stat_struct files_stat
= {
33 /* public. Not pretty! */
34 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(files_lock
);
36 /* SLAB cache for file structures */
37 static struct kmem_cache
*filp_cachep __read_mostly
;
39 static struct percpu_counter nr_files __cacheline_aligned_in_smp
;
41 static inline void file_free_rcu(struct rcu_head
*head
)
43 struct file
*f
= container_of(head
, struct file
, f_u
.fu_rcuhead
);
46 kmem_cache_free(filp_cachep
, f
);
49 static inline void file_free(struct file
*f
)
51 percpu_counter_dec(&nr_files
);
53 call_rcu(&f
->f_u
.fu_rcuhead
, file_free_rcu
);
57 * Return the total number of open files in the system
59 static int get_nr_files(void)
61 return percpu_counter_read_positive(&nr_files
);
65 * Return the maximum number of open files in the system
67 int get_max_files(void)
69 return files_stat
.max_files
;
71 EXPORT_SYMBOL_GPL(get_max_files
);
74 * Handle nr_files sysctl
76 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
77 int proc_nr_files(ctl_table
*table
, int write
,
78 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
80 files_stat
.nr_files
= get_nr_files();
81 return proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
84 int proc_nr_files(ctl_table
*table
, int write
,
85 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
91 /* Find an unused file structure and return a pointer to it.
92 * Returns NULL, if there are no more free file structures or
93 * we run out of memory.
95 * Be very careful using this. You are responsible for
96 * getting write access to any mount that you might assign
97 * to this filp, if it is opened for write. If this is not
98 * done, you will imbalance int the mount's writer count
99 * and a warning at __fput() time.
101 struct file
*get_empty_filp(void)
103 const struct cred
*cred
= current_cred();
108 * Privileged users can go above max_files
110 if (get_nr_files() >= files_stat
.max_files
&& !capable(CAP_SYS_ADMIN
)) {
112 * percpu_counters are inaccurate. Do an expensive check before
115 if (percpu_counter_sum_positive(&nr_files
) >= files_stat
.max_files
)
119 f
= kmem_cache_zalloc(filp_cachep
, GFP_KERNEL
);
123 percpu_counter_inc(&nr_files
);
124 if (security_file_alloc(f
))
127 INIT_LIST_HEAD(&f
->f_u
.fu_list
);
128 atomic_long_set(&f
->f_count
, 1);
129 rwlock_init(&f
->f_owner
.lock
);
130 f
->f_cred
= get_cred(cred
);
131 spin_lock_init(&f
->f_lock
);
132 eventpoll_init_file(f
);
133 /* f->f_version: 0 */
137 /* Ran out of filps - report that */
138 if (get_nr_files() > old_max
) {
139 printk(KERN_INFO
"VFS: file-max limit %d reached\n",
141 old_max
= get_nr_files();
151 EXPORT_SYMBOL(get_empty_filp
);
154 * alloc_file - allocate and initialize a 'struct file'
155 * @mnt: the vfsmount on which the file will reside
156 * @dentry: the dentry representing the new file
157 * @mode: the mode with which the new file will be opened
158 * @fop: the 'struct file_operations' for the new file
160 * Use this instead of get_empty_filp() to get a new
161 * 'struct file'. Do so because of the same initialization
162 * pitfalls reasons listed for init_file(). This is a
163 * preferred interface to using init_file().
165 * If all the callers of init_file() are eliminated, its
166 * code should be moved into this function.
168 struct file
*alloc_file(struct vfsmount
*mnt
, struct dentry
*dentry
,
169 fmode_t mode
, const struct file_operations
*fop
)
173 file
= get_empty_filp();
177 init_file(file
, mnt
, dentry
, mode
, fop
);
180 EXPORT_SYMBOL(alloc_file
);
183 * init_file - initialize a 'struct file'
184 * @file: the already allocated 'struct file' to initialized
185 * @mnt: the vfsmount on which the file resides
186 * @dentry: the dentry representing this file
187 * @mode: the mode the file is opened with
188 * @fop: the 'struct file_operations' for this file
190 * Use this instead of setting the members directly. Doing so
191 * avoids making mistakes like forgetting the mntget() or
192 * forgetting to take a write on the mnt.
194 * Note: This is a crappy interface. It is here to make
195 * merging with the existing users of get_empty_filp()
196 * who have complex failure logic easier. All users
197 * of this should be moving to alloc_file().
199 int init_file(struct file
*file
, struct vfsmount
*mnt
, struct dentry
*dentry
,
200 fmode_t mode
, const struct file_operations
*fop
)
203 file
->f_path
.dentry
= dentry
;
204 file
->f_path
.mnt
= mntget(mnt
);
205 file
->f_mapping
= dentry
->d_inode
->i_mapping
;
210 * These mounts don't really matter in practice
211 * for r/o bind mounts. They aren't userspace-
212 * visible. We do this for consistency, and so
213 * that we can do debugging checks at __fput()
215 if ((mode
& FMODE_WRITE
) && !special_file(dentry
->d_inode
->i_mode
)) {
216 file_take_write(file
);
217 error
= mnt_clone_write(mnt
);
222 EXPORT_SYMBOL(init_file
);
224 void fput(struct file
*file
)
226 if (atomic_long_dec_and_test(&file
->f_count
))
233 * drop_file_write_access - give up ability to write to a file
234 * @file: the file to which we will stop writing
236 * This is a central place which will give up the ability
237 * to write to @file, along with access to write through
240 void drop_file_write_access(struct file
*file
)
242 struct vfsmount
*mnt
= file
->f_path
.mnt
;
243 struct dentry
*dentry
= file
->f_path
.dentry
;
244 struct inode
*inode
= dentry
->d_inode
;
246 put_write_access(inode
);
248 if (special_file(inode
->i_mode
))
250 if (file_check_writeable(file
) != 0)
253 file_release_write(file
);
255 EXPORT_SYMBOL_GPL(drop_file_write_access
);
257 /* __fput is called from task context when aio completion releases the last
258 * last use of a struct file *. Do not use otherwise.
260 void __fput(struct file
*file
)
262 struct dentry
*dentry
= file
->f_path
.dentry
;
263 struct vfsmount
*mnt
= file
->f_path
.mnt
;
264 struct inode
*inode
= dentry
->d_inode
;
268 fsnotify_close(file
);
270 * The function eventpoll_release() should be the first called
271 * in the file cleanup chain.
273 eventpoll_release(file
);
274 locks_remove_flock(file
);
276 if (unlikely(file
->f_flags
& FASYNC
)) {
277 if (file
->f_op
&& file
->f_op
->fasync
)
278 file
->f_op
->fasync(-1, file
, 0);
280 if (file
->f_op
&& file
->f_op
->release
)
281 file
->f_op
->release(inode
, file
);
282 security_file_free(file
);
284 if (unlikely(S_ISCHR(inode
->i_mode
) && inode
->i_cdev
!= NULL
))
285 cdev_put(inode
->i_cdev
);
286 fops_put(file
->f_op
);
287 put_pid(file
->f_owner
.pid
);
289 if (file
->f_mode
& FMODE_WRITE
)
290 drop_file_write_access(file
);
291 file
->f_path
.dentry
= NULL
;
292 file
->f_path
.mnt
= NULL
;
298 struct file
*fget(unsigned int fd
)
301 struct files_struct
*files
= current
->files
;
304 file
= fcheck_files(files
, fd
);
306 if (!atomic_long_inc_not_zero(&file
->f_count
)) {
307 /* File object ref couldn't be taken */
320 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
322 * You can use this instead of fget if you satisfy all of the following
324 * 1) You must call fput_light before exiting the syscall and returning control
325 * to userspace (i.e. you cannot remember the returned struct file * after
326 * returning to userspace).
327 * 2) You must not call filp_close on the returned struct file * in between
328 * calls to fget_light and fput_light.
329 * 3) You must not clone the current task in between the calls to fget_light
332 * The fput_needed flag returned by fget_light should be passed to the
333 * corresponding fput_light.
335 struct file
*fget_light(unsigned int fd
, int *fput_needed
)
338 struct files_struct
*files
= current
->files
;
341 if (likely((atomic_read(&files
->count
) == 1))) {
342 file
= fcheck_files(files
, fd
);
345 file
= fcheck_files(files
, fd
);
347 if (atomic_long_inc_not_zero(&file
->f_count
))
350 /* Didn't get the reference, someone's freed */
360 void put_filp(struct file
*file
)
362 if (atomic_long_dec_and_test(&file
->f_count
)) {
363 security_file_free(file
);
369 void file_move(struct file
*file
, struct list_head
*list
)
374 list_move(&file
->f_u
.fu_list
, list
);
378 void file_kill(struct file
*file
)
380 if (!list_empty(&file
->f_u
.fu_list
)) {
382 list_del_init(&file
->f_u
.fu_list
);
387 int fs_may_remount_ro(struct super_block
*sb
)
391 /* Check that no files are currently opened for writing. */
393 list_for_each_entry(file
, &sb
->s_files
, f_u
.fu_list
) {
394 struct inode
*inode
= file
->f_path
.dentry
->d_inode
;
396 /* File with pending delete? */
397 if (inode
->i_nlink
== 0)
400 /* Writeable file? */
401 if (S_ISREG(inode
->i_mode
) && (file
->f_mode
& FMODE_WRITE
))
405 return 1; /* Tis' cool bro. */
412 * mark_files_ro - mark all files read-only
413 * @sb: superblock in question
415 * All files are marked read-only. We don't care about pending
416 * delete files so this should be used in 'force' mode only.
418 void mark_files_ro(struct super_block
*sb
)
424 list_for_each_entry(f
, &sb
->s_files
, f_u
.fu_list
) {
425 struct vfsmount
*mnt
;
426 if (!S_ISREG(f
->f_path
.dentry
->d_inode
->i_mode
))
430 if (!(f
->f_mode
& FMODE_WRITE
))
432 f
->f_mode
&= ~FMODE_WRITE
;
433 if (file_check_writeable(f
) != 0)
435 file_release_write(f
);
436 mnt
= mntget(f
->f_path
.mnt
);
439 * This can sleep, so we can't hold
440 * the file_list_lock() spinlock.
449 void __init
files_init(unsigned long mempages
)
453 filp_cachep
= kmem_cache_create("filp", sizeof(struct file
), 0,
454 SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
457 * One file with associated inode and dcache is very roughly 1K.
458 * Per default don't use more than 10% of our memory for files.
461 n
= (mempages
* (PAGE_SIZE
/ 1024)) / 10;
462 files_stat
.max_files
= n
;
463 if (files_stat
.max_files
< NR_FILE
)
464 files_stat
.max_files
= NR_FILE
;
466 percpu_counter_init(&nr_files
, 0);