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/init.h>
12 #include <linux/module.h>
14 #include <linux/security.h>
15 #include <linux/eventpoll.h>
16 #include <linux/rcupdate.h>
17 #include <linux/mount.h>
18 #include <linux/capability.h>
19 #include <linux/cdev.h>
20 #include <linux/fsnotify.h>
21 #include <linux/sysctl.h>
22 #include <linux/percpu_counter.h>
24 #include <asm/atomic.h>
26 /* sysctl tunables... */
27 struct files_stat_struct files_stat
= {
31 /* public. Not pretty! */
32 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(files_lock
);
34 static struct percpu_counter nr_files __cacheline_aligned_in_smp
;
36 static inline void file_free_rcu(struct rcu_head
*head
)
38 struct file
*f
= container_of(head
, struct file
, f_u
.fu_rcuhead
);
39 kmem_cache_free(filp_cachep
, f
);
42 static inline void file_free(struct file
*f
)
44 percpu_counter_dec(&nr_files
);
45 call_rcu(&f
->f_u
.fu_rcuhead
, file_free_rcu
);
49 * Return the total number of open files in the system
51 static int get_nr_files(void)
53 return percpu_counter_read_positive(&nr_files
);
57 * Return the maximum number of open files in the system
59 int get_max_files(void)
61 return files_stat
.max_files
;
63 EXPORT_SYMBOL_GPL(get_max_files
);
66 * Handle nr_files sysctl
68 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
69 int proc_nr_files(ctl_table
*table
, int write
, struct file
*filp
,
70 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
72 files_stat
.nr_files
= get_nr_files();
73 return proc_dointvec(table
, write
, filp
, buffer
, lenp
, ppos
);
76 int proc_nr_files(ctl_table
*table
, int write
, struct file
*filp
,
77 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
83 /* Find an unused file structure and return a pointer to it.
84 * Returns NULL, if there are no more free file structures or
85 * we run out of memory.
87 struct file
*get_empty_filp(void)
89 struct task_struct
*tsk
;
94 * Privileged users can go above max_files
96 if (get_nr_files() >= files_stat
.max_files
&& !capable(CAP_SYS_ADMIN
)) {
98 * percpu_counters are inaccurate. Do an expensive check before
101 if (percpu_counter_sum_positive(&nr_files
) >= files_stat
.max_files
)
105 f
= kmem_cache_zalloc(filp_cachep
, GFP_KERNEL
);
109 percpu_counter_inc(&nr_files
);
110 if (security_file_alloc(f
))
114 INIT_LIST_HEAD(&f
->f_u
.fu_list
);
115 atomic_set(&f
->f_count
, 1);
116 rwlock_init(&f
->f_owner
.lock
);
117 f
->f_uid
= tsk
->fsuid
;
118 f
->f_gid
= tsk
->fsgid
;
119 eventpoll_init_file(f
);
120 /* f->f_version: 0 */
124 /* Ran out of filps - report that */
125 if (get_nr_files() > old_max
) {
126 printk(KERN_INFO
"VFS: file-max limit %d reached\n",
128 old_max
= get_nr_files();
138 EXPORT_SYMBOL(get_empty_filp
);
140 void fastcall
fput(struct file
*file
)
142 if (atomic_dec_and_test(&file
->f_count
))
148 /* __fput is called from task context when aio completion releases the last
149 * last use of a struct file *. Do not use otherwise.
151 void fastcall
__fput(struct file
*file
)
153 struct dentry
*dentry
= file
->f_path
.dentry
;
154 struct vfsmount
*mnt
= file
->f_path
.mnt
;
155 struct inode
*inode
= dentry
->d_inode
;
159 fsnotify_close(file
);
161 * The function eventpoll_release() should be the first called
162 * in the file cleanup chain.
164 eventpoll_release(file
);
165 locks_remove_flock(file
);
167 if (file
->f_op
&& file
->f_op
->release
)
168 file
->f_op
->release(inode
, file
);
169 security_file_free(file
);
170 if (unlikely(S_ISCHR(inode
->i_mode
) && inode
->i_cdev
!= NULL
))
171 cdev_put(inode
->i_cdev
);
172 fops_put(file
->f_op
);
173 if (file
->f_mode
& FMODE_WRITE
)
174 put_write_access(inode
);
175 put_pid(file
->f_owner
.pid
);
177 file
->f_path
.dentry
= NULL
;
178 file
->f_path
.mnt
= NULL
;
184 struct file fastcall
*fget(unsigned int fd
)
187 struct files_struct
*files
= current
->files
;
190 file
= fcheck_files(files
, fd
);
192 if (!atomic_inc_not_zero(&file
->f_count
)) {
193 /* File object ref couldn't be taken */
206 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
207 * You can use this only if it is guranteed that the current task already
208 * holds a refcnt to that file. That check has to be done at fget() only
209 * and a flag is returned to be passed to the corresponding fput_light().
210 * There must not be a cloning between an fget_light/fput_light pair.
212 struct file fastcall
*fget_light(unsigned int fd
, int *fput_needed
)
215 struct files_struct
*files
= current
->files
;
218 if (likely((atomic_read(&files
->count
) == 1))) {
219 file
= fcheck_files(files
, fd
);
222 file
= fcheck_files(files
, fd
);
224 if (atomic_inc_not_zero(&file
->f_count
))
227 /* Didn't get the reference, someone's freed */
237 void put_filp(struct file
*file
)
239 if (atomic_dec_and_test(&file
->f_count
)) {
240 security_file_free(file
);
246 void file_move(struct file
*file
, struct list_head
*list
)
251 list_move(&file
->f_u
.fu_list
, list
);
255 void file_kill(struct file
*file
)
257 if (!list_empty(&file
->f_u
.fu_list
)) {
259 list_del_init(&file
->f_u
.fu_list
);
264 int fs_may_remount_ro(struct super_block
*sb
)
268 /* Check that no files are currently opened for writing. */
270 list_for_each(p
, &sb
->s_files
) {
271 struct file
*file
= list_entry(p
, struct file
, f_u
.fu_list
);
272 struct inode
*inode
= file
->f_path
.dentry
->d_inode
;
274 /* File with pending delete? */
275 if (inode
->i_nlink
== 0)
278 /* Writeable file? */
279 if (S_ISREG(inode
->i_mode
) && (file
->f_mode
& FMODE_WRITE
))
283 return 1; /* Tis' cool bro. */
289 void __init
files_init(unsigned long mempages
)
292 /* One file with associated inode and dcache is very roughly 1K.
293 * Per default don't use more than 10% of our memory for files.
296 n
= (mempages
* (PAGE_SIZE
/ 1024)) / 10;
297 files_stat
.max_files
= n
;
298 if (files_stat
.max_files
< NR_FILE
)
299 files_stat
.max_files
= NR_FILE
;
301 percpu_counter_init(&nr_files
, 0);