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, struct file *filp,
78 void __user *buffer, size_t *lenp, loff_t *ppos)
80 files_stat.nr_files = get_nr_files();
81 return proc_dointvec(table, write, filp, buffer, lenp, ppos);
84 int proc_nr_files(ctl_table *table, int write, struct file *filp,
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.
321 * You can use this only if it is guranteed that the current task already
322 * holds a refcnt to that file. That check has to be done at fget() only
323 * and a flag is returned to be passed to the corresponding fput_light().
324 * There must not be a cloning between an fget_light/fput_light pair.
326 struct file *fget_light(unsigned int fd, int *fput_needed)
329 struct files_struct *files = current->files;
332 if (likely((atomic_read(&files->count) == 1))) {
333 file = fcheck_files(files, fd);
336 file = fcheck_files(files, fd);
338 if (atomic_long_inc_not_zero(&file->f_count))
341 /* Didn't get the reference, someone's freed */
351 void put_filp(struct file *file)
353 if (atomic_long_dec_and_test(&file->f_count)) {
354 security_file_free(file);
360 void file_move(struct file *file, struct list_head *list)
365 list_move(&file->f_u.fu_list, list);
369 void file_kill(struct file *file)
371 if (!list_empty(&file->f_u.fu_list)) {
373 list_del_init(&file->f_u.fu_list);
378 int fs_may_remount_ro(struct super_block *sb)
382 /* Check that no files are currently opened for writing. */
384 list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
385 struct inode *inode = file->f_path.dentry->d_inode;
387 /* File with pending delete? */
388 if (inode->i_nlink == 0)
391 /* Writeable file? */
392 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
396 return 1; /* Tis' cool bro. */
403 * mark_files_ro - mark all files read-only
404 * @sb: superblock in question
406 * All files are marked read-only. We don't care about pending
407 * delete files so this should be used in 'force' mode only.
409 void mark_files_ro(struct super_block *sb)
415 list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
416 struct vfsmount *mnt;
417 if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
421 if (!(f->f_mode & FMODE_WRITE))
423 f->f_mode &= ~FMODE_WRITE;
424 if (file_check_writeable(f) != 0)
426 file_release_write(f);
427 mnt = mntget(f->f_path.mnt);
430 * This can sleep, so we can't hold
431 * the file_list_lock() spinlock.
440 void __init files_init(unsigned long mempages)
444 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
445 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
448 * One file with associated inode and dcache is very roughly 1K.
449 * Per default don't use more than 10% of our memory for files.
452 n = (mempages * (PAGE_SIZE / 1024)) / 10;
453 files_stat.max_files = n;
454 if (files_stat.max_files < NR_FILE)
455 files_stat.max_files = NR_FILE;
457 percpu_counter_init(&nr_files, 0);