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/eventpoll.h>
17 #include <linux/rcupdate.h>
18 #include <linux/mount.h>
19 #include <linux/capability.h>
20 #include <linux/cdev.h>
21 #include <linux/fsnotify.h>
22 #include <linux/sysctl.h>
23 #include <linux/lglock.h>
24 #include <linux/percpu_counter.h>
25 #include <linux/percpu.h>
26 #include <linux/hardirq.h>
27 #include <linux/task_work.h>
28 #include <linux/ima.h>
30 #include <linux/atomic.h>
34 /* sysctl tunables... */
35 struct files_stat_struct files_stat = {
39 DEFINE_STATIC_LGLOCK(files_lglock);
41 /* SLAB cache for file structures */
42 static struct kmem_cache *filp_cachep __read_mostly;
44 static struct percpu_counter nr_files __cacheline_aligned_in_smp;
46 static void file_free_rcu(struct rcu_head *head)
48 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
51 kmem_cache_free(filp_cachep, f);
54 static inline void file_free(struct file *f)
56 percpu_counter_dec(&nr_files);
58 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
62 * Return the total number of open files in the system
64 static long get_nr_files(void)
66 return percpu_counter_read_positive(&nr_files);
70 * Return the maximum number of open files in the system
72 unsigned long get_max_files(void)
74 return files_stat.max_files;
76 EXPORT_SYMBOL_GPL(get_max_files);
79 * Handle nr_files sysctl
81 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
82 int proc_nr_files(ctl_table *table, int write,
83 void __user *buffer, size_t *lenp, loff_t *ppos)
85 files_stat.nr_files = get_nr_files();
86 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
89 int proc_nr_files(ctl_table *table, int write,
90 void __user *buffer, size_t *lenp, loff_t *ppos)
96 /* Find an unused file structure and return a pointer to it.
97 * Returns an error pointer if some error happend e.g. we over file
98 * structures limit, run out of memory or operation is not permitted.
100 * Be very careful using this. You are responsible for
101 * getting write access to any mount that you might assign
102 * to this filp, if it is opened for write. If this is not
103 * done, you will imbalance int the mount's writer count
104 * and a warning at __fput() time.
106 struct file *get_empty_filp(void)
108 const struct cred *cred = current_cred();
114 * Privileged users can go above max_files
116 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
118 * percpu_counters are inaccurate. Do an expensive check before
121 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
125 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
127 return ERR_PTR(-ENOMEM);
129 percpu_counter_inc(&nr_files);
130 f->f_cred = get_cred(cred);
131 error = security_file_alloc(f);
132 if (unlikely(error)) {
134 return ERR_PTR(error);
137 INIT_LIST_HEAD(&f->f_u.fu_list);
138 atomic_long_set(&f->f_count, 1);
139 rwlock_init(&f->f_owner.lock);
140 spin_lock_init(&f->f_lock);
141 eventpoll_init_file(f);
142 /* f->f_version: 0 */
146 /* Ran out of filps - report that */
147 if (get_nr_files() > old_max) {
148 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
149 old_max = get_nr_files();
151 return ERR_PTR(-ENFILE);
155 * alloc_file - allocate and initialize a 'struct file'
156 * @mnt: the vfsmount on which the file will reside
157 * @dentry: the dentry representing the new file
158 * @mode: the mode with which the new file will be opened
159 * @fop: the 'struct file_operations' for the new file
161 * Use this instead of get_empty_filp() to get a new
162 * 'struct file'. Do so because of the same initialization
163 * pitfalls reasons listed for init_file(). This is a
164 * preferred interface to using init_file().
166 * If all the callers of init_file() are eliminated, its
167 * code should be moved into this function.
169 struct file *alloc_file(struct path *path, fmode_t mode,
170 const struct file_operations *fop)
174 file = get_empty_filp();
178 file->f_path = *path;
179 file->f_inode = path->dentry->d_inode;
180 file->f_mapping = path->dentry->d_inode->i_mapping;
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()
190 if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
191 file_take_write(file);
192 WARN_ON(mnt_clone_write(path->mnt));
194 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
195 i_readcount_inc(path->dentry->d_inode);
198 EXPORT_SYMBOL(alloc_file);
201 * drop_file_write_access - give up ability to write to a file
202 * @file: the file to which we will stop writing
204 * This is a central place which will give up the ability
205 * to write to @file, along with access to write through
208 static void drop_file_write_access(struct file *file)
210 struct vfsmount *mnt = file->f_path.mnt;
211 struct dentry *dentry = file->f_path.dentry;
212 struct inode *inode = dentry->d_inode;
214 put_write_access(inode);
216 if (special_file(inode->i_mode))
218 if (file_check_writeable(file) != 0)
220 __mnt_drop_write(mnt);
221 file_release_write(file);
224 /* the real guts of fput() - releasing the last reference to file
226 static void __fput(struct file *file)
228 struct dentry *dentry = file->f_path.dentry;
229 struct vfsmount *mnt = file->f_path.mnt;
230 struct inode *inode = dentry->d_inode;
234 fsnotify_close(file);
236 * The function eventpoll_release() should be the first called
237 * in the file cleanup chain.
239 eventpoll_release(file);
240 locks_remove_flock(file);
242 if (unlikely(file->f_flags & FASYNC)) {
243 if (file->f_op && file->f_op->fasync)
244 file->f_op->fasync(-1, file, 0);
247 if (file->f_op && file->f_op->release)
248 file->f_op->release(inode, file);
249 security_file_free(file);
250 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
251 !(file->f_mode & FMODE_PATH))) {
252 cdev_put(inode->i_cdev);
254 fops_put(file->f_op);
255 put_pid(file->f_owner.pid);
256 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
257 i_readcount_dec(inode);
258 if (file->f_mode & FMODE_WRITE)
259 drop_file_write_access(file);
260 file->f_path.dentry = NULL;
261 file->f_path.mnt = NULL;
262 file->f_inode = NULL;
268 static DEFINE_SPINLOCK(delayed_fput_lock);
269 static LIST_HEAD(delayed_fput_list);
270 static void delayed_fput(struct work_struct *unused)
273 spin_lock_irq(&delayed_fput_lock);
274 list_splice_init(&delayed_fput_list, &head);
275 spin_unlock_irq(&delayed_fput_lock);
276 while (!list_empty(&head)) {
277 struct file *f = list_first_entry(&head, struct file, f_u.fu_list);
278 list_del_init(&f->f_u.fu_list);
283 static void ____fput(struct callback_head *work)
285 __fput(container_of(work, struct file, f_u.fu_rcuhead));
289 * If kernel thread really needs to have the final fput() it has done
290 * to complete, call this. The only user right now is the boot - we
291 * *do* need to make sure our writes to binaries on initramfs has
292 * not left us with opened struct file waiting for __fput() - execve()
293 * won't work without that. Please, don't add more callers without
294 * very good reasons; in particular, never call that with locks
295 * held and never call that from a thread that might need to do
296 * some work on any kind of umount.
298 void flush_delayed_fput(void)
303 static DECLARE_WORK(delayed_fput_work, delayed_fput);
305 void fput(struct file *file)
307 if (atomic_long_dec_and_test(&file->f_count)) {
308 struct task_struct *task = current;
309 file_sb_list_del(file);
310 if (unlikely(in_interrupt() || task->flags & PF_KTHREAD)) {
312 spin_lock_irqsave(&delayed_fput_lock, flags);
313 list_add(&file->f_u.fu_list, &delayed_fput_list);
314 schedule_work(&delayed_fput_work);
315 spin_unlock_irqrestore(&delayed_fput_lock, flags);
318 init_task_work(&file->f_u.fu_rcuhead, ____fput);
319 task_work_add(task, &file->f_u.fu_rcuhead, true);
324 * synchronous analog of fput(); for kernel threads that might be needed
325 * in some umount() (and thus can't use flush_delayed_fput() without
326 * risking deadlocks), need to wait for completion of __fput() and know
327 * for this specific struct file it won't involve anything that would
328 * need them. Use only if you really need it - at the very least,
329 * don't blindly convert fput() by kernel thread to that.
331 void __fput_sync(struct file *file)
333 if (atomic_long_dec_and_test(&file->f_count)) {
334 struct task_struct *task = current;
335 file_sb_list_del(file);
336 BUG_ON(!(task->flags & PF_KTHREAD));
343 void put_filp(struct file *file)
345 if (atomic_long_dec_and_test(&file->f_count)) {
346 security_file_free(file);
347 file_sb_list_del(file);
352 static inline int file_list_cpu(struct file *file)
355 return file->f_sb_list_cpu;
357 return smp_processor_id();
361 /* helper for file_sb_list_add to reduce ifdefs */
362 static inline void __file_sb_list_add(struct file *file, struct super_block *sb)
364 struct list_head *list;
367 cpu = smp_processor_id();
368 file->f_sb_list_cpu = cpu;
369 list = per_cpu_ptr(sb->s_files, cpu);
373 list_add(&file->f_u.fu_list, list);
377 * file_sb_list_add - add a file to the sb's file list
379 * @sb: sb to add it to
381 * Use this function to associate a file with the superblock of the inode it
384 void file_sb_list_add(struct file *file, struct super_block *sb)
386 lg_local_lock(&files_lglock);
387 __file_sb_list_add(file, sb);
388 lg_local_unlock(&files_lglock);
392 * file_sb_list_del - remove a file from the sb's file list
393 * @file: file to remove
394 * @sb: sb to remove it from
396 * Use this function to remove a file from its superblock.
398 void file_sb_list_del(struct file *file)
400 if (!list_empty(&file->f_u.fu_list)) {
401 lg_local_lock_cpu(&files_lglock, file_list_cpu(file));
402 list_del_init(&file->f_u.fu_list);
403 lg_local_unlock_cpu(&files_lglock, file_list_cpu(file));
410 * These macros iterate all files on all CPUs for a given superblock.
411 * files_lglock must be held globally.
413 #define do_file_list_for_each_entry(__sb, __file) \
416 for_each_possible_cpu(i) { \
417 struct list_head *list; \
418 list = per_cpu_ptr((__sb)->s_files, i); \
419 list_for_each_entry((__file), list, f_u.fu_list)
421 #define while_file_list_for_each_entry \
427 #define do_file_list_for_each_entry(__sb, __file) \
429 struct list_head *list; \
430 list = &(sb)->s_files; \
431 list_for_each_entry((__file), list, f_u.fu_list)
433 #define while_file_list_for_each_entry \
439 * mark_files_ro - mark all files read-only
440 * @sb: superblock in question
442 * All files are marked read-only. We don't care about pending
443 * delete files so this should be used in 'force' mode only.
445 void mark_files_ro(struct super_block *sb)
449 lg_global_lock(&files_lglock);
450 do_file_list_for_each_entry(sb, f) {
451 if (!S_ISREG(file_inode(f)->i_mode))
455 if (!(f->f_mode & FMODE_WRITE))
457 spin_lock(&f->f_lock);
458 f->f_mode &= ~FMODE_WRITE;
459 spin_unlock(&f->f_lock);
460 if (file_check_writeable(f) != 0)
462 __mnt_drop_write(f->f_path.mnt);
463 file_release_write(f);
464 } while_file_list_for_each_entry;
465 lg_global_unlock(&files_lglock);
468 void __init files_init(unsigned long mempages)
472 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
473 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
476 * One file with associated inode and dcache is very roughly 1K.
477 * Per default don't use more than 10% of our memory for files.
480 n = (mempages * (PAGE_SIZE / 1024)) / 10;
481 files_stat.max_files = max_t(unsigned long, n, NR_FILE);
483 lg_lock_init(&files_lglock, "files_lglock");
484 percpu_counter_init(&nr_files, 0);