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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>
5b825c3a 16#include <linux/cred.h>
1da177e4 17#include <linux/eventpoll.h>
ab2af1f5 18#include <linux/rcupdate.h>
1da177e4 19#include <linux/mount.h>
16f7e0fe 20#include <linux/capability.h>
1da177e4 21#include <linux/cdev.h>
0eeca283 22#include <linux/fsnotify.h>
529bf6be
DS
23#include <linux/sysctl.h>
24#include <linux/percpu_counter.h>
6416ccb7 25#include <linux/percpu.h>
4a9d4b02 26#include <linux/task_work.h>
0552f879 27#include <linux/ima.h>
4248b0da 28#include <linux/swap.h>
529bf6be 29
60063497 30#include <linux/atomic.h>
1da177e4 31
e81e3f4d
EP
32#include "internal.h"
33
1da177e4
LT
34/* sysctl tunables... */
35struct files_stat_struct files_stat = {
36 .max_files = NR_FILE
37};
38
b6b3fdea
ED
39/* SLAB cache for file structures */
40static struct kmem_cache *filp_cachep __read_mostly;
41
529bf6be 42static struct percpu_counter nr_files __cacheline_aligned_in_smp;
1da177e4 43
5c33b183 44static void file_free_rcu(struct rcu_head *head)
1da177e4 45{
d76b0d9b
DH
46 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
47
48 put_cred(f->f_cred);
529bf6be 49 kmem_cache_free(filp_cachep, f);
1da177e4
LT
50}
51
529bf6be 52static inline void file_free(struct file *f)
1da177e4 53{
e8cff84f 54 security_file_free(f);
529bf6be
DS
55 percpu_counter_dec(&nr_files);
56 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
1da177e4
LT
57}
58
529bf6be
DS
59/*
60 * Return the total number of open files in the system
61 */
518de9b3 62static long get_nr_files(void)
1da177e4 63{
529bf6be 64 return percpu_counter_read_positive(&nr_files);
1da177e4
LT
65}
66
529bf6be
DS
67/*
68 * Return the maximum number of open files in the system
69 */
518de9b3 70unsigned long get_max_files(void)
ab2af1f5 71{
529bf6be 72 return files_stat.max_files;
ab2af1f5 73}
529bf6be
DS
74EXPORT_SYMBOL_GPL(get_max_files);
75
76/*
77 * Handle nr_files sysctl
78 */
79#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
1f7e0616 80int proc_nr_files(struct ctl_table *table, int write,
529bf6be
DS
81 void __user *buffer, size_t *lenp, loff_t *ppos)
82{
83 files_stat.nr_files = get_nr_files();
518de9b3 84 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
529bf6be
DS
85}
86#else
1f7e0616 87int proc_nr_files(struct ctl_table *table, int write,
529bf6be
DS
88 void __user *buffer, size_t *lenp, loff_t *ppos)
89{
90 return -ENOSYS;
91}
92#endif
ab2af1f5 93
1da177e4 94/* Find an unused file structure and return a pointer to it.
1afc99be
AV
95 * Returns an error pointer if some error happend e.g. we over file
96 * structures limit, run out of memory or operation is not permitted.
430e285e
DH
97 *
98 * Be very careful using this. You are responsible for
99 * getting write access to any mount that you might assign
100 * to this filp, if it is opened for write. If this is not
101 * done, you will imbalance int the mount's writer count
102 * and a warning at __fput() time.
1da177e4 103 */
ea73ea72 104struct file *alloc_empty_file(int flags, const struct cred *cred)
1da177e4 105{
518de9b3 106 static long old_max;
1afc99be
AV
107 struct file *f;
108 int error;
1da177e4
LT
109
110 /*
111 * Privileged users can go above max_files
112 */
529bf6be
DS
113 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
114 /*
115 * percpu_counters are inaccurate. Do an expensive check before
116 * we go and fail.
117 */
52d9f3b4 118 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
529bf6be
DS
119 goto over;
120 }
af4d2ecb 121
4975e45f 122 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
1afc99be
AV
123 if (unlikely(!f))
124 return ERR_PTR(-ENOMEM);
af4d2ecb 125
78d29788 126 f->f_cred = get_cred(cred);
1afc99be
AV
127 error = security_file_alloc(f);
128 if (unlikely(error)) {
e8cff84f 129 file_free_rcu(&f->f_u.fu_rcuhead);
1afc99be
AV
130 return ERR_PTR(error);
131 }
1da177e4 132
516e0cc5 133 atomic_long_set(&f->f_count, 1);
af4d2ecb 134 rwlock_init(&f->f_owner.lock);
68499914 135 spin_lock_init(&f->f_lock);
9c225f26 136 mutex_init(&f->f_pos_lock);
5a6b7951 137 eventpoll_init_file(f);
ea73ea72
AV
138 f->f_flags = flags;
139 f->f_mode = OPEN_FMODE(flags);
af4d2ecb 140 /* f->f_version: 0 */
e8cff84f 141 percpu_counter_inc(&nr_files);
af4d2ecb
KK
142 return f;
143
144over:
1da177e4 145 /* Ran out of filps - report that */
529bf6be 146 if (get_nr_files() > old_max) {
518de9b3 147 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
529bf6be 148 old_max = get_nr_files();
1da177e4 149 }
1afc99be 150 return ERR_PTR(-ENFILE);
1da177e4
LT
151}
152
ce8d2cdf
DH
153/**
154 * alloc_file - allocate and initialize a 'struct file'
a457606a
EB
155 *
156 * @path: the (dentry, vfsmount) pair for the new file
c9c554f2 157 * @flags: O_... flags with which the new file will be opened
ce8d2cdf 158 * @fop: the 'struct file_operations' for the new file
ce8d2cdf 159 */
c9c554f2 160struct file *alloc_file(const struct path *path, int flags,
2c48b9c4 161 const struct file_operations *fop)
ce8d2cdf
DH
162{
163 struct file *file;
ce8d2cdf 164
ea73ea72 165 file = alloc_empty_file(flags, current_cred());
1afc99be 166 if (IS_ERR(file))
39b65252 167 return file;
ce8d2cdf 168
2c48b9c4 169 file->f_path = *path;
dd37978c 170 file->f_inode = path->dentry->d_inode;
2c48b9c4 171 file->f_mapping = path->dentry->d_inode->i_mapping;
5660e13d 172 file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
c9c554f2 173 if ((file->f_mode & FMODE_READ) &&
84363182 174 likely(fop->read || fop->read_iter))
c9c554f2
AV
175 file->f_mode |= FMODE_CAN_READ;
176 if ((file->f_mode & FMODE_WRITE) &&
84363182 177 likely(fop->write || fop->write_iter))
c9c554f2 178 file->f_mode |= FMODE_CAN_WRITE;
f5d11409 179 file->f_mode |= FMODE_OPENED;
ce8d2cdf 180 file->f_op = fop;
c9c554f2 181 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
890275b5 182 i_readcount_inc(path->dentry->d_inode);
3d1e4631 183 return file;
ce8d2cdf 184}
73efc468 185EXPORT_SYMBOL(alloc_file);
ce8d2cdf 186
d7065da0 187/* the real guts of fput() - releasing the last reference to file
1da177e4 188 */
d7065da0 189static void __fput(struct file *file)
1da177e4 190{
0f7fc9e4
JJS
191 struct dentry *dentry = file->f_path.dentry;
192 struct vfsmount *mnt = file->f_path.mnt;
c77cecee 193 struct inode *inode = file->f_inode;
1da177e4 194
4d27f326
AV
195 if (unlikely(!(file->f_mode & FMODE_OPENED)))
196 goto out;
197
1da177e4 198 might_sleep();
0eeca283
RL
199
200 fsnotify_close(file);
1da177e4
LT
201 /*
202 * The function eventpoll_release() should be the first called
203 * in the file cleanup chain.
204 */
205 eventpoll_release(file);
78ed8a13 206 locks_remove_file(file);
1da177e4 207
bb02b186 208 ima_file_free(file);
233e70f4 209 if (unlikely(file->f_flags & FASYNC)) {
72c2d531 210 if (file->f_op->fasync)
233e70f4
AV
211 file->f_op->fasync(-1, file, 0);
212 }
72c2d531 213 if (file->f_op->release)
1da177e4 214 file->f_op->release(inode, file);
60ed8cf7
MS
215 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
216 !(file->f_mode & FMODE_PATH))) {
1da177e4 217 cdev_put(inode->i_cdev);
60ed8cf7 218 }
1da177e4 219 fops_put(file->f_op);
609d7fa9 220 put_pid(file->f_owner.pid);
890275b5
MZ
221 if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
222 i_readcount_dec(inode);
83f936c7
AV
223 if (file->f_mode & FMODE_WRITER) {
224 put_write_access(inode);
225 __mnt_drop_write(mnt);
226 }
1da177e4
LT
227 dput(dentry);
228 mntput(mnt);
4d27f326
AV
229out:
230 file_free(file);
1da177e4
LT
231}
232
4f5e65a1 233static LLIST_HEAD(delayed_fput_list);
4a9d4b02
AV
234static void delayed_fput(struct work_struct *unused)
235{
4f5e65a1 236 struct llist_node *node = llist_del_all(&delayed_fput_list);
b9ea557e 237 struct file *f, *t;
4f5e65a1 238
b9ea557e
BP
239 llist_for_each_entry_safe(f, t, node, f_u.fu_llist)
240 __fput(f);
4a9d4b02
AV
241}
242
243static void ____fput(struct callback_head *work)
244{
245 __fput(container_of(work, struct file, f_u.fu_rcuhead));
246}
247
248/*
249 * If kernel thread really needs to have the final fput() it has done
250 * to complete, call this. The only user right now is the boot - we
251 * *do* need to make sure our writes to binaries on initramfs has
252 * not left us with opened struct file waiting for __fput() - execve()
253 * won't work without that. Please, don't add more callers without
254 * very good reasons; in particular, never call that with locks
255 * held and never call that from a thread that might need to do
256 * some work on any kind of umount.
257 */
258void flush_delayed_fput(void)
259{
260 delayed_fput(NULL);
261}
262
c7314d74 263static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
4a9d4b02 264
d7065da0
AV
265void fput(struct file *file)
266{
4a9d4b02
AV
267 if (atomic_long_dec_and_test(&file->f_count)) {
268 struct task_struct *task = current;
e7b2c406 269
e7b2c406
ON
270 if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
271 init_task_work(&file->f_u.fu_rcuhead, ____fput);
272 if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
273 return;
64372501
AM
274 /*
275 * After this task has run exit_task_work(),
be49b30a 276 * task_work_add() will fail. Fall through to delayed
64372501
AM
277 * fput to avoid leaking *file.
278 */
4a9d4b02 279 }
4f5e65a1
ON
280
281 if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
c7314d74 282 schedule_delayed_work(&delayed_fput_work, 1);
4a9d4b02
AV
283 }
284}
285
286/*
287 * synchronous analog of fput(); for kernel threads that might be needed
288 * in some umount() (and thus can't use flush_delayed_fput() without
289 * risking deadlocks), need to wait for completion of __fput() and know
290 * for this specific struct file it won't involve anything that would
291 * need them. Use only if you really need it - at the very least,
292 * don't blindly convert fput() by kernel thread to that.
293 */
294void __fput_sync(struct file *file)
295{
296 if (atomic_long_dec_and_test(&file->f_count)) {
297 struct task_struct *task = current;
4a9d4b02 298 BUG_ON(!(task->flags & PF_KTHREAD));
d7065da0 299 __fput(file);
4a9d4b02 300 }
d7065da0
AV
301}
302
303EXPORT_SYMBOL(fput);
304
4248b0da 305void __init files_init(void)
b9ea557e 306{
b6b3fdea 307 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
f3f7c093 308 SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
4248b0da
MG
309 percpu_counter_init(&nr_files, 0, GFP_KERNEL);
310}
b6b3fdea 311
4248b0da
MG
312/*
313 * One file with associated inode and dcache is very roughly 1K. Per default
314 * do not use more than 10% of our memory for files.
315 */
316void __init files_maxfiles_init(void)
317{
318 unsigned long n;
319 unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2;
320
321 memreserve = min(memreserve, totalram_pages - 1);
322 n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
1da177e4 323
518de9b3 324 files_stat.max_files = max_t(unsigned long, n, NR_FILE);
b9ea557e 325}