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[linux-2.6.34.14-moxart.git] / fs / file_table.c
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1 /*
2 * linux/fs/file_table.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
6 */
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>
14 #include <linux/fs.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/percpu_counter.h>
24 #include <linux/ima.h>
26 #include <asm/atomic.h>
28 #include "internal.h"
30 /* sysctl tunables... */
31 struct files_stat_struct files_stat = {
32 .max_files = NR_FILE
35 /* public. Not pretty! */
36 __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
38 /* SLAB cache for file structures */
39 static struct kmem_cache *filp_cachep __read_mostly;
41 static struct percpu_counter nr_files __cacheline_aligned_in_smp;
43 static inline void file_free_rcu(struct rcu_head *head)
45 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
47 put_cred(f->f_cred);
48 kmem_cache_free(filp_cachep, f);
51 static inline void file_free(struct file *f)
53 percpu_counter_dec(&nr_files);
54 file_check_state(f);
55 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
59 * Return the total number of open files in the system
61 static int get_nr_files(void)
63 return percpu_counter_read_positive(&nr_files);
67 * Return the maximum number of open files in the system
69 int get_max_files(void)
71 return files_stat.max_files;
73 EXPORT_SYMBOL_GPL(get_max_files);
76 * Handle nr_files sysctl
78 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
79 int proc_nr_files(ctl_table *table, int write,
80 void __user *buffer, size_t *lenp, loff_t *ppos)
82 files_stat.nr_files = get_nr_files();
83 return proc_dointvec(table, write, buffer, lenp, ppos);
85 #else
86 int proc_nr_files(ctl_table *table, int write,
87 void __user *buffer, size_t *lenp, loff_t *ppos)
89 return -ENOSYS;
91 #endif
93 /* Find an unused file structure and return a pointer to it.
94 * Returns NULL, if there are no more free file structures or
95 * we run out of memory.
97 * Be very careful using this. You are responsible for
98 * getting write access to any mount that you might assign
99 * to this filp, if it is opened for write. If this is not
100 * done, you will imbalance int the mount's writer count
101 * and a warning at __fput() time.
103 struct file *get_empty_filp(void)
105 const struct cred *cred = current_cred();
106 static int old_max;
107 struct file * f;
110 * Privileged users can go above max_files
112 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
114 * percpu_counters are inaccurate. Do an expensive check before
115 * we go and fail.
117 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
118 goto over;
121 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
122 if (f == NULL)
123 goto fail;
125 percpu_counter_inc(&nr_files);
126 f->f_cred = get_cred(cred);
127 if (security_file_alloc(f))
128 goto fail_sec;
130 INIT_LIST_HEAD(&f->f_u.fu_list);
131 atomic_long_set(&f->f_count, 1);
132 rwlock_init(&f->f_owner.lock);
133 spin_lock_init(&f->f_lock);
134 eventpoll_init_file(f);
135 /* f->f_version: 0 */
136 return f;
138 over:
139 /* Ran out of filps - report that */
140 if (get_nr_files() > old_max) {
141 printk(KERN_INFO "VFS: file-max limit %d reached\n",
142 get_max_files());
143 old_max = get_nr_files();
145 goto fail;
147 fail_sec:
148 file_free(f);
149 fail:
150 return NULL;
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 path *path, fmode_t mode,
169 const struct file_operations *fop)
171 struct file *file;
173 file = get_empty_filp();
174 if (!file)
175 return NULL;
177 file->f_path = *path;
178 file->f_mapping = path->dentry->d_inode->i_mapping;
179 file->f_mode = mode;
180 file->f_op = fop;
183 * These mounts don't really matter in practice
184 * for r/o bind mounts. They aren't userspace-
185 * visible. We do this for consistency, and so
186 * that we can do debugging checks at __fput()
188 if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
189 file_take_write(file);
190 WARN_ON(mnt_clone_write(path->mnt));
192 ima_counts_get(file);
193 return file;
195 EXPORT_SYMBOL(alloc_file);
197 void fput(struct file *file)
199 if (atomic_long_dec_and_test(&file->f_count))
200 __fput(file);
203 EXPORT_SYMBOL(fput);
206 * drop_file_write_access - give up ability to write to a file
207 * @file: the file to which we will stop writing
209 * This is a central place which will give up the ability
210 * to write to @file, along with access to write through
211 * its vfsmount.
213 void drop_file_write_access(struct file *file)
215 struct vfsmount *mnt = file->f_path.mnt;
216 struct dentry *dentry = file->f_path.dentry;
217 struct inode *inode = dentry->d_inode;
219 put_write_access(inode);
221 if (special_file(inode->i_mode))
222 return;
223 if (file_check_writeable(file) != 0)
224 return;
225 mnt_drop_write(mnt);
226 file_release_write(file);
228 EXPORT_SYMBOL_GPL(drop_file_write_access);
230 /* __fput is called from task context when aio completion releases the last
231 * last use of a struct file *. Do not use otherwise.
233 void __fput(struct file *file)
235 struct dentry *dentry = file->f_path.dentry;
236 struct vfsmount *mnt = file->f_path.mnt;
237 struct inode *inode = dentry->d_inode;
239 might_sleep();
241 fsnotify_close(file);
243 * The function eventpoll_release() should be the first called
244 * in the file cleanup chain.
246 eventpoll_release(file);
247 locks_remove_flock(file);
249 if (unlikely(file->f_flags & FASYNC)) {
250 if (file->f_op && file->f_op->fasync)
251 file->f_op->fasync(-1, file, 0);
253 if (file->f_op && file->f_op->release)
254 file->f_op->release(inode, file);
255 security_file_free(file);
256 ima_file_free(file);
257 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
258 cdev_put(inode->i_cdev);
259 fops_put(file->f_op);
260 put_pid(file->f_owner.pid);
261 file_kill(file);
262 if (file->f_mode & FMODE_WRITE)
263 drop_file_write_access(file);
264 file->f_path.dentry = NULL;
265 file->f_path.mnt = NULL;
266 file_free(file);
267 dput(dentry);
268 mntput(mnt);
271 struct file *fget(unsigned int fd)
273 struct file *file;
274 struct files_struct *files = current->files;
276 rcu_read_lock();
277 file = fcheck_files(files, fd);
278 if (file) {
279 if (!atomic_long_inc_not_zero(&file->f_count)) {
280 /* File object ref couldn't be taken */
281 rcu_read_unlock();
282 return NULL;
285 rcu_read_unlock();
287 return file;
290 EXPORT_SYMBOL(fget);
293 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
294 * You can use this only if it is guranteed that the current task already
295 * holds a refcnt to that file. That check has to be done at fget() only
296 * and a flag is returned to be passed to the corresponding fput_light().
297 * There must not be a cloning between an fget_light/fput_light pair.
299 struct file *fget_light(unsigned int fd, int *fput_needed)
301 struct file *file;
302 struct files_struct *files = current->files;
304 *fput_needed = 0;
305 if (likely((atomic_read(&files->count) == 1))) {
306 file = fcheck_files(files, fd);
307 } else {
308 rcu_read_lock();
309 file = fcheck_files(files, fd);
310 if (file) {
311 if (atomic_long_inc_not_zero(&file->f_count))
312 *fput_needed = 1;
313 else
314 /* Didn't get the reference, someone's freed */
315 file = NULL;
317 rcu_read_unlock();
320 return file;
324 void put_filp(struct file *file)
326 if (atomic_long_dec_and_test(&file->f_count)) {
327 security_file_free(file);
328 file_kill(file);
329 file_free(file);
333 void file_move(struct file *file, struct list_head *list)
335 if (!list)
336 return;
337 file_list_lock();
338 list_move(&file->f_u.fu_list, list);
339 file_list_unlock();
342 void file_kill(struct file *file)
344 if (!list_empty(&file->f_u.fu_list)) {
345 file_list_lock();
346 list_del_init(&file->f_u.fu_list);
347 file_list_unlock();
351 int fs_may_remount_ro(struct super_block *sb)
353 struct file *file;
355 /* Check that no files are currently opened for writing. */
356 file_list_lock();
357 list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
358 struct inode *inode = file->f_path.dentry->d_inode;
360 /* File with pending delete? */
361 if (inode->i_nlink == 0)
362 goto too_bad;
364 /* Writeable file? */
365 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
366 goto too_bad;
368 file_list_unlock();
369 return 1; /* Tis' cool bro. */
370 too_bad:
371 file_list_unlock();
372 return 0;
376 * mark_files_ro - mark all files read-only
377 * @sb: superblock in question
379 * All files are marked read-only. We don't care about pending
380 * delete files so this should be used in 'force' mode only.
382 void mark_files_ro(struct super_block *sb)
384 struct file *f;
386 retry:
387 file_list_lock();
388 list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
389 struct vfsmount *mnt;
390 if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
391 continue;
392 if (!file_count(f))
393 continue;
394 if (!(f->f_mode & FMODE_WRITE))
395 continue;
396 spin_lock(&f->f_lock);
397 f->f_mode &= ~FMODE_WRITE;
398 spin_unlock(&f->f_lock);
399 if (file_check_writeable(f) != 0)
400 continue;
401 file_release_write(f);
402 mnt = mntget(f->f_path.mnt);
403 file_list_unlock();
405 * This can sleep, so we can't hold
406 * the file_list_lock() spinlock.
408 mnt_drop_write(mnt);
409 mntput(mnt);
410 goto retry;
412 file_list_unlock();
415 void __init files_init(unsigned long mempages)
417 int n;
419 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
420 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
423 * One file with associated inode and dcache is very roughly 1K.
424 * Per default don't use more than 10% of our memory for files.
427 n = (mempages * (PAGE_SIZE / 1024)) / 10;
428 files_stat.max_files = n;
429 if (files_stat.max_files < NR_FILE)
430 files_stat.max_files = NR_FILE;
431 files_defer_init();
432 percpu_counter_init(&nr_files, 0);