Blackfin arch: include linux/mm.h since we use PAGE_ALIGN and such
[linux-2.6/mini2440.git] / fs / file_table.c
blobbbeeac6efa1a85eca90bd59e85c620022502f3d7
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>
25 #include <asm/atomic.h>
27 /* sysctl tunables... */
28 struct files_stat_struct files_stat = {
29 .max_files = NR_FILE
32 /* public. Not pretty! */
33 __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
35 /* SLAB cache for file structures */
36 static struct kmem_cache *filp_cachep __read_mostly;
38 static struct percpu_counter nr_files __cacheline_aligned_in_smp;
40 static inline void file_free_rcu(struct rcu_head *head)
42 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
44 put_cred(f->f_cred);
45 kmem_cache_free(filp_cachep, f);
48 static inline void file_free(struct file *f)
50 percpu_counter_dec(&nr_files);
51 file_check_state(f);
52 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
56 * Return the total number of open files in the system
58 static int get_nr_files(void)
60 return percpu_counter_read_positive(&nr_files);
64 * Return the maximum number of open files in the system
66 int get_max_files(void)
68 return files_stat.max_files;
70 EXPORT_SYMBOL_GPL(get_max_files);
73 * Handle nr_files sysctl
75 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
76 int proc_nr_files(ctl_table *table, int write, struct file *filp,
77 void __user *buffer, size_t *lenp, loff_t *ppos)
79 files_stat.nr_files = get_nr_files();
80 return proc_dointvec(table, write, filp, buffer, lenp, ppos);
82 #else
83 int proc_nr_files(ctl_table *table, int write, struct file *filp,
84 void __user *buffer, size_t *lenp, loff_t *ppos)
86 return -ENOSYS;
88 #endif
90 /* Find an unused file structure and return a pointer to it.
91 * Returns NULL, if there are no more free file structures or
92 * we run out of memory.
94 * Be very careful using this. You are responsible for
95 * getting write access to any mount that you might assign
96 * to this filp, if it is opened for write. If this is not
97 * done, you will imbalance int the mount's writer count
98 * and a warning at __fput() time.
100 struct file *get_empty_filp(void)
102 const struct cred *cred = current_cred();
103 static int old_max;
104 struct file * f;
107 * Privileged users can go above max_files
109 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
111 * percpu_counters are inaccurate. Do an expensive check before
112 * we go and fail.
114 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
115 goto over;
118 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
119 if (f == NULL)
120 goto fail;
122 percpu_counter_inc(&nr_files);
123 if (security_file_alloc(f))
124 goto fail_sec;
126 INIT_LIST_HEAD(&f->f_u.fu_list);
127 atomic_long_set(&f->f_count, 1);
128 rwlock_init(&f->f_owner.lock);
129 f->f_cred = get_cred(cred);
130 eventpoll_init_file(f);
131 /* f->f_version: 0 */
132 return f;
134 over:
135 /* Ran out of filps - report that */
136 if (get_nr_files() > old_max) {
137 printk(KERN_INFO "VFS: file-max limit %d reached\n",
138 get_max_files());
139 old_max = get_nr_files();
141 goto fail;
143 fail_sec:
144 file_free(f);
145 fail:
146 return NULL;
149 EXPORT_SYMBOL(get_empty_filp);
152 * alloc_file - allocate and initialize a 'struct file'
153 * @mnt: the vfsmount on which the file will reside
154 * @dentry: the dentry representing the new file
155 * @mode: the mode with which the new file will be opened
156 * @fop: the 'struct file_operations' for the new file
158 * Use this instead of get_empty_filp() to get a new
159 * 'struct file'. Do so because of the same initialization
160 * pitfalls reasons listed for init_file(). This is a
161 * preferred interface to using init_file().
163 * If all the callers of init_file() are eliminated, its
164 * code should be moved into this function.
166 struct file *alloc_file(struct vfsmount *mnt, struct dentry *dentry,
167 fmode_t mode, const struct file_operations *fop)
169 struct file *file;
170 struct path;
172 file = get_empty_filp();
173 if (!file)
174 return NULL;
176 init_file(file, mnt, dentry, mode, fop);
177 return file;
179 EXPORT_SYMBOL(alloc_file);
182 * init_file - initialize a 'struct file'
183 * @file: the already allocated 'struct file' to initialized
184 * @mnt: the vfsmount on which the file resides
185 * @dentry: the dentry representing this file
186 * @mode: the mode the file is opened with
187 * @fop: the 'struct file_operations' for this file
189 * Use this instead of setting the members directly. Doing so
190 * avoids making mistakes like forgetting the mntget() or
191 * forgetting to take a write on the mnt.
193 * Note: This is a crappy interface. It is here to make
194 * merging with the existing users of get_empty_filp()
195 * who have complex failure logic easier. All users
196 * of this should be moving to alloc_file().
198 int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry,
199 fmode_t mode, const struct file_operations *fop)
201 int error = 0;
202 file->f_path.dentry = dentry;
203 file->f_path.mnt = mntget(mnt);
204 file->f_mapping = dentry->d_inode->i_mapping;
205 file->f_mode = mode;
206 file->f_op = fop;
209 * These mounts don't really matter in practice
210 * for r/o bind mounts. They aren't userspace-
211 * visible. We do this for consistency, and so
212 * that we can do debugging checks at __fput()
214 if ((mode & FMODE_WRITE) && !special_file(dentry->d_inode->i_mode)) {
215 file_take_write(file);
216 error = mnt_want_write(mnt);
217 WARN_ON(error);
219 return error;
221 EXPORT_SYMBOL(init_file);
223 void fput(struct file *file)
225 if (atomic_long_dec_and_test(&file->f_count))
226 __fput(file);
229 EXPORT_SYMBOL(fput);
232 * drop_file_write_access - give up ability to write to a file
233 * @file: the file to which we will stop writing
235 * This is a central place which will give up the ability
236 * to write to @file, along with access to write through
237 * its vfsmount.
239 void drop_file_write_access(struct file *file)
241 struct vfsmount *mnt = file->f_path.mnt;
242 struct dentry *dentry = file->f_path.dentry;
243 struct inode *inode = dentry->d_inode;
245 put_write_access(inode);
247 if (special_file(inode->i_mode))
248 return;
249 if (file_check_writeable(file) != 0)
250 return;
251 mnt_drop_write(mnt);
252 file_release_write(file);
254 EXPORT_SYMBOL_GPL(drop_file_write_access);
256 /* __fput is called from task context when aio completion releases the last
257 * last use of a struct file *. Do not use otherwise.
259 void __fput(struct file *file)
261 struct dentry *dentry = file->f_path.dentry;
262 struct vfsmount *mnt = file->f_path.mnt;
263 struct inode *inode = dentry->d_inode;
265 might_sleep();
267 fsnotify_close(file);
269 * The function eventpoll_release() should be the first called
270 * in the file cleanup chain.
272 eventpoll_release(file);
273 locks_remove_flock(file);
275 if (unlikely(file->f_flags & FASYNC)) {
276 if (file->f_op && file->f_op->fasync)
277 file->f_op->fasync(-1, file, 0);
279 if (file->f_op && file->f_op->release)
280 file->f_op->release(inode, file);
281 security_file_free(file);
282 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
283 cdev_put(inode->i_cdev);
284 fops_put(file->f_op);
285 put_pid(file->f_owner.pid);
286 file_kill(file);
287 if (file->f_mode & FMODE_WRITE)
288 drop_file_write_access(file);
289 file->f_path.dentry = NULL;
290 file->f_path.mnt = NULL;
291 file_free(file);
292 dput(dentry);
293 mntput(mnt);
296 struct file *fget(unsigned int fd)
298 struct file *file;
299 struct files_struct *files = current->files;
301 rcu_read_lock();
302 file = fcheck_files(files, fd);
303 if (file) {
304 if (!atomic_long_inc_not_zero(&file->f_count)) {
305 /* File object ref couldn't be taken */
306 rcu_read_unlock();
307 return NULL;
310 rcu_read_unlock();
312 return file;
315 EXPORT_SYMBOL(fget);
318 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
319 * You can use this only if it is guranteed that the current task already
320 * holds a refcnt to that file. That check has to be done at fget() only
321 * and a flag is returned to be passed to the corresponding fput_light().
322 * There must not be a cloning between an fget_light/fput_light pair.
324 struct file *fget_light(unsigned int fd, int *fput_needed)
326 struct file *file;
327 struct files_struct *files = current->files;
329 *fput_needed = 0;
330 if (likely((atomic_read(&files->count) == 1))) {
331 file = fcheck_files(files, fd);
332 } else {
333 rcu_read_lock();
334 file = fcheck_files(files, fd);
335 if (file) {
336 if (atomic_long_inc_not_zero(&file->f_count))
337 *fput_needed = 1;
338 else
339 /* Didn't get the reference, someone's freed */
340 file = NULL;
342 rcu_read_unlock();
345 return file;
349 void put_filp(struct file *file)
351 if (atomic_long_dec_and_test(&file->f_count)) {
352 security_file_free(file);
353 file_kill(file);
354 file_free(file);
358 void file_move(struct file *file, struct list_head *list)
360 if (!list)
361 return;
362 file_list_lock();
363 list_move(&file->f_u.fu_list, list);
364 file_list_unlock();
367 void file_kill(struct file *file)
369 if (!list_empty(&file->f_u.fu_list)) {
370 file_list_lock();
371 list_del_init(&file->f_u.fu_list);
372 file_list_unlock();
376 int fs_may_remount_ro(struct super_block *sb)
378 struct file *file;
380 /* Check that no files are currently opened for writing. */
381 file_list_lock();
382 list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
383 struct inode *inode = file->f_path.dentry->d_inode;
385 /* File with pending delete? */
386 if (inode->i_nlink == 0)
387 goto too_bad;
389 /* Writeable file? */
390 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
391 goto too_bad;
393 file_list_unlock();
394 return 1; /* Tis' cool bro. */
395 too_bad:
396 file_list_unlock();
397 return 0;
400 void __init files_init(unsigned long mempages)
402 int n;
404 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
405 SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
408 * One file with associated inode and dcache is very roughly 1K.
409 * Per default don't use more than 10% of our memory for files.
412 n = (mempages * (PAGE_SIZE / 1024)) / 10;
413 files_stat.max_files = n;
414 if (files_stat.max_files < NR_FILE)
415 files_stat.max_files = NR_FILE;
416 files_defer_init();
417 percpu_counter_init(&nr_files, 0);