core_pattern: allow passing of arguments to user mode helper when core_pattern is...
[linux-2.6/mini2440.git] / fs / file_table.c
blobce3f39a4798a362c615ed51a2be83e4b616c8a86
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/init.h>
12 #include <linux/module.h>
13 #include <linux/fs.h>
14 #include <linux/security.h>
15 #include <linux/eventpoll.h>
16 #include <linux/rcupdate.h>
17 #include <linux/mount.h>
18 #include <linux/capability.h>
19 #include <linux/cdev.h>
20 #include <linux/fsnotify.h>
21 #include <linux/sysctl.h>
22 #include <linux/percpu_counter.h>
24 #include <asm/atomic.h>
26 /* sysctl tunables... */
27 struct files_stat_struct files_stat = {
28 .max_files = NR_FILE
31 /* public. Not pretty! */
32 __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
34 static struct percpu_counter nr_files __cacheline_aligned_in_smp;
36 static inline void file_free_rcu(struct rcu_head *head)
38 struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
39 kmem_cache_free(filp_cachep, f);
42 static inline void file_free(struct file *f)
44 percpu_counter_dec(&nr_files);
45 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
49 * Return the total number of open files in the system
51 static int get_nr_files(void)
53 return percpu_counter_read_positive(&nr_files);
57 * Return the maximum number of open files in the system
59 int get_max_files(void)
61 return files_stat.max_files;
63 EXPORT_SYMBOL_GPL(get_max_files);
66 * Handle nr_files sysctl
68 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
69 int proc_nr_files(ctl_table *table, int write, struct file *filp,
70 void __user *buffer, size_t *lenp, loff_t *ppos)
72 files_stat.nr_files = get_nr_files();
73 return proc_dointvec(table, write, filp, buffer, lenp, ppos);
75 #else
76 int proc_nr_files(ctl_table *table, int write, struct file *filp,
77 void __user *buffer, size_t *lenp, loff_t *ppos)
79 return -ENOSYS;
81 #endif
83 /* Find an unused file structure and return a pointer to it.
84 * Returns NULL, if there are no more free file structures or
85 * we run out of memory.
87 struct file *get_empty_filp(void)
89 struct task_struct *tsk;
90 static int old_max;
91 struct file * f;
94 * Privileged users can go above max_files
96 if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
98 * percpu_counters are inaccurate. Do an expensive check before
99 * we go and fail.
101 if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
102 goto over;
105 f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
106 if (f == NULL)
107 goto fail;
109 percpu_counter_inc(&nr_files);
110 if (security_file_alloc(f))
111 goto fail_sec;
113 tsk = current;
114 INIT_LIST_HEAD(&f->f_u.fu_list);
115 atomic_set(&f->f_count, 1);
116 rwlock_init(&f->f_owner.lock);
117 f->f_uid = tsk->fsuid;
118 f->f_gid = tsk->fsgid;
119 eventpoll_init_file(f);
120 /* f->f_version: 0 */
121 return f;
123 over:
124 /* Ran out of filps - report that */
125 if (get_nr_files() > old_max) {
126 printk(KERN_INFO "VFS: file-max limit %d reached\n",
127 get_max_files());
128 old_max = get_nr_files();
130 goto fail;
132 fail_sec:
133 file_free(f);
134 fail:
135 return NULL;
138 EXPORT_SYMBOL(get_empty_filp);
140 void fastcall fput(struct file *file)
142 if (atomic_dec_and_test(&file->f_count))
143 __fput(file);
146 EXPORT_SYMBOL(fput);
148 /* __fput is called from task context when aio completion releases the last
149 * last use of a struct file *. Do not use otherwise.
151 void fastcall __fput(struct file *file)
153 struct dentry *dentry = file->f_path.dentry;
154 struct vfsmount *mnt = file->f_path.mnt;
155 struct inode *inode = dentry->d_inode;
157 might_sleep();
159 fsnotify_close(file);
161 * The function eventpoll_release() should be the first called
162 * in the file cleanup chain.
164 eventpoll_release(file);
165 locks_remove_flock(file);
167 if (file->f_op && file->f_op->release)
168 file->f_op->release(inode, file);
169 security_file_free(file);
170 if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
171 cdev_put(inode->i_cdev);
172 fops_put(file->f_op);
173 if (file->f_mode & FMODE_WRITE)
174 put_write_access(inode);
175 put_pid(file->f_owner.pid);
176 file_kill(file);
177 file->f_path.dentry = NULL;
178 file->f_path.mnt = NULL;
179 file_free(file);
180 dput(dentry);
181 mntput(mnt);
184 struct file fastcall *fget(unsigned int fd)
186 struct file *file;
187 struct files_struct *files = current->files;
189 rcu_read_lock();
190 file = fcheck_files(files, fd);
191 if (file) {
192 if (!atomic_inc_not_zero(&file->f_count)) {
193 /* File object ref couldn't be taken */
194 rcu_read_unlock();
195 return NULL;
198 rcu_read_unlock();
200 return file;
203 EXPORT_SYMBOL(fget);
206 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
207 * You can use this only if it is guranteed that the current task already
208 * holds a refcnt to that file. That check has to be done at fget() only
209 * and a flag is returned to be passed to the corresponding fput_light().
210 * There must not be a cloning between an fget_light/fput_light pair.
212 struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
214 struct file *file;
215 struct files_struct *files = current->files;
217 *fput_needed = 0;
218 if (likely((atomic_read(&files->count) == 1))) {
219 file = fcheck_files(files, fd);
220 } else {
221 rcu_read_lock();
222 file = fcheck_files(files, fd);
223 if (file) {
224 if (atomic_inc_not_zero(&file->f_count))
225 *fput_needed = 1;
226 else
227 /* Didn't get the reference, someone's freed */
228 file = NULL;
230 rcu_read_unlock();
233 return file;
237 void put_filp(struct file *file)
239 if (atomic_dec_and_test(&file->f_count)) {
240 security_file_free(file);
241 file_kill(file);
242 file_free(file);
246 void file_move(struct file *file, struct list_head *list)
248 if (!list)
249 return;
250 file_list_lock();
251 list_move(&file->f_u.fu_list, list);
252 file_list_unlock();
255 void file_kill(struct file *file)
257 if (!list_empty(&file->f_u.fu_list)) {
258 file_list_lock();
259 list_del_init(&file->f_u.fu_list);
260 file_list_unlock();
264 int fs_may_remount_ro(struct super_block *sb)
266 struct list_head *p;
268 /* Check that no files are currently opened for writing. */
269 file_list_lock();
270 list_for_each(p, &sb->s_files) {
271 struct file *file = list_entry(p, struct file, f_u.fu_list);
272 struct inode *inode = file->f_path.dentry->d_inode;
274 /* File with pending delete? */
275 if (inode->i_nlink == 0)
276 goto too_bad;
278 /* Writeable file? */
279 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
280 goto too_bad;
282 file_list_unlock();
283 return 1; /* Tis' cool bro. */
284 too_bad:
285 file_list_unlock();
286 return 0;
289 void __init files_init(unsigned long mempages)
291 int n;
292 /* One file with associated inode and dcache is very roughly 1K.
293 * Per default don't use more than 10% of our memory for files.
296 n = (mempages * (PAGE_SIZE / 1024)) / 10;
297 files_stat.max_files = n;
298 if (files_stat.max_files < NR_FILE)
299 files_stat.max_files = NR_FILE;
300 files_defer_init();
301 percpu_counter_init(&nr_files, 0);