blob: fa7849fae134b371a80b90f95fda9e19bfb185b5 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
11#include <linux/init.h>
12#include <linux/module.h>
13#include <linux/smp_lock.h>
14#include <linux/fs.h>
15#include <linux/security.h>
16#include <linux/eventpoll.h>
17#include <linux/mount.h>
18#include <linux/cdev.h>
19
20/* sysctl tunables... */
21struct files_stat_struct files_stat = {
22 .max_files = NR_FILE
23};
24
25EXPORT_SYMBOL(files_stat); /* Needed by unix.o */
26
27/* public. Not pretty! */
28 __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
29
30static DEFINE_SPINLOCK(filp_count_lock);
31
32/* slab constructors and destructors are called from arbitrary
33 * context and must be fully threaded - use a local spinlock
34 * to protect files_stat.nr_files
35 */
36void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags)
37{
38 if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
39 SLAB_CTOR_CONSTRUCTOR) {
40 unsigned long flags;
41 spin_lock_irqsave(&filp_count_lock, flags);
42 files_stat.nr_files++;
43 spin_unlock_irqrestore(&filp_count_lock, flags);
44 }
45}
46
47void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
48{
49 unsigned long flags;
50 spin_lock_irqsave(&filp_count_lock, flags);
51 files_stat.nr_files--;
52 spin_unlock_irqrestore(&filp_count_lock, flags);
53}
54
55static inline void file_free(struct file *f)
56{
57 kmem_cache_free(filp_cachep, f);
58}
59
60/* Find an unused file structure and return a pointer to it.
61 * Returns NULL, if there are no more free file structures or
62 * we run out of memory.
63 */
64struct file *get_empty_filp(void)
65{
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -070066 static int old_max;
Linus Torvalds1da177e2005-04-16 15:20:36 -070067 struct file * f;
68
69 /*
70 * Privileged users can go above max_files
71 */
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -070072 if (files_stat.nr_files >= files_stat.max_files &&
73 !capable(CAP_SYS_ADMIN))
74 goto over;
Linus Torvalds1da177e2005-04-16 15:20:36 -070075
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -070076 f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
77 if (f == NULL)
78 goto fail;
79
80 memset(f, 0, sizeof(*f));
81 if (security_file_alloc(f))
82 goto fail_sec;
83
84 eventpoll_init_file(f);
85 atomic_set(&f->f_count, 1);
86 f->f_uid = current->fsuid;
87 f->f_gid = current->fsgid;
88 rwlock_init(&f->f_owner.lock);
89 /* f->f_version: 0 */
90 INIT_LIST_HEAD(&f->f_list);
91 f->f_maxcount = INT_MAX;
92 return f;
93
94over:
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 /* Ran out of filps - report that */
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -070096 if (files_stat.nr_files > old_max) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 printk(KERN_INFO "VFS: file-max limit %d reached\n",
98 files_stat.max_files);
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -070099 old_max = files_stat.nr_files;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 }
Kirill Korotaevaf4d2ec2005-06-23 00:09:50 -0700101 goto fail;
102
103fail_sec:
104 file_free(f);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105fail:
106 return NULL;
107}
108
109EXPORT_SYMBOL(get_empty_filp);
110
111void fastcall fput(struct file *file)
112{
113 if (atomic_dec_and_test(&file->f_count))
114 __fput(file);
115}
116
117EXPORT_SYMBOL(fput);
118
119/* __fput is called from task context when aio completion releases the last
120 * last use of a struct file *. Do not use otherwise.
121 */
122void fastcall __fput(struct file *file)
123{
124 struct dentry *dentry = file->f_dentry;
125 struct vfsmount *mnt = file->f_vfsmnt;
126 struct inode *inode = dentry->d_inode;
127
128 might_sleep();
129 /*
130 * The function eventpoll_release() should be the first called
131 * in the file cleanup chain.
132 */
133 eventpoll_release(file);
134 locks_remove_flock(file);
135
136 if (file->f_op && file->f_op->release)
137 file->f_op->release(inode, file);
138 security_file_free(file);
139 if (unlikely(inode->i_cdev != NULL))
140 cdev_put(inode->i_cdev);
141 fops_put(file->f_op);
142 if (file->f_mode & FMODE_WRITE)
143 put_write_access(inode);
144 file_kill(file);
145 file->f_dentry = NULL;
146 file->f_vfsmnt = NULL;
147 file_free(file);
148 dput(dentry);
149 mntput(mnt);
150}
151
152struct file fastcall *fget(unsigned int fd)
153{
154 struct file *file;
155 struct files_struct *files = current->files;
156
157 spin_lock(&files->file_lock);
158 file = fcheck_files(files, fd);
159 if (file)
160 get_file(file);
161 spin_unlock(&files->file_lock);
162 return file;
163}
164
165EXPORT_SYMBOL(fget);
166
167/*
168 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
169 * You can use this only if it is guranteed that the current task already
170 * holds a refcnt to that file. That check has to be done at fget() only
171 * and a flag is returned to be passed to the corresponding fput_light().
172 * There must not be a cloning between an fget_light/fput_light pair.
173 */
174struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
175{
176 struct file *file;
177 struct files_struct *files = current->files;
178
179 *fput_needed = 0;
180 if (likely((atomic_read(&files->count) == 1))) {
181 file = fcheck_files(files, fd);
182 } else {
183 spin_lock(&files->file_lock);
184 file = fcheck_files(files, fd);
185 if (file) {
186 get_file(file);
187 *fput_needed = 1;
188 }
189 spin_unlock(&files->file_lock);
190 }
191 return file;
192}
193
194
195void put_filp(struct file *file)
196{
197 if (atomic_dec_and_test(&file->f_count)) {
198 security_file_free(file);
199 file_kill(file);
200 file_free(file);
201 }
202}
203
204void file_move(struct file *file, struct list_head *list)
205{
206 if (!list)
207 return;
208 file_list_lock();
209 list_move(&file->f_list, list);
210 file_list_unlock();
211}
212
213void file_kill(struct file *file)
214{
215 if (!list_empty(&file->f_list)) {
216 file_list_lock();
217 list_del_init(&file->f_list);
218 file_list_unlock();
219 }
220}
221
222int fs_may_remount_ro(struct super_block *sb)
223{
224 struct list_head *p;
225
226 /* Check that no files are currently opened for writing. */
227 file_list_lock();
228 list_for_each(p, &sb->s_files) {
229 struct file *file = list_entry(p, struct file, f_list);
230 struct inode *inode = file->f_dentry->d_inode;
231
232 /* File with pending delete? */
233 if (inode->i_nlink == 0)
234 goto too_bad;
235
236 /* Writeable file? */
237 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
238 goto too_bad;
239 }
240 file_list_unlock();
241 return 1; /* Tis' cool bro. */
242too_bad:
243 file_list_unlock();
244 return 0;
245}
246
247void __init files_init(unsigned long mempages)
248{
249 int n;
250 /* One file with associated inode and dcache is very roughly 1K.
251 * Per default don't use more than 10% of our memory for files.
252 */
253
254 n = (mempages * (PAGE_SIZE / 1024)) / 10;
255 files_stat.max_files = n;
256 if (files_stat.max_files < NR_FILE)
257 files_stat.max_files = NR_FILE;
258}