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>
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>
23
24#include <asm/atomic.h>
25
26/* sysctl tunables... */
27struct files_stat_struct files_stat = {
28	.max_files = NR_FILE
29};
30
31/* public. Not pretty! */
32__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
33
34static struct percpu_counter nr_files __cacheline_aligned_in_smp;
35
36static inline void file_free_rcu(struct rcu_head *head)
37{
38	struct file *f =  container_of(head, struct file, f_u.fu_rcuhead);
39	kmem_cache_free(filp_cachep, f);
40}
41
42static inline void file_free(struct file *f)
43{
44	percpu_counter_dec(&nr_files);
45	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
46}
47
48/*
49 * Return the total number of open files in the system
50 */
51static int get_nr_files(void)
52{
53	return percpu_counter_read_positive(&nr_files);
54}
55
56/*
57 * Return the maximum number of open files in the system
58 */
59int get_max_files(void)
60{
61	return files_stat.max_files;
62}
63EXPORT_SYMBOL_GPL(get_max_files);
64
65/*
66 * Handle nr_files sysctl
67 */
68#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
69int proc_nr_files(ctl_table *table, int write, struct file *filp,
70                     void __user *buffer, size_t *lenp, loff_t *ppos)
71{
72	files_stat.nr_files = get_nr_files();
73	return proc_dointvec(table, write, filp, buffer, lenp, ppos);
74}
75#else
76int proc_nr_files(ctl_table *table, int write, struct file *filp,
77                     void __user *buffer, size_t *lenp, loff_t *ppos)
78{
79	return -ENOSYS;
80}
81#endif
82
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.
86 */
87struct file *get_empty_filp(void)
88{
89	struct task_struct *tsk;
90	static int old_max;
91	struct file * f;
92
93	/*
94	 * Privileged users can go above max_files
95	 */
96	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
97		/*
98		 * percpu_counters are inaccurate.  Do an expensive check before
99		 * we go and fail.
100		 */
101		if (percpu_counter_sum(&nr_files) >= files_stat.max_files)
102			goto over;
103	}
104
105	f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
106	if (f == NULL)
107		goto fail;
108
109	percpu_counter_inc(&nr_files);
110	memset(f, 0, sizeof(*f));
111	if (security_file_alloc(f))
112		goto fail_sec;
113
114	tsk = current;
115	INIT_LIST_HEAD(&f->f_u.fu_list);
116	atomic_set(&f->f_count, 1);
117	rwlock_init(&f->f_owner.lock);
118	f->f_uid = tsk->fsuid;
119	f->f_gid = tsk->fsgid;
120	eventpoll_init_file(f);
121	/* f->f_version: 0 */
122	return f;
123
124over:
125	/* Ran out of filps - report that */
126	if (get_nr_files() > old_max) {
127		printk(KERN_INFO "VFS: file-max limit %d reached\n",
128					get_max_files());
129		old_max = get_nr_files();
130	}
131	goto fail;
132
133fail_sec:
134	file_free(f);
135fail:
136	return NULL;
137}
138
139EXPORT_SYMBOL(get_empty_filp);
140
141void fastcall fput(struct file *file)
142{
143	if (atomic_dec_and_test(&file->f_count))
144		__fput(file);
145}
146
147EXPORT_SYMBOL(fput);
148
149/* __fput is called from task context when aio completion releases the last
150 * last use of a struct file *.  Do not use otherwise.
151 */
152void fastcall __fput(struct file *file)
153{
154	struct dentry *dentry = file->f_path.dentry;
155	struct vfsmount *mnt = file->f_path.mnt;
156	struct inode *inode = dentry->d_inode;
157
158	might_sleep();
159
160	fsnotify_close(file);
161	/*
162	 * The function eventpoll_release() should be the first called
163	 * in the file cleanup chain.
164	 */
165	eventpoll_release(file);
166	locks_remove_flock(file);
167
168	if (file->f_op && file->f_op->release)
169		file->f_op->release(inode, file);
170	security_file_free(file);
171	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
172		cdev_put(inode->i_cdev);
173	fops_put(file->f_op);
174	if (file->f_mode & FMODE_WRITE)
175		put_write_access(inode);
176	put_pid(file->f_owner.pid);
177	file_kill(file);
178	file->f_path.dentry = NULL;
179	file->f_path.mnt = NULL;
180	file_free(file);
181	dput(dentry);
182	mntput(mnt);
183}
184
185struct file fastcall *fget(unsigned int fd)
186{
187	struct file *file;
188	struct files_struct *files = current->files;
189
190	rcu_read_lock();
191	file = fcheck_files(files, fd);
192	if (file) {
193		if (!atomic_inc_not_zero(&file->f_count)) {
194			/* File object ref couldn't be taken */
195			rcu_read_unlock();
196			return NULL;
197		}
198	}
199	rcu_read_unlock();
200
201	return file;
202}
203
204EXPORT_SYMBOL(fget);
205
206/*
207 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
208 * You can use this only if it is guranteed that the current task already
209 * holds a refcnt to that file. That check has to be done at fget() only
210 * and a flag is returned to be passed to the corresponding fput_light().
211 * There must not be a cloning between an fget_light/fput_light pair.
212 */
213struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
214{
215	struct file *file;
216	struct files_struct *files = current->files;
217
218	*fput_needed = 0;
219	if (likely((atomic_read(&files->count) == 1))) {
220		file = fcheck_files(files, fd);
221	} else {
222		rcu_read_lock();
223		file = fcheck_files(files, fd);
224		if (file) {
225			if (atomic_inc_not_zero(&file->f_count))
226				*fput_needed = 1;
227			else
228				/* Didn't get the reference, someone's freed */
229				file = NULL;
230		}
231		rcu_read_unlock();
232	}
233
234	return file;
235}
236
237
238void put_filp(struct file *file)
239{
240	if (atomic_dec_and_test(&file->f_count)) {
241		security_file_free(file);
242		file_kill(file);
243		file_free(file);
244	}
245}
246
247void file_move(struct file *file, struct list_head *list)
248{
249	if (!list)
250		return;
251	file_list_lock();
252	list_move(&file->f_u.fu_list, list);
253	file_list_unlock();
254}
255
256void file_kill(struct file *file)
257{
258	if (!list_empty(&file->f_u.fu_list)) {
259		file_list_lock();
260		list_del_init(&file->f_u.fu_list);
261		file_list_unlock();
262	}
263}
264
265int fs_may_remount_ro(struct super_block *sb)
266{
267	struct list_head *p;
268
269	/* Check that no files are currently opened for writing. */
270	file_list_lock();
271	list_for_each(p, &sb->s_files) {
272		struct file *file = list_entry(p, struct file, f_u.fu_list);
273		struct inode *inode = file->f_path.dentry->d_inode;
274
275		/* File with pending delete? */
276		if (inode->i_nlink == 0)
277			goto too_bad;
278
279		/* Writeable file? */
280		if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
281			goto too_bad;
282	}
283	file_list_unlock();
284	return 1; /* Tis' cool bro. */
285too_bad:
286	file_list_unlock();
287	return 0;
288}
289
290void __init files_init(unsigned long mempages)
291{
292	int n;
293	/* One file with associated inode and dcache is very roughly 1K.
294	 * Per default don't use more than 10% of our memory for files.
295	 */
296
297	n = (mempages * (PAGE_SIZE / 1024)) / 10;
298	files_stat.max_files = n;
299	if (files_stat.max_files < NR_FILE)
300		files_stat.max_files = NR_FILE;
301	files_defer_init();
302	percpu_counter_init(&nr_files, 0);
303}
304