[net-next-2.6.git] / fs / file_table.c

/*
 *  linux/fs/file_table.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
 */

#include <linux/string.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/eventpoll.h>
#include <linux/rcupdate.h>
#include <linux/mount.h>
#include <linux/capability.h>
#include <linux/cdev.h>
#include <linux/fsnotify.h>
#include <linux/sysctl.h>
#include <linux/percpu_counter.h>
#include <linux/ima.h>

#include <asm/atomic.h>

#include "internal.h"

/* sysctl tunables... */
struct files_stat_struct files_stat = {
	.max_files = NR_FILE
};

static __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);

/* SLAB cache for file structures */
static struct kmem_cache *filp_cachep __read_mostly;

static struct percpu_counter nr_files __cacheline_aligned_in_smp;

static inline void file_free_rcu(struct rcu_head *head)
{
	struct file *f = container_of(head, struct file, f_u.fu_rcuhead);

	put_cred(f->f_cred);
	kmem_cache_free(filp_cachep, f);
}

static inline void file_free(struct file *f)
{
	percpu_counter_dec(&nr_files);
	file_check_state(f);
	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
}

/*
 * Return the total number of open files in the system
 */
static int get_nr_files(void)
{
	return percpu_counter_read_positive(&nr_files);
}

/*
 * Return the maximum number of open files in the system
 */
int get_max_files(void)
{
	return files_stat.max_files;
}
EXPORT_SYMBOL_GPL(get_max_files);

/*
 * Handle nr_files sysctl
 */
#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
int proc_nr_files(ctl_table *table, int write,
                     void __user *buffer, size_t *lenp, loff_t *ppos)
{
	files_stat.nr_files = get_nr_files();
	return proc_dointvec(table, write, buffer, lenp, ppos);
}
#else
int proc_nr_files(ctl_table *table, int write,
                     void __user *buffer, size_t *lenp, loff_t *ppos)
{
	return -ENOSYS;
}
#endif

/* Find an unused file structure and return a pointer to it.
 * Returns NULL, if there are no more free file structures or
 * we run out of memory.
 *
 * Be very careful using this.  You are responsible for
 * getting write access to any mount that you might assign
 * to this filp, if it is opened for write.  If this is not
 * done, you will imbalance int the mount's writer count
 * and a warning at __fput() time.
 */
struct file *get_empty_filp(void)
{
	const struct cred *cred = current_cred();
	static int old_max;
	struct file * f;

	/*
	 * Privileged users can go above max_files
	 */
	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
		/*
		 * percpu_counters are inaccurate.  Do an expensive check before
		 * we go and fail.
		 */
		if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
			goto over;
	}

	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
	if (f == NULL)
		goto fail;

	percpu_counter_inc(&nr_files);
	if (security_file_alloc(f))
		goto fail_sec;

	INIT_LIST_HEAD(&f->f_u.fu_list);
	atomic_long_set(&f->f_count, 1);
	rwlock_init(&f->f_owner.lock);
	f->f_cred = get_cred(cred);
	spin_lock_init(&f->f_lock);
	eventpoll_init_file(f);
	/* f->f_version: 0 */
	return f;

over:
	/* Ran out of filps - report that */
	if (get_nr_files() > old_max) {
		printk(KERN_INFO "VFS: file-max limit %d reached\n",
					get_max_files());
		old_max = get_nr_files();
	}
	goto fail;

fail_sec:
	file_free(f);
fail:
	return NULL;
}

/**
 * alloc_file - allocate and initialize a 'struct file'
 * @mnt: the vfsmount on which the file will reside
 * @dentry: the dentry representing the new file
 * @mode: the mode with which the new file will be opened
 * @fop: the 'struct file_operations' for the new file
 *
 * Use this instead of get_empty_filp() to get a new
 * 'struct file'.  Do so because of the same initialization
 * pitfalls reasons listed for init_file().  This is a
 * preferred interface to using init_file().
 *
 * If all the callers of init_file() are eliminated, its
 * code should be moved into this function.
 */
struct file *alloc_file(struct path *path, fmode_t mode,
		const struct file_operations *fop)
{
	struct file *file;

	file = get_empty_filp();
	if (!file)
		return NULL;

	file->f_path = *path;
	file->f_mapping = path->dentry->d_inode->i_mapping;
	file->f_mode = mode;
	file->f_op = fop;

	/*
	 * These mounts don't really matter in practice
	 * for r/o bind mounts.  They aren't userspace-
	 * visible.  We do this for consistency, and so
	 * that we can do debugging checks at __fput()
	 */
	if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
		file_take_write(file);
		WARN_ON(mnt_clone_write(path->mnt));
	}
	ima_counts_get(file);
	return file;
}
EXPORT_SYMBOL(alloc_file);

/**
 * drop_file_write_access - give up ability to write to a file
 * @file: the file to which we will stop writing
 *
 * This is a central place which will give up the ability
 * to write to @file, along with access to write through
 * its vfsmount.
 */
void drop_file_write_access(struct file *file)
{
	struct vfsmount *mnt = file->f_path.mnt;
	struct dentry *dentry = file->f_path.dentry;
	struct inode *inode = dentry->d_inode;

	put_write_access(inode);

	if (special_file(inode->i_mode))
		return;
	if (file_check_writeable(file) != 0)
		return;
	mnt_drop_write(mnt);
	file_release_write(file);
}
EXPORT_SYMBOL_GPL(drop_file_write_access);

/* the real guts of fput() - releasing the last reference to file
 */
static void __fput(struct file *file)
{
	struct dentry *dentry = file->f_path.dentry;
	struct vfsmount *mnt = file->f_path.mnt;
	struct inode *inode = dentry->d_inode;

	might_sleep();

	fsnotify_close(file);
	/*
	 * The function eventpoll_release() should be the first called
	 * in the file cleanup chain.
	 */
	eventpoll_release(file);
	locks_remove_flock(file);

	if (unlikely(file->f_flags & FASYNC)) {
		if (file->f_op && file->f_op->fasync)
			file->f_op->fasync(-1, file, 0);
	}
	if (file->f_op && file->f_op->release)
		file->f_op->release(inode, file);
	security_file_free(file);
	ima_file_free(file);
	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
		cdev_put(inode->i_cdev);
	fops_put(file->f_op);
	put_pid(file->f_owner.pid);
	file_sb_list_del(file);
	if (file->f_mode & FMODE_WRITE)
		drop_file_write_access(file);
	file->f_path.dentry = NULL;
	file->f_path.mnt = NULL;
	file_free(file);
	dput(dentry);
	mntput(mnt);
}

void fput(struct file *file)
{
	if (atomic_long_dec_and_test(&file->f_count))
		__fput(file);
}

EXPORT_SYMBOL(fput);

struct file *fget(unsigned int fd)
{
	struct file *file;
	struct files_struct *files = current->files;

	rcu_read_lock();
	file = fcheck_files(files, fd);
	if (file) {
		if (!atomic_long_inc_not_zero(&file->f_count)) {
			/* File object ref couldn't be taken */
			rcu_read_unlock();
			return NULL;
		}
	}
	rcu_read_unlock();

	return file;
}

EXPORT_SYMBOL(fget);

/*
 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
 *
 * You can use this instead of fget if you satisfy all of the following
 * conditions:
 * 1) You must call fput_light before exiting the syscall and returning control
 *    to userspace (i.e. you cannot remember the returned struct file * after
 *    returning to userspace).
 * 2) You must not call filp_close on the returned struct file * in between
 *    calls to fget_light and fput_light.
 * 3) You must not clone the current task in between the calls to fget_light
 *    and fput_light.
 *
 * The fput_needed flag returned by fget_light should be passed to the
 * corresponding fput_light.
 */
struct file *fget_light(unsigned int fd, int *fput_needed)
{
	struct file *file;
	struct files_struct *files = current->files;

	*fput_needed = 0;
	if (likely((atomic_read(&files->count) == 1))) {
		file = fcheck_files(files, fd);
	} else {
		rcu_read_lock();
		file = fcheck_files(files, fd);
		if (file) {
			if (atomic_long_inc_not_zero(&file->f_count))
				*fput_needed = 1;
			else
				/* Didn't get the reference, someone's freed */
				file = NULL;
		}
		rcu_read_unlock();
	}

	return file;
}

void put_filp(struct file *file)
{
	if (atomic_long_dec_and_test(&file->f_count)) {
		security_file_free(file);
		file_sb_list_del(file);
		file_free(file);
	}
}

void file_sb_list_add(struct file *file, struct super_block *sb)
{
	spin_lock(&files_lock);
	BUG_ON(!list_empty(&file->f_u.fu_list));
	list_add(&file->f_u.fu_list, &sb->s_files);
	spin_unlock(&files_lock);
}

void file_sb_list_del(struct file *file)
{
	if (!list_empty(&file->f_u.fu_list)) {
		spin_lock(&files_lock);
		list_del_init(&file->f_u.fu_list);
		spin_unlock(&files_lock);
	}
}

int fs_may_remount_ro(struct super_block *sb)
{
	struct file *file;

	/* Check that no files are currently opened for writing. */
	spin_lock(&files_lock);
	list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
		struct inode *inode = file->f_path.dentry->d_inode;

		/* File with pending delete? */
		if (inode->i_nlink == 0)
			goto too_bad;

		/* Writeable file? */
		if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
			goto too_bad;
	}
	spin_unlock(&files_lock);
	return 1; /* Tis' cool bro. */
too_bad:
	spin_unlock(&files_lock);
	return 0;
}

/**
 *	mark_files_ro - mark all files read-only
 *	@sb: superblock in question
 *
 *	All files are marked read-only.  We don't care about pending
 *	delete files so this should be used in 'force' mode only.
 */
void mark_files_ro(struct super_block *sb)
{
	struct file *f;

retry:
	spin_lock(&files_lock);
	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
		struct vfsmount *mnt;
		if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
		       continue;
		if (!file_count(f))
			continue;
		if (!(f->f_mode & FMODE_WRITE))
			continue;
		spin_lock(&f->f_lock);
		f->f_mode &= ~FMODE_WRITE;
		spin_unlock(&f->f_lock);
		if (file_check_writeable(f) != 0)
			continue;
		file_release_write(f);
		mnt = mntget(f->f_path.mnt);
		/* This can sleep, so we can't hold the spinlock. */
		spin_unlock(&files_lock);
		mnt_drop_write(mnt);
		mntput(mnt);
		goto retry;
	}
	spin_unlock(&files_lock);
}

void __init files_init(unsigned long mempages)
{ 
	int n; 

	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
			SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);

	/*
	 * One file with associated inode and dcache is very roughly 1K.
	 * Per default don't use more than 10% of our memory for files. 
	 */ 

	n = (mempages * (PAGE_SIZE / 1024)) / 10;
	files_stat.max_files = n; 
	if (files_stat.max_files < NR_FILE)
		files_stat.max_files = NR_FILE;
	files_defer_init();
	percpu_counter_init(&nr_files, 0);
}
Commit	Line	Data
1da177e4 LT	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>
9f3acc31	11	#include <linux/fdtable.h>
1da177e4 LT	12	#include <linux/init.h>
1da177e4 LT	13	#include <linux/module.h>
1da177e4 LT	14	#include <linux/fs.h>
	15	#include <linux/security.h>
	16	#include <linux/eventpoll.h>
ab2af1f5	17	#include <linux/rcupdate.h>
1da177e4	18	#include <linux/mount.h>
16f7e0fe	19	#include <linux/capability.h>
1da177e4	20	#include <linux/cdev.h>
0eeca283	21	#include <linux/fsnotify.h>
529bf6be DS	22	#include <linux/sysctl.h>
529bf6be DS	23	#include <linux/percpu_counter.h>
0552f879	24	#include <linux/ima.h>
529bf6be DS	25
529bf6be DS	26	#include <asm/atomic.h>
1da177e4	27
e81e3f4d EP	28	#include "internal.h"
e81e3f4d EP	29
1da177e4 LT	30	/* sysctl tunables... */
	31	struct files_stat_struct files_stat = {
	32	.max_files = NR_FILE
	33	};
	34
ee2ffa0d	35	static __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
1da177e4	36
b6b3fdea ED	37	/* SLAB cache for file structures */
	38	static struct kmem_cache *filp_cachep __read_mostly;
	39
529bf6be	40	static struct percpu_counter nr_files __cacheline_aligned_in_smp;
1da177e4	41
529bf6be	42	static inline void file_free_rcu(struct rcu_head *head)
1da177e4	43	{
d76b0d9b DH	44	struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
	45
	46	put_cred(f->f_cred);
529bf6be	47	kmem_cache_free(filp_cachep, f);
1da177e4 LT	48	}
1da177e4 LT	49
529bf6be	50	static inline void file_free(struct file *f)
1da177e4	51	{
529bf6be	52	percpu_counter_dec(&nr_files);
ad775f5a	53	file_check_state(f);
529bf6be	54	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
1da177e4 LT	55	}
1da177e4 LT	56
529bf6be DS	57	/*
	58	* Return the total number of open files in the system
	59	*/
	60	static int get_nr_files(void)
1da177e4	61	{
529bf6be	62	return percpu_counter_read_positive(&nr_files);
1da177e4 LT	63	}
1da177e4 LT	64
529bf6be DS	65	/*
	66	* Return the maximum number of open files in the system
	67	*/
	68	int get_max_files(void)
ab2af1f5	69	{
529bf6be	70	return files_stat.max_files;
ab2af1f5	71	}
529bf6be DS	72	EXPORT_SYMBOL_GPL(get_max_files);
	73
	74	/*
	75	* Handle nr_files sysctl
	76	*/
	77	#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
8d65af78	78	int proc_nr_files(ctl_table *table, int write,
529bf6be DS	79	void __user buffer, size_t lenp, loff_t *ppos)
	80	{
	81	files_stat.nr_files = get_nr_files();
8d65af78	82	return proc_dointvec(table, write, buffer, lenp, ppos);
529bf6be DS	83	}
529bf6be DS	84	#else
8d65af78	85	int proc_nr_files(ctl_table *table, int write,
529bf6be DS	86	void __user buffer, size_t lenp, loff_t *ppos)
	87	{
	88	return -ENOSYS;
	89	}
	90	#endif
ab2af1f5	91
1da177e4 LT	92	/* Find an unused file structure and return a pointer to it.
	93	* Returns NULL, if there are no more free file structures or
	94	* we run out of memory.
430e285e DH	95	*
	96	* Be very careful using this. You are responsible for
	97	* getting write access to any mount that you might assign
	98	* to this filp, if it is opened for write. If this is not
	99	* done, you will imbalance int the mount's writer count
	100	* and a warning at __fput() time.
1da177e4 LT	101	*/
	102	struct file *get_empty_filp(void)
	103	{
86a264ab	104	const struct cred *cred = current_cred();
af4d2ecb	105	static int old_max;
1da177e4 LT	106	struct file * f;
	107
	108	/*
	109	* Privileged users can go above max_files
	110	*/
529bf6be DS	111	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
	112	/*
	113	* percpu_counters are inaccurate. Do an expensive check before
	114	* we go and fail.
	115	*/
52d9f3b4	116	if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
529bf6be DS	117	goto over;
529bf6be DS	118	}
af4d2ecb	119
4975e45f	120	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
af4d2ecb KK	121	if (f == NULL)
	122	goto fail;
	123
529bf6be	124	percpu_counter_inc(&nr_files);
af4d2ecb KK	125	if (security_file_alloc(f))
af4d2ecb KK	126	goto fail_sec;
1da177e4	127
5a6b7951	128	INIT_LIST_HEAD(&f->f_u.fu_list);
516e0cc5	129	atomic_long_set(&f->f_count, 1);
af4d2ecb	130	rwlock_init(&f->f_owner.lock);
d76b0d9b	131	f->f_cred = get_cred(cred);
68499914	132	spin_lock_init(&f->f_lock);
5a6b7951	133	eventpoll_init_file(f);
af4d2ecb	134	/* f->f_version: 0 */
af4d2ecb KK	135	return f;
	136
	137	over:
1da177e4	138	/* Ran out of filps - report that */
529bf6be	139	if (get_nr_files() > old_max) {
1da177e4	140	printk(KERN_INFO "VFS: file-max limit %d reached\n",
529bf6be DS	141	get_max_files());
529bf6be DS	142	old_max = get_nr_files();
1da177e4	143	}
af4d2ecb KK	144	goto fail;
	145
	146	fail_sec:
	147	file_free(f);
1da177e4 LT	148	fail:
	149	return NULL;
	150	}
	151
ce8d2cdf DH	152	/**
	153	* alloc_file - allocate and initialize a 'struct file'
	154	* @mnt: the vfsmount on which the file will reside
	155	* @dentry: the dentry representing the new file
	156	* @mode: the mode with which the new file will be opened
	157	* @fop: the 'struct file_operations' for the new file
	158	*
	159	* Use this instead of get_empty_filp() to get a new
	160	* 'struct file'. Do so because of the same initialization
	161	* pitfalls reasons listed for init_file(). This is a
	162	* preferred interface to using init_file().
	163	*
	164	* If all the callers of init_file() are eliminated, its
	165	* code should be moved into this function.
	166	*/
2c48b9c4 AV	167	struct file alloc_file(struct path path, fmode_t mode,
2c48b9c4 AV	168	const struct file_operations *fop)
ce8d2cdf DH	169	{
ce8d2cdf DH	170	struct file *file;
ce8d2cdf DH	171
	172	file = get_empty_filp();
	173	if (!file)
	174	return NULL;
	175
2c48b9c4 AV	176	file->f_path = *path;
2c48b9c4 AV	177	file->f_mapping = path->dentry->d_inode->i_mapping;
ce8d2cdf DH	178	file->f_mode = mode;
ce8d2cdf DH	179	file->f_op = fop;
4a3fd211 DH	180
	181	/*
	182	* These mounts don't really matter in practice
	183	* for r/o bind mounts. They aren't userspace-
	184	* visible. We do this for consistency, and so
	185	* that we can do debugging checks at __fput()
	186	*/
2c48b9c4	187	if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
ad775f5a	188	file_take_write(file);
385e3ed4	189	WARN_ON(mnt_clone_write(path->mnt));
4a3fd211	190	}
0552f879	191	ima_counts_get(file);
3d1e4631	192	return file;
ce8d2cdf	193	}
73efc468	194	EXPORT_SYMBOL(alloc_file);
ce8d2cdf	195
aceaf78d DH	196	/**
	197	* drop_file_write_access - give up ability to write to a file
	198	* @file: the file to which we will stop writing
	199	*
	200	* This is a central place which will give up the ability
	201	* to write to @file, along with access to write through
	202	* its vfsmount.
	203	*/
	204	void drop_file_write_access(struct file *file)
	205	{
4a3fd211	206	struct vfsmount *mnt = file->f_path.mnt;
aceaf78d DH	207	struct dentry *dentry = file->f_path.dentry;
	208	struct inode *inode = dentry->d_inode;
	209
	210	put_write_access(inode);
ad775f5a DH	211
	212	if (special_file(inode->i_mode))
	213	return;
	214	if (file_check_writeable(file) != 0)
	215	return;
	216	mnt_drop_write(mnt);
	217	file_release_write(file);
aceaf78d DH	218	}
	219	EXPORT_SYMBOL_GPL(drop_file_write_access);
	220
d7065da0	221	/* the real guts of fput() - releasing the last reference to file
1da177e4	222	*/
d7065da0	223	static void __fput(struct file *file)
1da177e4	224	{
0f7fc9e4 JJS	225	struct dentry *dentry = file->f_path.dentry;
0f7fc9e4 JJS	226	struct vfsmount *mnt = file->f_path.mnt;
1da177e4 LT	227	struct inode *inode = dentry->d_inode;
	228
	229	might_sleep();
0eeca283 RL	230
0eeca283 RL	231	fsnotify_close(file);
1da177e4 LT	232	/*
	233	* The function eventpoll_release() should be the first called
	234	* in the file cleanup chain.
	235	*/
	236	eventpoll_release(file);
	237	locks_remove_flock(file);
	238
233e70f4 AV	239	if (unlikely(file->f_flags & FASYNC)) {
	240	if (file->f_op && file->f_op->fasync)
	241	file->f_op->fasync(-1, file, 0);
	242	}
1da177e4 LT	243	if (file->f_op && file->f_op->release)
	244	file->f_op->release(inode, file);
	245	security_file_free(file);
89068c57	246	ima_file_free(file);
577c4eb0	247	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
1da177e4 LT	248	cdev_put(inode->i_cdev);
1da177e4 LT	249	fops_put(file->f_op);
609d7fa9	250	put_pid(file->f_owner.pid);
ee2ffa0d	251	file_sb_list_del(file);
aceaf78d DH	252	if (file->f_mode & FMODE_WRITE)
aceaf78d DH	253	drop_file_write_access(file);
0f7fc9e4 JJS	254	file->f_path.dentry = NULL;
0f7fc9e4 JJS	255	file->f_path.mnt = NULL;
1da177e4 LT	256	file_free(file);
	257	dput(dentry);
	258	mntput(mnt);
	259	}
	260
d7065da0 AV	261	void fput(struct file *file)
	262	{
	263	if (atomic_long_dec_and_test(&file->f_count))
	264	__fput(file);
	265	}
	266
	267	EXPORT_SYMBOL(fput);
	268
fc9b52cd	269	struct file *fget(unsigned int fd)
1da177e4 LT	270	{
	271	struct file *file;
	272	struct files_struct *files = current->files;
	273
ab2af1f5	274	rcu_read_lock();
1da177e4	275	file = fcheck_files(files, fd);
ab2af1f5	276	if (file) {
516e0cc5	277	if (!atomic_long_inc_not_zero(&file->f_count)) {
ab2af1f5 DS	278	/* File object ref couldn't be taken */
	279	rcu_read_unlock();
	280	return NULL;
	281	}
	282	}
	283	rcu_read_unlock();
	284
1da177e4 LT	285	return file;
	286	}
	287
	288	EXPORT_SYMBOL(fget);
	289
	290	/*
58939473 TB	291	* Lightweight file lookup - no refcnt increment if fd table isn't shared.
	292	*
	293	* You can use this instead of fget if you satisfy all of the following
	294	* conditions:
	295	* 1) You must call fput_light before exiting the syscall and returning control
	296	* to userspace (i.e. you cannot remember the returned struct file * after
	297	* returning to userspace).
	298	* 2) You must not call filp_close on the returned struct file * in between
	299	* calls to fget_light and fput_light.
	300	* 3) You must not clone the current task in between the calls to fget_light
	301	* and fput_light.
	302	*
	303	* The fput_needed flag returned by fget_light should be passed to the
	304	* corresponding fput_light.
1da177e4	305	*/
fc9b52cd	306	struct file fget_light(unsigned int fd, int fput_needed)
1da177e4 LT	307	{
	308	struct file *file;
	309	struct files_struct *files = current->files;
	310
	311	*fput_needed = 0;
	312	if (likely((atomic_read(&files->count) == 1))) {
	313	file = fcheck_files(files, fd);
	314	} else {
ab2af1f5	315	rcu_read_lock();
1da177e4 LT	316	file = fcheck_files(files, fd);
1da177e4 LT	317	if (file) {
516e0cc5	318	if (atomic_long_inc_not_zero(&file->f_count))
ab2af1f5 DS	319	*fput_needed = 1;
	320	else
	321	/* Didn't get the reference, someone's freed */
	322	file = NULL;
1da177e4	323	}
ab2af1f5	324	rcu_read_unlock();
1da177e4	325	}
ab2af1f5	326
1da177e4 LT	327	return file;
	328	}
	329
1da177e4 LT	330	void put_filp(struct file *file)
1da177e4 LT	331	{
516e0cc5	332	if (atomic_long_dec_and_test(&file->f_count)) {
1da177e4	333	security_file_free(file);
ee2ffa0d	334	file_sb_list_del(file);
1da177e4 LT	335	file_free(file);
	336	}
	337	}
	338
ee2ffa0d	339	void file_sb_list_add(struct file file, struct super_block sb)
1da177e4	340	{
ee2ffa0d NP	341	spin_lock(&files_lock);
	342	BUG_ON(!list_empty(&file->f_u.fu_list));
	343	list_add(&file->f_u.fu_list, &sb->s_files);
	344	spin_unlock(&files_lock);
1da177e4 LT	345	}
1da177e4 LT	346
ee2ffa0d	347	void file_sb_list_del(struct file *file)
1da177e4	348	{
2f512016	349	if (!list_empty(&file->f_u.fu_list)) {
ee2ffa0d	350	spin_lock(&files_lock);
2f512016	351	list_del_init(&file->f_u.fu_list);
ee2ffa0d	352	spin_unlock(&files_lock);
1da177e4 LT	353	}
	354	}
	355
	356	int fs_may_remount_ro(struct super_block *sb)
	357	{
cfdaf9e5	358	struct file *file;
1da177e4 LT	359
1da177e4 LT	360	/* Check that no files are currently opened for writing. */
ee2ffa0d	361	spin_lock(&files_lock);
cfdaf9e5	362	list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
0f7fc9e4	363	struct inode *inode = file->f_path.dentry->d_inode;
1da177e4 LT	364
	365	/* File with pending delete? */
	366	if (inode->i_nlink == 0)
	367	goto too_bad;
	368
	369	/* Writeable file? */
	370	if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
	371	goto too_bad;
	372	}
ee2ffa0d	373	spin_unlock(&files_lock);
1da177e4 LT	374	return 1; /* Tis' cool bro. */
1da177e4 LT	375	too_bad:
ee2ffa0d	376	spin_unlock(&files_lock);
1da177e4 LT	377	return 0;
	378	}
	379
864d7c4c	380	/**
	381	* mark_files_ro - mark all files read-only
	382	* @sb: superblock in question
	383	*
	384	* All files are marked read-only. We don't care about pending
	385	* delete files so this should be used in 'force' mode only.
	386	*/
	387	void mark_files_ro(struct super_block *sb)
	388	{
	389	struct file *f;
	390
	391	retry:
ee2ffa0d	392	spin_lock(&files_lock);
864d7c4c	393	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
	394	struct vfsmount *mnt;
	395	if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
	396	continue;
	397	if (!file_count(f))
	398	continue;
	399	if (!(f->f_mode & FMODE_WRITE))
	400	continue;
42e49608	401	spin_lock(&f->f_lock);
864d7c4c	402	f->f_mode &= ~FMODE_WRITE;
42e49608	403	spin_unlock(&f->f_lock);
864d7c4c	404	if (file_check_writeable(f) != 0)
	405	continue;
	406	file_release_write(f);
	407	mnt = mntget(f->f_path.mnt);
ee2ffa0d NP	408	/* This can sleep, so we can't hold the spinlock. */
ee2ffa0d NP	409	spin_unlock(&files_lock);
864d7c4c	410	mnt_drop_write(mnt);
	411	mntput(mnt);
	412	goto retry;
	413	}
ee2ffa0d	414	spin_unlock(&files_lock);
864d7c4c	415	}
864d7c4c	416
1da177e4 LT	417	void __init files_init(unsigned long mempages)
	418	{
	419	int n;
b6b3fdea ED	420
	421	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
	422	SLAB_HWCACHE_ALIGN \| SLAB_PANIC, NULL);
	423
	424	/*
	425	* One file with associated inode and dcache is very roughly 1K.
1da177e4 LT	426	* Per default don't use more than 10% of our memory for files.
	427	*/
	428
	429	n = (mempages * (PAGE_SIZE / 1024)) / 10;
	430	files_stat.max_files = n;
	431	if (files_stat.max_files < NR_FILE)
	432	files_stat.max_files = NR_FILE;
ab2af1f5	433	files_defer_init();
0216bfcf	434	percpu_counter_init(&nr_files, 0);
1da177e4	435	}