[deliverable/linux.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/percpu.h>
#include <linux/hardirq.h>
#include <linux/task_work.h>
#include <linux/ima.h>

#include <linux/atomic.h>

#include "internal.h"

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

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

static struct percpu_counter nr_files __cacheline_aligned_in_smp;

static 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);
	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
}

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

/*
 * Return the maximum number of open files in the system
 */
unsigned long 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(struct ctl_table *table, int write,
                     void __user *buffer, size_t *lenp, loff_t *ppos)
{
	files_stat.nr_files = get_nr_files();
	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}
#else
int proc_nr_files(struct 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 an error pointer if some error happend e.g. we over file
 * structures limit, run out of memory or operation is not permitted.
 *
 * 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 long old_max;
	struct file *f;
	int error;

	/*
	 * 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 (unlikely(!f))
		return ERR_PTR(-ENOMEM);

	percpu_counter_inc(&nr_files);
	f->f_cred = get_cred(cred);
	error = security_file_alloc(f);
	if (unlikely(error)) {
		file_free(f);
		return ERR_PTR(error);
	}

	atomic_long_set(&f->f_count, 1);
	rwlock_init(&f->f_owner.lock);
	spin_lock_init(&f->f_lock);
	mutex_init(&f->f_pos_lock);
	eventpoll_init_file(f);
	/* f->f_version: 0 */
	return f;

over:
	/* Ran out of filps - report that */
	if (get_nr_files() > old_max) {
		pr_info("VFS: file-max limit %lu reached\n", get_max_files());
		old_max = get_nr_files();
	}
	return ERR_PTR(-ENFILE);
}

/**
 * alloc_file - allocate and initialize a 'struct file'
 *
 * @path: the (dentry, vfsmount) pair for the new file
 * @mode: the mode with which the new file will be opened
 * @fop: the 'struct file_operations' for the new file
 */
struct file *alloc_file(struct path *path, fmode_t mode,
		const struct file_operations *fop)
{
	struct file *file;

	file = get_empty_filp();
	if (IS_ERR(file))
		return file;

	file->f_path = *path;
	file->f_inode = path->dentry->d_inode;
	file->f_mapping = path->dentry->d_inode->i_mapping;
	if ((mode & FMODE_READ) &&
	     likely(fop->read || fop->read_iter))
		mode |= FMODE_CAN_READ;
	if ((mode & FMODE_WRITE) &&
	     likely(fop->write || fop->write_iter))
		mode |= FMODE_CAN_WRITE;
	file->f_mode = mode;
	file->f_op = fop;
	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
		i_readcount_inc(path->dentry->d_inode);
	return file;
}
EXPORT_SYMBOL(alloc_file);

/* 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 = file->f_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_file(file);

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

static LLIST_HEAD(delayed_fput_list);
static void delayed_fput(struct work_struct *unused)
{
	struct llist_node *node = llist_del_all(&delayed_fput_list);
	struct llist_node *next;

	for (; node; node = next) {
		next = llist_next(node);
		__fput(llist_entry(node, struct file, f_u.fu_llist));
	}
}

static void ____fput(struct callback_head *work)
{
	__fput(container_of(work, struct file, f_u.fu_rcuhead));
}

/*
 * If kernel thread really needs to have the final fput() it has done
 * to complete, call this.  The only user right now is the boot - we
 * *do* need to make sure our writes to binaries on initramfs has
 * not left us with opened struct file waiting for __fput() - execve()
 * won't work without that.  Please, don't add more callers without
 * very good reasons; in particular, never call that with locks
 * held and never call that from a thread that might need to do
 * some work on any kind of umount.
 */
void flush_delayed_fput(void)
{
	delayed_fput(NULL);
}

static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);

void fput(struct file *file)
{
	if (atomic_long_dec_and_test(&file->f_count)) {
		struct task_struct *task = current;

		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
			init_task_work(&file->f_u.fu_rcuhead, ____fput);
			if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
				return;
			/*
			 * After this task has run exit_task_work(),
			 * task_work_add() will fail.  Fall through to delayed
			 * fput to avoid leaking *file.
			 */
		}

		if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
			schedule_delayed_work(&delayed_fput_work, 1);
	}
}

/*
 * synchronous analog of fput(); for kernel threads that might be needed
 * in some umount() (and thus can't use flush_delayed_fput() without
 * risking deadlocks), need to wait for completion of __fput() and know
 * for this specific struct file it won't involve anything that would
 * need them.  Use only if you really need it - at the very least,
 * don't blindly convert fput() by kernel thread to that.
 */
void __fput_sync(struct file *file)
{
	if (atomic_long_dec_and_test(&file->f_count)) {
		struct task_struct *task = current;
		BUG_ON(!(task->flags & PF_KTHREAD));
		__fput(file);
	}
}

EXPORT_SYMBOL(fput);

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

void __init files_init(unsigned long mempages)
{ 
	unsigned long 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 = max_t(unsigned long, n, NR_FILE);
	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
}
Commit	Line	Data
	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/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>
	24	#include <linux/percpu.h>
	25	#include <linux/hardirq.h>
	26	#include <linux/task_work.h>
	27	#include <linux/ima.h>
	28
	29	#include <linux/atomic.h>
	30
	31	#include "internal.h"
	32
	33	/* sysctl tunables... */
	34	struct files_stat_struct files_stat = {
	35	.max_files = NR_FILE
	36	};
	37
	38	/* SLAB cache for file structures */
	39	static struct kmem_cache *filp_cachep __read_mostly;
	40
	41	static struct percpu_counter nr_files __cacheline_aligned_in_smp;
	42
	43	static void file_free_rcu(struct rcu_head *head)
	44	{
	45	struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
	46
	47	put_cred(f->f_cred);
	48	kmem_cache_free(filp_cachep, f);
	49	}
	50
	51	static inline void file_free(struct file *f)
	52	{
	53	percpu_counter_dec(&nr_files);
	54	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
	55	}
	56
	57	/*
	58	* Return the total number of open files in the system
	59	*/
	60	static long get_nr_files(void)
	61	{
	62	return percpu_counter_read_positive(&nr_files);
	63	}
	64
	65	/*
	66	* Return the maximum number of open files in the system
	67	*/
	68	unsigned long get_max_files(void)
	69	{
	70	return files_stat.max_files;
	71	}
	72	EXPORT_SYMBOL_GPL(get_max_files);
	73
	74	/*
	75	* Handle nr_files sysctl
	76	*/
	77	#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
	78	int proc_nr_files(struct ctl_table *table, int write,
	79	void __user buffer, size_t lenp, loff_t *ppos)
	80	{
	81	files_stat.nr_files = get_nr_files();
	82	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	83	}
	84	#else
	85	int proc_nr_files(struct ctl_table *table, int write,
	86	void __user buffer, size_t lenp, loff_t *ppos)
	87	{
	88	return -ENOSYS;
	89	}
	90	#endif
	91
	92	/* Find an unused file structure and return a pointer to it.
	93	* Returns an error pointer if some error happend e.g. we over file
	94	* structures limit, run out of memory or operation is not permitted.
	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.
	101	*/
	102	struct file *get_empty_filp(void)
	103	{
	104	const struct cred *cred = current_cred();
	105	static long old_max;
	106	struct file *f;
	107	int error;
	108
	109	/*
	110	* Privileged users can go above max_files
	111	*/
	112	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
	113	/*
	114	* percpu_counters are inaccurate. Do an expensive check before
	115	* we go and fail.
	116	*/
	117	if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
	118	goto over;
	119	}
	120
	121	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
	122	if (unlikely(!f))
	123	return ERR_PTR(-ENOMEM);
	124
	125	percpu_counter_inc(&nr_files);
	126	f->f_cred = get_cred(cred);
	127	error = security_file_alloc(f);
	128	if (unlikely(error)) {
	129	file_free(f);
	130	return ERR_PTR(error);
	131	}
	132
	133	atomic_long_set(&f->f_count, 1);
	134	rwlock_init(&f->f_owner.lock);
	135	spin_lock_init(&f->f_lock);
	136	mutex_init(&f->f_pos_lock);
	137	eventpoll_init_file(f);
	138	/* f->f_version: 0 */
	139	return f;
	140
	141	over:
	142	/* Ran out of filps - report that */
	143	if (get_nr_files() > old_max) {
	144	pr_info("VFS: file-max limit %lu reached\n", get_max_files());
	145	old_max = get_nr_files();
	146	}
	147	return ERR_PTR(-ENFILE);
	148	}
	149
	150	/**
	151	* alloc_file - allocate and initialize a 'struct file'
	152	*
	153	* @path: the (dentry, vfsmount) pair for the new file
	154	* @mode: the mode with which the new file will be opened
	155	* @fop: the 'struct file_operations' for the new file
	156	*/
	157	struct file alloc_file(struct path path, fmode_t mode,
	158	const struct file_operations *fop)
	159	{
	160	struct file *file;
	161
	162	file = get_empty_filp();
	163	if (IS_ERR(file))
	164	return file;
	165
	166	file->f_path = *path;
	167	file->f_inode = path->dentry->d_inode;
	168	file->f_mapping = path->dentry->d_inode->i_mapping;
	169	if ((mode & FMODE_READ) &&
	170	likely(fop->read \|\| fop->read_iter))
	171	mode \|= FMODE_CAN_READ;
	172	if ((mode & FMODE_WRITE) &&
	173	likely(fop->write \|\| fop->write_iter))
	174	mode \|= FMODE_CAN_WRITE;
	175	file->f_mode = mode;
	176	file->f_op = fop;
	177	if ((mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
	178	i_readcount_inc(path->dentry->d_inode);
	179	return file;
	180	}
	181	EXPORT_SYMBOL(alloc_file);
	182
	183	/* the real guts of fput() - releasing the last reference to file
	184	*/
	185	static void __fput(struct file *file)
	186	{
	187	struct dentry *dentry = file->f_path.dentry;
	188	struct vfsmount *mnt = file->f_path.mnt;
	189	struct inode *inode = file->f_inode;
	190
	191	might_sleep();
	192
	193	fsnotify_close(file);
	194	/*
	195	* The function eventpoll_release() should be the first called
	196	* in the file cleanup chain.
	197	*/
	198	eventpoll_release(file);
	199	locks_remove_file(file);
	200
	201	if (unlikely(file->f_flags & FASYNC)) {
	202	if (file->f_op->fasync)
	203	file->f_op->fasync(-1, file, 0);
	204	}
	205	ima_file_free(file);
	206	if (file->f_op->release)
	207	file->f_op->release(inode, file);
	208	security_file_free(file);
	209	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
	210	!(file->f_mode & FMODE_PATH))) {
	211	cdev_put(inode->i_cdev);
	212	}
	213	fops_put(file->f_op);
	214	put_pid(file->f_owner.pid);
	215	if ((file->f_mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
	216	i_readcount_dec(inode);
	217	if (file->f_mode & FMODE_WRITER) {
	218	put_write_access(inode);
	219	__mnt_drop_write(mnt);
	220	}
	221	file->f_path.dentry = NULL;
	222	file->f_path.mnt = NULL;
	223	file->f_inode = NULL;
	224	file_free(file);
	225	dput(dentry);
	226	mntput(mnt);
	227	}
	228
	229	static LLIST_HEAD(delayed_fput_list);
	230	static void delayed_fput(struct work_struct *unused)
	231	{
	232	struct llist_node *node = llist_del_all(&delayed_fput_list);
	233	struct llist_node *next;
	234
	235	for (; node; node = next) {
	236	next = llist_next(node);
	237	__fput(llist_entry(node, struct file, f_u.fu_llist));
	238	}
	239	}
	240
	241	static void ____fput(struct callback_head *work)
	242	{
	243	__fput(container_of(work, struct file, f_u.fu_rcuhead));
	244	}
	245
	246	/*
	247	* If kernel thread really needs to have the final fput() it has done
	248	* to complete, call this. The only user right now is the boot - we
	249	* do need to make sure our writes to binaries on initramfs has
	250	* not left us with opened struct file waiting for __fput() - execve()
	251	* won't work without that. Please, don't add more callers without
	252	* very good reasons; in particular, never call that with locks
	253	* held and never call that from a thread that might need to do
	254	* some work on any kind of umount.
	255	*/
	256	void flush_delayed_fput(void)
	257	{
	258	delayed_fput(NULL);
	259	}
	260
	261	static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
	262
	263	void fput(struct file *file)
	264	{
	265	if (atomic_long_dec_and_test(&file->f_count)) {
	266	struct task_struct *task = current;
	267
	268	if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
	269	init_task_work(&file->f_u.fu_rcuhead, ____fput);
	270	if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
	271	return;
	272	/*
	273	* After this task has run exit_task_work(),
	274	* task_work_add() will fail. Fall through to delayed
	275	* fput to avoid leaking *file.
	276	*/
	277	}
	278
	279	if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
	280	schedule_delayed_work(&delayed_fput_work, 1);
	281	}
	282	}
	283
	284	/*
	285	* synchronous analog of fput(); for kernel threads that might be needed
	286	* in some umount() (and thus can't use flush_delayed_fput() without
	287	* risking deadlocks), need to wait for completion of __fput() and know
	288	* for this specific struct file it won't involve anything that would
	289	* need them. Use only if you really need it - at the very least,
	290	* don't blindly convert fput() by kernel thread to that.
	291	*/
	292	void __fput_sync(struct file *file)
	293	{
	294	if (atomic_long_dec_and_test(&file->f_count)) {
	295	struct task_struct *task = current;
	296	BUG_ON(!(task->flags & PF_KTHREAD));
	297	__fput(file);
	298	}
	299	}
	300
	301	EXPORT_SYMBOL(fput);
	302
	303	void put_filp(struct file *file)
	304	{
	305	if (atomic_long_dec_and_test(&file->f_count)) {
	306	security_file_free(file);
	307	file_free(file);
	308	}
	309	}
	310
	311	void __init files_init(unsigned long mempages)
	312	{
	313	unsigned long n;
	314
	315	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
	316	SLAB_HWCACHE_ALIGN \| SLAB_PANIC, NULL);
	317
	318	/*
	319	* One file with associated inode and dcache is very roughly 1K.
	320	* Per default don't use more than 10% of our memory for files.
	321	*/
	322
	323	n = (mempages * (PAGE_SIZE / 1024)) / 10;
	324	files_stat.max_files = max_t(unsigned long, n, NR_FILE);
	325	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
	326	}