[linux-block.git] / fs / file_table.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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/filelock.h>
#include <linux/security.h>
#include <linux/cred.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/task_work.h>
#include <linux/ima.h>
#include <linux/swap.h>
#include <linux/kmemleak.h>

#include <linux/atomic.h>

#include "internal.h"

/* sysctl tunables... */
static 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_rcuhead);

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

static inline void file_free(struct file *f)
{
	security_file_free(f);
	if (!(f->f_mode & FMODE_NOACCOUNT))
		percpu_counter_dec(&nr_files);
	call_rcu(&f->f_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);

#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)

/*
 * Handle nr_files sysctl
 */
static int proc_nr_files(struct ctl_table *table, int write, void *buffer,
			 size_t *lenp, loff_t *ppos)
{
	files_stat.nr_files = get_nr_files();
	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}

static struct ctl_table fs_stat_sysctls[] = {
	{
		.procname	= "file-nr",
		.data		= &files_stat,
		.maxlen		= sizeof(files_stat),
		.mode		= 0444,
		.proc_handler	= proc_nr_files,
	},
	{
		.procname	= "file-max",
		.data		= &files_stat.max_files,
		.maxlen		= sizeof(files_stat.max_files),
		.mode		= 0644,
		.proc_handler	= proc_doulongvec_minmax,
		.extra1		= SYSCTL_LONG_ZERO,
		.extra2		= SYSCTL_LONG_MAX,
	},
	{
		.procname	= "nr_open",
		.data		= &sysctl_nr_open,
		.maxlen		= sizeof(unsigned int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_minmax,
		.extra1		= &sysctl_nr_open_min,
		.extra2		= &sysctl_nr_open_max,
	},
	{ }
};

static int __init init_fs_stat_sysctls(void)
{
	register_sysctl_init("fs", fs_stat_sysctls);
	if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
		struct ctl_table_header *hdr;
		hdr = register_sysctl_mount_point("fs/binfmt_misc");
		kmemleak_not_leak(hdr);
	}
	return 0;
}
fs_initcall(init_fs_stat_sysctls);
#endif

static struct file *__alloc_file(int flags, const struct cred *cred)
{
	struct file *f;
	int error;

	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
	if (unlikely(!f))
		return ERR_PTR(-ENOMEM);

	f->f_cred = get_cred(cred);
	error = security_file_alloc(f);
	if (unlikely(error)) {
		file_free_rcu(&f->f_rcuhead);
		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);
	f->f_flags = flags;
	f->f_mode = OPEN_FMODE(flags);
	/* f->f_version: 0 */

	return f;
}

/* 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 *alloc_empty_file(int flags, const struct cred *cred)
{
	static long 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 = __alloc_file(flags, cred);
	if (!IS_ERR(f))
		percpu_counter_inc(&nr_files);

	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);
}

/*
 * Variant of alloc_empty_file() that doesn't check and modify nr_files.
 *
 * Should not be used unless there's a very good reason to do so.
 */
struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
{
	struct file *f = __alloc_file(flags, cred);

	if (!IS_ERR(f))
		f->f_mode |= FMODE_NOACCOUNT;

	return f;
}

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

	file = alloc_empty_file(flags, current_cred());
	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;
	file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
	file->f_sb_err = file_sample_sb_err(file);
	if (fop->llseek)
		file->f_mode |= FMODE_LSEEK;
	if ((file->f_mode & FMODE_READ) &&
	     likely(fop->read || fop->read_iter))
		file->f_mode |= FMODE_CAN_READ;
	if ((file->f_mode & FMODE_WRITE) &&
	     likely(fop->write || fop->write_iter))
		file->f_mode |= FMODE_CAN_WRITE;
	file->f_iocb_flags = iocb_flags(file);
	file->f_mode |= FMODE_OPENED;
	file->f_op = fop;
	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
		i_readcount_inc(path->dentry->d_inode);
	return file;
}

struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
				const char *name, int flags,
				const struct file_operations *fops)
{
	static const struct dentry_operations anon_ops = {
		.d_dname = simple_dname
	};
	struct qstr this = QSTR_INIT(name, strlen(name));
	struct path path;
	struct file *file;

	path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
	if (!path.dentry)
		return ERR_PTR(-ENOMEM);
	if (!mnt->mnt_sb->s_d_op)
		d_set_d_op(path.dentry, &anon_ops);
	path.mnt = mntget(mnt);
	d_instantiate(path.dentry, inode);
	file = alloc_file(&path, flags, fops);
	if (IS_ERR(file)) {
		ihold(inode);
		path_put(&path);
	}
	return file;
}
EXPORT_SYMBOL(alloc_file_pseudo);

struct file *alloc_file_clone(struct file *base, int flags,
				const struct file_operations *fops)
{
	struct file *f = alloc_file(&base->f_path, flags, fops);
	if (!IS_ERR(f)) {
		path_get(&f->f_path);
		f->f_mapping = base->f_mapping;
	}
	return f;
}

/* 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;
	fmode_t mode = file->f_mode;

	if (unlikely(!(file->f_mode & FMODE_OPENED)))
		goto out;

	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);

	ima_file_free(file);
	if (unlikely(file->f_flags & FASYNC)) {
		if (file->f_op->fasync)
			file->f_op->fasync(-1, file, 0);
	}
	if (file->f_op->release)
		file->f_op->release(inode, file);
	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
		     !(mode & FMODE_PATH))) {
		cdev_put(inode->i_cdev);
	}
	fops_put(file->f_op);
	put_pid(file->f_owner.pid);
	put_file_access(file);
	dput(dentry);
	if (unlikely(mode & FMODE_NEED_UNMOUNT))
		dissolve_on_fput(mnt);
	mntput(mnt);
out:
	file_free(file);
}

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 file *f, *t;

	llist_for_each_entry_safe(f, t, node, f_llist)
		__fput(f);
}

static void ____fput(struct callback_head *work)
{
	__fput(container_of(work, struct file, f_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);
}
EXPORT_SYMBOL_GPL(flush_delayed_fput);

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_rcuhead, ____fput);
			if (!task_work_add(task, &file->f_rcuhead, TWA_RESUME))
				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_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);
EXPORT_SYMBOL(__fput_sync);

void __init files_init(void)
{
	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
}

/*
 * One file with associated inode and dcache is very roughly 1K. Per default
 * do not use more than 10% of our memory for files.
 */
void __init files_maxfiles_init(void)
{
	unsigned long n;
	unsigned long nr_pages = totalram_pages();
	unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;

	memreserve = min(memreserve, nr_pages - 1);
	n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;

	files_stat.max_files = max_t(unsigned long, n, NR_FILE);
}
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0-only
	2	/*
	3	* linux/fs/file_table.c
	4	*
	5	* Copyright (C) 1991, 1992 Linus Torvalds
	6	* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
	7	*/
	8
	9	#include <linux/string.h>
	10	#include <linux/slab.h>
	11	#include <linux/file.h>
	12	#include <linux/fdtable.h>
	13	#include <linux/init.h>
	14	#include <linux/module.h>
	15	#include <linux/fs.h>
	16	#include <linux/filelock.h>
	17	#include <linux/security.h>
	18	#include <linux/cred.h>
	19	#include <linux/eventpoll.h>
	20	#include <linux/rcupdate.h>
	21	#include <linux/mount.h>
	22	#include <linux/capability.h>
	23	#include <linux/cdev.h>
	24	#include <linux/fsnotify.h>
	25	#include <linux/sysctl.h>
	26	#include <linux/percpu_counter.h>
	27	#include <linux/percpu.h>
	28	#include <linux/task_work.h>
	29	#include <linux/ima.h>
	30	#include <linux/swap.h>
	31	#include <linux/kmemleak.h>
	32
	33	#include <linux/atomic.h>
	34
	35	#include "internal.h"
	36
	37	/* sysctl tunables... */
	38	static struct files_stat_struct files_stat = {
	39	.max_files = NR_FILE
	40	};
	41
	42	/* SLAB cache for file structures */
	43	static struct kmem_cache *filp_cachep __read_mostly;
	44
	45	static struct percpu_counter nr_files __cacheline_aligned_in_smp;
	46
	47	static void file_free_rcu(struct rcu_head *head)
	48	{
	49	struct file *f = container_of(head, struct file, f_rcuhead);
	50
	51	put_cred(f->f_cred);
	52	kmem_cache_free(filp_cachep, f);
	53	}
	54
	55	static inline void file_free(struct file *f)
	56	{
	57	security_file_free(f);
	58	if (!(f->f_mode & FMODE_NOACCOUNT))
	59	percpu_counter_dec(&nr_files);
	60	call_rcu(&f->f_rcuhead, file_free_rcu);
	61	}
	62
	63	/*
	64	* Return the total number of open files in the system
	65	*/
	66	static long get_nr_files(void)
	67	{
	68	return percpu_counter_read_positive(&nr_files);
	69	}
	70
	71	/*
	72	* Return the maximum number of open files in the system
	73	*/
	74	unsigned long get_max_files(void)
	75	{
	76	return files_stat.max_files;
	77	}
	78	EXPORT_SYMBOL_GPL(get_max_files);
	79
	80	#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
	81
	82	/*
	83	* Handle nr_files sysctl
	84	*/
	85	static int proc_nr_files(struct ctl_table table, int write, void buffer,
	86	size_t lenp, loff_t ppos)
	87	{
	88	files_stat.nr_files = get_nr_files();
	89	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	90	}
	91
	92	static struct ctl_table fs_stat_sysctls[] = {
	93	{
	94	.procname = "file-nr",
	95	.data = &files_stat,
	96	.maxlen = sizeof(files_stat),
	97	.mode = 0444,
	98	.proc_handler = proc_nr_files,
	99	},
	100	{
	101	.procname = "file-max",
	102	.data = &files_stat.max_files,
	103	.maxlen = sizeof(files_stat.max_files),
	104	.mode = 0644,
	105	.proc_handler = proc_doulongvec_minmax,
	106	.extra1 = SYSCTL_LONG_ZERO,
	107	.extra2 = SYSCTL_LONG_MAX,
	108	},
	109	{
	110	.procname = "nr_open",
	111	.data = &sysctl_nr_open,
	112	.maxlen = sizeof(unsigned int),
	113	.mode = 0644,
	114	.proc_handler = proc_dointvec_minmax,
	115	.extra1 = &sysctl_nr_open_min,
	116	.extra2 = &sysctl_nr_open_max,
	117	},
	118	{ }
	119	};
	120
	121	static int __init init_fs_stat_sysctls(void)
	122	{
	123	register_sysctl_init("fs", fs_stat_sysctls);
	124	if (IS_ENABLED(CONFIG_BINFMT_MISC)) {
	125	struct ctl_table_header *hdr;
	126	hdr = register_sysctl_mount_point("fs/binfmt_misc");
	127	kmemleak_not_leak(hdr);
	128	}
	129	return 0;
	130	}
	131	fs_initcall(init_fs_stat_sysctls);
	132	#endif
	133
	134	static struct file __alloc_file(int flags, const struct cred cred)
	135	{
	136	struct file *f;
	137	int error;
	138
	139	f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
	140	if (unlikely(!f))
	141	return ERR_PTR(-ENOMEM);
	142
	143	f->f_cred = get_cred(cred);
	144	error = security_file_alloc(f);
	145	if (unlikely(error)) {
	146	file_free_rcu(&f->f_rcuhead);
	147	return ERR_PTR(error);
	148	}
	149
	150	atomic_long_set(&f->f_count, 1);
	151	rwlock_init(&f->f_owner.lock);
	152	spin_lock_init(&f->f_lock);
	153	mutex_init(&f->f_pos_lock);
	154	f->f_flags = flags;
	155	f->f_mode = OPEN_FMODE(flags);
	156	/* f->f_version: 0 */
	157
	158	return f;
	159	}
	160
	161	/* Find an unused file structure and return a pointer to it.
	162	* Returns an error pointer if some error happend e.g. we over file
	163	* structures limit, run out of memory or operation is not permitted.
	164	*
	165	* Be very careful using this. You are responsible for
	166	* getting write access to any mount that you might assign
	167	* to this filp, if it is opened for write. If this is not
	168	* done, you will imbalance int the mount's writer count
	169	* and a warning at __fput() time.
	170	*/
	171	struct file alloc_empty_file(int flags, const struct cred cred)
	172	{
	173	static long old_max;
	174	struct file *f;
	175
	176	/*
	177	* Privileged users can go above max_files
	178	*/
	179	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
	180	/*
	181	* percpu_counters are inaccurate. Do an expensive check before
	182	* we go and fail.
	183	*/
	184	if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
	185	goto over;
	186	}
	187
	188	f = __alloc_file(flags, cred);
	189	if (!IS_ERR(f))
	190	percpu_counter_inc(&nr_files);
	191
	192	return f;
	193
	194	over:
	195	/* Ran out of filps - report that */
	196	if (get_nr_files() > old_max) {
	197	pr_info("VFS: file-max limit %lu reached\n", get_max_files());
	198	old_max = get_nr_files();
	199	}
	200	return ERR_PTR(-ENFILE);
	201	}
	202
	203	/*
	204	* Variant of alloc_empty_file() that doesn't check and modify nr_files.
	205	*
	206	* Should not be used unless there's a very good reason to do so.
	207	*/
	208	struct file alloc_empty_file_noaccount(int flags, const struct cred cred)
	209	{
	210	struct file *f = __alloc_file(flags, cred);
	211
	212	if (!IS_ERR(f))
	213	f->f_mode \|= FMODE_NOACCOUNT;
	214
	215	return f;
	216	}
	217
	218	/**
	219	* alloc_file - allocate and initialize a 'struct file'
	220	*
	221	* @path: the (dentry, vfsmount) pair for the new file
	222	* @flags: O_... flags with which the new file will be opened
	223	* @fop: the 'struct file_operations' for the new file
	224	*/
	225	static struct file alloc_file(const struct path path, int flags,
	226	const struct file_operations *fop)
	227	{
	228	struct file *file;
	229
	230	file = alloc_empty_file(flags, current_cred());
	231	if (IS_ERR(file))
	232	return file;
	233
	234	file->f_path = *path;
	235	file->f_inode = path->dentry->d_inode;
	236	file->f_mapping = path->dentry->d_inode->i_mapping;
	237	file->f_wb_err = filemap_sample_wb_err(file->f_mapping);
	238	file->f_sb_err = file_sample_sb_err(file);
	239	if (fop->llseek)
	240	file->f_mode \|= FMODE_LSEEK;
	241	if ((file->f_mode & FMODE_READ) &&
	242	likely(fop->read \|\| fop->read_iter))
	243	file->f_mode \|= FMODE_CAN_READ;
	244	if ((file->f_mode & FMODE_WRITE) &&
	245	likely(fop->write \|\| fop->write_iter))
	246	file->f_mode \|= FMODE_CAN_WRITE;
	247	file->f_iocb_flags = iocb_flags(file);
	248	file->f_mode \|= FMODE_OPENED;
	249	file->f_op = fop;
	250	if ((file->f_mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
	251	i_readcount_inc(path->dentry->d_inode);
	252	return file;
	253	}
	254
	255	struct file alloc_file_pseudo(struct inode inode, struct vfsmount *mnt,
	256	const char *name, int flags,
	257	const struct file_operations *fops)
	258	{
	259	static const struct dentry_operations anon_ops = {
	260	.d_dname = simple_dname
	261	};
	262	struct qstr this = QSTR_INIT(name, strlen(name));
	263	struct path path;
	264	struct file *file;
	265
	266	path.dentry = d_alloc_pseudo(mnt->mnt_sb, &this);
	267	if (!path.dentry)
	268	return ERR_PTR(-ENOMEM);
	269	if (!mnt->mnt_sb->s_d_op)
	270	d_set_d_op(path.dentry, &anon_ops);
	271	path.mnt = mntget(mnt);
	272	d_instantiate(path.dentry, inode);
	273	file = alloc_file(&path, flags, fops);
	274	if (IS_ERR(file)) {
	275	ihold(inode);
	276	path_put(&path);
	277	}
	278	return file;
	279	}
	280	EXPORT_SYMBOL(alloc_file_pseudo);
	281
	282	struct file alloc_file_clone(struct file base, int flags,
	283	const struct file_operations *fops)
	284	{
	285	struct file *f = alloc_file(&base->f_path, flags, fops);
	286	if (!IS_ERR(f)) {
	287	path_get(&f->f_path);
	288	f->f_mapping = base->f_mapping;
	289	}
	290	return f;
	291	}
	292
	293	/* the real guts of fput() - releasing the last reference to file
	294	*/
	295	static void __fput(struct file *file)
	296	{
	297	struct dentry *dentry = file->f_path.dentry;
	298	struct vfsmount *mnt = file->f_path.mnt;
	299	struct inode *inode = file->f_inode;
	300	fmode_t mode = file->f_mode;
	301
	302	if (unlikely(!(file->f_mode & FMODE_OPENED)))
	303	goto out;
	304
	305	might_sleep();
	306
	307	fsnotify_close(file);
	308	/*
	309	* The function eventpoll_release() should be the first called
	310	* in the file cleanup chain.
	311	*/
	312	eventpoll_release(file);
	313	locks_remove_file(file);
	314
	315	ima_file_free(file);
	316	if (unlikely(file->f_flags & FASYNC)) {
	317	if (file->f_op->fasync)
	318	file->f_op->fasync(-1, file, 0);
	319	}
	320	if (file->f_op->release)
	321	file->f_op->release(inode, file);
	322	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
	323	!(mode & FMODE_PATH))) {
	324	cdev_put(inode->i_cdev);
	325	}
	326	fops_put(file->f_op);
	327	put_pid(file->f_owner.pid);
	328	put_file_access(file);
	329	dput(dentry);
	330	if (unlikely(mode & FMODE_NEED_UNMOUNT))
	331	dissolve_on_fput(mnt);
	332	mntput(mnt);
	333	out:
	334	file_free(file);
	335	}
	336
	337	static LLIST_HEAD(delayed_fput_list);
	338	static void delayed_fput(struct work_struct *unused)
	339	{
	340	struct llist_node *node = llist_del_all(&delayed_fput_list);
	341	struct file f, t;
	342
	343	llist_for_each_entry_safe(f, t, node, f_llist)
	344	__fput(f);
	345	}
	346
	347	static void ____fput(struct callback_head *work)
	348	{
	349	__fput(container_of(work, struct file, f_rcuhead));
	350	}
	351
	352	/*
	353	* If kernel thread really needs to have the final fput() it has done
	354	* to complete, call this. The only user right now is the boot - we
	355	* do need to make sure our writes to binaries on initramfs has
	356	* not left us with opened struct file waiting for __fput() - execve()
	357	* won't work without that. Please, don't add more callers without
	358	* very good reasons; in particular, never call that with locks
	359	* held and never call that from a thread that might need to do
	360	* some work on any kind of umount.
	361	*/
	362	void flush_delayed_fput(void)
	363	{
	364	delayed_fput(NULL);
	365	}
	366	EXPORT_SYMBOL_GPL(flush_delayed_fput);
	367
	368	static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
	369
	370	void fput(struct file *file)
	371	{
	372	if (atomic_long_dec_and_test(&file->f_count)) {
	373	struct task_struct *task = current;
	374
	375	if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
	376	init_task_work(&file->f_rcuhead, ____fput);
	377	if (!task_work_add(task, &file->f_rcuhead, TWA_RESUME))
	378	return;
	379	/*
	380	* After this task has run exit_task_work(),
	381	* task_work_add() will fail. Fall through to delayed
	382	* fput to avoid leaking *file.
	383	*/
	384	}
	385
	386	if (llist_add(&file->f_llist, &delayed_fput_list))
	387	schedule_delayed_work(&delayed_fput_work, 1);
	388	}
	389	}
	390
	391	/*
	392	* synchronous analog of fput(); for kernel threads that might be needed
	393	* in some umount() (and thus can't use flush_delayed_fput() without
	394	* risking deadlocks), need to wait for completion of __fput() and know
	395	* for this specific struct file it won't involve anything that would
	396	* need them. Use only if you really need it - at the very least,
	397	* don't blindly convert fput() by kernel thread to that.
	398	*/
	399	void __fput_sync(struct file *file)
	400	{
	401	if (atomic_long_dec_and_test(&file->f_count)) {
	402	struct task_struct *task = current;
	403	BUG_ON(!(task->flags & PF_KTHREAD));
	404	__fput(file);
	405	}
	406	}
	407
	408	EXPORT_SYMBOL(fput);
	409	EXPORT_SYMBOL(__fput_sync);
	410
	411	void __init files_init(void)
	412	{
	413	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
	414	SLAB_HWCACHE_ALIGN \| SLAB_PANIC \| SLAB_ACCOUNT, NULL);
	415	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
	416	}
	417
	418	/*
	419	* One file with associated inode and dcache is very roughly 1K. Per default
	420	* do not use more than 10% of our memory for files.
	421	*/
	422	void __init files_maxfiles_init(void)
	423	{
	424	unsigned long n;
	425	unsigned long nr_pages = totalram_pages();
	426	unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
	427
	428	memreserve = min(memreserve, nr_pages - 1);
	429	n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
	430
	431	files_stat.max_files = max_t(unsigned long, n, NR_FILE);
	432	}