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

/*
 *  fs/eventfd.c
 *
 *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
 *
 */

#include <linux/file.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched/signal.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/anon_inodes.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/kref.h>
#include <linux/eventfd.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

struct eventfd_ctx {
	struct kref kref;
	wait_queue_head_t wqh;
	/*
	 * Every time that a write(2) is performed on an eventfd, the
	 * value of the __u64 being written is added to "count" and a
	 * wakeup is performed on "wqh". A read(2) will return the "count"
	 * value to userspace, and will reset "count" to zero. The kernel
	 * side eventfd_signal() also, adds to the "count" counter and
	 * issue a wakeup.
	 */
	__u64 count;
	unsigned int flags;
};

/**
 * eventfd_signal - Adds @n to the eventfd counter.
 * @ctx: [in] Pointer to the eventfd context.
 * @n: [in] Value of the counter to be added to the eventfd internal counter.
 *          The value cannot be negative.
 *
 * This function is supposed to be called by the kernel in paths that do not
 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
 * value, and we signal this as overflow condition by returning a POLLERR
 * to poll(2).
 *
 * Returns the amount by which the counter was incremented.  This will be less
 * than @n if the counter has overflowed.
 */
__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
{
	unsigned long flags;

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ULLONG_MAX - ctx->count < n)
		n = ULLONG_MAX - ctx->count;
	ctx->count += n;
	if (waitqueue_active(&ctx->wqh))
		wake_up_locked_poll(&ctx->wqh, POLLIN);
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return n;
}
EXPORT_SYMBOL_GPL(eventfd_signal);

static void eventfd_free_ctx(struct eventfd_ctx *ctx)
{
	kfree(ctx);
}

static void eventfd_free(struct kref *kref)
{
	struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);

	eventfd_free_ctx(ctx);
}

/**
 * eventfd_ctx_get - Acquires a reference to the internal eventfd context.
 * @ctx: [in] Pointer to the eventfd context.
 *
 * Returns: In case of success, returns a pointer to the eventfd context.
 */
struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
{
	kref_get(&ctx->kref);
	return ctx;
}
EXPORT_SYMBOL_GPL(eventfd_ctx_get);

/**
 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
 * @ctx: [in] Pointer to eventfd context.
 *
 * The eventfd context reference must have been previously acquired either
 * with eventfd_ctx_get() or eventfd_ctx_fdget().
 */
void eventfd_ctx_put(struct eventfd_ctx *ctx)
{
	kref_put(&ctx->kref, eventfd_free);
}
EXPORT_SYMBOL_GPL(eventfd_ctx_put);

static int eventfd_release(struct inode *inode, struct file *file)
{
	struct eventfd_ctx *ctx = file->private_data;

	wake_up_poll(&ctx->wqh, POLLHUP);
	eventfd_ctx_put(ctx);
	return 0;
}

static unsigned int eventfd_poll(struct file *file, poll_table *wait)
{
	struct eventfd_ctx *ctx = file->private_data;
	unsigned int events = 0;
	u64 count;

	poll_wait(file, &ctx->wqh, wait);

	/*
	 * All writes to ctx->count occur within ctx->wqh.lock.  This read
	 * can be done outside ctx->wqh.lock because we know that poll_wait
	 * takes that lock (through add_wait_queue) if our caller will sleep.
	 *
	 * The read _can_ therefore seep into add_wait_queue's critical
	 * section, but cannot move above it!  add_wait_queue's spin_lock acts
	 * as an acquire barrier and ensures that the read be ordered properly
	 * against the writes.  The following CAN happen and is safe:
	 *
	 *     poll                               write
	 *     -----------------                  ------------
	 *     lock ctx->wqh.lock (in poll_wait)
	 *     count = ctx->count
	 *     __add_wait_queue
	 *     unlock ctx->wqh.lock
	 *                                        lock ctx->qwh.lock
	 *                                        ctx->count += n
	 *                                        if (waitqueue_active)
	 *                                          wake_up_locked_poll
	 *                                        unlock ctx->qwh.lock
	 *     eventfd_poll returns 0
	 *
	 * but the following, which would miss a wakeup, cannot happen:
	 *
	 *     poll                               write
	 *     -----------------                  ------------
	 *     count = ctx->count (INVALID!)
	 *                                        lock ctx->qwh.lock
	 *                                        ctx->count += n
	 *                                        **waitqueue_active is false**
	 *                                        **no wake_up_locked_poll!**
	 *                                        unlock ctx->qwh.lock
	 *     lock ctx->wqh.lock (in poll_wait)
	 *     __add_wait_queue
	 *     unlock ctx->wqh.lock
	 *     eventfd_poll returns 0
	 */
	count = READ_ONCE(ctx->count);

	if (count > 0)
		events |= POLLIN;
	if (count == ULLONG_MAX)
		events |= POLLERR;
	if (ULLONG_MAX - 1 > count)
		events |= POLLOUT;

	return events;
}

static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
{
	*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
	ctx->count -= *cnt;
}

/**
 * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
 * @ctx: [in] Pointer to eventfd context.
 * @wait: [in] Wait queue to be removed.
 * @cnt: [out] Pointer to the 64-bit counter value.
 *
 * Returns %0 if successful, or the following error codes:
 *
 * -EAGAIN      : The operation would have blocked.
 *
 * This is used to atomically remove a wait queue entry from the eventfd wait
 * queue head, and read/reset the counter value.
 */
int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
				  __u64 *cnt)
{
	unsigned long flags;

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	eventfd_ctx_do_read(ctx, cnt);
	__remove_wait_queue(&ctx->wqh, wait);
	if (*cnt != 0 && waitqueue_active(&ctx->wqh))
		wake_up_locked_poll(&ctx->wqh, POLLOUT);
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return *cnt != 0 ? 0 : -EAGAIN;
}
EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);

static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
			    loff_t *ppos)
{
	struct eventfd_ctx *ctx = file->private_data;
	ssize_t res;
	__u64 ucnt = 0;
	DECLARE_WAITQUEUE(wait, current);

	if (count < sizeof(ucnt))
		return -EINVAL;

	spin_lock_irq(&ctx->wqh.lock);
	res = -EAGAIN;
	if (ctx->count > 0)
		res = sizeof(ucnt);
	else if (!(file->f_flags & O_NONBLOCK)) {
		__add_wait_queue(&ctx->wqh, &wait);
		for (;;) {
			set_current_state(TASK_INTERRUPTIBLE);
			if (ctx->count > 0) {
				res = sizeof(ucnt);
				break;
			}
			if (signal_pending(current)) {
				res = -ERESTARTSYS;
				break;
			}
			spin_unlock_irq(&ctx->wqh.lock);
			schedule();
			spin_lock_irq(&ctx->wqh.lock);
		}
		__remove_wait_queue(&ctx->wqh, &wait);
		__set_current_state(TASK_RUNNING);
	}
	if (likely(res > 0)) {
		eventfd_ctx_do_read(ctx, &ucnt);
		if (waitqueue_active(&ctx->wqh))
			wake_up_locked_poll(&ctx->wqh, POLLOUT);
	}
	spin_unlock_irq(&ctx->wqh.lock);

	if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
		return -EFAULT;

	return res;
}

static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
			     loff_t *ppos)
{
	struct eventfd_ctx *ctx = file->private_data;
	ssize_t res;
	__u64 ucnt;
	DECLARE_WAITQUEUE(wait, current);

	if (count < sizeof(ucnt))
		return -EINVAL;
	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
		return -EFAULT;
	if (ucnt == ULLONG_MAX)
		return -EINVAL;
	spin_lock_irq(&ctx->wqh.lock);
	res = -EAGAIN;
	if (ULLONG_MAX - ctx->count > ucnt)
		res = sizeof(ucnt);
	else if (!(file->f_flags & O_NONBLOCK)) {
		__add_wait_queue(&ctx->wqh, &wait);
		for (res = 0;;) {
			set_current_state(TASK_INTERRUPTIBLE);
			if (ULLONG_MAX - ctx->count > ucnt) {
				res = sizeof(ucnt);
				break;
			}
			if (signal_pending(current)) {
				res = -ERESTARTSYS;
				break;
			}
			spin_unlock_irq(&ctx->wqh.lock);
			schedule();
			spin_lock_irq(&ctx->wqh.lock);
		}
		__remove_wait_queue(&ctx->wqh, &wait);
		__set_current_state(TASK_RUNNING);
	}
	if (likely(res > 0)) {
		ctx->count += ucnt;
		if (waitqueue_active(&ctx->wqh))
			wake_up_locked_poll(&ctx->wqh, POLLIN);
	}
	spin_unlock_irq(&ctx->wqh.lock);

	return res;
}

#ifdef CONFIG_PROC_FS
static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
{
	struct eventfd_ctx *ctx = f->private_data;

	spin_lock_irq(&ctx->wqh.lock);
	seq_printf(m, "eventfd-count: %16llx\n",
		   (unsigned long long)ctx->count);
	spin_unlock_irq(&ctx->wqh.lock);
}
#endif

static const struct file_operations eventfd_fops = {
#ifdef CONFIG_PROC_FS
	.show_fdinfo	= eventfd_show_fdinfo,
#endif
	.release	= eventfd_release,
	.poll		= eventfd_poll,
	.read		= eventfd_read,
	.write		= eventfd_write,
	.llseek		= noop_llseek,
};

/**
 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
 * @fd: [in] Eventfd file descriptor.
 *
 * Returns a pointer to the eventfd file structure in case of success, or the
 * following error pointer:
 *
 * -EBADF    : Invalid @fd file descriptor.
 * -EINVAL   : The @fd file descriptor is not an eventfd file.
 */
struct file *eventfd_fget(int fd)
{
	struct file *file;

	file = fget(fd);
	if (!file)
		return ERR_PTR(-EBADF);
	if (file->f_op != &eventfd_fops) {
		fput(file);
		return ERR_PTR(-EINVAL);
	}

	return file;
}
EXPORT_SYMBOL_GPL(eventfd_fget);

/**
 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
 * @fd: [in] Eventfd file descriptor.
 *
 * Returns a pointer to the internal eventfd context, otherwise the error
 * pointers returned by the following functions:
 *
 * eventfd_fget
 */
struct eventfd_ctx *eventfd_ctx_fdget(int fd)
{
	struct eventfd_ctx *ctx;
	struct fd f = fdget(fd);
	if (!f.file)
		return ERR_PTR(-EBADF);
	ctx = eventfd_ctx_fileget(f.file);
	fdput(f);
	return ctx;
}
EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);

/**
 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
 * @file: [in] Eventfd file pointer.
 *
 * Returns a pointer to the internal eventfd context, otherwise the error
 * pointer:
 *
 * -EINVAL   : The @fd file descriptor is not an eventfd file.
 */
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
{
	if (file->f_op != &eventfd_fops)
		return ERR_PTR(-EINVAL);

	return eventfd_ctx_get(file->private_data);
}
EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);

SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
{
	struct eventfd_ctx *ctx;
	int fd;

	/* Check the EFD_* constants for consistency.  */
	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);

	if (flags & ~EFD_FLAGS_SET)
		return -EINVAL;

	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;

	kref_init(&ctx->kref);
	init_waitqueue_head(&ctx->wqh);
	ctx->count = count;
	ctx->flags = flags;

	fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
			      O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
	if (fd < 0)
		eventfd_free_ctx(ctx);

	return fd;
}

SYSCALL_DEFINE1(eventfd, unsigned int, count)
{
	return sys_eventfd2(count, 0);
}
Commit	Line	Data
e1ad7468 DL	1	/*
	2	* fs/eventfd.c
	3	*
	4	* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
	5	*
	6	*/
	7
	8	#include <linux/file.h>
	9	#include <linux/poll.h>
	10	#include <linux/init.h>
	11	#include <linux/fs.h>
174cd4b1	12	#include <linux/sched/signal.h>
e1ad7468	13	#include <linux/kernel.h>
5a0e3ad6	14	#include <linux/slab.h>
e1ad7468 DL	15	#include <linux/list.h>
	16	#include <linux/spinlock.h>
	17	#include <linux/anon_inodes.h>
7747cdb2	18	#include <linux/syscalls.h>
630d9c47	19	#include <linux/export.h>
13389010 DL	20	#include <linux/kref.h>
13389010 DL	21	#include <linux/eventfd.h>
cbac5542 CG	22	#include <linux/proc_fs.h>
cbac5542 CG	23	#include <linux/seq_file.h>
e1ad7468 DL	24
e1ad7468 DL	25	struct eventfd_ctx {
13389010	26	struct kref kref;
e1ad7468 DL	27	wait_queue_head_t wqh;
	28	/*
	29	* Every time that a write(2) is performed on an eventfd, the
	30	* value of the __u64 being written is added to "count" and a
	31	* wakeup is performed on "wqh". A read(2) will return the "count"
	32	* value to userspace, and will reset "count" to zero. The kernel
13389010	33	* side eventfd_signal() also, adds to the "count" counter and
e1ad7468 DL	34	* issue a wakeup.
	35	*/
	36	__u64 count;
bcd0b235	37	unsigned int flags;
e1ad7468 DL	38	};
e1ad7468 DL	39
13389010 DL	40	/**
	41	* eventfd_signal - Adds @n to the eventfd counter.
	42	* @ctx: [in] Pointer to the eventfd context.
	43	* @n: [in] Value of the counter to be added to the eventfd internal counter.
	44	* The value cannot be negative.
	45	*
	46	* This function is supposed to be called by the kernel in paths that do not
	47	* allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
20d5a865	48	* value, and we signal this as overflow condition by returning a POLLERR
13389010 DL	49	* to poll(2).
13389010 DL	50	*
20d5a865	51	* Returns the amount by which the counter was incremented. This will be less
ee62c6b2	52	* than @n if the counter has overflowed.
e1ad7468	53	*/
ee62c6b2	54	__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
e1ad7468	55	{
e1ad7468 DL	56	unsigned long flags;
e1ad7468 DL	57
d48eb233	58	spin_lock_irqsave(&ctx->wqh.lock, flags);
e1ad7468	59	if (ULLONG_MAX - ctx->count < n)
ee62c6b2	60	n = ULLONG_MAX - ctx->count;
e1ad7468 DL	61	ctx->count += n;
e1ad7468 DL	62	if (waitqueue_active(&ctx->wqh))
39510888	63	wake_up_locked_poll(&ctx->wqh, POLLIN);
d48eb233	64	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
e1ad7468 DL	65
	66	return n;
	67	}
5718607b	68	EXPORT_SYMBOL_GPL(eventfd_signal);
e1ad7468	69
562787a5 DL	70	static void eventfd_free_ctx(struct eventfd_ctx *ctx)
	71	{
	72	kfree(ctx);
	73	}
	74
13389010 DL	75	static void eventfd_free(struct kref *kref)
	76	{
	77	struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
	78
562787a5	79	eventfd_free_ctx(ctx);
13389010 DL	80	}
	81
	82	/**
	83	* eventfd_ctx_get - Acquires a reference to the internal eventfd context.
	84	* @ctx: [in] Pointer to the eventfd context.
	85	*
	86	* Returns: In case of success, returns a pointer to the eventfd context.
	87	*/
	88	struct eventfd_ctx eventfd_ctx_get(struct eventfd_ctx ctx)
	89	{
	90	kref_get(&ctx->kref);
	91	return ctx;
	92	}
	93	EXPORT_SYMBOL_GPL(eventfd_ctx_get);
	94
	95	/**
	96	* eventfd_ctx_put - Releases a reference to the internal eventfd context.
	97	* @ctx: [in] Pointer to eventfd context.
	98	*
	99	* The eventfd context reference must have been previously acquired either
36182185	100	* with eventfd_ctx_get() or eventfd_ctx_fdget().
13389010 DL	101	*/
	102	void eventfd_ctx_put(struct eventfd_ctx *ctx)
	103	{
	104	kref_put(&ctx->kref, eventfd_free);
	105	}
	106	EXPORT_SYMBOL_GPL(eventfd_ctx_put);
	107
e1ad7468 DL	108	static int eventfd_release(struct inode inode, struct file file)
e1ad7468 DL	109	{
13389010 DL	110	struct eventfd_ctx *ctx = file->private_data;
	111
	112	wake_up_poll(&ctx->wqh, POLLHUP);
	113	eventfd_ctx_put(ctx);
e1ad7468 DL	114	return 0;
	115	}
	116
	117	static unsigned int eventfd_poll(struct file file, poll_table wait)
	118	{
	119	struct eventfd_ctx *ctx = file->private_data;
	120	unsigned int events = 0;
e22553e2	121	u64 count;
e1ad7468 DL	122
e1ad7468 DL	123	poll_wait(file, &ctx->wqh, wait);
a484c3dd PB	124
	125	/*
	126	* All writes to ctx->count occur within ctx->wqh.lock. This read
	127	* can be done outside ctx->wqh.lock because we know that poll_wait
	128	* takes that lock (through add_wait_queue) if our caller will sleep.
	129	*
	130	* The read _can_ therefore seep into add_wait_queue's critical
	131	* section, but cannot move above it! add_wait_queue's spin_lock acts
	132	* as an acquire barrier and ensures that the read be ordered properly
	133	* against the writes. The following CAN happen and is safe:
	134	*
	135	* poll write
	136	* ----------------- ------------
	137	* lock ctx->wqh.lock (in poll_wait)
	138	* count = ctx->count
	139	* __add_wait_queue
	140	* unlock ctx->wqh.lock
	141	* lock ctx->qwh.lock
	142	* ctx->count += n
	143	* if (waitqueue_active)
	144	* wake_up_locked_poll
	145	* unlock ctx->qwh.lock
	146	* eventfd_poll returns 0
	147	*
	148	* but the following, which would miss a wakeup, cannot happen:
	149	*
	150	* poll write
	151	* ----------------- ------------
	152	* count = ctx->count (INVALID!)
	153	* lock ctx->qwh.lock
	154	* ctx->count += n
	155	* waitqueue_active is false
	156	* no wake_up_locked_poll!
	157	* unlock ctx->qwh.lock
	158	* lock ctx->wqh.lock (in poll_wait)
	159	* __add_wait_queue
	160	* unlock ctx->wqh.lock
	161	* eventfd_poll returns 0
	162	*/
	163	count = READ_ONCE(ctx->count);
e1ad7468	164
e22553e2	165	if (count > 0)
e1ad7468	166	events \|= POLLIN;
e22553e2	167	if (count == ULLONG_MAX)
e1ad7468	168	events \|= POLLERR;
e22553e2	169	if (ULLONG_MAX - 1 > count)
e1ad7468	170	events \|= POLLOUT;
e1ad7468 DL	171
	172	return events;
	173	}
	174
cb289d62 DL	175	static void eventfd_ctx_do_read(struct eventfd_ctx ctx, __u64 cnt)
	176	{
	177	*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
	178	ctx->count -= *cnt;
	179	}
	180
	181	/**
	182	* eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
	183	* @ctx: [in] Pointer to eventfd context.
	184	* @wait: [in] Wait queue to be removed.
36182185	185	* @cnt: [out] Pointer to the 64-bit counter value.
cb289d62	186	*
36182185	187	* Returns %0 if successful, or the following error codes:
cb289d62 DL	188	*
	189	* -EAGAIN : The operation would have blocked.
	190	*
	191	* This is used to atomically remove a wait queue entry from the eventfd wait
	192	* queue head, and read/reset the counter value.
	193	*/
ac6424b9	194	int eventfd_ctx_remove_wait_queue(struct eventfd_ctx ctx, wait_queue_entry_t wait,
cb289d62 DL	195	__u64 *cnt)
	196	{
	197	unsigned long flags;
	198
	199	spin_lock_irqsave(&ctx->wqh.lock, flags);
	200	eventfd_ctx_do_read(ctx, cnt);
	201	__remove_wait_queue(&ctx->wqh, wait);
	202	if (*cnt != 0 && waitqueue_active(&ctx->wqh))
	203	wake_up_locked_poll(&ctx->wqh, POLLOUT);
	204	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
	205
	206	return *cnt != 0 ? 0 : -EAGAIN;
	207	}
	208	EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
	209
b6364572 EB	210	static ssize_t eventfd_read(struct file file, char __user buf, size_t count,
b6364572 EB	211	loff_t *ppos)
e1ad7468	212	{
b6364572	213	struct eventfd_ctx *ctx = file->private_data;
e1ad7468	214	ssize_t res;
b6364572	215	__u64 ucnt = 0;
e1ad7468 DL	216	DECLARE_WAITQUEUE(wait, current);
e1ad7468 DL	217
b6364572 EB	218	if (count < sizeof(ucnt))
	219	return -EINVAL;
	220
d48eb233	221	spin_lock_irq(&ctx->wqh.lock);
e1ad7468	222	res = -EAGAIN;
bcd0b235	223	if (ctx->count > 0)
b6364572 EB	224	res = sizeof(ucnt);
b6364572 EB	225	else if (!(file->f_flags & O_NONBLOCK)) {
e1ad7468	226	__add_wait_queue(&ctx->wqh, &wait);
cb289d62	227	for (;;) {
e1ad7468 DL	228	set_current_state(TASK_INTERRUPTIBLE);
e1ad7468 DL	229	if (ctx->count > 0) {
b6364572	230	res = sizeof(ucnt);
e1ad7468 DL	231	break;
	232	}
	233	if (signal_pending(current)) {
	234	res = -ERESTARTSYS;
	235	break;
	236	}
d48eb233	237	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468	238	schedule();
d48eb233	239	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	240	}
	241	__remove_wait_queue(&ctx->wqh, &wait);
	242	__set_current_state(TASK_RUNNING);
	243	}
b6364572 EB	244	if (likely(res > 0)) {
b6364572 EB	245	eventfd_ctx_do_read(ctx, &ucnt);
e1ad7468	246	if (waitqueue_active(&ctx->wqh))
39510888	247	wake_up_locked_poll(&ctx->wqh, POLLOUT);
e1ad7468	248	}
d48eb233	249	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468	250
b6364572 EB	251	if (res > 0 && put_user(ucnt, (__u64 __user *)buf))
b6364572 EB	252	return -EFAULT;
cb289d62	253
b6364572	254	return res;
cb289d62	255	}
e1ad7468 DL	256
	257	static ssize_t eventfd_write(struct file file, const char __user buf, size_t count,
	258	loff_t *ppos)
	259	{
	260	struct eventfd_ctx *ctx = file->private_data;
	261	ssize_t res;
	262	__u64 ucnt;
	263	DECLARE_WAITQUEUE(wait, current);
	264
	265	if (count < sizeof(ucnt))
	266	return -EINVAL;
	267	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
	268	return -EFAULT;
	269	if (ucnt == ULLONG_MAX)
	270	return -EINVAL;
d48eb233	271	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	272	res = -EAGAIN;
	273	if (ULLONG_MAX - ctx->count > ucnt)
	274	res = sizeof(ucnt);
	275	else if (!(file->f_flags & O_NONBLOCK)) {
	276	__add_wait_queue(&ctx->wqh, &wait);
	277	for (res = 0;;) {
	278	set_current_state(TASK_INTERRUPTIBLE);
	279	if (ULLONG_MAX - ctx->count > ucnt) {
	280	res = sizeof(ucnt);
	281	break;
	282	}
	283	if (signal_pending(current)) {
	284	res = -ERESTARTSYS;
	285	break;
	286	}
d48eb233	287	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468	288	schedule();
d48eb233	289	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	290	}
	291	__remove_wait_queue(&ctx->wqh, &wait);
	292	__set_current_state(TASK_RUNNING);
	293	}
bcd0b235	294	if (likely(res > 0)) {
e1ad7468 DL	295	ctx->count += ucnt;
e1ad7468 DL	296	if (waitqueue_active(&ctx->wqh))
39510888	297	wake_up_locked_poll(&ctx->wqh, POLLIN);
e1ad7468	298	}
d48eb233	299	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468 DL	300
	301	return res;
	302	}
	303
cbac5542	304	#ifdef CONFIG_PROC_FS
a3816ab0	305	static void eventfd_show_fdinfo(struct seq_file m, struct file f)
cbac5542 CG	306	{
cbac5542 CG	307	struct eventfd_ctx *ctx = f->private_data;
cbac5542 CG	308
cbac5542 CG	309	spin_lock_irq(&ctx->wqh.lock);
a3816ab0 JP	310	seq_printf(m, "eventfd-count: %16llx\n",
a3816ab0 JP	311	(unsigned long long)ctx->count);
cbac5542	312	spin_unlock_irq(&ctx->wqh.lock);
cbac5542 CG	313	}
	314	#endif
	315
e1ad7468	316	static const struct file_operations eventfd_fops = {
cbac5542 CG	317	#ifdef CONFIG_PROC_FS
	318	.show_fdinfo = eventfd_show_fdinfo,
	319	#endif
e1ad7468 DL	320	.release = eventfd_release,
	321	.poll = eventfd_poll,
	322	.read = eventfd_read,
	323	.write = eventfd_write,
6038f373	324	.llseek = noop_llseek,
e1ad7468 DL	325	};
e1ad7468 DL	326
13389010 DL	327	/**
	328	* eventfd_fget - Acquire a reference of an eventfd file descriptor.
	329	* @fd: [in] Eventfd file descriptor.
	330	*
	331	* Returns a pointer to the eventfd file structure in case of success, or the
	332	* following error pointer:
	333	*
	334	* -EBADF : Invalid @fd file descriptor.
	335	* -EINVAL : The @fd file descriptor is not an eventfd file.
	336	*/
e1ad7468 DL	337	struct file *eventfd_fget(int fd)
	338	{
	339	struct file *file;
	340
	341	file = fget(fd);
	342	if (!file)
	343	return ERR_PTR(-EBADF);
	344	if (file->f_op != &eventfd_fops) {
	345	fput(file);
	346	return ERR_PTR(-EINVAL);
	347	}
	348
	349	return file;
	350	}
5718607b	351	EXPORT_SYMBOL_GPL(eventfd_fget);
e1ad7468	352
13389010 DL	353	/**
	354	* eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
	355	* @fd: [in] Eventfd file descriptor.
	356	*
	357	* Returns a pointer to the internal eventfd context, otherwise the error
	358	* pointers returned by the following functions:
	359	*
	360	* eventfd_fget
	361	*/
	362	struct eventfd_ctx *eventfd_ctx_fdget(int fd)
	363	{
13389010	364	struct eventfd_ctx *ctx;
36a74117 AV	365	struct fd f = fdget(fd);
	366	if (!f.file)
	367	return ERR_PTR(-EBADF);
	368	ctx = eventfd_ctx_fileget(f.file);
	369	fdput(f);
13389010 DL	370	return ctx;
	371	}
	372	EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
	373
	374	/**
	375	* eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
	376	* @file: [in] Eventfd file pointer.
	377	*
	378	* Returns a pointer to the internal eventfd context, otherwise the error
	379	* pointer:
	380	*
	381	* -EINVAL : The @fd file descriptor is not an eventfd file.
	382	*/
	383	struct eventfd_ctx eventfd_ctx_fileget(struct file file)
	384	{
	385	if (file->f_op != &eventfd_fops)
	386	return ERR_PTR(-EINVAL);
	387
	388	return eventfd_ctx_get(file->private_data);
	389	}
	390	EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
	391
7d815165	392	SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
e1ad7468	393	{
e1ad7468	394	struct eventfd_ctx *ctx;
7d815165	395	int fd;
e1ad7468	396
e38b36f3 UD	397	/* Check the EFD_* constants for consistency. */
	398	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
	399	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
	400
bcd0b235	401	if (flags & ~EFD_FLAGS_SET)
7d815165	402	return -EINVAL;
b087498e	403
e1ad7468 DL	404	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
e1ad7468 DL	405	if (!ctx)
7d815165	406	return -ENOMEM;
e1ad7468	407
13389010	408	kref_init(&ctx->kref);
e1ad7468	409	init_waitqueue_head(&ctx->wqh);
e1ad7468	410	ctx->count = count;
bcd0b235	411	ctx->flags = flags;
e1ad7468	412
7d815165 EB	413	fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
	414	O_RDWR \| (flags & EFD_SHARED_FCNTL_FLAGS));
	415	if (fd < 0)
562787a5 DL	416	eventfd_free_ctx(ctx);
562787a5 DL	417
2030a42c	418	return fd;
e1ad7468 DL	419	}
e1ad7468 DL	420
d4e82042	421	SYSCALL_DEFINE1(eventfd, unsigned int, count)
b087498e UD	422	{
	423	return sys_eventfd2(count, 0);
	424	}
bcd0b235	425