[net-next-2.6.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.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/anon_inodes.h>
#include <linux/eventfd.h>

struct eventfd_ctx {
	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
	 * size eventfd_signal() also, adds to the "count" counter and
	 * issue a wakeup.
	 */
	__u64 count;
};

/*
 * Adds "n" to the eventfd counter "count". Returns "n" in case of
 * success, or a value lower then "n" in case of coutner overflow.
 * 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 returining a POLLERR to poll(2).
 */
int eventfd_signal(struct file *file, int n)
{
	struct eventfd_ctx *ctx = file->private_data;
	unsigned long flags;

	if (n < 0)
		return -EINVAL;
	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ULLONG_MAX - ctx->count < n)
		n = (int) (ULLONG_MAX - ctx->count);
	ctx->count += n;
	if (waitqueue_active(&ctx->wqh))
		wake_up_locked(&ctx->wqh);
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return n;
}

static int eventfd_release(struct inode *inode, struct file *file)
{
	kfree(file->private_data);
	return 0;
}

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

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

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ctx->count > 0)
		events |= POLLIN;
	if (ctx->count == ULLONG_MAX)
		events |= POLLERR;
	if (ULLONG_MAX - 1 > ctx->count)
		events |= POLLOUT;
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return events;
}

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;
	DECLARE_WAITQUEUE(wait, current);

	if (count < sizeof(ucnt))
		return -EINVAL;
	spin_lock_irq(&ctx->wqh.lock);
	res = -EAGAIN;
	ucnt = ctx->count;
	if (ucnt > 0)
		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 (ctx->count > 0) {
				ucnt = ctx->count;
				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 (res > 0) {
		ctx->count = 0;
		if (waitqueue_active(&ctx->wqh))
			wake_up_locked(&ctx->wqh);
	}
	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 (res > 0) {
		ctx->count += ucnt;
		if (waitqueue_active(&ctx->wqh))
			wake_up_locked(&ctx->wqh);
	}
	spin_unlock_irq(&ctx->wqh.lock);

	return res;
}

static const struct file_operations eventfd_fops = {
	.release	= eventfd_release,
	.poll		= eventfd_poll,
	.read		= eventfd_read,
	.write		= eventfd_write,
};

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;
}

asmlinkage long sys_eventfd(unsigned int count)
{
	int error, fd;
	struct eventfd_ctx *ctx;
	struct file *file;
	struct inode *inode;

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

	init_waitqueue_head(&ctx->wqh);
	ctx->count = count;

	/*
	 * When we call this, the initialization must be complete, since
	 * anon_inode_getfd() will install the fd.
	 */
	error = anon_inode_getfd(&fd, &inode, &file, "[eventfd]",
				 &eventfd_fops, ctx);
	if (!error)
		return fd;

	kfree(ctx);
	return error;
}
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>
	12	#include <linux/sched.h>
	13	#include <linux/kernel.h>
	14	#include <linux/list.h>
	15	#include <linux/spinlock.h>
	16	#include <linux/anon_inodes.h>
	17	#include <linux/eventfd.h>
	18
	19	struct eventfd_ctx {
e1ad7468 DL	20	wait_queue_head_t wqh;
	21	/*
	22	* Every time that a write(2) is performed on an eventfd, the
	23	* value of the __u64 being written is added to "count" and a
	24	* wakeup is performed on "wqh". A read(2) will return the "count"
	25	* value to userspace, and will reset "count" to zero. The kernel
	26	* size eventfd_signal() also, adds to the "count" counter and
	27	* issue a wakeup.
	28	*/
	29	__u64 count;
	30	};
	31
	32	/*
	33	* Adds "n" to the eventfd counter "count". Returns "n" in case of
	34	* success, or a value lower then "n" in case of coutner overflow.
	35	* This function is supposed to be called by the kernel in paths
	36	* that do not allow sleeping. In this function we allow the counter
	37	* to reach the ULLONG_MAX value, and we signal this as overflow
	38	* condition by returining a POLLERR to poll(2).
	39	*/
	40	int eventfd_signal(struct file *file, int n)
	41	{
	42	struct eventfd_ctx *ctx = file->private_data;
	43	unsigned long flags;
	44
	45	if (n < 0)
	46	return -EINVAL;
d48eb233	47	spin_lock_irqsave(&ctx->wqh.lock, flags);
e1ad7468 DL	48	if (ULLONG_MAX - ctx->count < n)
	49	n = (int) (ULLONG_MAX - ctx->count);
	50	ctx->count += n;
	51	if (waitqueue_active(&ctx->wqh))
	52	wake_up_locked(&ctx->wqh);
d48eb233	53	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
e1ad7468 DL	54
	55	return n;
	56	}
	57
	58	static int eventfd_release(struct inode inode, struct file file)
	59	{
	60	kfree(file->private_data);
	61	return 0;
	62	}
	63
	64	static unsigned int eventfd_poll(struct file file, poll_table wait)
	65	{
	66	struct eventfd_ctx *ctx = file->private_data;
	67	unsigned int events = 0;
	68	unsigned long flags;
	69
	70	poll_wait(file, &ctx->wqh, wait);
	71
d48eb233	72	spin_lock_irqsave(&ctx->wqh.lock, flags);
e1ad7468 DL	73	if (ctx->count > 0)
	74	events \|= POLLIN;
	75	if (ctx->count == ULLONG_MAX)
	76	events \|= POLLERR;
	77	if (ULLONG_MAX - 1 > ctx->count)
	78	events \|= POLLOUT;
d48eb233	79	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
e1ad7468 DL	80
	81	return events;
	82	}
	83
	84	static ssize_t eventfd_read(struct file file, char __user buf, size_t count,
	85	loff_t *ppos)
	86	{
	87	struct eventfd_ctx *ctx = file->private_data;
	88	ssize_t res;
	89	__u64 ucnt;
	90	DECLARE_WAITQUEUE(wait, current);
	91
	92	if (count < sizeof(ucnt))
	93	return -EINVAL;
d48eb233	94	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	95	res = -EAGAIN;
	96	ucnt = ctx->count;
	97	if (ucnt > 0)
	98	res = sizeof(ucnt);
	99	else if (!(file->f_flags & O_NONBLOCK)) {
	100	__add_wait_queue(&ctx->wqh, &wait);
	101	for (res = 0;;) {
	102	set_current_state(TASK_INTERRUPTIBLE);
	103	if (ctx->count > 0) {
	104	ucnt = ctx->count;
	105	res = sizeof(ucnt);
	106	break;
	107	}
	108	if (signal_pending(current)) {
	109	res = -ERESTARTSYS;
	110	break;
	111	}
d48eb233	112	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468	113	schedule();
d48eb233	114	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	115	}
	116	__remove_wait_queue(&ctx->wqh, &wait);
	117	__set_current_state(TASK_RUNNING);
	118	}
	119	if (res > 0) {
	120	ctx->count = 0;
	121	if (waitqueue_active(&ctx->wqh))
	122	wake_up_locked(&ctx->wqh);
	123	}
d48eb233	124	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468 DL	125	if (res > 0 && put_user(ucnt, (__u64 __user *) buf))
	126	return -EFAULT;
	127
	128	return res;
	129	}
	130
	131	static ssize_t eventfd_write(struct file file, const char __user buf, size_t count,
	132	loff_t *ppos)
	133	{
	134	struct eventfd_ctx *ctx = file->private_data;
	135	ssize_t res;
	136	__u64 ucnt;
	137	DECLARE_WAITQUEUE(wait, current);
	138
	139	if (count < sizeof(ucnt))
	140	return -EINVAL;
	141	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
	142	return -EFAULT;
	143	if (ucnt == ULLONG_MAX)
	144	return -EINVAL;
d48eb233	145	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	146	res = -EAGAIN;
	147	if (ULLONG_MAX - ctx->count > ucnt)
	148	res = sizeof(ucnt);
	149	else if (!(file->f_flags & O_NONBLOCK)) {
	150	__add_wait_queue(&ctx->wqh, &wait);
	151	for (res = 0;;) {
	152	set_current_state(TASK_INTERRUPTIBLE);
	153	if (ULLONG_MAX - ctx->count > ucnt) {
	154	res = sizeof(ucnt);
	155	break;
	156	}
	157	if (signal_pending(current)) {
	158	res = -ERESTARTSYS;
	159	break;
	160	}
d48eb233	161	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468	162	schedule();
d48eb233	163	spin_lock_irq(&ctx->wqh.lock);
e1ad7468 DL	164	}
	165	__remove_wait_queue(&ctx->wqh, &wait);
	166	__set_current_state(TASK_RUNNING);
	167	}
	168	if (res > 0) {
	169	ctx->count += ucnt;
	170	if (waitqueue_active(&ctx->wqh))
	171	wake_up_locked(&ctx->wqh);
	172	}
d48eb233	173	spin_unlock_irq(&ctx->wqh.lock);
e1ad7468 DL	174
	175	return res;
	176	}
	177
	178	static const struct file_operations eventfd_fops = {
	179	.release = eventfd_release,
	180	.poll = eventfd_poll,
	181	.read = eventfd_read,
	182	.write = eventfd_write,
	183	};
	184
	185	struct file *eventfd_fget(int fd)
	186	{
	187	struct file *file;
	188
	189	file = fget(fd);
	190	if (!file)
	191	return ERR_PTR(-EBADF);
	192	if (file->f_op != &eventfd_fops) {
	193	fput(file);
	194	return ERR_PTR(-EINVAL);
	195	}
	196
	197	return file;
	198	}
	199
	200	asmlinkage long sys_eventfd(unsigned int count)
	201	{
	202	int error, fd;
	203	struct eventfd_ctx *ctx;
	204	struct file *file;
	205	struct inode *inode;
	206
	207	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
	208	if (!ctx)
	209	return -ENOMEM;
	210
	211	init_waitqueue_head(&ctx->wqh);
e1ad7468 DL	212	ctx->count = count;
	213
	214	/*
	215	* When we call this, the initialization must be complete, since
	216	* anon_inode_getfd() will install the fd.
	217	*/
	218	error = anon_inode_getfd(&fd, &inode, &file, "[eventfd]",
	219	&eventfd_fops, ctx);
	220	if (!error)
	221	return fd;
	222
	223	kfree(ctx);
	224	return error;
	225	}
	226