[linux.git] / fs / fifo.c

/*
 *  linux/fs/fifo.c
 *
 *  written by Paul H. Hargrove
 *
 *  Fixes:
 *	10-06-1999, AV: fixed OOM handling in fifo_open(), moved
 *			initialization there, switched to external
 *			allocation of pipe_inode_info.
 */

#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/pipe_fs_i.h>

static int wait_for_partner(struct inode* inode, unsigned int *cnt)
{
	int cur = *cnt;	

	while (cur == *cnt) {
		pipe_wait(inode->i_pipe);
		if (signal_pending(current))
			break;
	}
	return cur == *cnt ? -ERESTARTSYS : 0;
}

static void wake_up_partner(struct inode* inode)
{
	wake_up_interruptible(&inode->i_pipe->wait);
}

static int fifo_open(struct inode *inode, struct file *filp)
{
	struct pipe_inode_info *pipe;
	int ret;

	mutex_lock(&inode->i_mutex);
	pipe = inode->i_pipe;
	if (!pipe) {
		ret = -ENOMEM;
		pipe = alloc_pipe_info(inode);
		if (!pipe)
			goto err_nocleanup;
		inode->i_pipe = pipe;
	}
	filp->f_version = 0;

	/* We can only do regular read/write on fifos */
	filp->f_mode &= (FMODE_READ | FMODE_WRITE);

	switch (filp->f_mode) {
	case FMODE_READ:
	/*
	 *  O_RDONLY
	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
	 *  opened, even when there is no process writing the FIFO.
	 */
		filp->f_op = &read_pipefifo_fops;
		pipe->r_counter++;
		if (pipe->readers++ == 0)
			wake_up_partner(inode);

		if (!pipe->writers) {
			if ((filp->f_flags & O_NONBLOCK)) {
				/* suppress POLLHUP until we have
				 * seen a writer */
				filp->f_version = pipe->w_counter;
			} else {
				if (wait_for_partner(inode, &pipe->w_counter))
					goto err_rd;
			}
		}
		break;
	
	case FMODE_WRITE:
	/*
	 *  O_WRONLY
	 *  POSIX.1 says that O_NONBLOCK means return -1 with
	 *  errno=ENXIO when there is no process reading the FIFO.
	 */
		ret = -ENXIO;
		if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
			goto err;

		filp->f_op = &write_pipefifo_fops;
		pipe->w_counter++;
		if (!pipe->writers++)
			wake_up_partner(inode);

		if (!pipe->readers) {
			if (wait_for_partner(inode, &pipe->r_counter))
				goto err_wr;
		}
		break;
	
	case FMODE_READ | FMODE_WRITE:
	/*
	 *  O_RDWR
	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
	 *  This implementation will NEVER block on a O_RDWR open, since
	 *  the process can at least talk to itself.
	 */
		filp->f_op = &rdwr_pipefifo_fops;

		pipe->readers++;
		pipe->writers++;
		pipe->r_counter++;
		pipe->w_counter++;
		if (pipe->readers == 1 || pipe->writers == 1)
			wake_up_partner(inode);
		break;

	default:
		ret = -EINVAL;
		goto err;
	}

	/* Ok! */
	mutex_unlock(&inode->i_mutex);
	return 0;

err_rd:
	if (!--pipe->readers)
		wake_up_interruptible(&pipe->wait);
	ret = -ERESTARTSYS;
	goto err;

err_wr:
	if (!--pipe->writers)
		wake_up_interruptible(&pipe->wait);
	ret = -ERESTARTSYS;
	goto err;

err:
	if (!pipe->readers && !pipe->writers)
		free_pipe_info(inode);

err_nocleanup:
	mutex_unlock(&inode->i_mutex);
	return ret;
}

/*
 * Dummy default file-operations: the only thing this does
 * is contain the open that then fills in the correct operations
 * depending on the access mode of the file...
 */
const struct file_operations def_fifo_fops = {
	.open		= fifo_open,	/* will set read_ or write_pipefifo_fops */
	.llseek		= noop_llseek,
};
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/fifo.c
	3	*
	4	* written by Paul H. Hargrove
	5	*
	6	* Fixes:
	7	* 10-06-1999, AV: fixed OOM handling in fifo_open(), moved
	8	* initialization there, switched to external
	9	* allocation of pipe_inode_info.
	10	*/
	11
	12	#include <linux/mm.h>
1da177e4	13	#include <linux/fs.h>
e8edc6e0	14	#include <linux/sched.h>
1da177e4 LT	15	#include <linux/pipe_fs_i.h>
1da177e4 LT	16
05d290d6	17	static int wait_for_partner(struct inode* inode, unsigned int *cnt)
1da177e4 LT	18	{
1da177e4 LT	19	int cur = *cnt;
3a326a2c IM	20
	21	while (cur == *cnt) {
	22	pipe_wait(inode->i_pipe);
	23	if (signal_pending(current))
1da177e4 LT	24	break;
1da177e4 LT	25	}
05d290d6	26	return cur == *cnt ? -ERESTARTSYS : 0;
1da177e4 LT	27	}
	28
	29	static void wake_up_partner(struct inode* inode)
	30	{
9aeedfc4	31	wake_up_interruptible(&inode->i_pipe->wait);
1da177e4 LT	32	}
	33
	34	static int fifo_open(struct inode inode, struct file filp)
	35	{
923f4f23	36	struct pipe_inode_info *pipe;
1da177e4 LT	37	int ret;
1da177e4 LT	38
9aeedfc4	39	mutex_lock(&inode->i_mutex);
923f4f23 IM	40	pipe = inode->i_pipe;
923f4f23 IM	41	if (!pipe) {
1da177e4	42	ret = -ENOMEM;
923f4f23 IM	43	pipe = alloc_pipe_info(inode);
923f4f23 IM	44	if (!pipe)
1da177e4	45	goto err_nocleanup;
923f4f23	46	inode->i_pipe = pipe;
1da177e4 LT	47	}
	48	filp->f_version = 0;
	49
	50	/* We can only do regular read/write on fifos */
	51	filp->f_mode &= (FMODE_READ \| FMODE_WRITE);
	52
	53	switch (filp->f_mode) {
aeb5d727	54	case FMODE_READ:
1da177e4 LT	55	/*
	56	* O_RDONLY
	57	* POSIX.1 says that O_NONBLOCK means return with the FIFO
	58	* opened, even when there is no process writing the FIFO.
	59	*/
d2d9648e	60	filp->f_op = &read_pipefifo_fops;
923f4f23 IM	61	pipe->r_counter++;
923f4f23 IM	62	if (pipe->readers++ == 0)
1da177e4 LT	63	wake_up_partner(inode);
1da177e4 LT	64
923f4f23	65	if (!pipe->writers) {
1da177e4 LT	66	if ((filp->f_flags & O_NONBLOCK)) {
	67	/* suppress POLLHUP until we have
	68	* seen a writer */
923f4f23	69	filp->f_version = pipe->w_counter;
ff38c083	70	} else {
05d290d6	71	if (wait_for_partner(inode, &pipe->w_counter))
1da177e4 LT	72	goto err_rd;
	73	}
	74	}
	75	break;
	76
aeb5d727	77	case FMODE_WRITE:
1da177e4 LT	78	/*
	79	* O_WRONLY
	80	* POSIX.1 says that O_NONBLOCK means return -1 with
	81	* errno=ENXIO when there is no process reading the FIFO.
	82	*/
	83	ret = -ENXIO;
923f4f23	84	if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
1da177e4 LT	85	goto err;
1da177e4 LT	86
d2d9648e	87	filp->f_op = &write_pipefifo_fops;
923f4f23 IM	88	pipe->w_counter++;
923f4f23 IM	89	if (!pipe->writers++)
1da177e4 LT	90	wake_up_partner(inode);
1da177e4 LT	91
923f4f23	92	if (!pipe->readers) {
05d290d6	93	if (wait_for_partner(inode, &pipe->r_counter))
1da177e4 LT	94	goto err_wr;
	95	}
	96	break;
	97
aeb5d727	98	case FMODE_READ \| FMODE_WRITE:
1da177e4 LT	99	/*
	100	* O_RDWR
	101	* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
	102	* This implementation will NEVER block on a O_RDWR open, since
	103	* the process can at least talk to itself.
	104	*/
d2d9648e	105	filp->f_op = &rdwr_pipefifo_fops;
1da177e4	106
923f4f23 IM	107	pipe->readers++;
	108	pipe->writers++;
	109	pipe->r_counter++;
	110	pipe->w_counter++;
	111	if (pipe->readers == 1 \|\| pipe->writers == 1)
1da177e4 LT	112	wake_up_partner(inode);
	113	break;
	114
	115	default:
	116	ret = -EINVAL;
	117	goto err;
	118	}
	119
	120	/* Ok! */
9aeedfc4	121	mutex_unlock(&inode->i_mutex);
1da177e4 LT	122	return 0;
	123
	124	err_rd:
923f4f23 IM	125	if (!--pipe->readers)
923f4f23 IM	126	wake_up_interruptible(&pipe->wait);
1da177e4 LT	127	ret = -ERESTARTSYS;
	128	goto err;
	129
	130	err_wr:
923f4f23 IM	131	if (!--pipe->writers)
923f4f23 IM	132	wake_up_interruptible(&pipe->wait);
1da177e4 LT	133	ret = -ERESTARTSYS;
	134	goto err;
	135
	136	err:
923f4f23	137	if (!pipe->readers && !pipe->writers)
1da177e4 LT	138	free_pipe_info(inode);
	139
	140	err_nocleanup:
9aeedfc4	141	mutex_unlock(&inode->i_mutex);
1da177e4 LT	142	return ret;
	143	}
	144
	145	/*
	146	* Dummy default file-operations: the only thing this does
	147	* is contain the open that then fills in the correct operations
	148	* depending on the access mode of the file...
	149	*/
4b6f5d20	150	const struct file_operations def_fifo_fops = {
d2d9648e	151	.open = fifo_open, /* will set read_ or write_pipefifo_fops */
6038f373	152	.llseek = noop_llseek,
1da177e4	153	};