[linux-2.6-block.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/slab.h>
#include <linux/smp_lock.h>
#include <linux/fs.h>
#include <linux/pipe_fs_i.h>

static void 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;
	}
}

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)
{
	int ret;

	mutex_lock(&inode->i_mutex);
	if (!inode->i_pipe) {
		ret = -ENOMEM;
		inode->i_pipe = alloc_pipe_info(inode);
		if (!inode->i_pipe)
			goto err_nocleanup;
	}
	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 1:
	/*
	 *  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_fifo_fops;
		inode->i_pipe->r_counter++;
		if (inode->i_pipe->readers++ == 0)
			wake_up_partner(inode);

		if (!inode->i_pipe->writers) {
			if ((filp->f_flags & O_NONBLOCK)) {
				/* suppress POLLHUP until we have
				 * seen a writer */
				filp->f_version = inode->i_pipe->w_counter;
			} else 
			{
				wait_for_partner(inode, &inode->i_pipe->w_counter);
				if(signal_pending(current))
					goto err_rd;
			}
		}
		break;
	
	case 2:
	/*
	 *  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) && !inode->i_pipe->readers)
			goto err;

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

		if (!inode->i_pipe->readers) {
			wait_for_partner(inode, &inode->i_pipe->r_counter);
			if (signal_pending(current))
				goto err_wr;
		}
		break;
	
	case 3:
	/*
	 *  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_fifo_fops;

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

	default:
		ret = -EINVAL;
		goto err;
	}

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

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

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

err:
	if (!inode->i_pipe->readers && !inode->i_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 pipe_fops */
};
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>
	13	#include <linux/slab.h>
	14	#include <linux/smp_lock.h>
	15	#include <linux/fs.h>
	16	#include <linux/pipe_fs_i.h>
	17
3a326a2c	18	static void wait_for_partner(struct inode* inode, unsigned int *cnt)
1da177e4 LT	19	{
1da177e4 LT	20	int cur = *cnt;
3a326a2c IM	21
	22	while (cur == *cnt) {
	23	pipe_wait(inode->i_pipe);
	24	if (signal_pending(current))
1da177e4 LT	25	break;
	26	}
	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	{
	36	int ret;
	37
9aeedfc4	38	mutex_lock(&inode->i_mutex);
1da177e4 LT	39	if (!inode->i_pipe) {
1da177e4 LT	40	ret = -ENOMEM;
3a326a2c IM	41	inode->i_pipe = alloc_pipe_info(inode);
3a326a2c IM	42	if (!inode->i_pipe)
1da177e4 LT	43	goto err_nocleanup;
	44	}
	45	filp->f_version = 0;
	46
	47	/* We can only do regular read/write on fifos */
	48	filp->f_mode &= (FMODE_READ \| FMODE_WRITE);
	49
	50	switch (filp->f_mode) {
	51	case 1:
	52	/*
	53	* O_RDONLY
	54	* POSIX.1 says that O_NONBLOCK means return with the FIFO
	55	* opened, even when there is no process writing the FIFO.
	56	*/
	57	filp->f_op = &read_fifo_fops;
9aeedfc4 IM	58	inode->i_pipe->r_counter++;
9aeedfc4 IM	59	if (inode->i_pipe->readers++ == 0)
1da177e4 LT	60	wake_up_partner(inode);
1da177e4 LT	61
9aeedfc4	62	if (!inode->i_pipe->writers) {
1da177e4 LT	63	if ((filp->f_flags & O_NONBLOCK)) {
	64	/* suppress POLLHUP until we have
	65	* seen a writer */
9aeedfc4	66	filp->f_version = inode->i_pipe->w_counter;
1da177e4 LT	67	} else
1da177e4 LT	68	{
9aeedfc4	69	wait_for_partner(inode, &inode->i_pipe->w_counter);
1da177e4 LT	70	if(signal_pending(current))
	71	goto err_rd;
	72	}
	73	}
	74	break;
	75
	76	case 2:
	77	/*
	78	* O_WRONLY
	79	* POSIX.1 says that O_NONBLOCK means return -1 with
	80	* errno=ENXIO when there is no process reading the FIFO.
	81	*/
	82	ret = -ENXIO;
9aeedfc4	83	if ((filp->f_flags & O_NONBLOCK) && !inode->i_pipe->readers)
1da177e4 LT	84	goto err;
	85
	86	filp->f_op = &write_fifo_fops;
9aeedfc4 IM	87	inode->i_pipe->w_counter++;
9aeedfc4 IM	88	if (!inode->i_pipe->writers++)
1da177e4 LT	89	wake_up_partner(inode);
1da177e4 LT	90
9aeedfc4 IM	91	if (!inode->i_pipe->readers) {
9aeedfc4 IM	92	wait_for_partner(inode, &inode->i_pipe->r_counter);
1da177e4 LT	93	if (signal_pending(current))
	94	goto err_wr;
	95	}
	96	break;
	97
	98	case 3:
	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	*/
	105	filp->f_op = &rdwr_fifo_fops;
	106
9aeedfc4 IM	107	inode->i_pipe->readers++;
	108	inode->i_pipe->writers++;
	109	inode->i_pipe->r_counter++;
	110	inode->i_pipe->w_counter++;
	111	if (inode->i_pipe->readers == 1 \|\| inode->i_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:
9aeedfc4 IM	125	if (!--inode->i_pipe->readers)
9aeedfc4 IM	126	wake_up_interruptible(&inode->i_pipe->wait);
1da177e4 LT	127	ret = -ERESTARTSYS;
	128	goto err;
	129
	130	err_wr:
9aeedfc4 IM	131	if (!--inode->i_pipe->writers)
9aeedfc4 IM	132	wake_up_interruptible(&inode->i_pipe->wait);
1da177e4 LT	133	ret = -ERESTARTSYS;
	134	goto err;
	135
	136	err:
9aeedfc4	137	if (!inode->i_pipe->readers && !inode->i_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 = {
1da177e4 LT	151	.open = fifo_open, /* will set read or write pipe_fops */
1da177e4 LT	152	};