[mirror_ubuntu-zesty-kernel.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 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)
{
	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 {
				wait_for_partner(inode, &pipe->w_counter);
				if(signal_pending(current))
					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) {
			wait_for_partner(inode, &pipe->r_counter);
			if (signal_pending(current))
				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
3a326a2c	17	static void 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;
	25	}
	26	}
	27
	28	static void wake_up_partner(struct inode* inode)
	29	{
9aeedfc4	30	wake_up_interruptible(&inode->i_pipe->wait);
1da177e4 LT	31	}
	32
	33	static int fifo_open(struct inode inode, struct file filp)
	34	{
923f4f23	35	struct pipe_inode_info *pipe;
1da177e4 LT	36	int ret;
1da177e4 LT	37
9aeedfc4	38	mutex_lock(&inode->i_mutex);
923f4f23 IM	39	pipe = inode->i_pipe;
923f4f23 IM	40	if (!pipe) {
1da177e4	41	ret = -ENOMEM;
923f4f23 IM	42	pipe = alloc_pipe_info(inode);
923f4f23 IM	43	if (!pipe)
1da177e4	44	goto err_nocleanup;
923f4f23	45	inode->i_pipe = pipe;
1da177e4 LT	46	}
	47	filp->f_version = 0;
	48
	49	/* We can only do regular read/write on fifos */
	50	filp->f_mode &= (FMODE_READ \| FMODE_WRITE);
	51
	52	switch (filp->f_mode) {
aeb5d727	53	case FMODE_READ:
1da177e4 LT	54	/*
	55	* O_RDONLY
	56	* POSIX.1 says that O_NONBLOCK means return with the FIFO
	57	* opened, even when there is no process writing the FIFO.
	58	*/
d2d9648e	59	filp->f_op = &read_pipefifo_fops;
923f4f23 IM	60	pipe->r_counter++;
923f4f23 IM	61	if (pipe->readers++ == 0)
1da177e4 LT	62	wake_up_partner(inode);
1da177e4 LT	63
923f4f23	64	if (!pipe->writers) {
1da177e4 LT	65	if ((filp->f_flags & O_NONBLOCK)) {
	66	/* suppress POLLHUP until we have
	67	* seen a writer */
923f4f23	68	filp->f_version = pipe->w_counter;
ff38c083	69	} else {
923f4f23	70	wait_for_partner(inode, &pipe->w_counter);
1da177e4 LT	71	if(signal_pending(current))
	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 IM	92	if (!pipe->readers) {
923f4f23 IM	93	wait_for_partner(inode, &pipe->r_counter);
1da177e4 LT	94	if (signal_pending(current))
	95	goto err_wr;
	96	}
	97	break;
	98
aeb5d727	99	case FMODE_READ \| FMODE_WRITE:
1da177e4 LT	100	/*
	101	* O_RDWR
	102	* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
	103	* This implementation will NEVER block on a O_RDWR open, since
	104	* the process can at least talk to itself.
	105	*/
d2d9648e	106	filp->f_op = &rdwr_pipefifo_fops;
1da177e4	107
923f4f23 IM	108	pipe->readers++;
	109	pipe->writers++;
	110	pipe->r_counter++;
	111	pipe->w_counter++;
	112	if (pipe->readers == 1 \|\| pipe->writers == 1)
1da177e4 LT	113	wake_up_partner(inode);
	114	break;
	115
	116	default:
	117	ret = -EINVAL;
	118	goto err;
	119	}
	120
	121	/* Ok! */
9aeedfc4	122	mutex_unlock(&inode->i_mutex);
1da177e4 LT	123	return 0;
	124
	125	err_rd:
923f4f23 IM	126	if (!--pipe->readers)
923f4f23 IM	127	wake_up_interruptible(&pipe->wait);
1da177e4 LT	128	ret = -ERESTARTSYS;
	129	goto err;
	130
	131	err_wr:
923f4f23 IM	132	if (!--pipe->writers)
923f4f23 IM	133	wake_up_interruptible(&pipe->wait);
1da177e4 LT	134	ret = -ERESTARTSYS;
	135	goto err;
	136
	137	err:
923f4f23	138	if (!pipe->readers && !pipe->writers)
1da177e4 LT	139	free_pipe_info(inode);
	140
	141	err_nocleanup:
9aeedfc4	142	mutex_unlock(&inode->i_mutex);
1da177e4 LT	143	return ret;
	144	}
	145
	146	/*
	147	* Dummy default file-operations: the only thing this does
	148	* is contain the open that then fills in the correct operations
	149	* depending on the access mode of the file...
	150	*/
4b6f5d20	151	const struct file_operations def_fifo_fops = {
d2d9648e	152	.open = fifo_open, /* will set read_ or write_pipefifo_fops */
6038f373	153	.llseek = noop_llseek,
1da177e4	154	};