[mirror_ubuntu-bionic-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/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)
{
	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 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;
		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 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) && !pipe->readers)
			goto err;

		filp->f_op = &write_fifo_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 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;

		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 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	{
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) {
	54	case 1:
	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	*/
	60	filp->f_op = &read_fifo_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;
1da177e4 LT	70	} else
1da177e4 LT	71	{
923f4f23	72	wait_for_partner(inode, &pipe->w_counter);
1da177e4 LT	73	if(signal_pending(current))
	74	goto err_rd;
	75	}
	76	}
	77	break;
	78
	79	case 2:
	80	/*
	81	* O_WRONLY
	82	* POSIX.1 says that O_NONBLOCK means return -1 with
	83	* errno=ENXIO when there is no process reading the FIFO.
	84	*/
	85	ret = -ENXIO;
923f4f23	86	if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
1da177e4 LT	87	goto err;
	88
	89	filp->f_op = &write_fifo_fops;
923f4f23 IM	90	pipe->w_counter++;
923f4f23 IM	91	if (!pipe->writers++)
1da177e4 LT	92	wake_up_partner(inode);
1da177e4 LT	93
923f4f23 IM	94	if (!pipe->readers) {
923f4f23 IM	95	wait_for_partner(inode, &pipe->r_counter);
1da177e4 LT	96	if (signal_pending(current))
	97	goto err_wr;
	98	}
	99	break;
	100
	101	case 3:
	102	/*
	103	* O_RDWR
	104	* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
	105	* This implementation will NEVER block on a O_RDWR open, since
	106	* the process can at least talk to itself.
	107	*/
	108	filp->f_op = &rdwr_fifo_fops;
	109
923f4f23 IM	110	pipe->readers++;
	111	pipe->writers++;
	112	pipe->r_counter++;
	113	pipe->w_counter++;
	114	if (pipe->readers == 1 \|\| pipe->writers == 1)
1da177e4 LT	115	wake_up_partner(inode);
	116	break;
	117
	118	default:
	119	ret = -EINVAL;
	120	goto err;
	121	}
	122
	123	/* Ok! */
9aeedfc4	124	mutex_unlock(&inode->i_mutex);
1da177e4 LT	125	return 0;
	126
	127	err_rd:
923f4f23 IM	128	if (!--pipe->readers)
923f4f23 IM	129	wake_up_interruptible(&pipe->wait);
1da177e4 LT	130	ret = -ERESTARTSYS;
	131	goto err;
	132
	133	err_wr:
923f4f23 IM	134	if (!--pipe->writers)
923f4f23 IM	135	wake_up_interruptible(&pipe->wait);
1da177e4 LT	136	ret = -ERESTARTSYS;
	137	goto err;
	138
	139	err:
923f4f23	140	if (!pipe->readers && !pipe->writers)
1da177e4 LT	141	free_pipe_info(inode);
	142
	143	err_nocleanup:
9aeedfc4	144	mutex_unlock(&inode->i_mutex);
1da177e4 LT	145	return ret;
	146	}
	147
	148	/*
	149	* Dummy default file-operations: the only thing this does
	150	* is contain the open that then fills in the correct operations
	151	* depending on the access mode of the file...
	152	*/
4b6f5d20	153	const struct file_operations def_fifo_fops = {
1da177e4 LT	154	.open = fifo_open, /* will set read or write pipe_fops */
1da177e4 LT	155	};