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/*
* 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);
if(signal_pending(current))
break;
}
}
static void wake_up_partner(struct inode* inode)
{
wake_up_interruptible(PIPE_WAIT(*inode));
}
static int fifo_open(struct inode *inode, struct file *filp)
{
int ret;
mutex_lock(PIPE_MUTEX(*inode));
if (!inode->i_pipe) {
ret = -ENOMEM;
if(!pipe_new(inode))
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;
PIPE_RCOUNTER(*inode)++;
if (PIPE_READERS(*inode)++ == 0)
wake_up_partner(inode);
if (!PIPE_WRITERS(*inode)) {
if ((filp->f_flags & O_NONBLOCK)) {
/* suppress POLLHUP until we have
* seen a writer */
filp->f_version = PIPE_WCOUNTER(*inode);
} else
{
wait_for_partner(inode, &PIPE_WCOUNTER(*inode));
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(*inode))
goto err;
filp->f_op = &write_fifo_fops;
PIPE_WCOUNTER(*inode)++;
if (!PIPE_WRITERS(*inode)++)
wake_up_partner(inode);
if (!PIPE_READERS(*inode)) {
wait_for_partner(inode, &PIPE_RCOUNTER(*inode));
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(*inode)++;
PIPE_WRITERS(*inode)++;
PIPE_RCOUNTER(*inode)++;
PIPE_WCOUNTER(*inode)++;
if (PIPE_READERS(*inode) == 1 || PIPE_WRITERS(*inode) == 1)
wake_up_partner(inode);
break;
default:
ret = -EINVAL;
goto err;
}
/* Ok! */
mutex_unlock(PIPE_MUTEX(*inode));
return 0;
err_rd:
if (!--PIPE_READERS(*inode))
wake_up_interruptible(PIPE_WAIT(*inode));
ret = -ERESTARTSYS;
goto err;
err_wr:
if (!--PIPE_WRITERS(*inode))
wake_up_interruptible(PIPE_WAIT(*inode));
ret = -ERESTARTSYS;
goto err;
err:
if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode))
free_pipe_info(inode);
err_nocleanup:
mutex_unlock(PIPE_MUTEX(*inode));
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...
*/
struct file_operations def_fifo_fops = {
.open = fifo_open, /* will set read or write pipe_fops */
};
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