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1627 |
jcastillo |
/*
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* linux/fs/fifo.c
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*
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* written by Paul H. Hargrove
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/fcntl.h>
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#include <linux/mm.h>
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static int fifo_open(struct inode * inode,struct file * filp)
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{
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int retval = 0;
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unsigned long page;
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switch( filp->f_mode ) {
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case 1:
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/*
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* O_RDONLY
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* POSIX.1 says that O_NONBLOCK means return with the FIFO
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* opened, even when there is no process writing the FIFO.
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*/
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filp->f_op = &connecting_fifo_fops;
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if (!PIPE_READERS(*inode)++)
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wake_up_interruptible(&PIPE_WAIT(*inode));
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if (!(filp->f_flags & O_NONBLOCK) && !PIPE_WRITERS(*inode)) {
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PIPE_RD_OPENERS(*inode)++;
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while (!PIPE_WRITERS(*inode)) {
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if (current->signal & ~current->blocked) {
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retval = -ERESTARTSYS;
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break;
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}
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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}
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if (!--PIPE_RD_OPENERS(*inode))
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wake_up_interruptible(&PIPE_WAIT(*inode));
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}
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while (PIPE_WR_OPENERS(*inode))
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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if (PIPE_WRITERS(*inode))
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filp->f_op = &read_fifo_fops;
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if (retval && !--PIPE_READERS(*inode))
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wake_up_interruptible(&PIPE_WAIT(*inode));
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break;
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case 2:
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/*
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* O_WRONLY
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* POSIX.1 says that O_NONBLOCK means return -1 with
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* errno=ENXIO when there is no process reading the FIFO.
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*/
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if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode)) {
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retval = -ENXIO;
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break;
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}
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filp->f_op = &write_fifo_fops;
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if (!PIPE_WRITERS(*inode)++)
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wake_up_interruptible(&PIPE_WAIT(*inode));
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if (!PIPE_READERS(*inode)) {
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PIPE_WR_OPENERS(*inode)++;
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while (!PIPE_READERS(*inode)) {
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if (current->signal & ~current->blocked) {
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retval = -ERESTARTSYS;
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break;
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}
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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}
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if (!--PIPE_WR_OPENERS(*inode))
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wake_up_interruptible(&PIPE_WAIT(*inode));
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}
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while (PIPE_RD_OPENERS(*inode))
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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if (retval && !--PIPE_WRITERS(*inode))
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wake_up_interruptible(&PIPE_WAIT(*inode));
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break;
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case 3:
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/*
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* O_RDWR
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* POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
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* This implementation will NEVER block on a O_RDWR open, since
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* the process can at least talk to itself.
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*/
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filp->f_op = &rdwr_fifo_fops;
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if (!PIPE_READERS(*inode)++)
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wake_up_interruptible(&PIPE_WAIT(*inode));
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while (PIPE_WR_OPENERS(*inode))
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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if (!PIPE_WRITERS(*inode)++)
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wake_up_interruptible(&PIPE_WAIT(*inode));
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while (PIPE_RD_OPENERS(*inode))
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interruptible_sleep_on(&PIPE_WAIT(*inode));
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break;
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default:
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retval = -EINVAL;
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}
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if (retval || PIPE_BASE(*inode))
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return retval;
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page = __get_free_page(GFP_KERNEL);
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if (PIPE_BASE(*inode)) {
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free_page(page);
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return 0;
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}
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if (!page)
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return -ENOMEM;
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PIPE_LOCK(*inode) = 0;
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PIPE_START(*inode) = PIPE_LEN(*inode) = 0;
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PIPE_BASE(*inode) = (char *) page;
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return 0;
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}
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/*
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* Dummy default file-operations: the only thing this does
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* is contain the open that then fills in the correct operations
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* depending on the access mode of the file...
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*/
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static struct file_operations def_fifo_fops = {
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NULL,
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NULL,
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NULL,
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NULL,
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NULL,
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NULL,
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NULL,
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fifo_open, /* will set read or write pipe_fops */
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NULL,
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NULL
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};
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struct inode_operations fifo_inode_operations = {
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&def_fifo_fops, /* default file operations */
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NULL, /* create */
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NULL, /* lookup */
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NULL, /* link */
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NULL, /* unlink */
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NULL, /* symlink */
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NULL, /* mkdir */
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NULL, /* rmdir */
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NULL, /* mknod */
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NULL, /* rename */
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NULL, /* readlink */
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NULL, /* follow_link */
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NULL, /* readpage */
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NULL, /* writepage */
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NULL, /* bmap */
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NULL, /* truncate */
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NULL /* permission */
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};
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void init_fifo(struct inode * inode)
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{
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inode->i_op = &fifo_inode_operations;
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inode->i_pipe = 1;
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PIPE_LOCK(*inode) = 0;
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PIPE_BASE(*inode) = NULL;
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PIPE_START(*inode) = PIPE_LEN(*inode) = 0;
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PIPE_RD_OPENERS(*inode) = PIPE_WR_OPENERS(*inode) = 0;
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PIPE_WAIT(*inode) = NULL;
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PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0;
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}
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