156 lines
3.1 KiB
C
156 lines
3.1 KiB
C
/*
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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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* Fixes:
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* 10-06-1999, AV: fixed OOM handling in fifo_open(), moved
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* initialization there, switched to external
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* allocation of pipe_inode_info.
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*/
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/pipe_fs_i.h>
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static void wait_for_partner(struct inode* inode, unsigned int *cnt)
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{
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int cur = *cnt;
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while (cur == *cnt) {
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pipe_wait(inode->i_pipe);
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if (signal_pending(current))
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break;
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}
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}
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static void wake_up_partner(struct inode* inode)
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{
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wake_up_interruptible(&inode->i_pipe->wait);
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}
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static int fifo_open(struct inode *inode, struct file *filp)
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{
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struct pipe_inode_info *pipe;
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int ret;
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mutex_lock(&inode->i_mutex);
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pipe = inode->i_pipe;
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if (!pipe) {
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ret = -ENOMEM;
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pipe = alloc_pipe_info(inode);
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if (!pipe)
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goto err_nocleanup;
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inode->i_pipe = pipe;
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}
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filp->f_version = 0;
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/* We can only do regular read/write on fifos */
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filp->f_mode &= (FMODE_READ | FMODE_WRITE);
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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 = &read_fifo_fops;
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pipe->r_counter++;
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if (pipe->readers++ == 0)
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wake_up_partner(inode);
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if (!pipe->writers) {
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if ((filp->f_flags & O_NONBLOCK)) {
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/* suppress POLLHUP until we have
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* seen a writer */
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filp->f_version = pipe->w_counter;
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} else
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{
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wait_for_partner(inode, &pipe->w_counter);
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if(signal_pending(current))
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goto err_rd;
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}
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}
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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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ret = -ENXIO;
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if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
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goto err;
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filp->f_op = &write_fifo_fops;
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pipe->w_counter++;
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if (!pipe->writers++)
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wake_up_partner(inode);
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if (!pipe->readers) {
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wait_for_partner(inode, &pipe->r_counter);
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if (signal_pending(current))
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goto err_wr;
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}
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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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pipe->readers++;
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pipe->writers++;
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pipe->r_counter++;
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pipe->w_counter++;
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if (pipe->readers == 1 || pipe->writers == 1)
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wake_up_partner(inode);
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break;
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default:
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ret = -EINVAL;
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goto err;
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}
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/* Ok! */
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mutex_unlock(&inode->i_mutex);
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return 0;
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err_rd:
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if (!--pipe->readers)
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wake_up_interruptible(&pipe->wait);
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ret = -ERESTARTSYS;
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goto err;
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err_wr:
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if (!--pipe->writers)
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wake_up_interruptible(&pipe->wait);
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ret = -ERESTARTSYS;
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goto err;
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err:
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if (!pipe->readers && !pipe->writers)
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free_pipe_info(inode);
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err_nocleanup:
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mutex_unlock(&inode->i_mutex);
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return ret;
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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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const struct file_operations def_fifo_fops = {
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.open = fifo_open, /* will set read or write pipe_fops */
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};
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