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fs/fifo.c
3.2 KB
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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> |
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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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{ int cur = *cnt; |
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while (cur == *cnt) { pipe_wait(inode->i_pipe); if (signal_pending(current)) |
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break; } } static void wake_up_partner(struct inode* inode) { |
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wake_up_interruptible(&inode->i_pipe->wait); |
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} static int fifo_open(struct inode *inode, struct file *filp) { |
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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; if (!pipe) { |
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ret = -ENOMEM; |
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pipe = alloc_pipe_info(inode); if (!pipe) |
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goto err_nocleanup; |
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inode->i_pipe = pipe; |
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} filp->f_version = 0; /* We can only do regular read/write on fifos */ filp->f_mode &= (FMODE_READ | FMODE_WRITE); switch (filp->f_mode) { |
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case FMODE_READ: |
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/* * O_RDONLY * POSIX.1 says that O_NONBLOCK means return with the FIFO * opened, even when there is no process writing the FIFO. */ |
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filp->f_op = &read_pipefifo_fops; |
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pipe->r_counter++; 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)) { /* suppress POLLHUP until we have * seen a writer */ |
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filp->f_version = pipe->w_counter; |
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} else { |
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wait_for_partner(inode, &pipe->w_counter); |
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if(signal_pending(current)) goto err_rd; } } break; |
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case FMODE_WRITE: |
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/* * O_WRONLY * POSIX.1 says that O_NONBLOCK means return -1 with * errno=ENXIO when there is no process reading the FIFO. */ 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_pipefifo_fops; |
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pipe->w_counter++; if (!pipe->writers++) |
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wake_up_partner(inode); |
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if (!pipe->readers) { wait_for_partner(inode, &pipe->r_counter); |
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if (signal_pending(current)) goto err_wr; } break; |
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case FMODE_READ | FMODE_WRITE: |
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/* * 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. */ |
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filp->f_op = &rdwr_pipefifo_fops; |
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|
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pipe->readers++; pipe->writers++; pipe->r_counter++; pipe->w_counter++; if (pipe->readers == 1 || pipe->writers == 1) |
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wake_up_partner(inode); break; default: ret = -EINVAL; goto err; } /* Ok! */ |
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mutex_unlock(&inode->i_mutex); |
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return 0; err_rd: |
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if (!--pipe->readers) wake_up_interruptible(&pipe->wait); |
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ret = -ERESTARTSYS; goto err; err_wr: |
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if (!--pipe->writers) wake_up_interruptible(&pipe->wait); |
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ret = -ERESTARTSYS; goto err; err: |
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if (!pipe->readers && !pipe->writers) |
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free_pipe_info(inode); err_nocleanup: |
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mutex_unlock(&inode->i_mutex); |
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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... */ |
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const struct file_operations def_fifo_fops = { |
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.open = fifo_open, /* will set read_ or write_pipefifo_fops */ |
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.llseek = noop_llseek, |
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}; |