/* * 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 */ };