1 files changed, 155 insertions, 0 deletions
diff --git a/fs/fifo.c b/fs/fifo.c
new file mode 100644
index 00000000000..5455916241f
--- /dev/null
+++ b/fs/fifo.c
@@ -0,0 +1,155 @@
+/*
+ *  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;
+
+	ret = -ERESTARTSYS;
+	if (down_interruptible(PIPE_SEM(*inode)))
+		goto err_nolock_nocleanup;
+
+	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! */
+	up(PIPE_SEM(*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:
+	up(PIPE_SEM(*inode));
+
+err_nolock_nocleanup:
+	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 */
+};