[PATCH] Make the new merged pipe writes check for SIGPIPE

The new pipe buffer merging doesn't check for the "no readers" case, so
with small writes that coalesce, we may not get a timely SIGPIPE/EPIPE
notification to the writer.
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/pipe.c

@@ -235,6 +235,12 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
 	down(PIPE_SEM(*inode));
 	info = inode->i_pipe;
 
+	if (!PIPE_READERS(*inode)) {
+		send_sig(SIGPIPE, current, 0);
+		ret = -EPIPE;
+		goto out;
+	}
+
 	/* We try to merge small writes */
 	if (info->nrbufs && total_len < PAGE_SIZE) {
 		int lastbuf = (info->curbuf + info->nrbufs - 1) & (PIPE_BUFFERS-1);