From: Dave Chinner <dchinner@redhat.com>
Date: Wed, 12 Dec 2018 17:42:40 +0000 (-0600)
Subject: io: open pipes in non-blocking mode
X-Git-Tag: v4.20.0-rc1~20
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1a05efba;p=thirdparty%2Fxfsprogs-dev.git

io: open pipes in non-blocking mode

So that O_RDONLY open commands (such as from copy_range) do not
block forever waiting on a non-existent writer.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Tulak <jtulak@redhat.com>
[sandeen: initialize st per djwong's suggestion]
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---

diff --git a/io/open.c b/io/open.c
index 6ea3e9a20..21c0e054f 100644
--- a/io/open.c
+++ b/io/open.c
@@ -56,6 +56,7 @@ openfile(
 	struct fs_path	*fs_path)
 {
 	struct fs_path	*fsp;
+	struct stat	st = { 0 };
 	int		fd;
 	int		oflags;
 
@@ -79,6 +80,18 @@ openfile(
 	if (flags & IO_NOFOLLOW)
 		oflags |= O_NOFOLLOW;
 
+	/*
+	 * if we've been passed a pipe to open, don't block waiting for a
+	 * reader or writer to appear. We want to either succeed or error out
+	 * immediately.
+	 */
+	if (stat(path, &st) < 0 && errno != ENOENT) {
+		perror("stat");
+		return -1;
+	}
+	if (S_ISFIFO(st.st_mode))
+		oflags |= O_NONBLOCK;
+
 	fd = open(path, oflags, mode);
 	if (fd < 0) {
 		if (errno == EISDIR &&