From: Ian Kent <ikent@redhat.com>
Date: Tue, 12 Aug 2008 12:27:34 +0800
Subject: [autofs4] check communication pipe is valid for write
Message-id: 20080812042732.15842.11351.stgit@web.messagingengine.com
O-Subject: [RHEL 5.3 PATCH 12/20] autofs4 - check kernel communication pipe is valid for write [Realted: bz452139]
Bugzilla: 452139

This patch is an upstream bug fix and shoud be associated with
bug 452139.

It is possible for an autofs mount to become catatonic (and for the
daemon communication pipe to become NULL) after a wait has been
initiallized but before the request has been sent to the daemon. We
need to check for this before sending the request packet.

Signed-off-by: Ian Kent <raven@themaw.net>

diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index 5103f3d..8849768 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -96,6 +96,7 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 {
 	union autofs_packet_union pkt;
 	size_t pktsz;
+	struct file *pipe = NULL;
 
 	DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 		wq->wait_queue_token, wq->name.len, wq->name.name, type);
@@ -160,8 +161,19 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 		return;
 	}
 
-	if (autofs4_write(sbi->pipe, &pkt, pktsz))
-		autofs4_catatonic_mode(sbi);
+	/* Check if we have become catatonic */
+	mutex_lock(&sbi->wq_mutex);
+	if (!sbi->catatonic) {
+		pipe = sbi->pipe;
+		get_file(pipe);
+	}
+	mutex_unlock(&sbi->wq_mutex);
+
+	if (pipe) {
+		if (autofs4_write(pipe, &pkt, pktsz))
+			autofs4_catatonic_mode(sbi);
+		fput(pipe);
+	}
 }
 
 static int autofs4_getpath(struct autofs_sb_info *sbi,