From: Tom Zanussi <zanussi@comcast.net>
Date: Tue, 9 Dec 2008 21:14:10 +0000 (-0800)
Subject: relayfs: fix infinite loop with splice()
X-Git-Tag: v2.6.28-rc8~31
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?p=linux-2.6-omap-h63xx.git;a=commitdiff_plain;h=fbb5b7ae4b442f1923513dc6165a66c7a7f29073

relayfs: fix infinite loop with splice()

Running kmemtraced, which uses splice() on relayfs, causes a hard lock on
x86-64 SMP.  As described by Tom Zanussi:

  It looks like you hit the same problem as described here:

  commit 8191ecd1d14c6914c660dfa007154860a7908857

      splice: fix infinite loop in generic_file_splice_read()

  relay uses the same loop but it never got noticed or fixed.

Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Tested-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/relay.c b/kernel/relay.c
index 32b0befdcb6..09ac2008f77 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1317,12 +1317,9 @@ static ssize_t relay_file_splice_read(struct file *in,
 		if (ret < 0)
 			break;
 		else if (!ret) {
-			if (spliced)
-				break;
-			if (flags & SPLICE_F_NONBLOCK) {
+			if (flags & SPLICE_F_NONBLOCK)
 				ret = -EAGAIN;
-				break;
-			}
+			break;
 		}
 
 		*ppos += ret;