linux-kernel - [PATCH] relayfs: fix infinite loop with splice()

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Date:	Fri, 24 Oct 2008 10:48:23 +0300 (EEST)
From:	Pekka J Enberg <penberg@...helsinki.fi>
To:	akpm@...ux-foundation.org
cc:	zanussi@...cast.net, mathieu.desnoyers@...ymtl.ca,
	linux-kernel@...r.kernel.org
Subject: [PATCH] relayfs: fix infinite loop with splice()

From: Tom Zanussi <zanussi@...cast.net>

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@...ymtl.ca>
Tested-by: Pekka Enberg <penberg@...helsinki.fi>
Signed-off-by: Tom Zanussi <tzanussi@...il.com>
Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
---
 kernel/relay.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/relay.c b/kernel/relay.c
index 8d13a78..6a4d439 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1318,12 +1318,9 @@ 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;
-- 
1.5.4.3

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