[PATCH 2/5] xen-blkback: fix foreach_grant_safe to handle empty lists

From: Roger Pau Monne <roger.pau@citrix.com>
To: xen-devel@lists.xen.org, linux-kernel@vger.kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: [PATCH 2/5] xen-blkback: fix foreach_grant_safe to handle empty lists
Date: Mon, 18 Mar 2013 17:49:33 +0100	[thread overview]
Message-ID: <1363625376-35612-3-git-send-email-roger.pau__20215.8855194741$1363625581$gmane$org@citrix.com> (raw)
In-Reply-To: <1363625376-35612-1-git-send-email-roger.pau@citrix.com>

We may use foreach_grant_safe in the future with empty lists, so make
sure we can handle them.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: xen-devel@lists.xen.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/block/xen-blkback/blkback.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index d909acf0..7319f67 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -164,7 +164,7 @@ static void make_response(struct xen_blkif *blkif, u64 id,
 
 #define foreach_grant_safe(pos, n, rbtree, node) \
 	for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
-	     (n) = rb_next(&(pos)->node); \
+	     (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 	     &(pos)->node != NULL; \
 	     (pos) = container_of(n, typeof(*(pos)), node), \
 	     (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
-- 
1.7.7.5 (Apple Git-26)


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