From 39fe1a7f4e325645a2d26b90f2951a4206dd4201 Mon Sep 17 00:00:00 2001
From: Jan Beulich <JBeulich@novell.com>
Date: Tue, 17 May 2011 11:07:05 +0100
Subject: [PATCH] --- yaml --- r: 251269 b: refs/heads/master c:
 8ab521506c4dbb144f0c04c55e3d8bec42c1b2b9 h: refs/heads/master i:   251267:
 d28a53a5a799e8682129b993421c6023bff052a6 v: v3

---
 [refs]                                    |  2 +-
 trunk/drivers/block/xen-blkback/blkback.c | 15 ++++++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 60bb4447a619..281dc21d48b0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 496b318eb65558c1a3a4fe882cb9da6d1dc6493a
+refs/heads/master: 8ab521506c4dbb144f0c04c55e3d8bec42c1b2b9
diff --git a/trunk/drivers/block/xen-blkback/blkback.c b/trunk/drivers/block/xen-blkback/blkback.c
index dba55e3a4a86..c73910cc28c9 100644
--- a/trunk/drivers/block/xen-blkback/blkback.c
+++ b/trunk/drivers/block/xen-blkback/blkback.c
@@ -175,8 +175,14 @@ static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 	if ((operation != READ) && vbd->readonly)
 		goto out;
 
-	if (unlikely((req->sector_number + req->nr_sects) > vbd_sz(vbd)))
-		goto out;
+	if (likely(req->nr_sects)) {
+		blkif_sector_t end = req->sector_number + req->nr_sects;
+
+		if (unlikely(end < req->sector_number))
+			goto out;
+		if (unlikely(end > vbd_sz(vbd)))
+			goto out;
+	}
 
 	req->dev  = vbd->pdevice;
 	req->bdev = vbd->bdev;
@@ -538,11 +544,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	case BLKIF_OP_FLUSH_DISKCACHE:
 		blkif->st_f_req++;
 		operation = WRITE_FLUSH;
-		/*
-		 * The frontend likes to set this to -1, which xen_vbd_translate
-		 * is alergic too.
-		 */
-		req->u.rw.sector_number = 0;
 		break;
 	case BLKIF_OP_WRITE_BARRIER:
 	default: