From: Kei Tokunaga <ktokunag@redhat.com>
Subject: [RHEL5.1 PATCH][XEN] guest using blktap tries to access beyond end 	of disk
Date: Wed, 08 Aug 2007 12:06:14 -0400
Bugzilla: 247696
Message-Id: <46B9E9F6.6070400@redhat.com>
Changelog: [XEN] blktap tries to access beyond end of disk


bz247696
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=247696

Attached patch removed unnecessary debug code, which was to check
the access range to a disk image.  Actually, the check code was
wrong and caused the following spew on dom0's console when configured
to use a disk image accessed via blktap for its storage.

Example console spew:

blk_tap: BLKTAP: READ request sector[8192002,16000], Total [8192000]
blk_tap: BLKTAP: Sector request greaterthan size
blk_tap: BLKTAP: READ request sector[8192034,16000], Total [8192000]
blk_tap: BLKTAP: Sector request greaterthan size
blk_tap: BLKTAP: READ request sector[8192066,16000], Total [8192000]
blk_tap: BLKTAP: Sector request greaterthan size
blk_tap: BLKTAP: READ request sector[8192098,16000], Total [8192000]
blk_tap: BLKTAP: Sector request greaterthan size
blk_tap: BLKTAP: READ request sector[8192013,16000], Total [8192000]
blk_tap: BLKTAP: Sector request greaterthan size

The fix-patch is upstream:
  http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/1372bc676080

Attached patch applies to -38.  We have verified that it worked on -37.

Thanks,
Kei

---

 linux-2.6.18.ia64-kei/drivers/xen/blktap/blktapmain.c |   14 --------------
 1 file changed, 14 deletions(-)

diff -puN drivers/xen/blktap/blktapmain.c~bz247696 drivers/xen/blktap/blktapmain.c
--- linux-2.6.18.ia64/drivers/xen/blktap/blktapmain.c~bz247696	2007-08-08 10:42:51.000000000 -0400
+++ linux-2.6.18.ia64-kei/drivers/xen/blktap/blktapmain.c	2007-08-08 10:43:08.000000000 -0400
@@ -1153,7 +1153,6 @@ static void dispatch_rw_block_io(blkif_t
 	unsigned int nseg;
 	int ret, i;
 	tap_blkif_t *info = tapfds[blkif->dev_num];
-	uint64_t sector;
 	
 	blkif_request_t *target;
 	int pending_idx = RTN_PEND_IDX(pending_req,pending_req->mem_idx);
@@ -1201,19 +1200,6 @@ static void dispatch_rw_block_io(blkif_t
 		uvaddr = MMAP_VADDR(info->user_vstart, usr_idx, i);
 		kvaddr = idx_to_kaddr(mmap_idx, pending_idx, i);
 
-		sector = req->sector_number + ((PAGE_SIZE / 512) * i);
-		if( (blkif->sectors > 0) && (sector >= blkif->sectors) ) {
-			WPRINTK("BLKTAP: Sector request greater" 
-			       "than size\n");
-			WPRINTK("BLKTAP: %s request sector" 
-			       "[%llu,%llu], Total [%llu]\n",
-			       (req->operation == 
-				BLKIF_OP_WRITE ? "WRITE" : "READ"),
-				(long long unsigned) sector,
-				(long long unsigned) sector>>9,
-				(long long unsigned) blkif->sectors);
-		}
-
 		flags = GNTMAP_host_map;
 		if (operation == WRITE)
 			flags |= GNTMAP_readonly;

_