Patchwork [2/2] Revert "block/vpc: Fix size calculation"

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Submitter Stefan Hajnoczi
Date Feb. 12, 2013, 12:33 p.m.
Message ID <1360672423-2286-3-git-send-email-stefanha@redhat.com>
Download mbox | patch
Permalink /patch/219844/
State New
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Comments

Stefan Hajnoczi - Feb. 12, 2013, 12:33 p.m.
This reverts commit f880defbb06708d30a38ce9f2667067626acdd38.

Jeff Cody's testing revealed that the interpretation of size differs
even between VirtualPC and HyperV.  Revert this so there is time to
consider the impact of any backwards incompatible behavior this change
creates.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/vpc.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

Patch

diff --git a/block/vpc.c b/block/vpc.c
index b4ff564..82229ef 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -34,8 +34,6 @@ 
 
 #define HEADER_SIZE 512
 
-#define VHD_SECTOR_SIZE 512
-
 //#define CACHE
 
 enum vhd_type {
@@ -206,13 +204,11 @@  static int vpc_open(BlockDriverState *bs, int flags)
     /* Write 'checksum' back to footer, or else will leave it with zero. */
     footer->checksum = be32_to_cpu(checksum);
 
-    /* The visible size of a image in Virtual PC depends on the guest:
-     * QEMU and other emulators report the real size (here in sectors).
-     * All modern operating systems use this real size.
-     * Very old operating systems use CHS values to calculate the total size.
-     * This calculated size is usually smaller than the real size.
-     */
-    bs->total_sectors = be64_to_cpu(footer->size) / VHD_SECTOR_SIZE;
+    // The visible size of a image in Virtual PC depends on the geometry
+    // rather than on the size stored in the footer (the size in the footer
+    // is too large usually)
+    bs->total_sectors = (int64_t)
+        be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl;
 
     /* Allow a maximum disk size of approximately 2 TB */
     if (bs->total_sectors >= 65535LL * 255 * 255) {