vpc: Don't round up already aligned BAT sizes

As reported on Launchpad, Azure apparently doesn't accept images for
upload that are not both aligned to 1 MB blocks and have a BAT size that
matches the image size exactly.

As far as I can tell, there is no real reason why we create a BAT that
is one entry longer than necessary for aligned image sizes, so change
that.

(Even though the condition is only mentioned as "should" in the spec and
previous products accepted larger BATs - but we'll try to maintain
compatibility with as many of Microsoft's ever-changing interpretations
of the VHD spec as possible.)

Fixes: https://bugs.launchpad.net/bugs/1870098
Reported-by: Tobias Witek
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200402093603.2369-1-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 3f6de653b946fe849330208becf79d6af7e876cb)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/vpc.c b/block/vpc.c
index a65550298e195af52c51a31d1f9f7993b0183543..21b08033a6ab56115c6258b7ef3c2493ab5f7693 100644 (file)
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -835,7 +835,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf,
 
     /* Write the footer (twice: at the beginning and at the end) */
     block_size = 0x200000;
-    num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
+    num_bat_entries = DIV_ROUND_UP(total_sectors, block_size / 512);
 
     ret = blk_pwrite(blk, offset, buf, HEADER_SIZE, 0);
     if (ret < 0) {