[Qemu-devel] [PATCH] vdi: Fix image opening and creation for odd disk sizes

[Stefan Weil <weil@mail.berlios.de>]

This patch fixes a regression introduced by commit
95a2f9bc588c3f83375d87b0a9394f89a1bcfada.

The fix is based on a patch from Kevin Wolf. Here his comment:

"The number of blocks needs to be rounded up to cover all of the virtual hard
disk. Without this fix, we can't even open our own images if their size is not
a multiple of the block size."

While Kevin's patch addressed vdi_create, my modification also fixes
vdi_open which now accepts any image which is large enough to hold
the blocks.

I also decided to keep the original code in vdi_create which rounds down.
Rounding works in both directions, and there are good arguments for both,
so I just left the original simple code.

It is very important to use the rounded value for the new disk size, too -
otherwise VirtualBox cannot open our disk image.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: François Revol <revol@free.fr>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
---
 block/vdi.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index 1d257b4..2213819 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -414,8 +414,8 @@ static int vdi_open(BlockDriverState *bs, int flags)
     } else if (header.block_size != 1 * MiB) {
         logout("unsupported block size %u B\n", header.block_size);
         goto fail;
-    } else if ((header.disk_size + header.block_size - 1) / header.block_size !=
-               (uint64_t)header.blocks_in_image) {
+    } else if (header.disk_size < 
+               (uint64_t)header.blocks_in_image * header.block_size) {
         logout("unexpected block number %u B\n", header.blocks_in_image);
         goto fail;
     } else if (!uuid_is_null(header.uuid_link)) {
@@ -827,7 +827,10 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options)
         return -errno;
     }
 
+    /* VirtualBox wants a disk size which is a multiple of the block size. */
     blocks = bytes / block_size;
+    bytes = blocks * block_size;
+
     bmap_size = blocks * sizeof(uint32_t);
     bmap_size = ((bmap_size + SECTOR_SIZE - 1) & ~(SECTOR_SIZE -1));
 
-- 
1.7.0