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

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

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 images with odd disk sizes as well as
images created with old versions of qemu-img.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: François Revol <revol@free.fr>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
---
 block/vdi.c |   29 +++++++++++++++++++++--------
 1 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index 1ce18d5..362c898 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -405,19 +405,12 @@ static int vdi_open(BlockDriverState *bs, int flags)
         /* We only support data blocks which start on a sector boundary. */
         logout("unsupported data offset 0x%x B\n", header.offset_data);
         goto fail;
-    } else if (header.disk_size % SECTOR_SIZE != 0) {
-        logout("unsupported disk size %" PRIu64 " B\n", header.disk_size);
-        goto fail;
     } else if (header.sector_size != SECTOR_SIZE) {
         logout("unsupported sector size %u B\n", header.sector_size);
         goto fail;
     } 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) {
-        logout("unexpected block number %u B\n", header.blocks_in_image);
-        goto fail;
     } else if (!uuid_is_null(header.uuid_link)) {
         logout("link uuid != 0, unsupported\n");
         goto fail;
@@ -426,6 +419,23 @@ static int vdi_open(BlockDriverState *bs, int flags)
         goto fail;
     }
 
+    if (header.disk_size % SECTOR_SIZE != 0) {
+        /* 'VBoxManage convertfromraw' can create images with odd disk sizes.
+           We accept them but round the disk size to the next multiple of
+           SECTOR_SIZE. */
+        logout("odd disk size %" PRIu64 " B, round up\n", header.disk_size);
+        header.disk_size += SECTOR_SIZE - 1;
+        header.disk_size &= ~(SECTOR_SIZE - 1);
+    }
+
+    if (header.disk_size >
+        (uint64_t)header.blocks_in_image * header.block_size) {
+        /* Old versions of qemu-img could create images with too large
+           disk sizes. We accept them but truncate the disk size. */
+        logout("large disk size %" PRIu64 " B, truncated\n", header.disk_size);
+        header.disk_size = (uint64_t)header.blocks_in_image * header.block_size;
+    }
+
     bs->total_sectors = header.disk_size / SECTOR_SIZE;
 
     s->block_size = header.block_size;
@@ -829,7 +839,10 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options)
         return -errno;
     }
 
-    blocks = bytes / block_size;
+    /* We need enough blocks to store the given disk size,
+       so always round up. */
+    blocks = (bytes + block_size - 1) / block_size;
+
     bmap_size = blocks * sizeof(uint32_t);
     bmap_size = ((bmap_size + SECTOR_SIZE - 1) & ~(SECTOR_SIZE -1));
 
-- 
1.7.1