diff options
Diffstat (limited to 'block/vdi.c')
| -rw-r--r-- | block/vdi.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/block/vdi.c b/block/vdi.c index e1d211c9f7..39070b75e8 100644 --- a/block/vdi.c +++ b/block/vdi.c @@ -120,8 +120,18 @@ typedef unsigned char uuid_t[16]; #define VDI_IS_ALLOCATED(X) ((X) < VDI_DISCARDED) -/* max blocks in image is (0xffffffff / 4) */ -#define VDI_BLOCKS_IN_IMAGE_MAX 0x3fffffff +/* The bmap will take up VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) bytes; since + * the bmap is read and written in a single operation, its size needs to be + * limited to INT_MAX; furthermore, when opening an image, the bmap size is + * rounded up to be aligned on BDRV_SECTOR_SIZE. + * Therefore this should satisfy the following: + * VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) + BDRV_SECTOR_SIZE == INT_MAX + 1 + * (INT_MAX + 1 is the first value not representable as an int) + * This guarantees that any value below or equal to the constant will, when + * multiplied by sizeof(uint32_t) and rounded up to a BDRV_SECTOR_SIZE boundary, + * still be below or equal to INT_MAX. */ +#define VDI_BLOCKS_IN_IMAGE_MAX \ + ((unsigned)((INT_MAX + 1u - BDRV_SECTOR_SIZE) / sizeof(uint32_t))) #define VDI_DISK_SIZE_MAX ((uint64_t)VDI_BLOCKS_IN_IMAGE_MAX * \ (uint64_t)DEFAULT_CLUSTER_SIZE) |