From 92413c16be8eee53a3b60739f2a28a1463651f47 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Thu, 4 May 2017 01:11:17 +0200 Subject: [PATCH] qcow2: Fix preallocation size formula When calculating the number of reftable entries, we should actually use the number of refblocks and not (wrongly[1]) re-calculate it. [1] "Wrongly" means: Dividing the number of clusters by the number of entries per refblock and rounding down instead of up. Reported-by: Eric Blake Signed-off-by: Max Reitz Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf --- block/qcow2.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 1c2697732b..8caf800529 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2139,7 +2139,7 @@ static int qcow2_create2(const char *filename, int64_t total_size, * too, as long as the bulk is allocated here). Therefore, using * floating point arithmetic is fine. */ int64_t meta_size = 0; - uint64_t nreftablee, nrefblocke, nl1e, nl2e; + uint64_t nreftablee, nrefblocke, nl1e, nl2e, refblock_count; int64_t aligned_total_size = align_offset(total_size, cluster_size); int refblock_bits, refblock_size; /* refcount entry size in bytes */ @@ -2182,11 +2182,12 @@ static int qcow2_create2(const char *filename, int64_t total_size, nrefblocke = (aligned_total_size + meta_size + cluster_size) / (cluster_size - rces - rces * sizeof(uint64_t) / cluster_size); - meta_size += DIV_ROUND_UP(nrefblocke, refblock_size) * cluster_size; + refblock_count = DIV_ROUND_UP(nrefblocke, refblock_size); + meta_size += refblock_count * cluster_size; /* total size of refcount tables */ - nreftablee = nrefblocke / refblock_size; - nreftablee = align_offset(nreftablee, cluster_size / sizeof(uint64_t)); + nreftablee = align_offset(refblock_count, + cluster_size / sizeof(uint64_t)); meta_size += nreftablee * sizeof(uint64_t); qemu_opt_set_number(opts, BLOCK_OPT_SIZE,