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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 <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2017-05-04 01:11:17 +02:00 committed by Kevin Wolf
parent de9efdb334
commit 92413c16be
1 changed files with 5 additions and 4 deletions
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block/qcow2.c
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@ -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,