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qcow2: Calculate refcount block entry count

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The size of a refblock entry is (in theory) variable; calculate
therefore the number of entries per refblock and the according bit shift
(1 << x == entry count) when opening an image.

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 2014-10-22 14:09:28 +02:00 committed by Kevin Wolf
parent 9ebd844805
commit 1d13d65466
2 changed files with 5 additions and 0 deletions
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3
block/qcow2.c
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@ -698,6 +698,9 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
s->l2_size = 1 << s->l2_bits;
/* 2^(s->refcount_order - 3) is the refcount width in bytes */
s->refcount_block_bits = s->cluster_bits - (s->refcount_order - 3);
s->refcount_block_size = 1 << s->refcount_block_bits;
bs->total_sectors = header.size / 512;
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;

2
block/qcow2.h
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@ -223,6 +223,8 @@ typedef struct BDRVQcowState {
int l2_size;
int l1_size;
int l1_vm_state_index;
int refcount_block_bits;
int refcount_block_size;
int csize_shift;
int csize_mask;
uint64_t cluster_offset_mask;