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qcow2: Add offset_to_l1_index() 

Similar to offset_to_l2_index(), this function returns the index in
the L1 table for a given guest offset. This is only used in a couple
of places and it's not a particularly complex calculation, but it
makes the code a bit more readable.

Although in the qcow2_get_cluster_offset() case the old code was
taking advantage of the l1_bits variable, we're going to get rid of
the other uses of l1_bits in a later patch anyway, so it doesn't make
sense to keep it just for this.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: a5f626fed526b7459a0425fad06d823d18df8522.1517840877.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2018-02-05 16:33:12 +02:00 committed by Max Reitz
parent 6e6fa7605e
commit 05b5b6ee54
2 changed files with 7 additions and 2 deletions
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4
block/qcow2-cluster.c
View File

@ -540,7 +540,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
/* seek to the l2 offset in the l1 table */
l1_index = offset >> l1_bits;
l1_index = offset_to_l1_index(s, offset);
if (l1_index >= s->l1_size) {
type = QCOW2_CLUSTER_UNALLOCATED;
goto out;
@ -663,7 +663,7 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
/* seek to the l2 offset in the l1 table */
l1_index = offset >> (s->l2_bits + s->cluster_bits);
l1_index = offset_to_l1_index(s, offset);
if (l1_index >= s->l1_size) {
ret = qcow2_grow_l1_table(bs, l1_index + 1, false);
if (ret < 0) {

5
block/qcow2.h
View File

@ -463,6 +463,11 @@ static inline int64_t size_to_l1(BDRVQcow2State *s, int64_t size)
return (size + (1ULL << shift) - 1) >> shift;
}
static inline int offset_to_l1_index(BDRVQcow2State *s, uint64_t offset)
{
return offset >> (s->l2_bits + s->cluster_bits);
}
static inline int offset_to_l2_index(BDRVQcow2State *s, int64_t offset)
{
return (offset >> s->cluster_bits) & (s->l2_size - 1);