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qcow2: Add l2_slice_size field to BDRVQcow2State

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The BDRVQcow2State structure contains an l2_size field, which stores
the number of 64-bit entries in an L2 table.

For efficiency reasons we want to be able to load slices instead of
full L2 tables, so we need to know how many entries an L2 slice can
hold.

An L2 slice is the portion of an L2 table that is loaded by the qcow2
cache. At the moment that cache can only load complete tables,
therefore an L2 slice has the same size as an L2 table (one cluster)
and l2_size == l2_slice_size.

Later we'll allow smaller slices, but until then we have to use this
new l2_slice_size field to make the rest of the code ready for that.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: adb048595f9fb5dfb110c802a8b3c3be3b937f37.1517840877.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2018-02-05 16:33:13 +02:00 committed by Max Reitz
parent 05b5b6ee54
commit 3c2e511a24
2 changed files with 4 additions and 0 deletions
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3
block/qcow2.c
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@ -807,6 +807,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,
typedef struct Qcow2ReopenState {
Qcow2Cache *l2_table_cache;
Qcow2Cache *refcount_block_cache;
int l2_slice_size; /* Number of entries in a slice of the L2 table */
bool use_lazy_refcounts;
int overlap_check;
bool discard_passthrough[QCOW2_DISCARD_MAX];
@ -888,6 +889,7 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
}
}
r->l2_slice_size = s->cluster_size / sizeof(uint64_t);
r->l2_table_cache = qcow2_cache_create(bs, l2_cache_size);
r->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size);
if (r->l2_table_cache == NULL || r->refcount_block_cache == NULL) {
@ -1051,6 +1053,7 @@ static void qcow2_update_options_commit(BlockDriverState *bs,
}
s->l2_table_cache = r->l2_table_cache;
s->refcount_block_cache = r->refcount_block_cache;
s->l2_slice_size = r->l2_slice_size;
s->overlap_check = r->overlap_check;
s->use_lazy_refcounts = r->use_lazy_refcounts;

1
block/qcow2.h
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@ -251,6 +251,7 @@ typedef struct BDRVQcow2State {
int cluster_bits;
int cluster_size;
int cluster_sectors;
int l2_slice_size;
int l2_bits;
int l2_size;
int l1_size;