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qcow2: add shrink image support

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This patch add shrinking of the image file for qcow2. As a result, this allows
us to reduce the virtual image size and free up space on the disk without
copying the image. Image can be fragmented and shrink is done by punching holes
in the image file.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170918124230.8152-4-pbutsykin@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Pavel Butsykin 2017-09-18 15:42:29 +03:00 • committed by Max Reitz
parent f71c08ea8e
commit 46b732cdf3
5 changed files with 227 additions and 12 deletions
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14
block/qcow2.h
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@ -521,6 +521,18 @@ static inline uint64_t refcount_diff(uint64_t r1, uint64_t r2)
return r1 > r2 ? r1 - r2 : r2 - r1;
}
static inline
uint32_t offset_to_reftable_index(BDRVQcow2State *s, uint64_t offset)
{
return offset >> (s->refcount_block_bits + s->cluster_bits);
}
static inline uint64_t get_refblock_offset(BDRVQcow2State *s, uint64_t offset)
{
uint32_t index = offset_to_reftable_index(s, offset);
return s->refcount_table[index] & REFT_OFFSET_MASK;
}
/* qcow2.c functions */
int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t sector_num, int nb_sectors);
@ -584,10 +596,12 @@ int qcow2_inc_refcounts_imrt(BlockDriverState *bs, BdrvCheckResult *res,
int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
BlockDriverAmendStatusCB *status_cb,
void *cb_opaque, Error **errp);
int qcow2_shrink_reftable(BlockDriverState *bs);
/* qcow2-cluster.c functions */
int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
bool exact_size);
int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t max_size);
int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index);
int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset);
int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num,