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qcow2: Get rid of additional sync on COW 

We always have a sync for the refcount update when a new cluster is
allocated. If we move this past the COW, we can save an additional sync.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-09-17 17:02:09 +02:00
parent 29216ed14f
commit 9f8e668eb1
1 changed files with 8 additions and 2 deletions
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10
block/qcow2-cluster.c
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@ -415,7 +415,7 @@ static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
&s->aes_encrypt_key);
}
BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
ret = bdrv_write_sync(bs->file, (cluster_offset >> 9) + n_start,
ret = bdrv_write(bs->file, (cluster_offset >> 9) + n_start,
s->cluster_data, n);
if (ret < 0)
return ret;
@ -714,6 +714,13 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
(i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
}
/*
* Before we update the L2 table to actually point to the new cluster, we
* need to be sure that the refcounts have been increased and COW was
* handled.
*/
bdrv_flush(bs->file);
ret = write_l2_entries(bs, l2_table, l2_offset, l2_index, m->nb_clusters);
if (ret < 0) {
qcow2_l2_cache_reset(bs);
@ -865,7 +872,6 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
QLIST_REMOVE(m, next_in_flight);
return cluster_offset;
}
bdrv_flush(bs->file);
/* save info needed for meta data update */
m->offset = offset;