From 2c25b8131631c39145fe1f5b7745943e0e0c0406 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 1 Sep 2010 12:40:52 +0200 Subject: qcow2: Remove unnecessary flush after L2 write When a new cluster was allocated, we only need a flush after the write to the L2 table if it was a COW and we need to decrease the refcounts of the old clusters. Signed-off-by: Kevin Wolf (cherry picked from commit 7ec5e6a4ca43494949465f9f9f3d9e4c7c620503) --- block/qcow2-cluster.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 166922f8be..f562b1602e 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -655,7 +655,7 @@ static int write_l2_entries(BlockDriverState *bs, uint64_t *l2_table, int ret; BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE); - ret = bdrv_pwrite_sync(bs->file, l2_offset + start_offset, + ret = bdrv_pwrite(bs->file, l2_offset + start_offset, &l2_table[l2_start_index], len); if (ret < 0) { return ret; @@ -718,9 +718,17 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) goto err; } - for (i = 0; i < j; i++) - qcow2_free_any_clusters(bs, - be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED, 1); + /* + * If this was a COW, we need to decrease the refcount of the old cluster. + * Also flush bs->file to get the right order for L2 and refcount update. + */ + if (j != 0) { + bdrv_flush(bs->file); + for (i = 0; i < j; i++) { + qcow2_free_any_clusters(bs, + be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED, 1); + } + } ret = 0; err: -- cgit v1.2.1