From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=54681 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OqmCr-0005Fd-Gn for qemu-devel@nongnu.org; Wed, 01 Sep 2010 08:14:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OqmCq-0004D3-Fo for qemu-devel@nongnu.org; Wed, 01 Sep 2010 08:14:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37597) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OqmCq-0004Cr-6t for qemu-devel@nongnu.org; Wed, 01 Sep 2010 08:14:20 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o81CEJNR031012 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 1 Sep 2010 08:14:19 -0400 From: Kevin Wolf Date: Wed, 1 Sep 2010 14:14:32 +0200 Message-Id: <1283343272-6773-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH] qcow2: Remove unnecessary flush after L2 write List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com 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 --- block/qcow2-cluster.c | 16 ++++++++++++---- 1 files changed, 12 insertions(+), 4 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index b023148..0ce24d6 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -656,7 +656,7 @@ 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; @@ -719,9 +719,17 @@ 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: -- 1.7.2.2