From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=40712 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OweOn-0006Re-N3 for qemu-devel@nongnu.org; Fri, 17 Sep 2010 13:06:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OweOm-0000oh-6S for qemu-devel@nongnu.org; Fri, 17 Sep 2010 13:06:57 -0400 Received: from mail-yx0-f173.google.com ([209.85.213.173]:58935) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OweOm-0000oY-2F for qemu-devel@nongnu.org; Fri, 17 Sep 2010 13:06:56 -0400 Received: by yxs7 with SMTP id 7so1016415yxs.4 for ; Fri, 17 Sep 2010 10:06:55 -0700 (PDT) Message-ID: <4C93A01F.40706@codemonkey.ws> Date: Fri, 17 Sep 2010 12:06:39 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 2/4] qcow2: Move sync out of update_refcount References: <1284740318-20838-1-git-send-email-kwolf@redhat.com> <1284740318-20838-3-git-send-email-kwolf@redhat.com> In-Reply-To: <1284740318-20838-3-git-send-email-kwolf@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org On 09/17/2010 11:18 AM, Kevin Wolf wrote: > Note that the flush is omitted intentionally in qcow2_free_clusters. If > anything, we can leak clusters here if we lose the writes. > > Signed-off-by: Kevin Wolf > Cluster leaking gets picked up by bdrv_check though, right? I think I've convinced myself that leaking clusters is not an acceptable behavior from a security perspective but as long as it's detectable via bdrv_check, qcow2 could implement an online check to address it. Regards, Anthony Liguori > --- > block/qcow2-refcount.c | 13 +++++++++++-- > 1 files changed, 11 insertions(+), 2 deletions(-) > > diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c > index 7dc75d1..4fc3f80 100644 > --- a/block/qcow2-refcount.c > +++ b/block/qcow2-refcount.c > @@ -261,6 +261,8 @@ static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index) > goto fail_block; > } > > + bdrv_flush(bs->file); > + > /* Initialize the new refcount block only after updating its refcount, > * update_refcount uses the refcount cache itself */ > memset(s->refcount_block_cache, 0, s->cluster_size); > @@ -551,8 +553,6 @@ fail: > dummy = update_refcount(bs, offset, cluster_offset - offset, -addend); > } > > - bdrv_flush(bs->file); > - > return ret; > } > > @@ -575,6 +575,8 @@ static int update_cluster_refcount(BlockDriverState *bs, > return ret; > } > > + bdrv_flush(bs->file); > + > return get_refcount(bs, cluster_index); > } > > @@ -626,6 +628,9 @@ int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size) > if (ret< 0) { > return ret; > } > + > + bdrv_flush(bs->file); > + > return offset; > } > > @@ -803,6 +808,10 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, > if (ret< 0) { > goto fail; > } > + > + /* TODO Flushing once for the whole function should > + * be enough */ > + bdrv_flush(bs->file); > } > /* compressed clusters are never modified */ > refcount = 2; >