From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35986) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cdefv-0003pS-2b for qemu-devel@nongnu.org; Tue, 14 Feb 2017 10:05:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cdeft-0004FX-RJ for qemu-devel@nongnu.org; Tue, 14 Feb 2017 10:05:51 -0500 Date: Tue, 14 Feb 2017 23:05:39 +0800 From: Fam Zheng Message-ID: <20170214150539.GC20715@lemon.lan> References: <1487083704-51658-1-git-send-email-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1487083704-51658-1-git-send-email-vsementsov@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH] backup: allow target without .bdrv_get_info List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, kwolf@redhat.com, jcody@redhat.com, jsnow@redhat.com, den@openvz.org, stefanha@redhat.com On Tue, 02/14 17:48, Vladimir Sementsov-Ogievskiy wrote: > Currently backup to nbd target is broken, as nbd doesn't have > .bdrv_get_info realization. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > > Hi all! > > Since commit > > commit 4c9bca7e39a6e07ad02c1dcde3478363344ec60b > Author: John Snow > Date: Thu Feb 25 15:58:30 2016 -0500 > > block/backup: avoid copying less than full target clusters > > backup to nbd target is broken, we have "Couldn't determine the cluster size of > the target image". > > Proposed NBD protocol extension - NBD_OPT_INFO should finally solve this problem. > But until it is not realized, we need allow backup to nbd target due to backward > compatibility. > > Furthermore, is it entirely ok to disallow backup if bds lacks .bdrv_get_info? > Which behavior should be default: to fail backup or to use default cluster size? > > block/backup.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/block/backup.c b/block/backup.c > index ea38733..095a390 100644 > --- a/block/backup.c > +++ b/block/backup.c > @@ -638,7 +638,10 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, > * backup cluster size is smaller than the target cluster size. Even for > * targets with a backing file, try to avoid COW if possible. */ > ret = bdrv_get_info(target, &bdi); > - if (ret < 0 && !target->backing) { > + if (ret == -ENOTSUP) { > + /* Cluster size is not defined */ > + job->cluster_size = BACKUP_CLUSTER_SIZE_DEFAULT; > + } else if (ret < 0 && !target->backing) { > error_setg_errno(errp, -ret, > "Couldn't determine the cluster size of the target image, " > "which has no backing file"); > -- > 1.8.3.1 > Target not having .bdrv_get_info means 'some sane assumptions are okay' to me, so Reviewed-by: Fam Zheng (But we are going to have a .bdrv_get_info after NBD_OPT_INFO, right?)