From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cdyG1-0000ZR-BN for qemu-devel@nongnu.org; Wed, 15 Feb 2017 07:00:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cdyG0-0008BN-E5 for qemu-devel@nongnu.org; Wed, 15 Feb 2017 07:00:25 -0500 Date: Wed, 15 Feb 2017 20:00:15 +0800 From: Fam Zheng Message-ID: <20170215120015.GC1134@lemon.lan> References: <1487156985-18321-1-git-send-email-vsementsov@virtuozzo.com> <20170215113324.GA1134@lemon.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v2] 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 Wed, 02/15 14:42, Vladimir Sementsov-Ogievskiy wrote: > 15.02.2017 14:33, Fam Zheng wrote: > > On Wed, 02/15 14:09, 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 > > > --- > > > > > > v2: add WARNING > > > > > > === > > > > > > 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. > > If you respin, including above in the commit message is even better, IMO. > > > > > 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 | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/block/backup.c b/block/backup.c > > > index ea38733..a464b63 100644 > > > --- a/block/backup.c > > > +++ b/block/backup.c > > > @@ -638,7 +638,15 @@ 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 */ > > > + error_report("WARNING: Target block device doesn't provide information " > > > + "about block size and it doesn't have backing file. " > > > + "Default block size of %u bytes is used. If actual block " > > > + "size of target exceeds this default, destination image " > > > + "may become unusable"); > > "Image unusable" might be too strong here because it sounds like a serious > > damage to the image, while actually what we mean is "backup unusable". > > Finally, "... default, backup may be unusable"? Yes, looks good. Fam