From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60484) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cdgkA-00063y-LY for qemu-devel@nongnu.org; Tue, 14 Feb 2017 12:18:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cdgk9-00055O-FQ for qemu-devel@nongnu.org; Tue, 14 Feb 2017 12:18:22 -0500 References: <1487083704-51658-1-git-send-email-vsementsov@virtuozzo.com> From: John Snow Message-ID: <33339f34-9cc3-ca0c-07c1-36c18ba034d2@redhat.com> Date: Tue, 14 Feb 2017 12:18:13 -0500 MIME-Version: 1.0 In-Reply-To: <1487083704-51658-1-git-send-email-vsementsov@virtuozzo.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable 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 , qemu-block@nongnu.org, qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, jcody@redhat.com, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org On 02/14/2017 09:48 AM, Vladimir Sementsov-Ogievskiy wrote: > Currently backup to nbd target is broken, as nbd doesn't have > .bdrv_get_info realization. >=20 > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- >=20 > Hi all! >=20 > Since commit >=20 > commit 4c9bca7e39a6e07ad02c1dcde3478363344ec60b > Author: John Snow > Date: Thu Feb 25 15:58:30 2016 -0500 >=20 > block/backup: avoid copying less than full target clusters >=20 Tch. > backup to nbd target is broken, we have "Couldn't determine the cluster= size of > the target image". >=20 > Proposed NBD protocol extension - NBD_OPT_INFO should finally solve thi= s problem. > But until it is not realized, we need allow backup to nbd target due to= backward > compatibility. >=20 > Furthermore, is it entirely ok to disallow backup if bds lacks .bdrv_ge= t_info? > Which behavior should be default: to fail backup or to use default clus= ter size? >=20 > block/backup.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) >=20 > 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, Bl= ockDriverState *bs, > * backup cluster size is smaller than the target cluster size. Ev= en for > * targets with a backing file, try to avoid COW if possible. */ > ret =3D bdrv_get_info(target, &bdi); > - if (ret < 0 && !target->backing) { > + if (ret =3D=3D -ENOTSUP) { > + /* Cluster size is not defined */ > + job->cluster_size =3D BACKUP_CLUSTER_SIZE_DEFAULT; I realize this is necessary for backwards compatibility, but perhaps we need a warning message that explains why this backup *may* not be usable in the incremental/top cases. (I think none/full should be ok?) > + } 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"); >=20 --=20 =97js