From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47373) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ce30R-0007dt-OR for qemu-devel@nongnu.org; Wed, 15 Feb 2017 12:04:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ce30Q-0004S3-TD for qemu-devel@nongnu.org; Wed, 15 Feb 2017 12:04:39 -0500 Date: Wed, 15 Feb 2017 12:04:30 -0500 From: Jeff Cody Message-ID: <20170215170430.GC19045@localhost.localdomain> References: <1487170693-28224-1-git-send-email-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1487170693-28224-1-git-send-email-vsementsov@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH v3] 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, jsnow@redhat.com, famz@redhat.com, den@openvz.org, stefanha@redhat.com On Wed, Feb 15, 2017 at 05:58:13PM +0300, 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 > --- > > v3: fix compilation (I feel like an idiot) > adjust wording (Fam) > > 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. > > 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 | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/block/backup.c b/block/backup.c > index ea38733..d800a24 100644 > --- a/block/backup.c > +++ b/block/backup.c > @@ -638,7 +638,16 @@ 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 */ > + fprintf(stderr, > + "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, backup may be unusable", > + BACKUP_CLUSTER_SIZE_DEFAULT); You should use error_report, like in your v2 patch. Just make sure to include qemu/error-report.h. > + 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 >