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Tue, 12 May 2020 18:48:07 +0000 (UTC) Date: Tue, 12 May 2020 20:48:04 +0200 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v2 3/4] mirror: Make sure that source and target size match Message-ID: <20200512184804.GL5951@linux.fritz.box> References: <20200511135825.219437-1-kwolf@redhat.com> <20200511135825.219437-4-kwolf@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=kwolf@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/12 14:17:24 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jsnow@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 12.05.2020 um 19:15 hat Vladimir Sementsov-Ogievskiy geschrieben: > 11.05.2020 16:58, Kevin Wolf wrote: > > If the target is shorter than the source, mirror would copy data until > > it reaches the end of the target and then fail with an I/O error when > > trying to write past the end. > > > > If the target is longer than the source, the mirror job would complete > > successfully, but the target wouldn't actually be an accurate copy of > > the source image (it would contain some additional garbage at the end). > > > > Fix this by checking that both images have the same size when the job > > starts. > > > > Signed-off-by: Kevin Wolf > > Message-Id: <20200507145228.323412-3-kwolf@redhat.com> > > Reviewed-by: Eric Blake > > Signed-off-by: Kevin Wolf > > --- > > block/mirror.c | 21 ++++++++++++--------- > > 1 file changed, 12 insertions(+), 9 deletions(-) > > > > diff --git a/block/mirror.c b/block/mirror.c > > index aca95c9bc9..201ffa26f9 100644 > > --- a/block/mirror.c > > +++ b/block/mirror.c > > @@ -872,6 +872,7 @@ static int coroutine_fn mirror_run(Job *job, Error **errp) > > BlockDriverState *target_bs = blk_bs(s->target); > > bool need_drain = true; > > int64_t length; > > + int64_t target_length; > > BlockDriverInfo bdi; > > char backing_filename[2]; /* we only need 2 characters because we are only > > checking for a NULL string */ > > @@ -887,24 +888,26 @@ static int coroutine_fn mirror_run(Job *job, Error **errp) > > goto immediate_exit; > > } > > + target_length = blk_getlength(s->target); > > + if (target_length < 0) { > > + ret = target_length; > > + goto immediate_exit; > > + } > > + > > /* Active commit must resize the base image if its size differs from the > > * active layer. */ > > if (s->base == blk_bs(s->target)) { > > - int64_t base_length; > > - > > - base_length = blk_getlength(s->target); > > - if (base_length < 0) { > > - ret = base_length; > > - goto immediate_exit; > > - } > > - > > - if (s->bdev_length > base_length) { > > + if (s->bdev_length > target_length) { > > ret = blk_truncate(s->target, s->bdev_length, false, > > PREALLOC_MODE_OFF, 0, NULL); > > if (ret < 0) { > > goto immediate_exit; > > } > > } > > Hmm, interesting, if base is larger, is our behavior correct? Blockdev > becomes larger after commit and old data becomes available? I think we > should zero the tail after old EOF or shrink the target.. Yes, I agree, we should shrink it. But active commit is a different case than what I'm fixing in this patch, so I left it unmodified. We'll probably need a third series for commit after backup and mirror. > > + } else if (s->bdev_length != target_length) { > > + error_setg(errp, "Source and target image have different sizes"); > > + ret = -EINVAL; > > Seems, the only case, when mirror_run() sets errp. And, therefore, the > only correct one.. job_update_rc() takes care to fill job->err (with strerror()) if it hasn't been set yet, so the other places aren't strictly wrong, but probably provide suboptimal error messages. Kevin