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envelope-from=den@virtuozzo.com; helo=EUR04-HE1-obe.outbound.protection.outlook.com X-Spam_score_int: -51 X-Spam_score: -5.2 X-Spam_bar: ----- X-Spam_report: (-5.2 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-3.058, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/30/23 22:31, Mike Maslenkin wrote: > Add a check that destination file exists and do not call bdrv_create for > this case. > > Currently `qemu-img dd` command destroys content of destination file. > Effectively this means that parameters (geometry) of destination image > file are changing. This can be undesirable behavior for user especially > if format of destination image does not support resizing. > > Steps to reproduce: > 1. Create empty disk image with some non default size. > `qemu-img create -f qcow2 $DEST_IMG 3T` > Remember that `qemu-img info $DEST_IMG` returns: > virtual size: 3 TiB (3298534883328 bytes) > disk size: 240 KiB > cluster_size: 65536 > 2. Run `qemu-img dd -O qcow2 of=$DEST_IMG if=$SRC_IMG bs=1M count=100` > 3. Check `qemu-img info $DEST_IMG` output: > virtual size: 100 MiB (104857600 bytes) > disk size: 112 MiB > cluster_size: 65536 > > Parameters of $DEST_IMG were changed. Actually `qemu-img dd` has created > a new disk based on current default geometry for particular format. > For example for "parallels" format default BAT for 256GB disk is written > to empty file prior writing disk image data. > > With this patch virtual disk metadata and geometry of a destination image > are preserved. As another visible change of `qemu-img dd` behavior is that > if destination image is less than source it can finish with error (similar > to "dd" utility): > qemu-img: error while writing to output image file: Input/output error > > Signed-off-by: Mike Maslenkin > --- > diff from v1: removed additional fprintf call leaved in patch by accident > --- > qemu-img.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/qemu-img.c b/qemu-img.c > index a48edb71015c..1a83c14212fb 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -5150,13 +5150,15 @@ static int img_dd(int argc, char **argv) > size - in.bsz * in.offset, &error_abort); > } > > - ret = bdrv_create(drv, out.filename, opts, &local_err); > - if (ret < 0) { > - error_reportf_err(local_err, > - "%s: error while creating output image: ", > - out.filename); > - ret = -1; > - goto out; > + if (!g_file_test(out.filename, G_FILE_TEST_EXISTS)) { > + ret = bdrv_create(drv, out.filename, opts, &local_err); > + if (ret < 0) { > + error_reportf_err(local_err, > + "%s: error while creating output image: ", > + out.filename); > + ret = -1; > + goto out; > + } > } > > /* TODO, we can't honour --image-opts for the target, may be it would be worth to follow conventional 'dd' approach, i.e. add conv=nocreat option which will do the trick? Den