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Thu, 13 Jun 2019 13:45:40 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.187]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4CCF4541F0; Thu, 13 Jun 2019 13:45:30 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org References: <20190529154654.95870-1-vsementsov@virtuozzo.com> <20190529154654.95870-3-vsementsov@virtuozzo.com> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Thu, 13 Jun 2019 15:45:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190529154654.95870-3-vsementsov@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="VBikqgUIMp5eS9iZMySBLyDSJ9uABLP83" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Thu, 13 Jun 2019 13:45:40 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v8 2/7] block: swap operation order in bdrv_append 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: fam@euphon.net, kwolf@redhat.com, stefanha@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --VBikqgUIMp5eS9iZMySBLyDSJ9uABLP83 Content-Type: multipart/mixed; boundary="B9JQ2dXiD0TDdJGgtq2mpVBPIemm3Z9DM"; protected-headers="v1" From: Max Reitz To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: fam@euphon.net, stefanha@redhat.com, jsnow@redhat.com, kwolf@redhat.com, den@openvz.org, eblake@redhat.com Message-ID: Subject: Re: [PATCH v8 2/7] block: swap operation order in bdrv_append References: <20190529154654.95870-1-vsementsov@virtuozzo.com> <20190529154654.95870-3-vsementsov@virtuozzo.com> In-Reply-To: <20190529154654.95870-3-vsementsov@virtuozzo.com> --B9JQ2dXiD0TDdJGgtq2mpVBPIemm3Z9DM Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 29.05.19 17:46, Vladimir Sementsov-Ogievskiy wrote: > bs_top parents may conflict with bs_new backing child permissions, so > let's do bdrv_replace_node first, it covers more possible cases. >=20 > It is needed for further implementation of backup-top filter, which > don't want to share write permission on its backing child. >=20 > Side effect is that we may set backing hd when device name is already > available, so 085 iotest output is changed. >=20 > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block.c | 11 ++++++++--- > tests/qemu-iotests/085.out | 2 +- > 2 files changed, 9 insertions(+), 4 deletions(-) >=20 > diff --git a/block.c b/block.c > index e6e9770704..57216f4115 100644 > --- a/block.c > +++ b/block.c > @@ -4088,22 +4088,27 @@ void bdrv_append(BlockDriverState *bs_new, Bloc= kDriverState *bs_top, > { > Error *local_err =3D NULL; > =20 > - bdrv_set_backing_hd(bs_new, bs_top, &local_err); > + bdrv_ref(bs_top); > + > + bdrv_replace_node(bs_top, bs_new, &local_err); > if (local_err) { > error_propagate(errp, local_err); > + error_prepend(errp, "Failed to replace node: "); > goto out; > } > =20 > - bdrv_replace_node(bs_top, bs_new, &local_err); > + bdrv_set_backing_hd(bs_new, bs_top, &local_err); > if (local_err) { > + bdrv_replace_node(bs_new, bs_top, &error_abort); Hm. I see the need for switching this stuff around, but this &error_abort is much more difficult to verify than the previous one for bdrv_set_backing_hd(..., NULL, ...). I think it at least warrants a comment why the order has to be this way (using git blame has the disadvantage of fading over time as other people modify a piece of code), and why this &error_abort is safe. Max > error_propagate(errp, local_err); > - bdrv_set_backing_hd(bs_new, NULL, &error_abort); > + error_prepend(errp, "Failed to set backing: "); > goto out; > } > =20 > /* bs_new is now referenced by its new parents, we don't need the > * additional reference any more. */ > out: > + bdrv_unref(bs_top); > bdrv_unref(bs_new); > } > =20 > diff --git a/tests/qemu-iotests/085.out b/tests/qemu-iotests/085.out > index 6edf107f55..e5a2645bf5 100644 > --- a/tests/qemu-iotests/085.out > +++ b/tests/qemu-iotests/085.out > @@ -74,7 +74,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=3DIMGFMT size=3D1= 34217728 backing_file=3DTEST_DIR/ > =20 > =3D=3D=3D Invalid command - snapshot node used as backing hd =3D=3D=3D= > =20 > -{"error": {"class": "GenericError", "desc": "Node 'snap_11' is busy: n= ode is used as backing hd of 'snap_12'"}} > +{"error": {"class": "GenericError", "desc": "Node 'snap_11' is busy: n= ode is used as backing hd of 'virtio0'"}} > =20 > =3D=3D=3D Invalid command - snapshot node has a backing image =3D=3D=3D= > =20 >=20 --B9JQ2dXiD0TDdJGgtq2mpVBPIemm3Z9DM-- --VBikqgUIMp5eS9iZMySBLyDSJ9uABLP83 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl0CU3gACgkQ9AfbAGHV z0AzAgf/QX4kOVLV81+sA+F3llCweKYZHciFDmKGQMXsemeD3gZO0kpI1eN9FZzy vrzCTvXDbggumkK20wTpETW63rO/MAAk51is6PMFFvOpbP6xoQSSqUo2bwv073kK NZWtYiNxS+/mUWG4AUSIiKgzaZMlA/qe6WwGSJijmlUA3H760F4Oqvjhpa4Y6b0E 2pf8wMCzV21EYg0iYS4LFbcfpZlXfhLai1B4x/bV6yfYBI1bw/8lX9rmmBR6AdtS eaddYkW7MRGRj3PSaJZ9dCR5bAc9hPqOxZnWzp0kasP5xrLW7dHfKVu3jYbgFcW3 Fo8bxssKVsfPf6gh3CYwPo+h1NozXg== =n/2+ -----END PGP SIGNATURE----- --VBikqgUIMp5eS9iZMySBLyDSJ9uABLP83--