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Fri, 14 Jun 2019 16:10:38 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0868A17F51; Fri, 14 Jun 2019 16:10:36 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-21-mreitz@redhat.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: Fri, 14 Jun 2019 18:10:35 +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: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ctcaaKpKA8YYOxM1TYGpilOAkU9QXaJNW" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 14 Jun 2019 16:10:38 +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 v5 20/42] block/snapshot: Fall back to storage child 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: Kevin Wolf , "qemu-devel@nongnu.org" 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) --ctcaaKpKA8YYOxM1TYGpilOAkU9QXaJNW Content-Type: multipart/mixed; boundary="kUEaJo29yHoS4aalAe0IC9cmD2UQ8ZUQ6"; protected-headers="v1" From: Max Reitz To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" Cc: "qemu-devel@nongnu.org" , Kevin Wolf Message-ID: Subject: Re: [PATCH v5 20/42] block/snapshot: Fall back to storage child References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-21-mreitz@redhat.com> In-Reply-To: --kUEaJo29yHoS4aalAe0IC9cmD2UQ8ZUQ6 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 14.06.19 17:22, Vladimir Sementsov-Ogievskiy wrote: > 13.06.2019 1:09, Max Reitz wrote: >> If the top node's driver does not provide snapshot functionality and w= e >> want to go down the chain, we should go towards the child which stores= >> the data, i.e. the storage child. >> >> bdrv_snapshot_goto() becomes a bit weird because we may have to redire= ct >> the actual child pointer, so it only works if the storage child is >> bs->file or bs->backing (and then we have to find out which it is). >> >> Signed-off-by: Max Reitz >> --- >> block/snapshot.c | 74 ++++++++++++++++++++++++++++++++++------------= -- >> 1 file changed, 53 insertions(+), 21 deletions(-) >> >> diff --git a/block/snapshot.c b/block/snapshot.c >> index f2f48f926a..58cd667f3a 100644 >> --- a/block/snapshot.c >> +++ b/block/snapshot.c >> @@ -154,8 +154,9 @@ int bdrv_can_snapshot(BlockDriverState *bs) >> } >> =20 >> if (!drv->bdrv_snapshot_create) { >> - if (bs->file !=3D NULL) { >> - return bdrv_can_snapshot(bs->file->bs); >> + BlockDriverState *storage_bs =3D bdrv_storage_bs(bs); >> + if (storage_bs) { >> + return bdrv_can_snapshot(storage_bs); >> } >> return 0; >> } >=20 > Hmm is it correct at all doing a snapshot, when top format node doesn't= support it, > metadata child doesn't support it and storage child supports? Doing sna= pshots of > storage child seems useless, as data file must be in sync with metadata= =2E You=E2=80=99re right. That=E2=80=99s actually a bug already. VMDK can store data in multiple children, but it does not support snapshots. So if you store such a split VMDK disk on an RBD volume, it is possible that just the descriptor file is snapshotted, but nothing else. Hmmm. I think the best way is to check whether there is exactly one child that is not the bdrv_filtered_cow_child(). If so, we can go down to it and snapshot it. Otherwise, the node does not support snapshots. Max --kUEaJo29yHoS4aalAe0IC9cmD2UQ8ZUQ6-- --ctcaaKpKA8YYOxM1TYGpilOAkU9QXaJNW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl0DxvsACgkQ9AfbAGHV z0CrOAf+OBUyvgVlN40IW1njIOGrPouBI7ulsvvNU1YNGz/0FQDWBgux1dCDSDOz Tdr1om+rJiKbzpvKG4iLqj6MThQxvOMv6+/+kBShvY3M9Ae2C1wybW58ugmum8DF Ap87m1fTkC/WinpYKC/qz+mPOtw38+SiMSWh9nVMzgl0iu0oGYPY/1X9lhNmolm2 1cBW7lKYmXevVjy16iPFE+UAlzrJTHb9TFgbgBMvRR2fyrzJtXLGxC0jLvKQ3vio s1EAilc27EW30qIOma3JCUoYnk9OHJ75ixOIizgTqJikvB03seIUbZRtFiD0r6xO ENz0uos0JKH1haC2HyZkU6/SKXu97A== =ViG+ -----END PGP SIGNATURE----- --ctcaaKpKA8YYOxM1TYGpilOAkU9QXaJNW--