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Thu, 26 Sep 2019 11:03:58 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.151]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9E0846CE40; Thu, 26 Sep 2019 11:03:56 +0000 (UTC) Subject: Re: [PATCH 06/22] block: Add bdrv_recurse_can_replace() To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20190920152804.12875-1-mreitz@redhat.com> <20190920152804.12875-7-mreitz@redhat.com> <37b5883c-b4e9-4b9d-fae4-8a1f0b04cd54@virtuozzo.com> From: Max Reitz 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: <3cdf9ba3-d79c-b62b-cccf-3fd444c0e252@redhat.com> Date: Thu, 26 Sep 2019 13:03:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <37b5883c-b4e9-4b9d-fae4-8a1f0b04cd54@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="pdYScZK8JiNDa2ipGbmGD3v75iI6BkysL" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.71]); Thu, 26 Sep 2019 11:03:58 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 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 , Alberto Garcia , "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) --pdYScZK8JiNDa2ipGbmGD3v75iI6BkysL Content-Type: multipart/mixed; boundary="1xh6BKN9IhAqShQl3luLDb2P4Qdjgb1KL" --1xh6BKN9IhAqShQl3luLDb2P4Qdjgb1KL Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 25.09.19 14:39, Vladimir Sementsov-Ogievskiy wrote: > 20.09.2019 18:27, Max Reitz wrote: >> After a couple of follow-up patches, this function will replace >> bdrv_recurse_is_first_non_filter() in check_to_replace_node(). >> >> bdrv_recurse_is_first_non_filter() is both not sufficiently specific f= or >> check_to_replace_node() (it allows cases that should not be allowed, >> like replacing child nodes of quorum with dissenting data that have mo= re >> parents than just quorum), and it is too restrictive (it is perfectly >> fine to replace filters). >> >> Signed-off-by: Max Reitz >> --- >> include/block/block_int.h | 10 ++++++++++ >> block.c | 38 +++++++++++++++++++++++++++++++++++++= + >> 2 files changed, 48 insertions(+) >> >> diff --git a/include/block/block_int.h b/include/block/block_int.h >> index 5fd4f17d93..0be7d12f04 100644 >> --- a/include/block/block_int.h >> +++ b/include/block/block_int.h >> @@ -103,6 +103,13 @@ struct BlockDriver { >> */ >> bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs, >> BlockDriverState *candi= date); >> + /* >> + * Return true if @to_replace can be replaced by a BDS with the >> + * same data as @bs without it affecting @bs's behavior (that is,= >> + * without it being visible to @bs's parents). >> + */ >> + bool (*bdrv_recurse_can_replace)(BlockDriverState *bs, >> + BlockDriverState *to_replace); >> =20 >> int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *= filename); >> int (*bdrv_probe_device)(const char *filename); >> @@ -1254,6 +1261,9 @@ void bdrv_format_default_perms(BlockDriverState = *bs, BdrvChild *c, >> uint64_t perm, uint64_t shared, >> uint64_t *nperm, uint64_t *nshared); >> =20 >> +bool bdrv_recurse_can_replace(BlockDriverState *bs, >> + BlockDriverState *to_replace); >> + >> /* >> * Default implementation for drivers to pass bdrv_co_block_status()= to >> * their file. >> diff --git a/block.c b/block.c >> index 7d99ca692c..a2deca4ac9 100644 >> --- a/block.c >> +++ b/block.c >> @@ -6206,6 +6206,44 @@ bool bdrv_recurse_is_first_non_filter(BlockDriv= erState *bs, >> return false; >> } >> =20 >> +/* >> + * This function checks whether the given @to_replace is allowed to b= e >> + * replaced by a node that always shows the same data as @bs. This i= s >> + * used for example to verify whether the mirror job can replace >> + * @to_replace by the target mirrored from @bs. >> + * To be replaceable, @bs and @to_replace may either be guaranteed to= >> + * always show the same data (because they are only connected through= >> + * filters), or some driver may allow replacing one of its children >> + * because it can guarantee that this child's data is not visible at >> + * all (for example, for dissenting quorum children that have no othe= r >> + * parents). >> + */ >> +bool bdrv_recurse_can_replace(BlockDriverState *bs, >> + BlockDriverState *to_replace) >> +{ >> + if (!bs || !bs->drv) { >> + return false; >> + } >> + >> + if (bs =3D=3D to_replace) { >> + return true; >> + } >> + >> + /* For filters, we can recurse on our own */ >> + if (bs->drv->is_filter) { >> + BdrvChild *child =3D bs->file ?: bs->backing; >=20 > then, maybe asset(!bs->drv->bdrv_recurse_can_replace) It=E2=80=99s actually the other way around. As you find yourself, blkver= ify is a filter and has its own implementation. That is entirely correct because we cannot recurse to just bs->file in blkverify's case. So we should first invoke the driver-specific function, and then have the generic filter code. Max >> + return bdrv_recurse_can_replace(child->bs, to_replace); >> + } >=20 > or, this may be filter-skipping loop instead of recursion, like >=20 > while (bs && bs->drv && bs->drv->is_filter) { > bs =3D (bs->file ?: bs->backing)->bs; > } >=20 > at function start. >=20 > either way: >=20 > Reviewed-by: Vladimir Sementsov-Ogievskiy >=20 >> + >> + /* See what the driver can do */ >> + if (bs->drv->bdrv_recurse_can_replace) { >> + return bs->drv->bdrv_recurse_can_replace(bs, to_replace); >> + } >> + >> + /* Safe default */ >> + return false; >> +} >> + >> BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,= >> const char *node_name, Error= **errp) >> { >> >=20 >=20 --1xh6BKN9IhAqShQl3luLDb2P4Qdjgb1KL-- --pdYScZK8JiNDa2ipGbmGD3v75iI6BkysL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEyBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl2MmxsACgkQ9AfbAGHV z0DW8Af4tvgpUvfJ8qrXU1MCLnrXF0WqVQY1s9ZmFZlddHD4lqOrgstXs0tDXS9x 41HrdcpTQfIQUGkAEu3En3KOK5btP4sPVZhN3ydYifbiTyrsbaAJXlQz1u9n/zNz b5awGZmSKSGTbl2CYEHdR9IvSWKcNwhXgt2+B6mfYNA5ODUCYMRK+duWL1/z2Tf2 n2vC8Q9lODZi64T/CSM8OaIoSVZeO7LjXFmuarAg0TVIu3uhZBRM/Dyx198t5mpS P3LdPkf68lyufzwfObDnuGtD1JEEsGKkpnouwOlLPl1VDcoC6q2T5ZtbVqcimXgV f3CluiZd+8Y4HGpvCXEas2Vx9CIR =4kmX -----END PGP SIGNATURE----- --pdYScZK8JiNDa2ipGbmGD3v75iI6BkysL--