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Fri, 29 Nov 2019 10:23:51 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-206-40.brq.redhat.com [10.40.206.40]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CBABF19C4F; Fri, 29 Nov 2019 10:23:49 +0000 (UTC) Subject: Re: [PATCH for-5.0 v2 06/23] block: Add bdrv_recurse_can_replace() To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20191111160216.197086-1-mreitz@redhat.com> <20191111160216.197086-7-mreitz@redhat.com> <5370cd61-413a-0208-541c-49894ad0c630@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: Date: Fri, 29 Nov 2019 11:23:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <5370cd61-413a-0208-541c-49894ad0c630@virtuozzo.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="VybphVaT0HhmcYlCTJPgfN43ZhFoLxlsx" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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) --VybphVaT0HhmcYlCTJPgfN43ZhFoLxlsx Content-Type: multipart/mixed; boundary="b6h5Pviy6scTzhRnfLSn32gQwp1sG6M1W" --b6h5Pviy6scTzhRnfLSn32gQwp1sG6M1W Content-Type: text/plain; charset=WINDOWS-1252 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 29.11.19 10:34, Vladimir Sementsov-Ogievskiy wrote: > 11.11.2019 19:01, 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 for >> check_to_replace_node() (it allows cases that should not be allowed, >> like replacing child nodes of quorum with dissenting data that have more >> parents than just quorum), and it is too restrictive (it is perfectly >> fine to replace filters). >> >> Signed-off-by: Max Reitz >> --- >> block.c | 38 ++++++++++++++++++++++++++++++++++++++ >> include/block/block_int.h | 10 ++++++++++ >> 2 files changed, 48 insertions(+) >> >> diff --git a/block.c b/block.c >> index 9b1049786a..de53addeb0 100644 >> --- a/block.c >> +++ b/block.c >> @@ -6205,6 +6205,44 @@ bool bdrv_recurse_is_first_non_filter(BlockDriver= State *bs, >> return false; >> } >> =20 >> +/* >> + * This function checks whether the given @to_replace is allowed to be >> + * replaced by a node that always shows the same data as @bs. This is >> + * 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 other >> + * 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; >> + } >> + >> + /* See what the driver can do */ >> + if (bs->drv->bdrv_recurse_can_replace) { >> + return bs->drv->bdrv_recurse_can_replace(bs, to_replace); >> + } >> + >> + /* For filters without an own implementation, we can recurse on our= own */ >> + if (bs->drv->is_filter) { >> + BdrvChild *child =3D bs->file ?: bs->backing; >=20 > should we check that child !=3D NULL ? I=92d say that normally (once they are open) filters must have a child, and so I=92d make it an assertion. But then again an assertion isn=92t muc= h better than the dereferencing that follows, I think. :? Max >> + return bdrv_recurse_can_replace(child->bs, to_replace); >> + } >> + >> + /* Safe default */ >> + return false; >> +} >> + >> BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs, >> const char *node_name, Error *= *errp) >> { >> diff --git a/include/block/block_int.h b/include/block/block_int.h >> index dd033d0b37..75f03dcc38 100644 >> --- a/include/block/block_int.h >> +++ b/include/block/block_int.h >> @@ -102,6 +102,13 @@ struct BlockDriver { >> */ >> bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs, >> BlockDriverState *candida= te); >> + /* >> + * 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 *fi= lename); >> int (*bdrv_probe_device)(const char *filename); >> @@ -1264,6 +1271,9 @@ void bdrv_format_default_perms(BlockDriverState *b= s, 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() t= o >> * their file. >> >=20 >=20 --b6h5Pviy6scTzhRnfLSn32gQwp1sG6M1W-- --VybphVaT0HhmcYlCTJPgfN43ZhFoLxlsx Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl3g8bMACgkQ9AfbAGHV z0A+LQf/Ztu5DPdEOjUvyTjc4OnjaAtEvjQHhjvTleY/lN7XY/tYe8tygvrnNIuR 3sI4W8OWLMc4pM3g62NXGgtWYWQl+7eZi6nX2hw5Qzu51T2kffBrrM9uZQH1+5s0 ocvjEY97FQAH8c+iD1gda25Sx1ra+aVzZJyQF4kjJJiFFkKccfhw8/LP6x4lqDFg lm9rAkbXb6P/9dxZEhky59h5sQwPFRNWI6Bqu2WGwadKV2vndBzhKwwZP80jA8QE 8Exci/TSDCJAZ3EzJdqnWTyMamyDo8bTgDDSZ59BlS67EPBNnZlwG/i9qZSE9xhB N4+SlDmQqKM27bGzqEOUqDzMcmoO4w== =Y0Id -----END PGP SIGNATURE----- --VybphVaT0HhmcYlCTJPgfN43ZhFoLxlsx--