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Fri, 14 Jun 2019 16:02:24 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 74873605CA; Fri, 14 Jun 2019 16:02:21 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-15-mreitz@redhat.com> <837ee511-af51-3062-8a2e-41adde1023b3@virtuozzo.com> <616b970a-2c06-11d8-8f91-c607fd986e18@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 18:02:19 +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="m2DOqb10zjGW1N3kHJaLWfIySfUCykX0c" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Fri, 14 Jun 2019 16:02:24 +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 14/42] block: Use CAFs when working with backing chains 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) --m2DOqb10zjGW1N3kHJaLWfIySfUCykX0c Content-Type: multipart/mixed; boundary="kzgfAfa8hrRlGSmW6bnqX4uljFledJH56"; 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 14/42] block: Use CAFs when working with backing chains References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-15-mreitz@redhat.com> <837ee511-af51-3062-8a2e-41adde1023b3@virtuozzo.com> <616b970a-2c06-11d8-8f91-c607fd986e18@redhat.com> In-Reply-To: --kzgfAfa8hrRlGSmW6bnqX4uljFledJH56 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 14.06.19 16:31, Vladimir Sementsov-Ogievskiy wrote: > 14.06.2019 16:50, Max Reitz wrote: >> On 14.06.19 15:26, Vladimir Sementsov-Ogievskiy wrote: >>> 13.06.2019 1:09, Max Reitz wrote: >>>> Use child access functions when iterating through backing chains so >>>> filters do not break the chain. >>>> >>>> Signed-off-by: Max Reitz >>>> --- >>>> block.c | 40 ++++++++++++++++++++++++++++------------ >>>> 1 file changed, 28 insertions(+), 12 deletions(-) >>>> >>>> diff --git a/block.c b/block.c >>>> index 11f37983d9..505b3e9a01 100644 >>>> --- a/block.c >>>> +++ b/block.c >> >> [...] >> >>>> @@ -4273,11 +4274,18 @@ int bdrv_change_backing_file(BlockDriverStat= e *bs, >>>> BlockDriverState *bdrv_find_overlay(BlockDriverState *active, >>>> BlockDriverState *bs) >>>> { >>>> - while (active && bs !=3D backing_bs(active)) { >>>> - active =3D backing_bs(active); >>>> + bs =3D bdrv_skip_rw_filters(bs); >>>> + active =3D bdrv_skip_rw_filters(active); >>>> + >>>> + while (active) { >>>> + BlockDriverState *next =3D bdrv_backing_chain_next(active);= >>>> + if (bs =3D=3D next) { >>>> + return active; >>>> + } >>>> + active =3D next; >>>> } >>>> =20 >>>> - return active; >>>> + return NULL; >>>> } >>> >>> Semantics changed for this function. >>> It is used in two places >>> 1. from bdrv_find_base wtih @bs=3DNULL, it should be unchanged, as I = hope we will never have >>> filter node as a bottom of some valid chain >>> >>> 2. from qmp_block_commit, only to check op-blocker... hmmm. I really = don't understand, >>> why do we check BLOCK_OP_TYPE_COMMIT_TARGET on top_bs overlay.. top_b= s overlay is out of the job, >>> what is this check for? >> >> There is a loop before this check which checks that the same blocker i= s >> not set on any nodes between top and base (both inclusive). I guess >> non-active commit checks the node above @top, too, because its backing= >> file will change. >=20 > So in this case frozen chain works better. Perhaps. The op blockers are in this weird state anyway. I don=E2=80=99= t think we even need them any more, because the permissions were intended to replace them (they were originally called =E2=80=9Cfine-grained op blocke= rs=E2=80=9D, I seem to remember). I dare not touch them. >>>> /* Given a BDS, searches for the base layer. */ >> >> [...] >> >>>> @@ -5149,7 +5165,7 @@ BlockDriverState *bdrv_find_backing_image(Bloc= kDriverState *bs, >>>> char *backing_file_full_ret; >>>> =20 >>>> if (strcmp(backing_file, curr_bs->backing_file) =3D=3D= 0) { >>> >>> hmm, interesting, what bs->backing_file now means? It's strange enoug= h to store such field on >>> bds, when we have backing link anyway.. >> >> Patch 37 has you covered. :-) >> >=20 > Hmm, if it has removed this field, but it doesn't) Because it=E2=80=99s needed. (Just not in the current form, but that=E2=80= =99s what 37 is for.) > So, we finished with some object, called "overlay", but it is not an ov= erlay of bs, it's overlay of > first non-implicit filtered node in bs backing chain, it may be found b= y bdrv_find_overlay() helper (which is > almost unused and my be safely dropped), and filename of this "overlay"= is stored in bs->backing_file string > variable, keeping in mind that bs->backing is pointer to backing child = of bs which is completely another thing? I don=E2=80=99t quite see what you mean. There is no =E2=80=9Coverlay=E2= =80=9D in this function. > Oh, no, everything related to filename-based backing chain logic is not= for me o_O. If something doesn't work > with filename-based logic users should use node-names.. In theory yes, but that isn=E2=80=99t an option for qemu-img commit, for = example. > And I'd prefer to deprecate filename based interfaces at all. Me too. https://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg04878.html :-/ Max --kzgfAfa8hrRlGSmW6bnqX4uljFledJH56-- --m2DOqb10zjGW1N3kHJaLWfIySfUCykX0c Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl0DxQsACgkQ9AfbAGHV z0BrdwgAv9CqLmG/eeDoX/mxJxNK2xMFfOlFS+L7hrtRx79IHZWWB54EGiy7wmS6 tsuSxQm4yf8VR0Q7KFzC5LvjJnErVWOVVXLloFJ5OBuxHRbMvNF+S6oqp3bR8YDo qcffxuBEOQC3x1Lg5QnP7VzERIDTsVPmSnxx+XYqBL4UJZJmeTE5sB96U4EFAp8H iqh57cfvid9KRHkdcDiPrvX6MNXpdB317SPQzsn3f9Z70kIGeogy1YMrm/mTtXRq rtZqw+s+4pqlSFT1+0gpwmO798lDL9UWAiQDF44lTTo+mFMBsO3vJgtI7uGdAzMe Pc/a/8NpDJgWrc+fNpgZTaL0x+tKuQ== =BqB8 -----END PGP SIGNATURE----- --m2DOqb10zjGW1N3kHJaLWfIySfUCykX0c--