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Wed, 19 Jun 2019 15:59:05 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-116-121.ams2.redhat.com [10.36.116.121]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 66D4F60DDF; Wed, 19 Jun 2019 15:59:02 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-34-mreitz@redhat.com> <2670e61d-6c9b-9499-8e41-01c294379e47@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: <761c245d-3bb3-5fb3-21e4-0085caaffd2a@redhat.com> Date: Wed, 19 Jun 2019 17:59:00 +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: <2670e61d-6c9b-9499-8e41-01c294379e47@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TMm68YVbdx51DVC82A4rsXB1gYYFOtHhW" 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 [10.5.110.38]); Wed, 19 Jun 2019 15:59:12 +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 33/42] blockdev: Fix active commit choice 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) --TMm68YVbdx51DVC82A4rsXB1gYYFOtHhW Content-Type: multipart/mixed; boundary="u8O6Uywk09yJb06jfYQujAKRWbkmfYvvi"; protected-headers="v1" From: Max Reitz To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" Cc: "qemu-devel@nongnu.org" , Kevin Wolf Message-ID: <761c245d-3bb3-5fb3-21e4-0085caaffd2a@redhat.com> Subject: Re: [PATCH v5 33/42] blockdev: Fix active commit choice References: <20190612221004.2317-1-mreitz@redhat.com> <20190612221004.2317-34-mreitz@redhat.com> <2670e61d-6c9b-9499-8e41-01c294379e47@virtuozzo.com> In-Reply-To: <2670e61d-6c9b-9499-8e41-01c294379e47@virtuozzo.com> --u8O6Uywk09yJb06jfYQujAKRWbkmfYvvi Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 19.06.19 11:31, Vladimir Sementsov-Ogievskiy wrote: > 13.06.2019 1:09, Max Reitz wrote: >> We have to perform an active commit whenever the top node has a parent= >> that has taken the WRITE permission on it. >> >> Signed-off-by: Max Reitz >> --- >> blockdev.c | 24 +++++++++++++++++++++--- >> 1 file changed, 21 insertions(+), 3 deletions(-) >> >> diff --git a/blockdev.c b/blockdev.c >> index a464cabf9e..5370f3b738 100644 >> --- a/blockdev.c >> +++ b/blockdev.c >> @@ -3294,6 +3294,7 @@ void qmp_block_commit(bool has_job_id, const cha= r *job_id, const char *device, >> */ >> BlockdevOnError on_error =3D BLOCKDEV_ON_ERROR_REPORT; >> int job_flags =3D JOB_DEFAULT; >> + uint64_t top_perm, top_shared; >> =20 >> if (!has_speed) { >> speed =3D 0; >> @@ -3406,14 +3407,31 @@ void qmp_block_commit(bool has_job_id, const c= har *job_id, const char *device, >> goto out; >> } >> =20 >> - if (top_bs =3D=3D bs) { >> + /* >> + * Active commit is required if and only if someone has taken a >> + * WRITE permission on the top node. Historically, we have alway= s >> + * used active commit for top nodes, so continue that practice. >> + * (Active commit is never really wrong.) >=20 > Hmm, if we start active commit when nobody has write access, than > we leave a possibility to someone to get this access during commit. Isn=E2=80=99t that blocked by the commit filter? If it isn=E2=80=99t, it= should be. > And during > passive commit write access is blocked. So, may be right way is do acti= ve commit > always? Benefits: > 1. One code path. and it shouldn't be worse when no writers, without gu= est writes > mirror code shouldn't work worse than passive commit, if it is, it shou= ld be fixed. > 2. Possibility of write access if user needs it during commit > 3. I'm sure that active commit (mirror code) actually works faster, as = it uses > async requests and smarter handling of block status. Disadvantage: Something may break because the basic commit job does not emit BLOCK_JOB_READY and thus does not require block-job-complete. Technically everything should expect jobs to potentially emit BLOCK_JOB_READY, but who knows. I think we=E2=80=99d want at least a deprecation period. Max >> + */ >> + bdrv_get_cumulative_perm(top_bs, &top_perm, &top_shared); >> + if (top_perm & BLK_PERM_WRITE || >> + bdrv_skip_rw_filters(top_bs) =3D=3D bdrv_skip_rw_filters(bs))= >> + { >> if (has_backing_file) { >> error_setg(errp, "'backing-file' specified," >> " but 'top' is the active layer"); >> goto out; >> } >> - commit_active_start(has_job_id ? job_id : NULL, bs, base_bs, >> - job_flags, speed, on_error, >> + if (!has_job_id) { >> + /* >> + * Emulate here what block_job_create() does, because it >> + * is possible that @bs !=3D @top_bs (the block job shoul= d >> + * be named after @bs, even if @top_bs is the actual >> + * source) >> + */ >> + job_id =3D bdrv_get_device_name(bs); >> + } >> + commit_active_start(job_id, top_bs, base_bs, job_flags, speed= , on_error, >> filter_node_name, NULL, NULL, false, &lo= cal_err); >> } else { >> BlockDriverState *overlay_bs =3D bdrv_find_overlay(bs, top_b= s); >> >=20 >=20 --u8O6Uywk09yJb06jfYQujAKRWbkmfYvvi-- --TMm68YVbdx51DVC82A4rsXB1gYYFOtHhW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl0KW8UACgkQ9AfbAGHV z0BBfQf+OViWz5s7I7NvMQhk+Vk+jyQ7tDQ8oBqg3I5DT14trM9uFAQ3z74I5A06 73hh0sqMAbpCs06KraxK/NH2kJRLBJLi7iX6JM5QIi8/3nerCMY2m36Dd3MkFCSw 57UJaHhh3DK/9wfqVBC3Igj81J08mUpUl/PpfRWyI4e0xCkHERkTqJ5Jq+RGke5l ZTLjDeAYBvYY+4VzgdU8qU57FW3dlMsXBbqihVrpMhVQOACQnGIuYU/MfZwcLZd5 JhXbpEPNbX732t488t36wSAv44C8lRieSmfRVJxMkjBJpBXerkuVEB7JAOUmypMx STnBQHM1WG08KhuGvTXkBxfuoY+6sg== =Z9j7 -----END PGP SIGNATURE----- --TMm68YVbdx51DVC82A4rsXB1gYYFOtHhW--