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Wed, 29 May 2019 11:53:04 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" References: <20190506153429.52737-1-vsementsov@virtuozzo.com> <20190506153429.52737-4-vsementsov@virtuozzo.com> <5a18f815-ed81-fd58-5f48-9ffe944f0ea4@virtuozzo.com> <3f1e1a61-41ba-cbd9-4dce-8516227336d5@redhat.com> <2a950448-96b1-e48a-684f-3c8e1bdfecf1@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: <3a1e038c-bd09-5aa2-19a3-56e2819ea01d@redhat.com> Date: Wed, 29 May 2019 13:53:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <2a950448-96b1-e48a-684f-3c8e1bdfecf1@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qb1QLDnWyOLulVQCXLvv343s3RLw19mOS" X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Wed, 29 May 2019 11:53:20 +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 X-Content-Filtered-By: Mailman/MimeDel 2.1.21 Subject: Re: [Qemu-devel] [PATCH v6 3/3] block/stream: introduce a bottom node X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "fam@euphon.net" , "kwolf@redhat.com" , "berto@igalia.com" , Denis Lunev , "wencongyang2@huawei.com" , "xiechanglong.d@gmail.com" , "stefanha@redhat.com" , Andrey Shinkevich , "jsnow@redhat.com" 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) --qb1QLDnWyOLulVQCXLvv343s3RLw19mOS From: Max Reitz To: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" Cc: "xiechanglong.d@gmail.com" , "wencongyang2@huawei.com" , "fam@euphon.net" , "stefanha@redhat.com" , "kwolf@redhat.com" , "jsnow@redhat.com" , Andrey Shinkevich , Denis Lunev , "berto@igalia.com" Message-ID: <3a1e038c-bd09-5aa2-19a3-56e2819ea01d@redhat.com> Subject: Re: [PATCH v6 3/3] block/stream: introduce a bottom node References: <20190506153429.52737-1-vsementsov@virtuozzo.com> <20190506153429.52737-4-vsementsov@virtuozzo.com> <5a18f815-ed81-fd58-5f48-9ffe944f0ea4@virtuozzo.com> <3f1e1a61-41ba-cbd9-4dce-8516227336d5@redhat.com> <2a950448-96b1-e48a-684f-3c8e1bdfecf1@virtuozzo.com> In-Reply-To: <2a950448-96b1-e48a-684f-3c8e1bdfecf1@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 29.05.19 13:44, Vladimir Sementsov-Ogievskiy wrote: > 29.05.2019 14:23, Max Reitz wrote: >> On 29.05.19 09:34, Vladimir Sementsov-Ogievskiy wrote: >>> 28.05.2019 20:33, Max Reitz wrote: >>>> On 06.05.19 17:34, Vladimir Sementsov-Ogievskiy wrote: >>>>> From: Andrey Shinkevich >>>>> >>>>> The bottom node is the intermediate block device that has the base = as its >>>>> backing image. It is used instead of the base node while a block st= ream >>>>> job is running to avoid dependency on the base that may change due = to the >>>>> parallel jobs. The change may take place due to a filter node as we= ll that >>>>> is inserted between the base and the intermediate bottom node. It o= ccurs >>>>> when the base node is the top one for another commit or stream job.= >>>>> After the introduction of the bottom node, don't freeze its backing= child, >>>>> that's the base, anymore. >>>>> >>>>> Suggested-by: Vladimir Sementsov-Ogievskiy >>>>> Signed-off-by: Andrey Shinkevich >>>>> Reviewed-by: Vladimir Sementsov-Ogievskiy >>>>> Reviewed-by: Alberto Garcia >>>>> --- >>>>> block/stream.c | 49 +++++++++++++++++++++---------------= ------ >>>>> tests/qemu-iotests/245 | 4 ++-- >>>>> 2 files changed, 27 insertions(+), 26 deletions(-) >>>>> >>>>> diff --git a/block/stream.c b/block/stream.c >>>>> index 65b13b27e0..fc97c89f81 100644 >>>>> --- a/block/stream.c >>>>> +++ b/block/stream.c >>>> >>>> [...] >>>> >>>>> @@ -248,26 +250,25 @@ void stream_start(const char *job_id, BlockDr= iverState *bs, >>>>> * already have our own plans. Also don't allow resize as th= e image size is >>>>> * queried only at the job start and then cached. */ >>>>> s =3D block_job_create(job_id, &stream_job_driver, NULL, bs,= >>>>> - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE= _UNCHANGED | >>>>> - BLK_PERM_GRAPH_MOD, >>>>> - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE= _UNCHANGED | >>>>> - BLK_PERM_WRITE, >>>>> + basic_flags | BLK_PERM_GRAPH_MOD, >>>>> + basic_flags | BLK_PERM_WRITE, >>>>> speed, creation_flags, NULL, NULL, errp= ); >>>>> if (!s) { >>>>> goto fail; >>>>> } >>>>> =20 >>>>> - /* Block all intermediate nodes between bs and base, because t= hey will >>>>> - * disappear from the chain after this operation. The streamin= g job reads >>>>> - * every block only once, assuming that it doesn't change, so = block writes >>>>> - * and resizes. */ >>>>> - for (iter =3D backing_bs(bs); iter && iter !=3D base; iter =3D= backing_bs(iter)) { >>>>> - block_job_add_bdrv(&s->common, "intermediate node", iter, = 0, >>>>> - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRI= TE_UNCHANGED, >>>>> - &error_abort); >>>>> + /* >>>>> + * Block all intermediate nodes between bs and bottom (inclusi= ve), because >>>>> + * they will disappear from the chain after this operation. Th= e streaming >>>>> + * job reads every block only once, assuming that it doesn't c= hange, so >>>>> + * forbid writes and resizes. >>>>> + */ >>>>> + for (iter =3D bs; iter !=3D bottom; iter =3D backing_bs(iter))= { >>>>> + block_job_add_bdrv(&s->common, "intermediate node", backin= g_bs(iter), >>>>> + 0, basic_flags, &error_abort); >>>> >>>> I don=E2=80=99t understand this change. Isn=E2=80=99t it doing exac= tly the same as before? >>>> >>>> (If so, I just find it harder to read because every iteration isn=E2= =80=99t >>>> about @iter but backing_bs(iter).) >>> >>> Hm, it's the same, but not using base. We may save old loop if calcul= ate base exactly before >>> the loop (or at least not separated from it by any yield-point) >> >> But we are still in stream_start() here. base cannot have changed yet= , >> can it? >> >> (I don=E2=80=99t even think this is about yield points. As long as >> stream_start() doesn=E2=80=99t return, the QMP monitor won=E2=80=99t r= eceive any new >> commands.) >> >=20 > But block graph may be modified not only from qmp. From block jobs too.= If base is another filter, it may > be dropped in any time. Ah, yes, that=E2=80=99s true. And I suppose that can happen in bdrv_reopen_set_read_only(). Hm. OK, I still don=E2=80=99t like the loop how it is currently written. May= be I=E2=80=99d like it better with s/iter/parent_bs/? Well, or you proposed would work, too, i.e. base =3D backing_bs(bottom) just before the loop =E2=80=93 with a comment that explains why we need t= hat. That=E2=80=99s probably better. Max --qb1QLDnWyOLulVQCXLvv343s3RLw19mOS Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAlzucp8ACgkQ9AfbAGHV z0DzEwf/SW5ZreKlclygwuvK9KZ+lRQ3130CpblpVgwQJnwUqkXp8XRZtmOZKXEz uKggIpbT9O733CLz+qwUeFCz8Y0nDjdSzPOEJ3rYGCIzWVRs+JOWoB+bv2Eqdy86 Foaqc6zf1lhWn4jpOuP6jbo4/O+y3C5U/i/ZvNn5PiNhrSW7YYc8qkV6MhGlGdHe OrAmQOHJDMi8xVqiNg5cwfyD6OD+2u1V4YWPTS0qKUY/JOF7DTVW/4plXi/EUOC6 MlSm7PPQSatcgPznkwkOZ2gqlVMOw6dXwbnofAmlJAKe8M5Gs2r8wyq0AggrCbWi 9y9Xr438XCVdYeIG3LnLJGeLfy4spQ== =fqu6 -----END PGP SIGNATURE----- --qb1QLDnWyOLulVQCXLvv343s3RLw19mOS--