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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: <3f1e1a61-41ba-cbd9-4dce-8516227336d5@redhat.com> Date: Wed, 29 May 2019 13:23:40 +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: <5a18f815-ed81-fd58-5f48-9ffe944f0ea4@virtuozzo.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lKz1hIAgBBTKcepYsGQPjEKA0TFNP3iMr" 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]); Wed, 29 May 2019 11:23:58 +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) --lKz1hIAgBBTKcepYsGQPjEKA0TFNP3iMr 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: <3f1e1a61-41ba-cbd9-4dce-8516227336d5@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> In-Reply-To: <5a18f815-ed81-fd58-5f48-9ffe944f0ea4@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 stre= am >>> 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 well= that >>> is inserted between the base and the intermediate bottom node. It occ= urs >>> 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 c= hild, >>> 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, BlockDriv= erState *bs, >>> * already have our own plans. Also don't allow resize as the i= mage 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_U= NCHANGED | >>> - BLK_PERM_GRAPH_MOD, >>> - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_U= NCHANGED | >>> - 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 the= y will >>> - * disappear from the chain after this operation. The streaming = job reads >>> - * every block only once, assuming that it doesn't change, so bl= ock writes >>> - * and resizes. */ >>> - for (iter =3D backing_bs(bs); iter && iter !=3D base; iter =3D b= acking_bs(iter)) { >>> - block_job_add_bdrv(&s->common, "intermediate node", iter, 0,= >>> - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE= _UNCHANGED, >>> - &error_abort); >>> + /* >>> + * Block all intermediate nodes between bs and bottom (inclusive= ), because >>> + * they will disappear from the chain after this operation. The = streaming >>> + * job reads every block only once, assuming that it doesn't cha= nge, 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", backing_= bs(iter), >>> + 0, basic_flags, &error_abort); >> >> I don=E2=80=99t understand this change. Isn=E2=80=99t it doing exactl= y 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).) >=20 > Hm, it's the same, but not using base. We may save old loop if calculat= e 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 rece= ive any new commands.) 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