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Tue, 7 Apr 2020 11:27:19 +0000 (UTC) Subject: Re: [PATCH for-5.0 v2 2/3] block: Increase BB.in_flight for coroutine interfaces To: Kevin Wolf References: <20200406171403.6761-1-kwolf@redhat.com> <20200406171403.6761-3-kwolf@redhat.com> <5c5ee71e-f2d7-201d-73d1-2ee9a68b042a@redhat.com> <20200407111304.GD7695@linux.fritz.box> 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: <3c0ed069-7eeb-e2f1-1afb-d5690cc3cf9d@redhat.com> Date: Tue, 7 Apr 2020 13:27:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200407111304.GD7695@linux.fritz.box> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="sohvAw7ojPy96Thl8BMSwBnwbQFQExz8r" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] 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: vsementsov@virtuozzo.com, qemu-block@nongnu.org, s.reiter@proxmox.com, qemu-devel@nongnu.org, t.lamprecht@proxmox.com, stefanha@redhat.com, dietmar@proxmox.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) --sohvAw7ojPy96Thl8BMSwBnwbQFQExz8r Content-Type: multipart/mixed; boundary="LD9MDaXrh5NqYIbYVYGHF5nhiDwmGHNLh" --LD9MDaXrh5NqYIbYVYGHF5nhiDwmGHNLh Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 07.04.20 13:13, Kevin Wolf wrote: > Am 07.04.2020 um 12:15 hat Max Reitz geschrieben: >> On 07.04.20 12:04, Max Reitz wrote: >>> On 06.04.20 19:14, Kevin Wolf wrote: >>>> External callers of blk_co_*() don't currently increase the >>>> BlockBackend.in_flight counter, but calls from blk_aio_*() do, so ther= e >>>> is an inconsistency whether the counter has been increased or not. >>>> >>>> This patch moves the actual operations to static functions that can >>>> later know they will always be called with in_flight increased exactly >>>> once, even for external callers using the blk_co_*() coroutine >>>> interfaces. >>>> >>>> If the public blk_co_*() interface is unused, remove it. >>>> >>>> Signed-off-by: Kevin Wolf >>>> --- >>>> include/sysemu/block-backend.h | 1 - >>>> block/block-backend.c | 94 +++++++++++++++++++++++++++------= - >>>> 2 files changed, 76 insertions(+), 19 deletions(-) >>> >>> Reviewed-by: Max Reitz >> >> On second thought (I assumed this would be addressed by the third >> patch), blk_prw() no longer increments in_flight, but the blk_co_* >> functions do that now. In v1, blk_prw() did that. >> >> I thought we=E2=80=99d want blk_prw() to set in_flight, just like blk_ai= o_prwv() >> does, and then let the synchronous functions that use blk_prw() pass the >> blk_do_* functions to it. >=20 > Does it make a difference, though? You mean because blk_prw() has a fast path for =E2=80=9Calready in coroutin= e=E2=80=9D? Perhaps not. Still, feels a bit weird to me not to have in_flight incremented around a potential POLL loop. Maybe mostly I was wondering why v1 did and v2 didn=E2=80=99t. *shrug* Max > But the change should be easy enough (inc/dec in blk_prw() and the let > *_entry() call blk_do_*() instead of blk_co_*()) that I guess I can just > do it and send a v3. >=20 > Kevin >=20 --LD9MDaXrh5NqYIbYVYGHF5nhiDwmGHNLh-- --sohvAw7ojPy96Thl8BMSwBnwbQFQExz8r Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6MY5UACgkQ9AfbAGHV z0CREggAtMsfDlI4LP6sqasqOg2w6rVxvX8phWTym63o/YKjdmPF/weeMurSIsS0 o3cI5Ao/QfrkssNllR5oQplP+k3yZdH8NLfyoYH2qnyfc6OaKlLLZJ7MEILOU5nK e/G/6kYjjKUQfhM3gaTRcFUvry0qfYzi2/r2wXI3SKQ8Zth/ezmg3uwNwW5hjDdm cUgTRyNOvbG1D5+c1BLSWa77sieb7pbh1Gm15FLcDFtKu+/FdYHE2KNy+ZPhsNWM boB6SwEKDY8hRqNl27Z8wZvoDcqc1qXPF7Co89PQqlcjNiRnY3pkUENdJ1SiR45d Hefs6elVmJC7qslpB4FaxYNP25aNxw== =9bT4 -----END PGP SIGNATURE----- --sohvAw7ojPy96Thl8BMSwBnwbQFQExz8r--