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To: Nitesh Shetty Cc: Damien Le Moal , Jens Axboe , Jonathan Corbet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Keith Busch , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Alexander Viro , Christian Brauner , Jan Kara , martin.petersen@oracle.com, david@fromorbit.com, hare@suse.de, damien.lemoal@opensource.wdc.com, anuj20.g@samsung.com, joshi.k@samsung.com, nitheshshetty@gmail.com, gost.dev@samsung.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, dm-devel@lists.linux.dev, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org References: <20240520102033.9361-1-nj.shetty@samsung.com> <20240520102033.9361-3-nj.shetty@samsung.com> <20240529061736.rubnzwkkavgsgmie@nj.shetty@samsung.com> <9f1ec1c1-e1b8-48ac-b7ff-8efb806a1bc8@kernel.org> <665850bd.050a0220.a5e6b.5b72SMTPIN_ADDED_BROKEN@mx.google.com> Content-Language: en-US From: Bart Van Assche In-Reply-To: <665850bd.050a0220.a5e6b.5b72SMTPIN_ADDED_BROKEN@mx.google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240530_101130_954036_7CB6F54C X-CRM114-Status: GOOD ( 11.25 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 5/30/24 00:16, Nitesh Shetty wrote: > +static inline bool blk_copy_offload_attempt_combine(struct request_que= ue *q, > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = struct bio *bio) > +{ > +=C2=A0=C2=A0=C2=A0 struct blk_plug *plug =3D current->plug; > +=C2=A0=C2=A0=C2=A0 struct request *rq; > + > +=C2=A0=C2=A0=C2=A0 if (!plug || rq_list_empty(plug->mq_list)) > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return false; > + > +=C2=A0=C2=A0=C2=A0 rq_list_for_each(&plug->mq_list, rq) { > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (rq->q =3D=3D q) { > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if = (!blk_copy_offload_combine(rq, bio)) > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 return true; > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bre= ak; > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } > + > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Only keep iterating= plug list for combines if we have multiple > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * queues > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!plug->multiple_queues) > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bre= ak; > +=C2=A0=C2=A0=C2=A0 } > +=C2=A0=C2=A0=C2=A0 return false; > +} This new approach has the following two disadvantages: * Without plug, REQ_OP_COPY_SRC and REQ_OP_COPY_DST are not combined. The= se two operation types are the only operation types for which not using a plu= g causes an I/O failure. * A loop is required to combine the REQ_OP_COPY_SRC and REQ_OP_COPY_DST o= perations. Please switch to the approach Hannes suggested, namely bio chaining. Chai= ning REQ_OP_COPY_SRC and REQ_OP_COPY_DST bios before these are submitted elimi= nates the two disadvantages mentioned above. Thanks, Bart.