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From:   Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>
To:     Logan Gunthorpe <logang@deltatee.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
CC:     Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
        Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Max Gurtovoy <maxg@mellanox.com>,
        Stephen Bates <sbates@raithlin.com>
Subject: Re: [PATCH v13 7/9] nvmet-passthru: Add passthru code to process
 commands
Thread-Topic: [PATCH v13 7/9] nvmet-passthru: Add passthru code to process
 commands
Thread-Index: AQHWKhRpuphoSoz88kOAfqTRprM+0g==
Date:   Thu, 11 Jun 2020 23:45:10 +0000
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References: <20200514172253.6445-1-logang@deltatee.com>
 <20200514172253.6445-8-logang@deltatee.com>
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On 5/14/20 10:23 AM, Logan Gunthorpe wrote:=0A=
> +=0A=
> +static void nvmet_passthru_execute_cmd(struct nvmet_req *req)=0A=
> +{=0A=
> +	struct nvme_ctrl *ctrl =3D nvmet_req_passthru_ctrl(req);=0A=
> +	struct nvme_ns *ns =3D NULL;=0A=
> +	struct request *rq =3D NULL;=0A=
> +	struct request_queue *q;=0A=
> +	u32 effects;=0A=
> +	u16 status;=0A=
> +	int ret;=0A=
> +=0A=
> +	if (likely(req->sq->qid !=3D 0)) {=0A=
> +		u32 nsid =3D le32_to_cpu(req->cmd->common.nsid);=0A=
> +=0A=
> +		ns =3D nvme_find_get_ns(ctrl, nsid);=0A=
> +		if (unlikely(!ns)) {=0A=
> +			pr_err("failed to get passthru ns nsid:%u\n", nsid);=0A=
> +			status =3D NVME_SC_INVALID_NS | NVME_SC_DNR;=0A=
> +			goto fail_out;=0A=
> +		}=0A=
> +	}=0A=
> +=0A=
> +	if (ns)=0A=
> +		q =3D ns->queue;=0A=
> +	else=0A=
> +		q =3D ctrl->admin_q;=0A=
=0A=
Is it possible to avoid explicit if.. else in fast path given that the=0A=
condition exists and we can take an advantage of that, how about=0A=
following ?=0A=
=0A=
diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.=
c=0A=
index 9e71fdfbdbb3..4f8e022d254c 100644=0A=
--- a/drivers/nvme/target/passthru.c=0A=
+++ b/drivers/nvme/target/passthru.c=0A=
@@ -84,9 +84,9 @@ static int nvmet_passthru_map_sg(struct nvmet_req =0A=
*req, struct request *rq)=0A=
  static void nvmet_passthru_execute_cmd(struct nvmet_req *req)=0A=
  {=0A=
         struct nvme_ctrl *ctrl =3D nvmet_req_passthru_ctrl(req);=0A=
+       struct request_queue *q =3D ctrl->admin_q;=0A=
         struct nvme_ns *ns =3D NULL;=0A=
         struct request *rq =3D NULL;=0A=
-       struct request_queue *q;=0A=
         u32 effects;=0A=
         u16 status;=0A=
         int ret;=0A=
@@ -100,12 +100,8 @@ static void nvmet_passthru_execute_cmd(struct =0A=
nvmet_req *req)=0A=
                         status =3D NVME_SC_INVALID_NS | NVME_SC_DNR;=0A=
                         goto fail_out;=0A=
                 }=0A=
-       }=0A=
-=0A=
-       if (ns)=0A=
                 q =3D ns->queue;=0A=
-       else=0A=
-               q =3D ctrl->admin_q;=0A=
+       }=0A=
=0A=
         rq =3D nvme_alloc_request(q, req->cmd, BLK_MQ_REQ_NOWAIT, =0A=
NVME_QID_ANY);=0A=
         if (IS_ERR(rq)) {=0A=
=0A=