linux-kernel - Re: [PATCH] block: remove redundant req_op in blk_rq_is

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Message-ID: <41a739cb-1d17-3713-0648-1f91e2267cbc@nvidia.com>
Date:   Mon, 22 May 2023 09:31:54 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     "linan666@...weicloud.com" <linan666@...weicloud.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linan122@...wei.com" <linan122@...wei.com>,
        "yukuai3@...wei.com" <yukuai3@...wei.com>,
        "yi.zhang@...wei.com" <yi.zhang@...wei.com>,
        "houtao1@...wei.com" <houtao1@...wei.com>,
        "yangerkun@...wei.com" <yangerkun@...wei.com>
Subject: Re: [PATCH] block: remove redundant req_op in blk_rq_is_passthrough

On 5/22/23 01:53, linan666@...weicloud.com wrote:
> From: Li Nan <linan122@...wei.com>
>
> op &= REQ_OP_MASK in blk_op_is_passthrough() is exactly what req_op() do.
> Therefore, it is redundant to call req_op() for blk_op_is_passthrough().

I couldn't understand commit log, feel free to ignore following
if others are okay with it :-

req_op() returns the REQ_OP_XXX with req->cmd_flags & REQ_OP_MASKS.

blk_op_is_passthrugh() masks op with REQ_OP_MASKS to compare
REQ_OP_XXX with passthrough requests REQ_OP_IN/REQ_OP_OUT.
  245
  246 static inline bool blk_op_is_passthrough(blk_opf_t op)
  247 {
  248         op &= REQ_OP_MASK;
  249         return op == REQ_OP_DRV_IN || op == REQ_OP_DRV_OUT;
  250 }
  251

Passing req_op(rq) argument to blk_op_is_passthru() results in double
masking of request flags first in req_op() and again in
blk_op_is_passthrough().

Avoid that by passing req->cmd_flags instead of req_op(req) as
an argument to blk_op_is_passthrough() when it is called from
blk_rq_is_passthruough().


irrespective of above suggestion, looks good.

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>

-ck