linux-kernel - Re: [PATCH] blk-throtl: avoid double charge of bio IOPS due to split

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Date:   Mon, 10 Jan 2022 18:51:26 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     brookxu <brookxu.cn@...il.com>
Cc:     tj@...nel.org, axboe@...nel.dk, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-throtl: avoid double charge of bio IOPS due to split

Hi Chunguang,

On Mon, Jan 10, 2022 at 04:29:23PM +0800, brookxu wrote:
> From: Chunguang Xu <brookxu@...cent.com>
> 
> After commit 900e08075202("block: move queue enter logic into
> blk_mq_submit_bio()"), submit_bio_checks() moved to __submit_bio_fops()
> and blk_mq_submit_bio(). The IOs go through blk_mq_submit_bio()
> may be splited before entering blk-throtl, so we need to check
> whether the BIO is throttled, and only update the io_split_cnt
> for the THROTTLED bio to avoid double charge.

Today Jens has merged the patch[1] of "block: don't protect
submit_bio_checks by q_usage_counter", so the behavior is switched
back to previous behavior: running bio check before calling
blk_mq_submit_bio() or ->submit_bio().

Then looks your patch isn't needn't any more.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-5.17/block&id=9d497e2941c30a060ba62d5485b3bc9d91ffb09e


Thanks,
Ming