linux-kernel - Re: [PATCH v6 2/2] block: cancel all throttled bios in del

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Date:   Mon, 24 Jan 2022 11:50:11 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Ming Lei <ming.lei@...hat.com>
CC:     <mkoutny@...e.com>, <paulmck@...nel.org>, <tj@...nel.org>,
        <axboe@...nel.dk>, <cgroups@...r.kernel.org>,
        <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>
Subject: Re: [PATCH v6 2/2] block: cancel all throttled bios in del_gendisk()

在 2022/01/12 11:05, Ming Lei 写道:
> Hello Yu Kuai,
> 
> On Mon, Jan 10, 2022 at 09:47:58PM +0800, Yu Kuai wrote:
>> Throttled bios can't be issued after del_gendisk() is done, thus
>> it's better to cancel them immediately rather than waiting for
>> throttle is done.
>>
>> For example, if user thread is throttled with low bps while it's
>> issuing large io, and the device is deleted. The user thread will
>> wait for a long time for io to return.
>>
>> Noted this patch is mainly from revertion of commit 32e3374304c7
>> ("blk-throttle: remove tg_drain_bios") and commit b77412372b68
>> ("blk-throttle: remove blk_throtl_drain").
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>>   block/blk-throttle.c | 77 ++++++++++++++++++++++++++++++++++++++++++++
>>   block/blk-throttle.h |  2 ++
>>   block/genhd.c        |  2 ++
>>   3 files changed, 81 insertions(+)
> 
> Just wondering why not take the built-in way in throtl_upgrade_state() for
> canceling throttled bios? Something like the following, then we can avoid
> to re-invent the wheel.

Hi, Tejun

Both ways can fix the problem, which way do you prefer?

Thanks,
Kuai