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Message-ID: <7f6cb343-bf97-c73a-c3da-c22d7543bd4a@huaweicloud.com>
Date: Tue, 11 Oct 2022 20:59:34 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Yu Kuai <yukuai1@...weicloud.com>,
Jinlong Chen <chenjinlong2016@...look.com>, axboe@...nel.dk
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
"yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block: put the reference of the io scheduler module after
switching back
Hi!
在 2022/10/11 20:54, Yu Kuai 写道:
> Hi!
>
> 在 2022/10/11 18:21, Jinlong Chen 写道:
>> We got a reference of the io scheduler module in
>> blk_mq_elv_switch_none to prevent the module from
>> being removed. We need to put that reference back
>> once we are done.
>
> However, if blk_mq_elv_switch_none() failed due to OOM, and module
> reference is not acquired, blk_mq_elv_switch_back() will still be
> called. This seems not to be the right fix.
Please ignore this.
I got it now if switch none failed, old queue is not added to the list,
and later blk_lookup_qe_pair() will fail to lookup the queue.
Thanks,
Kuai
>
> Thanks,
> Kuai
>>
>> Signed-off-by: Jinlong Chen <chenjinlong2016@...look.com>
>> ---
>> block/blk-mq.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 8070b6c10e8d..8dfe3bf3e599 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -4595,6 +4595,13 @@ static void blk_mq_elv_switch_back(struct
>> list_head *head,
>> mutex_lock(&q->sysfs_lock);
>> elevator_switch(q, t);
>> + /**
>> + * We got a reference of the io scheduler module in
>> + * blk_mq_elv_switch_none to prevent the module from
>> + * being removed. We need to put that reference back
>> + * once we are done.
>> + */
>> + module_put(t->elevator_owner);
>> mutex_unlock(&q->sysfs_lock);
>> }
>>
>
> .
>
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