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Date: Thu, 13 Oct 2022 21:22:41 +0800 From: Yu Kuai <yukuai1@...weicloud.com> To: 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] blk-mq: put the reference of the io scheduler module after switching back Hi, 在 2022/10/13 21:03, Jinlong Chen 写道: > Sorry for the disturbance. > > This patch is just wrong. elevator_switch_mq does not increase the reference > count of the io scheduler module to which we are switching. Hence, we do not > need to put the reference back manually. I'm confused here, cause I do think this patch make sense. blk_mq_update_nr_hw_queues // for each queue using the tagset blk_mq_freeze_queue // if current elevator is not none, swith to none blk_mq_elv_switch_none // elevator need to be switched back, got a reference to // prevent module to be removed. __module_get elevator_switch(q, NULL); // switch back from none elevator blk_mq_elv_switch_back -> should release the module reference here blk_mq_unfreeze_queue By the way, I do not test yet, but I think problem can be reporduced: 1. modprobe bfq 2. switch elevator to bfq 3. trigger blk_mq_update_nr_hw_queues 4. switch elevator to none 5. rmmod bfq will fail Thanks, Kuai > > Sincerely > Jinlong Chen > . >
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