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From: Ming Lei <ming.lei@redhat.com>
To: Nilay Shroff <nilay@linux.ibm.com>
Cc: linux-block@vger.kernel.org, axboe@kernel.dk,
	yukuai1@huaweicloud.com, hch@lst.de, shinichiro.kawasaki@wdc.com,
	kch@nvidia.com, gjoyce@ibm.com
Subject: Re: [PATCHv3 2/3] block: decrement block_rq_qos static key in rq_qos_del()
Date: Thu, 14 Aug 2025 19:33:17 +0800	[thread overview]
Message-ID: <aJ3JfYZgihDTvWXq@fedora> (raw)
In-Reply-To: <20250814082612.500845-3-nilay@linux.ibm.com>

On Thu, Aug 14, 2025 at 01:54:58PM +0530, Nilay Shroff wrote:
> rq_qos_add() increments the block_rq_qos static key when a QoS
> policy is attached. When a QoS policy is removed via rq_qos_del(),
> we must symmetrically decrement the static key. If this removal drops
> the last QoS policy from the queue (q->rq_qos becomes NULL), the
> static branch can be disabled and the jump label patched to a NOP,
> avoiding overhead on the hot path.
> 
> This change ensures rq_qos_add()/rq_qos_del() keep the
> block_rq_qos static key balanced and prevents leaving the branch
> permanently enabled after the last policy is removed.
> 
> Fixes: 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key")
> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming


  parent reply	other threads:[~2025-08-14 11:33 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-14  8:24 [PATCHv3 0/3] block: blk-rq-qos: replace static key with atomic bitop Nilay Shroff
2025-08-14  8:24 ` [PATCHv3 1/3] block: skip q->rq_qos check in rq_qos_done_bio() Nilay Shroff
2025-08-14  8:59   ` Yu Kuai
2025-08-14 11:12   ` Ming Lei
2025-08-14  8:24 ` [PATCHv3 2/3] block: decrement block_rq_qos static key in rq_qos_del() Nilay Shroff
2025-08-14  9:14   ` Yu Kuai
2025-08-14 11:33   ` Ming Lei [this message]
2025-08-14  8:24 ` [PATCHv3 3/3] block: avoid cpu_hotplug_lock depedency on freeze_lock Nilay Shroff
2025-08-14  9:21   ` Yu Kuai
2025-08-14 12:44   ` Ming Lei
2025-08-14 12:57     ` Nilay Shroff
2025-08-14 13:38       ` Ming Lei
2025-08-14 14:31         ` Nilay Shroff
2025-08-15  0:13           ` Ming Lei
2025-08-15  1:04             ` Yu Kuai
2025-08-15  7:59               ` Ming Lei
2025-08-15  8:39                 ` Yu Kuai
2025-08-15  9:43             ` Nilay Shroff
2025-08-15 13:24               ` Ming Lei
2025-08-15 18:33                 ` Nilay Shroff
2025-08-16  1:01                   ` Yu Kuai
2025-08-16  1:59   ` Ming Lei
2025-08-21 12:19 ` [PATCHv3 0/3] block: blk-rq-qos: replace static key with atomic bitop Nilay Shroff
2025-08-21 13:11   ` Jens Axboe
2025-08-21 13:11 ` Jens Axboe

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