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Tue, 07 Jan 2025 05:25:36 -0500 X-MC-Unique: w5dnKRt2PPm84kKWsCv9qg-1 X-Mimecast-MFC-AGG-ID: w5dnKRt2PPm84kKWsCv9qg Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A16BB19560A3; Tue, 7 Jan 2025 10:25:32 +0000 (UTC) Received: from fedora (unknown [10.72.116.66]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 318F5195605F; Tue, 7 Jan 2025 10:25:25 +0000 (UTC) Date: Tue, 7 Jan 2025 18:25:20 +0800 From: Ming Lei To: Nilay Shroff Cc: Christoph Hellwig , Jens Axboe , Damien Le Moal , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, nbd@other.debian.org, linux-scsi@vger.kernel.org, usb-storage@lists.one-eyed-alien.net Subject: Re: [PATCH 4/8] block: add a store_limit operations for sysfs entries Message-ID: References: <20250107063120.1011593-1-hch@lst.de> <20250107063120.1011593-5-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250107_022540_558833_8BD47464 X-CRM114-Status: GOOD ( 21.05 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Jan 07, 2025 at 01:21:14PM +0530, Nilay Shroff wrote: > > > On 1/7/25 12:55 PM, Ming Lei wrote: > > On Tue, Jan 07, 2025 at 07:30:36AM +0100, Christoph Hellwig wrote: > >> De-duplicate the code for updating queue limits by adding a store_limit > >> method that allows having common code handle the actual queue limits > >> update. > >> > >> Note that this is a pure refactoring patch and does not address the > >> existing freeze vs limits lock order problem in the refactored code, > >> which will be addressed next. > >> > >> Signed-off-by: Christoph Hellwig ... > > Order between freeze and ->sysfs_lock is changed, and it may cause new > > lockdep warning because we may freeze queue first before acquiring > > ->sysfs_lock in del_gendisk(). > > > On contrary, in elevator_disable() and elevator_switch() we acquire > ->sysfs_lock first before freezing the queue. I think this is a mess and > we need to fix ordering. We need to decide ordering rules. IMO, the > correct order should be to acquire ->sysfs_lock before freezing queue. > Likewise with this patch now we acquire ->limits_lock before freezing the > queue. __blk_mq_update_nr_hw_queues() freezes queue before acquiring ->syfs_lock too. So yes, it is a mess wrt. order between ->sysfs_lock and freezing queue. Thanks, Ming