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Mon, 16 Nov 2020 20:05:06 -0500 X-MC-Unique: WQGDqBW8Nfm1as1OpFAbTA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6FD32CE670; Tue, 17 Nov 2020 01:05:04 +0000 (UTC) Received: from T590 (ovpn-12-215.pek2.redhat.com [10.72.12.215]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 20CAC5D9D2; Tue, 17 Nov 2020 01:04:52 +0000 (UTC) Date: Tue, 17 Nov 2020 09:04:48 +0800 From: Ming Lei To: Christoph Hellwig Subject: Re: [PATCH 1/3] blk-mq: add new API of blk_mq_hctx_set_fq_lock_class Message-ID: <20201117010448.GA56247@T590> References: <20201112075526.947079-1-ming.lei@redhat.com> <20201112075526.947079-2-ming.lei@redhat.com> <20201116172658.GJ22007@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201116172658.GJ22007@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201116_200513_742177_108FEEC4 X-CRM114-Status: GOOD ( 18.55 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , Bart Van Assche , Qian Cai , John Garry , linux-nvme@lists.infradead.org, Kashyap Desai , linux-block@vger.kernel.org, Sumit Saxena , Hannes Reinecke Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, Nov 16, 2020 at 06:26:58PM +0100, Christoph Hellwig wrote: > On Thu, Nov 12, 2020 at 03:55:24PM +0800, Ming Lei wrote: > > flush_end_io() may be called recursively from some driver, such as > > nvme-loop, so lockdep may complain 'possible recursive locking'. > > Commit b3c6a5997541("block: Fix a lockdep complaint triggered by > > request queue flushing") tried to address this issue by assigning > > dynamically allocated per-flush-queue lock class. This solution > > adds synchronize_rcu() for each hctx's release handler, and causes > > horrible SCSI MQ probe delay(more than half an hour on megaraid sas). > > > > Add new API of blk_mq_hctx_set_fq_lock_class() for these drivers, so > > we just need to use driver specific lock class for avoiding the > > lockdep warning of 'possible recursive locking'. > > I'd turn this into an inline function to avoid the (although very > minimal) cost when LOCKDEP is not enabled. blk_mq_hctx_set_fq_lock_class() is just one-shot thing, do you really care the cost? thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme