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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	Bart Van Assche <bvanassche@acm.org>, Qian Cai <cai@redhat.com>,
	John Garry <john.garry@huawei.com>,
	linux-nvme@lists.infradead.org,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	linux-block@vger.kernel.org,
	Sumit Saxena <sumit.saxena@broadcom.com>,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 1/3] blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
Date: Tue, 17 Nov 2020 09:16:10 +0800	[thread overview]
Message-ID: <20201117011610.GB56247@T590> (raw)
In-Reply-To: <20201117010448.GA56247@T590>

On Tue, Nov 17, 2020 at 09:05:04AM +0800, Ming Lei wrote:
> 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?

Forget to mention, 'blk_flush_queue' is one private structure inside block
layer, so we can't define as inline.

thanks,
Ming


WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	Bart Van Assche <bvanassche@acm.org>, Qian Cai <cai@redhat.com>,
	John Garry <john.garry@huawei.com>,
	linux-nvme@lists.infradead.org,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	linux-block@vger.kernel.org,
	Sumit Saxena <sumit.saxena@broadcom.com>,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 1/3] blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
Date: Tue, 17 Nov 2020 09:16:10 +0800	[thread overview]
Message-ID: <20201117011610.GB56247@T590> (raw)
In-Reply-To: <20201117010448.GA56247@T590>

On Tue, Nov 17, 2020 at 09:05:04AM +0800, Ming Lei wrote:
> 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?

Forget to mention, 'blk_flush_queue' is one private structure inside block
layer, so we can't define as inline.

thanks,
Ming


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Linux-nvme@lists.infradead.org
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  reply	other threads:[~2020-11-17  1:17 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12  7:55 [PATCH 0/3] blk-mq/nvme-loop: use nvme-loop's lock class for addressing lockdep false positive warning Ming Lei
2020-11-12  7:55 ` Ming Lei
2020-11-12  7:55 ` [PATCH 1/3] blk-mq: add new API of blk_mq_hctx_set_fq_lock_class Ming Lei
2020-11-12  7:55   ` Ming Lei
2020-11-16 17:26   ` Christoph Hellwig
2020-11-16 17:26     ` Christoph Hellwig
2020-11-17  1:04     ` Ming Lei
2020-11-17  1:04       ` Ming Lei
2020-11-17  1:16       ` Ming Lei [this message]
2020-11-17  1:16         ` Ming Lei
2020-11-17  6:46         ` Kashyap Desai
2020-11-17  6:46           ` Kashyap Desai
2020-11-12  7:55 ` [PATCH 2/3] nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class Ming Lei
2020-11-12  7:55   ` Ming Lei
2020-11-16 17:27   ` Christoph Hellwig
2020-11-16 17:27     ` Christoph Hellwig
2020-11-12  7:55 ` [PATCH 3/3] Revert "block: Fix a lockdep complaint triggered by request queue flushing" Ming Lei
2020-11-12  7:55   ` Ming Lei
2020-11-12 15:12   ` Bart Van Assche
2020-11-12 15:12     ` Bart Van Assche
2020-11-12 15:29     ` Bart Van Assche
2020-11-12 15:29       ` Bart Van Assche
2020-11-13  1:11       ` Ming Lei
2020-11-13  1:11         ` Ming Lei
2020-11-13  1:27   ` [PATCH V2 " Ming Lei
2020-11-13  1:27     ` Ming Lei
2020-11-16 17:27     ` Christoph Hellwig
2020-11-16 17:27       ` Christoph Hellwig
2020-11-25  1:31 ` [PATCH 0/3] blk-mq/nvme-loop: use nvme-loop's lock class for addressing lockdep false positive warning Ming Lei
2020-11-25  1:31   ` Ming Lei
2020-11-30  2:36 ` Ming Lei
2020-11-30  2:36   ` Ming Lei
2020-12-02 19:07   ` Qian Cai
2020-12-02 19:07     ` Qian Cai
2020-12-03  0:50     ` Ming Lei
2020-12-03  0:50       ` Ming Lei
2020-12-03  1:23       ` Qian Cai
2020-12-03  1:23         ` Qian Cai

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