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From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Waiman Long <longman@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-ext4@vger.kernel.org, cluster-devel@redhat.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: RFC: hold i_rwsem until aio completes
Date: Wed, 15 Jan 2020 07:54:06 +0100
Message-ID: <20200115065406.GB21219@lst.de> (raw)
In-Reply-To: <20200114184707.GA10467@bombadil.infradead.org>

On Tue, Jan 14, 2020 at 10:47:07AM -0800, Matthew Wilcox wrote:
> It would be helpful if we could also use the same lockdep logic
> for PageLocked.  Again, it's a case where returning to userspace with
> PageLock held is fine, because we're expecting an interrupt to come in
> and drop the lock for us.

Yes, this is a very typical pattern for I/O.  Besides the page and
buffer head bit locks it also applies to the semaphore in the xfs_buf
structure and probably various other places that currently used hand
crafted or legacy locking primitives to escape lockdep.

> Perhaps the right answer is, from lockdep's point of view, to mark the
> lock as being released at the point where we submit the I/O.  Then
> in the completion path release the lock without telling lockdep we
> released it.

That is similar to what the fsfreeze code does, but I don't think it
is very optimal, as misses to track any dependencies after I/O
submission, and at least some of the completions paths do take
locks.  But it might be a start.

  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 16:12 Christoph Hellwig
2020-01-14 16:12 ` [PATCH 01/12] mm: fix a comment in sys_swapon Christoph Hellwig
2020-02-10 23:29   ` Andrew Morton
2020-02-12  7:37     ` Christoph Hellwig
2020-01-14 16:12 ` [PATCH 02/12] locking/rwsem: Exit early when held by an anonymous owner Christoph Hellwig
2020-01-14 18:17   ` Waiman Long
2020-01-14 18:25     ` Christoph Hellwig
2020-01-14 18:33       ` Waiman Long
2020-01-14 18:55       ` Waiman Long
2020-01-14 16:12 ` [PATCH 03/12] xfs: fix IOCB_NOWAIT handling in xfs_file_dio_aio_read Christoph Hellwig
2020-01-14 16:12 ` [PATCH 04/12] gfs2: move setting current->backing_dev_info Christoph Hellwig
2020-01-14 16:12 ` [PATCH 05/12] gfs2: fix O_SYNC write handling Christoph Hellwig
2020-02-06 15:31   ` [Cluster-devel] " Andreas Gruenbacher
2020-01-14 16:12 ` [PATCH 06/12] iomap: pass a flags value to iomap_dio_rw Christoph Hellwig
2020-01-14 16:12 ` [PATCH 07/12] iomap: allow holding i_rwsem until aio completion Christoph Hellwig
2020-01-14 16:12 ` [PATCH 08/12] ext4: hold i_rwsem until AIO completes Christoph Hellwig
2020-01-14 21:50   ` Theodore Y. Ts'o
2020-01-15  6:48     ` Christoph Hellwig
2020-01-14 16:12 ` [PATCH 09/12] gfs2: " Christoph Hellwig
2020-01-14 16:12 ` [PATCH 10/12] xfs: " Christoph Hellwig
2020-01-14 16:12 ` [PATCH 11/12] xfs: don't set IOMAP_DIO_SYNCHRONOUS for unaligned I/O Christoph Hellwig
2020-01-14 16:12 ` [PATCH 12/12] iomap: remove the inode_dio_begin/end calls Christoph Hellwig
2020-01-14 18:47 ` RFC: hold i_rwsem until aio completes Matthew Wilcox
2020-01-15  6:54   ` Christoph Hellwig [this message]
2020-01-14 19:27 ` Jason Gunthorpe
2020-01-15  6:56   ` Christoph Hellwig
2020-01-15 13:24     ` Jason Gunthorpe
2020-01-15 14:33       ` Peter Zijlstra
2020-01-15 14:49         ` Jason Gunthorpe
2020-01-15 19:03           ` Waiman Long
2020-01-15 19:07             ` Christoph Hellwig
2020-01-18 22:40         ` Matthew Wilcox
2020-01-15 15:36       ` Christoph Hellwig
2020-01-15 16:26         ` Jason Gunthorpe
2020-01-16 14:00 ` Jan Kara
2020-02-03 17:44   ` Christoph Hellwig
2020-01-18  9:28 ` Dave Chinner
2020-02-03 17:46   ` Christoph Hellwig
2020-02-03 23:02     ` Dave Chinner

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