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From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@lst.de>
Cc: 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: Tue, 4 Feb 2020 10:02:09 +1100
Message-ID: <20200203230209.GC20628@dread.disaster.area> (raw)
In-Reply-To: <20200203174641.GA20035@lst.de>

On Mon, Feb 03, 2020 at 06:46:41PM +0100, Christoph Hellwig wrote:
> On Sat, Jan 18, 2020 at 08:28:38PM +1100, Dave Chinner wrote:
> > I think it's pretty gross, actually. It  makes the same mistake made
> > with locking in the old direct IO code - it encodes specific lock
> > operations via flags into random locations in the DIO path. This is
> > a very slippery slope, and IMO it is an layering violation to encode
> > specific filesystem locking smeantics into a layer that is supposed
> > to be generic and completely filesystem agnostic. i.e.  this
> > mechanism breaks if a filesystem moves to a different type of lock
> > (e.g. range locks), and history teaches us that we'll end up making
> > a horrible, unmaintainable mess to support different locking
> > mechanisms and contexts.
> > 
> > I think that we should be moving to a model where the filesystem
> > provides an unlock method in the iomap operations structure, and if
> > the method is present in iomap_dio_complete() it gets called for the
> > filesystem to unlock the inode at the appropriate point. This also
> > allows the filesystem to provide a different method for read or
> > write unlock, depending on what type of lock it held at submission.
> > This gets rid of the need for the iomap code to know what type of
> > lock the caller holds, too.
> 
> I'd rather avoid yet another method.  But I think with a little
> tweaking we can move the unlock into the ->end_io method.

That would work, too :)

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

      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
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 [this message]

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