linux-ext4 - Re: [PATCH] ext4: fix race aio-dio vs freeze

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Date:	Tue, 24 Nov 2015 08:07:23 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Jan Kara <jack@...e.cz>
Cc:	Dmitry Monakhov <dmonakhov@...nvz.org>, linux-ext4@...r.kernel.org,
	tytso@....edu, xfs@....sgi.com, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] ext4: fix race aio-dio vs freeze_fs

On Tue, Nov 24, 2015 at 02:24:21PM +0100, Jan Kara wrote:
> Well, this problem seems to suggest that we have the freeze protection for
> AIO writes wrong. We should call file_end_write() from aio_complete() and
> not from aio_run_iocb()... I believe XFS and other filesystems may have
> problems with this as well (CCed). Attached patch (so far only compile
> tested since my test machine is pondering on something else) should fix
> this.

Sounds like one way to do it, but we'd really want a vfs_* helper for
this so that it doesn't have to duplicated in other write_iter users
like the loop driver, which seems to be missing file
file_start_write/file_end_write entirely.
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