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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: xfs@oss.sgi.com, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org
Subject: Re: aio completions vs file_accessed race, was: Re: [PATCH 7/8] xfs: split direct I/O and DAX path
Date: Thu, 29 Sep 2016 13:33:20 -0700
Message-ID: <20160929203320.GE14092@birch.djwong.org> (raw)
In-Reply-To: <20160929201849.GB5872@lst.de>

On Thu, Sep 29, 2016 at 10:18:49PM +0200, Christoph Hellwig wrote:
> On Thu, Sep 29, 2016 at 10:18:34PM +0200, Christoph Hellwig wrote:
> > Can you try the patch below?  That just moves the file_accessed call
> > before the I/O, similar to how we handle timestamp updates on the write
> > side.  generic_file_read_iter will also need a similar update.
> 
> And now with patch:
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 349f328..6919412 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -270,6 +270,8 @@ xfs_file_dio_aio_read(
>  		return -EINVAL;
>  	}
>  
> +	file_accessed(iocb->ki_filp);
> +
>  	/*
>  	 * Locking is a bit tricky here. If we take an exclusive lock for direct
>  	 * IO, we effectively serialise all new concurrent read IO to this file
> @@ -324,7 +326,6 @@ xfs_file_dio_aio_read(
>  	}
>  	xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
>  
> -	file_accessed(iocb->ki_filp);
>  	return ret;
>  }
>  

I noticed that g/323 only breaks when the XFS is on a real disk; on
pmem it works fine with or without the patch.

That said, it makes the crash go away and the patch looks ok, so:
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Tested-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-22 15:27 xfs: untangle the direct I/O and DAX path, fix DAX locking Christoph Hellwig
2016-06-22 15:27 ` [PATCH 1/8] xfs: don't pass ioflags around in the ioctl path Christoph Hellwig
2016-06-22 15:27 ` [PATCH 2/8] xfs: kill ioflags Christoph Hellwig
2016-06-22 15:27 ` [PATCH 3/8] xfs: remove s_maxbytes enforcement in xfs_file_read_iter Christoph Hellwig
2016-06-22 15:27 ` [PATCH 4/8] xfs: split xfs_file_read_iter into buffered and direct I/O helpers Christoph Hellwig
2016-06-22 15:27 ` [PATCH 5/8] xfs: stop using generic_file_read_iter for direct I/O Christoph Hellwig
2016-06-22 15:27 ` [PATCH 6/8] xfs: direct calls in the direct I/O path Christoph Hellwig
2016-06-22 15:27 ` [PATCH 7/8] xfs: split direct I/O and DAX path Christoph Hellwig
2016-09-29  2:53   ` Darrick J. Wong
2016-09-29  8:38     ` aio completions vs file_accessed race, was: " Christoph Hellwig
2016-09-29 20:18       ` Christoph Hellwig
2016-09-29 20:18         ` Christoph Hellwig
2016-09-29 20:33           ` Darrick J. Wong [this message]
2016-06-22 15:27 ` [PATCH 8/8] xfs: fix locking for DAX writes Christoph Hellwig
2016-06-23 14:22   ` Boaz Harrosh
2016-06-23 23:24 ` xfs: untangle the direct I/O and DAX path, fix DAX locking Dave Chinner
2016-06-24  1:14   ` Dan Williams
2016-06-24  7:13     ` Dave Chinner
2016-06-24  7:31       ` Christoph Hellwig
2016-06-24  7:26   ` Christoph Hellwig
2016-06-24 23:00     ` Dave Chinner
2016-06-28 13:10       ` Christoph Hellwig
2016-06-28 13:27         ` Boaz Harrosh
2016-06-28 13:39           ` Christoph Hellwig
2016-06-28 13:56             ` Boaz Harrosh
2016-06-28 15:39               ` Christoph Hellwig
2016-06-29 12:23                 ` Boaz Harrosh

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