aio completions vs file_accessed race, was: Re: [PATCH 7/8] xfs: split direct I/O and DAX path

[Christoph Hellwig]

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;
 }