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Date: Thu, 12 Jan 2017 05:56:03 -0800
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] xfs: fix eofblocks race with file extending async dio
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>  		if (need_iolock) {
>  			if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL))
>  				return -EAGAIN;
>  		}
> +		inode_dio_wait(VFS_I(ip));

inode_dio_wait generally is only safe to call with i_rwsem held
exclsuively, so if we'd need the call for the !need_iolock this would
be broken.  Fortunately we don't even need the call in that case, so
this should be safe.  I'd still prefer to move the inode_dio_wait call
into the need_iolock block to make that clear, though.