linux-kernel - Re: [PATCH v3 04/12] fs/xfs: Clean up DAX support check

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Message-ID: <20200211055745.GG10776@dread.disaster.area>
Date:   Tue, 11 Feb 2020 16:57:45 +1100
From:   Dave Chinner <david@...morbit.com>
To:     ira.weiny@...el.com
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Christoph Hellwig <hch@....de>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 04/12] fs/xfs: Clean up DAX support check

On Sat, Feb 08, 2020 at 11:34:37AM -0800, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> Rather than open coding xfs_inode_supports_dax() in
> xfs_ioctl_setattr_dax_invalidate() export xfs_inode_supports_dax() and
> call it in preparation for swapping dax flags.
> 
> This also means updating xfs_inode_supports_dax() to return true for a
> directory.

That's not correct. This now means S_DAX gets set on directory inodes
because both xfs_inode_supports_dax() and the on-disk inode flag
checks return true in xfs_diflags_to_iflags(). Hence when we
instantiate a directory inode with a DAX inherit hint set on it
we'll set S_DAX on the inode and so IS_DAX() will return true for
directory inodes...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com