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Date:   Mon, 13 Apr 2020 08:52:51 -0700
From:   "Darrick J. Wong" <darrick.wong@oracle.com>
To:     ira.weiny@intel.com
Cc:     linux-kernel@vger.kernel.org,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Chinner <david@fromorbit.com>,
        Christoph Hellwig <hch@lst.de>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
        Jeff Moyer <jmoyer@redhat.com>, linux-ext4@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH V7 5/9] fs/xfs: Create function xfs_inode_enable_dax()
Message-ID: <20200413155251.GU6742@magnolia>
References: <20200413054046.1560106-1-ira.weiny@intel.com>
 <20200413054046.1560106-6-ira.weiny@intel.com>
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On Sun, Apr 12, 2020 at 10:40:42PM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> xfs_inode_supports_dax() should reflect if the inode can support DAX not
> that it is enabled for DAX.
> 
> Change the use of xfs_inode_supports_dax() to reflect only if the inode
> and underlying storage support dax.
> 
> Add a new function xfs_inode_enable_dax() which reflects if the inode
> should be enabled for DAX.
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes from v6:
> 	Change enable checks to be sequential logic.
> 	Update for 2 bit tri-state option.
> 	Make 'static' consistent.
> 	Don't set S_DAX if !CONFIG_FS_DAX
> 
> Changes from v5:
> 	Update to reflect the new tri-state mount option
> 
> Changes from v3:
> 	Update functions and names to be more clear
> 	Update commit message
> 	Merge with
> 		'fs/xfs: Clean up DAX support check'
> 		don't allow IS_DAX() on a directory
> 		use STATIC macro for static
> 		make xfs_inode_supports_dax() static
> ---
>  fs/xfs/xfs_iops.c | 34 +++++++++++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 81f2f93caec0..37bd15b55878 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1244,12 +1244,11 @@ xfs_inode_supports_dax(
>  	struct xfs_mount	*mp = ip->i_mount;
>  
>  	/* Only supported on non-reflinked files. */
> -	if (!S_ISREG(VFS_I(ip)->i_mode) || xfs_is_reflink_inode(ip))
> +	if (xfs_is_reflink_inode(ip))
>  		return false;
>  
> -	/* DAX mount option or DAX iflag must be set. */
> -	if (!(mp->m_flags & XFS_MOUNT_DAX) &&
> -	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
> +	/* Only supported on regular files. */
> +	if (!S_ISREG(VFS_I(ip)->i_mode))
>  		return false;

Why separate the !S_ISREG and the is_reflink_inode checks?

The part about "Change the use of xfs_inode_supports_dax() to reflect
only if the inode and underlying storage support dax" would be a lot
more straightforward if this hunk only removed the DIFLAG2_DAX check.

The rest of the patch looks ok.

--D

>  
>  	/* Block size must match page size */
> @@ -1260,6 +1259,31 @@ xfs_inode_supports_dax(
>  	return xfs_inode_buftarg(ip)->bt_daxdev != NULL;
>  }
>  
> +#ifdef CONFIG_FS_DAX
> +static bool
> +xfs_inode_enable_dax(
> +	struct xfs_inode *ip)
> +{
> +	if (ip->i_mount->m_flags & XFS_MOUNT_NODAX)
> +		return false;
> +	if (!xfs_inode_supports_dax(ip))
> +		return false;
> +	if (ip->i_mount->m_flags & XFS_MOUNT_DAX)
> +		return true;
> +	if (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)
> +		return true;
> +	return false;
> +}
> +#else /* !CONFIG_FS_DAX */
> +static bool
> +xfs_inode_enable_dax(
> +	struct xfs_inode *ip)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_FS_DAX */
> +
> +
>  STATIC void
>  xfs_diflags_to_iflags(
>  	struct inode		*inode,
> @@ -1278,7 +1302,7 @@ xfs_diflags_to_iflags(
>  		inode->i_flags |= S_SYNC;
>  	if (flags & XFS_DIFLAG_NOATIME)
>  		inode->i_flags |= S_NOATIME;
> -	if (xfs_inode_supports_dax(ip))
> +	if (xfs_inode_enable_dax(ip))
>  		inode->i_flags |= S_DAX;
>  }
>  
> -- 
> 2.25.1
>