Re: [PATCH V5 05/12] fs/xfs: Create function xfs_inode_enable_dax()

From: Dave Chinner <david@fromorbit.com>
To: ira.weiny@intel.com
Cc: linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH V5 05/12] fs/xfs: Create function xfs_inode_enable_dax()
Date: Mon, 2 Mar 2020 09:37:45 +1100	[thread overview]
Message-ID: <20200301223745.GE10776@dread.disaster.area> (raw)
In-Reply-To: <20200227052442.22524-6-ira.weiny@intel.com>

On Wed, Feb 26, 2020 at 09:24:35PM -0800, 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 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 | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 81f2f93caec0..ff711efc5247 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1237,19 +1237,18 @@ static const struct inode_operations xfs_inline_symlink_inode_operations = {
>  };
>  
>  /* Figure out if this file actually supports DAX. */
> -static bool
> +STATIC bool
>  xfs_inode_supports_dax(
>  	struct xfs_inode	*ip)
>  {
>  	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 split the initial check? The "non-reflinked files" comment is
pretty explicit, so splitting it just to add a "only support on
regular files" comment doesn't actually add any value here.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com