Re: [PATCH V8 06/11] fs/xfs: Create function xfs_inode_enable_dax()

From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: ira.weiny@intel.com
Cc: linux-kernel@vger.kernel.org, Jan Kara <jack@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Jeff Moyer <jmoyer@redhat.com>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH V8 06/11] fs/xfs: Create function xfs_inode_enable_dax()
Date: Wed, 15 Apr 2020 08:17:42 -0700	[thread overview]
Message-ID: <20200415151742.GP6742@magnolia> (raw)
In-Reply-To: <20200415064523.2244712-7-ira.weiny@intel.com>

On Tue, Apr 14, 2020 at 11:45:18PM -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 v7:
> 	Move S_ISREG check first
> 	use IS_ENABLED(CONFIG_FS_DAX) rather than duplicated function
> 
> 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 | 28 ++++++++++++++++++++++------
>  1 file changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index a6e634631da8..2ecc2b2050ab 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1243,13 +1243,12 @@ 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))
> +	/* Only supported on regular files. */
> +	if (!S_ISREG(VFS_I(ip)->i_mode))
>  		return false;
>  
> -	/* DAX mount option or DAX iflag must be set. */
> -	if (!(mp->m_flags & XFS_MOUNT_DAX_ALWAYS) &&
> -	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
> +	/* Only supported on non-reflinked files. */
> +	if (xfs_is_reflink_inode(ip))
>  		return false;
>  
>  	/* Block size must match page size */
> @@ -1260,6 +1259,23 @@ xfs_inode_supports_dax(
>  	return xfs_inode_buftarg(ip)->bt_daxdev != NULL;
>  }
>  
> +static bool
> +xfs_inode_enable_dax(
> +	struct xfs_inode *ip)
> +{
> +	if (!IS_ENABLED(CONFIG_FS_DAX))
> +		return false;
> +	if (ip->i_mount->m_flags & XFS_MOUNT_DAX_NEVER)
> +		return false;
> +	if (!xfs_inode_supports_dax(ip))
> +		return false;
> +	if (ip->i_mount->m_flags & XFS_MOUNT_DAX_ALWAYS)
> +		return true;
> +	if (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)
> +		return true;
> +	return false;

You could simplify the last two lines by making them read:

return ip->i_d.di_flags2 & XFS_DIFLAG2_DAX;

But it's probably not worth respinning the whole thing just for that.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> +}
> +
>  STATIC void
>  xfs_diflags_to_iflags(
>  	struct inode		*inode,
> @@ -1278,7 +1294,7 @@ 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
> 