linux-kernel - Re: [PATCH V6 5/8] fs/xfs: Create function xfs_inode_enable

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Date:   Wed, 8 Apr 2020 10:05:33 +1000
From:   Dave Chinner <david@...morbit.com>
To:     ira.weiny@...el.com
Cc:     linux-kernel@...r.kernel.org,
        "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>,
        Jeff Moyer <jmoyer@...hat.com>, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V6 5/8] fs/xfs: Create function xfs_inode_enable_dax()

On Tue, Apr 07, 2020 at 11:29:55AM -0700, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.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@...el.com>
....
>  
> +STATIC bool
> +xfs_inode_enable_dax(
> +	struct xfs_inode *ip)
> +{
> +	u32 dax_mode = xfs_mount_dax_mode(ip->i_mount);
> +
> +	if (dax_mode == XFS_DAX_NEVER || !xfs_inode_supports_dax(ip))
> +		return false;
> +	if (dax_mode == XFS_DAX_ALWAYS || ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)
> +		return true;

These compound || statements are better written as single conditions
as they are all sequential logic checks and we can't skip over
checks.

	if (mp->m_flags & XFS_MOUNT_DAX_NEVER)
		return false;
	if (!xfs_inode_supports_dax(ip))
		return false;
	if (mp->m_flags & XFS_MOUNT_DAX_ALWAYS)
		return true;
	if (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)
		return true;
	return false;

Cheers,

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