linux-kernel - Re: [PATCH V7 5/9] fs/xfs: Create function xfs_inode_enable

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Date:   Tue, 14 Apr 2020 13:43:50 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-kernel@...r.kernel.org,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        "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 V7 5/9] fs/xfs: Create function xfs_inode_enable_dax()

On Tue, Apr 14, 2020 at 08:27:18AM +0200, Christoph Hellwig wrote:
> On Sun, Apr 12, 2020 at 10:40:42PM -0700, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 

[snip]

> > 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;
> 
> To me it would make sense to check S_ISREG before reflink, as it seems
> more logical.

Done.

> 
> > +#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 */
> 
> Just throw in a
> 
> 	if (!IS_ENABLED(CONFIG_FS_DAX))
> 		return false;
> 
> as the first statement of the full version and avoid the stub entirely?

Sure, less code that way.  Done.

Ira