linux-kernel - Re: [PATCH RFC 6/8] fs/ext4: Update ext4_should_use

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Date:   Fri, 17 Apr 2020 10:16:57 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Jan Kara <jack@...e.cz>
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>,
        Christoph Hellwig <hch@....de>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jeff Moyer <jmoyer@...hat.com>,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH RFC 6/8] fs/ext4: Update ext4_should_use_dax()

On Wed, Apr 15, 2020 at 03:58:34PM +0200, Jan Kara wrote:
> On Mon 13-04-20 21:00:28, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > Change the logic of ext4_should_use_dax() to support using the inode dax
> > flag OR the overriding tri-state mount option.
> > 
> > While we are at it change the function to ext4_enable_dax() as this
> > better reflects the ask.
> 
> I disagree with the renaming. ext4_enable_dax() suggests it enables
> something. It does not. I'd either leave ext4_should_use_dax() or maybe
> change it to ext4_should_enable_dax() if you really like the "enable" word
> :).

Ok that does sound better.  And I've changed it in the xfs series as well.

but I kept Darrick's review on that patch...

> 
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> >  fs/ext4/inode.c | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index fa0ff78dc033..e9d582e516bc 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4383,9 +4383,11 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
> >  		!ext4_test_inode_state(inode, EXT4_STATE_XATTR));
> >  }
> >  
> > -static bool ext4_should_use_dax(struct inode *inode)
> > +static bool ext4_enable_dax(struct inode *inode)
> >  {
> > -	if (!test_opt(inode->i_sb, DAX))
> > +	unsigned int flags = EXT4_I(inode)->i_flags;
> > +
> > +	if (test_opt2(inode->i_sb, NODAX))
> >  		return false;
> >  	if (!S_ISREG(inode->i_mode))
> >  		return false;
> > @@ -4397,7 +4399,13 @@ static bool ext4_should_use_dax(struct inode *inode)
> >  		return false;
> >  	if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
> >  		return false;
> > -	return true;
> > +	if (!bdev_dax_supported(inode->i_sb->s_bdev,
> > +				inode->i_sb->s_blocksize))
> > +		return false;
> > +	if (test_opt(inode->i_sb, DAX))
> > +		return true;
> > +
> > +	return (flags & EXT4_DAX_FL) == EXT4_DAX_FL;
> 
> flags & EXT4_DAX_FL is enough here, isn't it?

Yes, changed.

Ira

> 
> 								Honza
> 
> >  }
> >  
> >  void ext4_set_inode_flags(struct inode *inode)
> > @@ -4415,7 +4423,7 @@ void ext4_set_inode_flags(struct inode *inode)
> >  		new_fl |= S_NOATIME;
> >  	if (flags & EXT4_DIRSYNC_FL)
> >  		new_fl |= S_DIRSYNC;
> > -	if (ext4_should_use_dax(inode))
> > +	if (ext4_enable_dax(inode))
> >  		new_fl |= S_DAX;
> >  	if (flags & EXT4_ENCRYPT_FL)
> >  		new_fl |= S_ENCRYPTED;
> > -- 
> > 2.25.1
> > 
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR