linux-ext4 - Re: [RFC PATCH v1 29/30] fs: track whether the i_version has been queried with an i

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Date:   Fri, 03 Mar 2017 19:43:21 -0500
From:   Jeff Layton <jlayton@...hat.com>
To:     NeilBrown <neil@...wn.name>, linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-xfs@...r.kernel.org
Subject: Re: [RFC PATCH v1 29/30] fs: track whether the i_version has been
 queried with an i_state flag

On Sat, 2017-03-04 at 11:03 +1100, NeilBrown wrote:
> On Wed, Dec 21 2016, Jeff Layton wrote:
> 
> > @@ -2072,7 +2093,12 @@ inode_cmp_iversion(const struct inode *inode, const u64 old)
> >  static inline bool
> >  inode_iversion_need_inc(struct inode *inode)
> >  {
> > -	return true;
> > +	bool ret;
> > +
> > +	spin_lock(&inode->i_lock);
> > +	ret = inode->i_state & I_VERS_BUMP;
> > +	spin_unlock(&inode->i_lock);
> > +	return ret;
> >  }
> >  
> 
> I know this code gets removed, so this isn't really important.
> By why do you take the spinlock here?  What are you racing again?
> 
> Thanks,
> NeilBrown

I think I was worried about I_VERS_BUMP being set or cleared during an
increment or query. It is quite possible that that spinlock is not
necessary.
-- 
Jeff Layton <jlayton@...hat.com>