linux-kernel - Re: [PATCH 12/13] dcache: remove dentries from LRU before putting on dispose list

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Date:	Tue, 23 Aug 2011 19:57:52 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, khlebnikov@...nvz.org
Subject: Re: [PATCH 12/13] dcache: remove dentries from LRU before putting on
 dispose list

On Tue, Aug 23, 2011 at 05:35:20AM -0400, Christoph Hellwig wrote:
> > diff --git a/fs/dcache.c b/fs/dcache.c
> > index b931415..79bf47c 100644
> > --- a/fs/dcache.c
> > +++ b/fs/dcache.c
> > @@ -269,10 +269,10 @@ static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
> >  	spin_lock(&dentry->d_sb->s_dentry_lru_lock);
> >  	if (list_empty(&dentry->d_lru)) {
> >  		list_add_tail(&dentry->d_lru, list);
> > -		dentry->d_sb->s_nr_dentry_unused++;
> > -		this_cpu_inc(nr_dentry_unused);
> >  	} else {
> >  		list_move_tail(&dentry->d_lru, list);
> > +		dentry->d_sb->s_nr_dentry_unused--;
> > +		this_cpu_dec(nr_dentry_unused);
> >  	}
> >  	spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
> 
> I suspect at this point it might be more obvious to simply remove
> dentry_lru_move_list.  Just call dentry_lru_del to remove it from the
> lru, and then we can add it to the local dispose list without the need
> of any locking, similar to how it is done for inodes already.

Yeah, that is what is done in the next patch when converting to the
generic LRU list code. I can probably pull this back into this patch
and just remove dentry_lru_move_list(0 right here.

> 
> >  		if (dentry->d_count) {
> > -			dentry_lru_del(dentry);
> >  			spin_unlock(&dentry->d_lock);
> >  			continue;
> >  		}
> > @@ -789,6 +794,8 @@ relock:
> >  			spin_unlock(&dentry->d_lock);
> >  		} else {
> >  			list_move_tail(&dentry->d_lru, &tmp);
> > +			this_cpu_dec(nr_dentry_unused);
> > +			sb->s_nr_dentry_unused--;
> 
> It might be more obvious to use __dentry_lru_del + an opencoded list_add
> here.

This goes away completely in the next patch, so I don't think it
matters that much...

Cheers,

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