Re: [PATCH v7 04/31] dcache: remove dentries from LRU before putting on dispose list

[Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>]

On Tue, May 14, 2013 at 04:43:04PM +0400, Glauber Costa wrote:
> On 05/14/2013 09:46 AM, Dave Chinner wrote:
> > [ v2: don't decrement nr unused twice, spotted by Sha Zhengju ]
> > [ v7: (dchinner)
> > - shrink list leaks dentries when inode/parent can't be locked in
> >   dentry_kill().
> > - fix the scope of the sb locking inside shrink_dcache_sb()
> > - remove the readdition of dentry_lru_prune(). ]
> 
> Dave,
> 
> dentry_lru_prune was removed because it would only prune the dentry if
> it was in the LRU list, and it has to be always pruned (61572bb1).
> 
> You don't reintroduce dentry_lru_prune here, so the two locations which
> prune dentries read as follows:
> 
> 
>         if (dentry->d_flags & DCACHE_OP_PRUNE)
>                 dentry->d_op->d_prune(dentry);
> 
>         dentry_lru_del(dentry);
> 
> I believe this is wrong. My old version would do:
> 
> +static void dentry_lru_prune(struct dentry *dentry)
> +{
> +	/*
> +	 * inform the fs via d_prune that this dentry is about to be
> +	 * unhashed and destroyed.
> +	 */
> +	if (dentry->d_flags & DCACHE_OP_PRUNE)
> +		dentry->d_op->d_prune(dentry);
> +
> +	if (list_empty(&dentry->d_lru))
> +		return;
> +
> +	if ((dentry->d_flags & DCACHE_SHRINK_LIST)) {
> +		list_del_init(&dentry->d_lru);
> +		dentry->d_flags &= ~DCACHE_SHRINK_LIST;
> +	} else {
> +		spin_lock(&dentry->d_sb->s_dentry_lru_lock);
> +		__dentry_lru_del(dentry);
> +		spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
> +	}
> +}
> 
> Which is SHRINK_LIST aware.

Right. Did I mention I was seeing a panic on a later patch? That's
because this patch removed the DCACHE_SHRINK_LIST check. So, the
DCACHE_SHRINK_LIST needs to move into dentry_lru_del(), and
dentry_lru_prune() can still go away. That's what my current version
of this patch does - I just didn't post it last night because it was
still running tests when I went to bed....

Cheers,

Dave.
-- 
Dave Chinner
david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org