linux-kernel - Re: [PATCH 3/9] slab: simplify shutdown_memcg

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Message-ID: <20170114153801.GB32693@mtj.duckdns.org>
Date:   Sat, 14 Jan 2017 10:38:01 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Vladimir Davydov <vdavydov@...antool.org>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, jsvana@...com,
        hannes@...xchg.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 3/9] slab: simplify shutdown_memcg_caches()

On Sat, Jan 14, 2017 at 04:27:22PM +0300, Vladimir Davydov wrote:
> > -	 * Second, shutdown all caches left from memory cgroups that are now
> > -	 * offline.
> > +	 * Shutdown all caches.
> >  	 */
> >  	list_for_each_entry_safe(c, c2, &s->memcg_params.list,
> >  				 memcg_params.list)
> >  		shutdown_cache(c);
> 
> The point of this complexity was to leave caches that happen to have
> objects when kmem_cache_destroy() is called on the list, so that they
> could be reused later. This behavior was inherited from the global

Ah, right, I misread the branch.  I don't quite get how the cache can
be reused later tho?  This is called when the memcg gets released and
a clear error condition - the caller, kmem_cache_destroy(), handles it
as an error condition too.

> caches - if kmem_cache_destroy() is called on a cache that still has
> object, we print a warning message and don't destroy the cache. This
> patch changes this behavior.

Hmm... yeah, we're missing the error return propagation.  I think
that's the only meaningful difference tho, right?  Will update the
patch.

Thanks!

-- 
tejun