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Date: Fri, 13 Apr 2018 15:59:23 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 3/3] dcache: account external names as indirectly
 reclaimable memory
Message-ID: <20180413135923.GT17484@dhcp22.suse.cz>
References: <20180305133743.12746-1-guro@fb.com>
 <20180305133743.12746-5-guro@fb.com>
 <20180413133519.GA213834@rodete-laptop-imager.corp.google.com>
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To: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Johannes Weiner <hannes@cmpxchg.org>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com

On Fri 13-04-18 22:35:19, Minchan Kim wrote:
> On Mon, Mar 05, 2018 at 01:37:43PM +0000, Roman Gushchin wrote:
[...]
> > @@ -1614,9 +1623,11 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
> >  		name = &slash_name;
> >  		dname = dentry->d_iname;
> >  	} else if (name->len > DNAME_INLINE_LEN-1) {
> > -		size_t size = offsetof(struct external_name, name[1]);
> > -		struct external_name *p = kmalloc(size + name->len,
> > -						  GFP_KERNEL_ACCOUNT);
> > +		struct external_name *p;
> > +
> > +		reclaimable = offsetof(struct external_name, name[1]) +
> > +			name->len;
> > +		p = kmalloc(reclaimable, GFP_KERNEL_ACCOUNT);
> 
> Can't we use kmem_cache_alloc with own cache created with SLAB_RECLAIM_ACCOUNT
> if they are reclaimable? 

No, because names have different sizes and so we would basically have to
duplicate many caches.
-- 
Michal Hocko
SUSE Labs