linux-kernel - Re: [PATCH 3/4] mm: Add free()

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Message-ID: <20180325235603.GA18737@bombadil.infradead.org>
Date:   Sun, 25 Mar 2018 16:56:03 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     linux-mm@...ck.org, Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/4] mm: Add free()

On Fri, Mar 23, 2018 at 08:14:21AM -0700, Matthew Wilcox wrote:
> On Fri, Mar 23, 2018 at 04:33:24PM +0300, Kirill Tkhai wrote:
> > > +	page = virt_to_head_page(ptr);
> > > +	if (likely(PageSlab(page)))
> > > +		return kmem_cache_free(page->slab_cache, (void *)ptr);
> > 
> > It seems slab_cache is not generic for all types of slabs. SLOB does not care about it:
> 
> Oof.  I was sure I checked that.  You're quite right that it doesn't ...
> this should fix that problem:

This patch was complete rubbish.  The point of SLOB is that it mixes
sizes within the same page, and doesn't store the size when allocating
from a slab.  So there is no way to tell.  I'm going to think about this
some more.