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Date:   Tue, 10 Apr 2018 09:26:19 -0500 (CDT)
From:   Christopher Lameter <cl@linux.com>
To:     Matthew Wilcox <willy@infradead.org>
cc:     linux-mm@kvack.org, Matthew Wilcox <mawilcox@microsoft.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@redhat.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        stable@vger.kernel.org
Subject: Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a
 constructor
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References: <20180410125351.15837-1-willy@infradead.org> <alpine.DEB.2.20.1804100920110.27333@nuc-kabylake>
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On Tue, 10 Apr 2018, Christopher Lameter wrote:

> On Tue, 10 Apr 2018, Matthew Wilcox wrote:
>
> > __GFP_ZERO requests that the object be initialised to all-zeroes,
> > while the purpose of a constructor is to initialise an object to a
> > particular pattern.  We cannot do both.  Add a warning to catch any
> > users who mistakenly pass a __GFP_ZERO flag when allocating a slab with
> > a constructor.
>
> Can we move this check out of the critical paths and check for
> a ctor and GFP_ZERO when calling the page allocator? F.e. in
> allocate_slab()?

The ctor's are run at that point from setup_object() so it makes sense.