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Date: Tue, 10 Apr 2018 09:21:20 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
Subject: Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a
 constructor
In-Reply-To: <20180410125351.15837-1-willy@infradead.org>
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References: <20180410125351.15837-1-willy@infradead.org>
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Sender: owner-linux-mm@kvack.org
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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

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()?