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Tue, 10 Apr 2018 09:53:11 -0400 Received: from mail-qk0-f196.google.com ([209.85.220.196]:46949 "EHLO mail-qk0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753149AbeDJNxJ (ORCPT ); Tue, 10 Apr 2018 09:53:09 -0400 X-Google-Smtp-Source: AIpwx483NjWs3z5Z2IrQbwTO10o0nJ+aDdu9K4fjRhc3weT/7FRBCmy3f2rHWKYuEsxXiQt6deK1Lg== Subject: Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a constructor To: Matthew Wilcox , linux-mm@kvack.org Cc: Matthew Wilcox , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , linux-kernel@vger.kernel.org, Jan Kara , Jeff Layton , Mel Gorman , stable@vger.kernel.org References: <20180410125351.15837-1-willy@infradead.org> From: Eric Dumazet Message-ID: Date: Tue, 10 Apr 2018 06:53:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180410125351.15837-1-willy@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 04/10/2018 05:53 AM, Matthew Wilcox wrote: > From: Matthew Wilcox > > __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. > > Fixes: d07dbea46405 ("Slab allocators: support __GFP_ZERO in all allocators") > Signed-off-by: Matthew Wilcox > Cc: stable@vger.kernel.org Since there are probably no bug to fix, what about adding the extra check only for some DEBUG option ? How many caches are still using ctor these days ?