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[104.223.48.154]) by mx.google.com with ESMTPS id ba5si13888034plb.24.2019.04.14.19.46.44 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 14 Apr 2019 19:46:45 -0700 (PDT) Received-SPF: pass (google.com: domain of herbert@gondor.apana.org.au designates 104.223.48.154 as permitted sender) client-ip=104.223.48.154; Authentication-Results: mx.google.com; spf=pass (google.com: domain of herbert@gondor.apana.org.au designates 104.223.48.154 as permitted sender) smtp.mailfrom=herbert@gondor.apana.org.au Received: from gondobar.mordor.me.apana.org.au ([192.168.128.4] helo=gondobar) by deadmen.hmeau.com with esmtps (Exim 4.89 #2 (Debian)) id 1hFrdU-0001NG-T0; Mon, 15 Apr 2019 10:46:21 +0800 Received: from herbert by gondobar with local (Exim 4.89) (envelope-from ) id 1hFrdP-0003On-6f; Mon, 15 Apr 2019 10:46:15 +0800 Date: Mon, 15 Apr 2019 10:46:15 +0800 From: Herbert Xu To: Matthew Wilcox Cc: Kees Cook , Eric Biggers , Rik van Riel , linux-crypto , Dmitry Vyukov , Geert Uytterhoeven , linux-security-module , Linux ARM , Linux Kernel Mailing List , Laura Abbott , linux-mm@kvack.org Subject: Re: [PATCH] crypto: testmgr - allocate buffers with __GFP_COMP Message-ID: <20190415024615.f765e7oagw26ezam@gondor.apana.org.au> References: <20190411192607.GD225654@gmail.com> <20190411192827.72551-1-ebiggers@kernel.org> <20190415022412.GA29714@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190415022412.GA29714@bombadil.infradead.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Apr 14, 2019 at 07:24:12PM -0700, Matthew Wilcox wrote: > On Thu, Apr 11, 2019 at 01:32:32PM -0700, Kees Cook wrote: > > > @@ -156,7 +156,8 @@ static int __testmgr_alloc_buf(char *buf[XBUFSIZE], int order) > > > int i; > > > > > > for (i = 0; i < XBUFSIZE; i++) { > > > - buf[i] = (char *)__get_free_pages(GFP_KERNEL, order); > > > + buf[i] = (char *)__get_free_pages(GFP_KERNEL | __GFP_COMP, > > > + order); > > > > Is there a reason __GFP_COMP isn't automatically included in all page > > allocations? (Or rather, it seems like the exception is when things > > should NOT be considered part of the same allocation, so something > > like __GFP_SINGLE should exist?.) > > The question is not whether or not things should be considered part of the > same allocation. The question is whether the allocation is of a compound > page or of N consecutive pages. Now you're asking what the difference is, > and it's whether you need to be able to be able to call compound_head(), > compound_order(), PageTail() or use a compound_dtor. If you don't, then > you can save some time at allocation & free by not specifying __GFP_COMP. Thanks for clarifying Matthew. Eric, this means that we should not use __GFP_COMP here just to silent what is clearly a broken warning. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt