Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758139Ab1FJWBZ (ORCPT ); Fri, 10 Jun 2011 18:01:25 -0400 Received: from smtp-out.google.com ([74.125.121.67]:28412 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754222Ab1FJWBX (ORCPT ); Fri, 10 Jun 2011 18:01:23 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=X/3g/ERoBjcdP8TMo89iidt4ZUeRG3UTl9gC3+uPtEzbezexNFHazeWq5yFVE5E+U8 XVCHpwMlunhe2yAV2jRw== Date: Fri, 10 Jun 2011 15:01:15 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Russell King - ARM Linux , Linus Torvalds cc: Dmitry Eremin-Solenikov , Andrew Morton , KOSAKI Motohiro , tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mel@csn.ul.ie, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, pavel@ucw.cz Subject: Re: [PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing In-Reply-To: <20110610185858.GN24424@n2100.arm.linux.org.uk> Message-ID: References: <20110601181918.GO3660@n2100.arm.linux.org.uk> <4DF1C9DE.4070605@jp.fujitsu.com> <20110610004331.13672278.akpm@linux-foundation.org> <20110610091233.GJ24424@n2100.arm.linux.org.uk> <20110610185858.GN24424@n2100.arm.linux.org.uk> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1910 Lines: 42 On Fri, 10 Jun 2011, Russell King - ARM Linux wrote: > > > > Should one submit a patch adding a warning to GFP_DMA allocations > > > > w/o ZONE_DMA, or the idea of the original patch is wrong? > > > > > > Linus was far from impressed by the original commit, saying: > > > | Using GFP_DMA is reasonable in a driver - on platforms where that > > > | matters, it should allocate from the DMA zone, on platforms where it > > > | doesn't matter it should be a no-op. > > > > > > So no, not even a warning. > > > > > > > Any words of wisdom for users with CONFIG_ZONE_DMA=n that actually use > > drivers where they need GFP_DMA? The page allocator should just silently > > return memory from anywhere? > > See Linus' reply. I quote again "on platforms where it doesn't matter it > should be a no-op". If _you_ have a problem with that _you_ need to > discuss it with _Linus_, not me. I'm not going to be a middle-man sitting > between two people with different opinions. > We're talking about two different things. Linus is saying that if GFP_DMA should be a no-op if the hardware doesn't require DMA memory because the kernel was correctly compiled without CONFIG_ZONE_DMA. I'm asking about a kernel that was incorrectly compiled without CONFIG_ZONE_DMA and now we're returning memory from anywhere even though we actually require GFP_DMA. If you don't want to form an opinion of your own, then I have no problem cc'ing Linus on it. I don't think he'd object to a #ifndef CONFIG_ZONE_DMA WARN_ON_ONCE(1, "%s (%d): allocating DMA memory without DMA support -- " "enable CONFIG_ZONE_DMA if needed.\n", current->comm, current->pid); #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/