Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759452Ab1CaWvi (ORCPT ); Thu, 31 Mar 2011 18:51:38 -0400 Received: from mail-ew0-f46.google.com ([209.85.215.46]:52479 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752605Ab1CaWvg (ORCPT ); Thu, 31 Mar 2011 18:51:36 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:content-type:to:cc:subject:references:date:mime-version :content-transfer-encoding:from:organization:message-id:in-reply-to :user-agent; b=jj928NlbwBr+mARkEoXnUt0Uq97ED+HT+koDYmkX4FI6pKdNz82FhL1O0SHgTeJczf FCmnuWr5UtSN5LXKJ5rCk6tuGrJ9nXE8ZoyowOf3DAsD/3m0/Qu9EJc5Bu2G2mUeV9U+ HP9fldOSUhjmz/DJicDMb9UvPQYH8wAThQFgQ= Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes To: "Dave Hansen" Cc: "Marek Szyprowski" , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, linux-mm@kvack.org, "Kyungmin Park" , "Andrew Morton" , "KAMEZAWA Hiroyuki" , "Ankita Garg" , "Daniel Walker" , "Johan MOSSBERG" , "Mel Gorman" , "Pawel Osciak" Subject: Re: [PATCH 04/12] mm: alloc_contig_freed_pages() added References: <1301577368-16095-1-git-send-email-m.szyprowski@samsung.com> <1301577368-16095-5-git-send-email-m.szyprowski@samsung.com> <1301587083.31087.1032.camel@nimitz> <1301606078.31087.1275.camel@nimitz> <1301610411.30870.29.camel@nimitz> Date: Fri, 01 Apr 2011 00:51:32 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: "Michal Nazarewicz" Organization: Google Message-ID: In-Reply-To: <1301610411.30870.29.camel@nimitz> User-Agent: Opera Mail/11.01 (Linux) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2260 Lines: 53 On Fri, 01 Apr 2011 00:26:51 +0200, Dave Hansen wrote: > On Fri, 2011-04-01 at 00:18 +0200, Michal Nazarewicz wrote: >> On Thu, 31 Mar 2011 23:14:38 +0200, Dave Hansen wrote: >> > We BUG_ON() in bootmem. Basically if we try to allocate an early-boot >> > structure and fail, we're screwed. We can't keep running without an >> > inode hash, or a mem_map[]. >> > >> > This looks like it's going to at least get partially used in drivers, >> at >> > least from the examples. Are these kinds of things that, if the >> driver >> > fails to load, that the system is useless and hosed? Or, is it >> > something where we might limp along to figure out what went wrong >> before >> > we reboot? >> >> Bug in the above place does not mean that we could not allocate >> memory. It means caller is broken. > > Could you explain that a bit? > > Is this a case where a device is mapped to a very *specific* range of > physical memory and no where else? What are the reasons for not marking > it off limits at boot? I also saw some bits of isolation and migration > in those patches. Can't the migration fail? The function is called from alloc_contig_range() (see patch 05/12) which makes sure that the PFN is valid. Situation where there is not enough space is caught earlier in alloc_contig_range(). alloc_contig_freed_pages() must be given a valid PFN range such that all the pages in that range are free (as in are within the region tracked by page allocator) and of MIGRATETYPE_ISOLATE so that page allocator won't touch them. That's why invalid PFN is a bug in the caller and not an exception that has to be handled. Also, the function is not called during boot time. It is called while system is already running. -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michal "mina86" Nazarewicz (o o) ooo +----------ooO--(_)--Ooo-- -- 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/