From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx144.postini.com [74.125.245.144]) by kanga.kvack.org (Postfix) with SMTP id 93C4E6B004A for ; Thu, 26 Apr 2012 22:23:53 -0400 (EDT) Message-ID: <4F9A0360.3030900@kernel.org> Date: Fri, 27 Apr 2012 11:24:32 +0900 From: Minchan Kim MIME-Version: 1.0 Subject: Re: [RFC] propagate gfp_t to page table alloc functions References: <1335171318-4838-1-git-send-email-minchan@kernel.org> <4F963742.2030607@jp.fujitsu.com> <4F963B8E.9030105@kernel.org> <4F965413.9010305@kernel.org> <20120424143015.99fd8d4a.akpm@linux-foundation.org> <4F973BF2.4080406@jp.fujitsu.com> <4F973FB8.6050103@jp.fujitsu.com> <20120424172554.c9c330dd.akpm@linux-foundation.org> <4F98914C.2060505@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: KAMEZAWA Hiroyuki , Andrew Morton , KOSAKI Motohiro , Nick Piggin , Ingo Molnar , x86@kernel.org, Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 04/26/2012 09:20 AM, David Rientjes wrote: > On Thu, 26 Apr 2012, KAMEZAWA Hiroyuki wrote: > >>> Or do we instead do this: >>> >>> - some_function(foo, bar, GFP_NOIO); >>> + old_gfp = set_current_gfp(GFP_NOIO); >>> + some_function(foo, bar); >>> + set_current_gfp(old_gfp); >>> >>> So the rule is "if the code was using an explicit GFP_foo then convert >>> it to use set_current_gfp(). If the code was receiving a gfp_t >>> variable from the caller then delete that arg". >>> >>> Or something like that. It's all too hopelessly impractical to bother >>> discussing - 20 years too late! >>> >>> >>> otoh, maybe a constrained version of this could be used to address the >>> vmalloc() problem alone. >>> >> >> Yes, I think it will be good start. >> > > Maybe a per-thread_info variant of gfp_allowed_mask? So Andrew's > set_current_gfp() becomes set_current_gfp_allowed() that does > > void set_current_gfp_allowed(gfp_t gfp_mask) > { > current->gfp_allowed = gfp_mask & gfp_allowed_mask; > } > > and then the page allocator does > > gfp_mask &= current->gfp_allowed; > > rather than how it currently does > > gfp_mask &= gfp_allowed_mask; > > and then the caller of set_current_gfp_allowed() cleans up with > set_current_gfp_allowed(__GFP_BITS_MASK). Caller should restore old gfp_mask instead of __GFP_BITS_MASK in case of nesting.And how do we care of atomic context? I was about to add warning in __vmalloc internal if caller uses GFP_NOIO, GFP_NOFS, GFP_ATOMIC with Nick's comment and let them make to fix it. But it seems Andrew doesn't agree. Andrew, please tell me your opinion for fixing this problem. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org