From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id 816636B0044 for ; Tue, 24 Apr 2012 03:19:22 -0400 (EDT) Message-ID: <4F965413.9010305@kernel.org> Date: Tue, 24 Apr 2012 16:19:47 +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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Nick Piggin Cc: KAMEZAWA Hiroyuki , Andrew Morton , Ingo Molnar , x86@kernel.org, Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 04/24/2012 03:13 PM, Nick Piggin wrote: > 2012/4/24 Minchan Kim : >> On 04/24/2012 02:16 PM, KAMEZAWA Hiroyuki wrote: >> >>> (2012/04/23 17:55), Minchan Kim wrote: >>> >>>> As I test some code, I found a problem about deadlock by lockdep. >>>> The reason I saw the message is __vmalloc calls map_vm_area which calls >>>> pud/pmd_alloc without gfp_t. so although we call __vmalloc with >>>> GFP_ATOMIC or GFP_NOIO, it ends up allocating pages with GFP_KERNEL. >>>> The should be a BUG. This patch fixes it by passing gfp_to to low page >>>> table allocate functions. >>>> >>>> Signed-off-by: Minchan Kim >>> >>> >>> Hmm ? vmalloc should support GFP_ATOMIC ? >> >> >> I'm not sure but alloc_large_system_hash already has used. >> And it's not specific on GFP_ATOMIC. >> We have to care of GFP_NOFS and GFP_NOIO to prevent deadlock on reclaim >> context. >> There are some places to use GFP_NOFS and we don't emit any warning >> message in case of that. > > What's the lockdep warning? It's just some private-test code, not-mainlined and lockdep warning is like this. [ INFO: inconsistent lock state ] 3.4.0-rc3-next-20120417+ #80 Not tainted --------------------------------- inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage. It seems test code calls vmalloc inside reclaim context so that it enters reclaim context, again by map_vm_area which allocates pages with GFP_KERNEL. Of course, I can avoid this problem by fixing the caller but during I look into this problem, found other places to use gfp_t with "context restriction". > > vmalloc was never supposed to use gfp flags for allocation "context" > restriction. I.e., it > was always supposed to have blocking, fs, and io capable allocation > context. The flags > were supposed to be a memory type modifier. You mean "zone modifiers"? > > These different classes of flags is a bit of a problem and source of > confusion we have. > We should be doing more checks for them, of course. It might need some warning in __vmalloc and family which use gfp_t if the caller use context flags. > > I suspect you need to fix the caller? Hmm, there are several places to use GFP_NOIO and GFP_NOFS even, GFP_ATOMIC. I believe it's not trivial now. > > Thanks, > Nick > > -- > 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 > -- 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