From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754687AbbCBUdK (ORCPT ); Mon, 2 Mar 2015 15:33:10 -0500 Received: from mail-wg0-f54.google.com ([74.125.82.54]:34752 "EHLO mail-wg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753836AbbCBUdI (ORCPT ); Mon, 2 Mar 2015 15:33:08 -0500 Date: Mon, 2 Mar 2015 21:33:04 +0100 From: Michal Hocko To: David Miller Cc: linux-mm@kvack.org, akpm@linux-foundation.org, hannes@cmpxchg.org, rientjes@google.com, david@fromorbit.com, tytso@mit.edu, mgorman@suse.de, penguin-kernel@I-love.SAKURA.ne.jp, sparclinux@vger.kernel.org, vipul@chelsio.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 3/4] sparc: remove __GFP_NOFAIL reuquirement Message-ID: <20150302203304.GA20513@dhcp22.suse.cz> References: <1425304483-7987-1-git-send-email-mhocko@suse.cz> <1425304483-7987-4-git-send-email-mhocko@suse.cz> <20150302.150405.2072800922470200977.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150302.150405.2072800922470200977.davem@davemloft.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 02-03-15 15:04:05, David S. Miller wrote: > From: Michal Hocko > Date: Mon, 2 Mar 2015 14:54:42 +0100 > > > mdesc_kmalloc is currently requiring __GFP_NOFAIL allocation although it > > seems that the allocation failure is handled by all callers (via > > mdesc_alloc). __GFP_NOFAIL is a strong liability for the memory > > allocator and so the users are discouraged to use the flag unless the > > allocation failure is really a nogo. Drop the flag here as this doesn't > > seem to be the case. > > > > Signed-off-by: Michal Hocko > > It is a serious failure. > > If we miss an MDESC update due to this allocation failure, the update > is not an event which gets retransmitted so we will lose the updated > machine description forever. > > We really need this allocation to succeed. OK, thanks for the clarification. This wasn't clear from the commit which has introduced this code. I will drop this patch. Would you accept something like the following instead? --- diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c index 99632a87e697..26c80e18d7b1 100644 --- a/arch/sparc/kernel/mdesc.c +++ b/arch/sparc/kernel/mdesc.c @@ -130,26 +130,26 @@ static struct mdesc_mem_ops memblock_mdesc_ops = { static struct mdesc_handle *mdesc_kmalloc(unsigned int mdesc_size) { unsigned int handle_size; + struct mdesc_handle *hp; + unsigned long addr; void *base; handle_size = (sizeof(struct mdesc_handle) - sizeof(struct mdesc_hdr) + mdesc_size); + /* + * Allocation has to succeed because mdesc update would be missed + * and such events are not retransmitted. + */ base = kmalloc(handle_size + 15, GFP_KERNEL | __GFP_NOFAIL); - if (base) { - struct mdesc_handle *hp; - unsigned long addr; - - addr = (unsigned long)base; - addr = (addr + 15UL) & ~15UL; - hp = (struct mdesc_handle *) addr; + addr = (unsigned long)base; + addr = (addr + 15UL) & ~15UL; + hp = (struct mdesc_handle *) addr; - mdesc_handle_init(hp, handle_size, base); - return hp; - } + mdesc_handle_init(hp, handle_size, base); - return NULL; + return hp; } static void mdesc_kfree(struct mdesc_handle *hp) -- Michal Hocko SUSE Labs