From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753252AbeEURJR (ORCPT ); Mon, 21 May 2018 13:09:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:50633 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753065AbeEURJQ (ORCPT ); Mon, 21 May 2018 13:09:16 -0400 Date: Mon, 21 May 2018 19:06:32 +0200 From: David Sterba To: Matthew Wilcox Cc: Huaisheng HS1 Ye , Michal Hocko , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "pasha.tatashin@oracle.com" , "alexander.levin@verizon.com" , "hannes@cmpxchg.org" , "penguin-kernel@I-love.SAKURA.ne.jp" , "colyli@suse.de" , NingTing Cheng , "linux-kernel@vger.kernel.org" Subject: Re: [External] Re: [PATCH 2/3] include/linux/gfp.h: use unsigned int in gfp_zone Message-ID: <20180521170632.GY6649@suse.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Matthew Wilcox , Huaisheng HS1 Ye , Michal Hocko , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "pasha.tatashin@oracle.com" , "alexander.levin@verizon.com" , "hannes@cmpxchg.org" , "penguin-kernel@I-love.SAKURA.ne.jp" , "colyli@suse.de" , NingTing Cheng , "linux-kernel@vger.kernel.org" References: <20180506134814.GB7362@bombadil.infradead.org> <20180506185532.GA13604@bombadil.infradead.org> <20180507184410.GA12361@bombadil.infradead.org> <20180507212500.bdphwfhk55w6vlbb@twin.jikos.cz> <20180508002547.GA16338@bombadil.infradead.org> <20180509093659.jalprmufpwspya26@twin.jikos.cz> <20180515115404.GD31599@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180515115404.GD31599@bombadil.infradead.org> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 15, 2018 at 04:54:04AM -0700, Matthew Wilcox wrote: > > > Subject: btrfs: Allocate extents from ZONE_NORMAL > > > From: Matthew Wilcox > > > > > > If anyone ever passes a GFP_DMA or GFP_MOVABLE allocation flag to > > > allocate_extent_state, it will try to allocate memory from the wrong zone. > > > We just want to allocate memory from ZONE_NORMAL, so use GFP_RECLAIM_MASK > > > to get what we want. > > > > Looks good to me. > > > > > Signed-off-by: Matthew Wilcox > > > > > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > > > index e99b329002cf..4e4a67b7b29d 100644 > > > --- a/fs/btrfs/extent_io.c > > > +++ b/fs/btrfs/extent_io.c > > > @@ -216,12 +216,7 @@ static struct extent_state *alloc_extent_state(gfp_t mask) > > > { > > > struct extent_state *state; > > > > > > - /* > > > - * The given mask might be not appropriate for the slab allocator, > > > - * drop the unsupported bits > > > - */ > > > - mask &= ~(__GFP_DMA32|__GFP_HIGHMEM); > > > > I've noticed there's GFP_SLAB_BUG_MASK that's basically open coded here, > > but this would not filter out the placement flags. > > > > > - state = kmem_cache_alloc(extent_state_cache, mask); > > > > I'd prefer some comment here, it's not obvious why the mask is used. > > Sorry, I dropped the ball on this. Would you prefer: > > /* Allocate from ZONE_NORMAL */ > state = kmem_cache_alloc(extent_state_cache, mask & GFP_RECLAIM_MASK); > > or > > /* > * Callers may pass in a mask which indicates they want to allocate > * from a special zone, so clear those bits here rather than forcing > * each caller to do it. We only want to use their mask to indicate > * what strategies the memory allocator can use to free memory. > */ > state = kmem_cache_alloc(extent_state_cache, mask & GFP_RECLAIM_MASK); > > I tend to lean towards being more terse, but it's not about me, it's > about whoever reads this code next. I prefer the latter variant, it's clear that it's some MM stuff. Thanks.