Return-Path: Received: from mx2.suse.de ([195.135.220.15]:50282 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S942421AbdAIN7H (ORCPT ); Mon, 9 Jan 2017 08:59:07 -0500 Date: Mon, 9 Jan 2017 14:59:01 +0100 From: Michal Hocko To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Dave Chinner , djwong@kernel.org, "Theodore Ts'o" , Chris Mason , David Sterba , Jan Kara , ceph-devel@vger.kernel.org, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, logfs@logfs.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mtd@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, linux-f2fs-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, LKML Subject: Re: [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Message-ID: <20170109135901.GJ7495@dhcp22.suse.cz> References: <20170106141107.23953-1-mhocko@kernel.org> <20170106141107.23953-4-mhocko@kernel.org> <86dbce74-a532-2f98-6a63-4dbad77b2aa1@suse.cz> <20170109134210.GI7495@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170109134210.GI7495@dhcp22.suse.cz> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon 09-01-17 14:42:10, Michal Hocko wrote: > On Mon 09-01-17 14:04:21, Vlastimil Babka wrote: [...] > Now that you have opened this I have noticed that the code is wrong > here because GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK would overwrite > the removed GFP_FS. Blee, it wouldn't because ~GFP_RECLAIM_MASK will not contain neither GFP_FS nor GFP_IO. So all is good here. > I guess it would be better and less error prone > to move the current_gfp_context part into the direct reclaim entry - > do_try_to_free_pages - and put the comment like this well, after more thinking about we, should probably keep it where it is. If for nothing else try_to_free_mem_cgroup_pages has a tracepoint which prints the gfp mask so we should use the filtered one. So let's just scratch this follow up fix. > --- > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 4ea6b610f20e..df7975185f11 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2756,6 +2756,13 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, > int initial_priority = sc->priority; > unsigned long total_scanned = 0; > unsigned long writeback_threshold; > + > + /* > + * Make sure that the gfp context properly handles scope gfp mask. > + * This might weaken the reclaim context (e.g. make it GFP_NOFS or > + * GFP_NOIO). > + */ > + sc->gfp_mask = current_gfp_context(sc->gfp_mask); > retry: > delayacct_freepages_start(); > > @@ -2949,7 +2956,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > unsigned long nr_reclaimed; > struct scan_control sc = { > .nr_to_reclaim = SWAP_CLUSTER_MAX, > - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)), > + .gfp_mask = gfp_mask, > .reclaim_idx = gfp_zone(gfp_mask), > .order = order, > .nodemask = nodemask, > @@ -3029,8 +3036,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, > int nid; > struct scan_control sc = { > .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), > - .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) | > - (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), > + .gfp_mask = GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK, > .reclaim_idx = MAX_NR_ZONES - 1, > .target_mem_cgroup = memcg, > .priority = DEF_PRIORITY, > @@ -3723,7 +3729,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in > int classzone_idx = gfp_zone(gfp_mask); > struct scan_control sc = { > .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), > - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)), > + .gfp_mask = gfp_mask, > .order = order, > .priority = NODE_RECLAIM_PRIORITY, > .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE), > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs