From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751842AbdCANYo (ORCPT ); Wed, 1 Mar 2017 08:24:44 -0500 Received: from mx2.suse.de ([195.135.220.15]:41352 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750704AbdCANYi (ORCPT ); Wed, 1 Mar 2017 08:24:38 -0500 Date: Wed, 1 Mar 2017 13:09:48 +0100 From: Michal Hocko To: Nikolay Borisov Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, vbabka.lkml@gmail.com, linux-mm@kvack.org, mingo@redhat.com Subject: Re: [PATCH v3] lockdep: Teach lockdep about memalloc_noio_save Message-ID: <20170301120947.GE1124@dhcp22.suse.cz> References: <1488367797-27278-1-git-send-email-nborisov@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1488367797-27278-1-git-send-email-nborisov@suse.com> 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 Wed 01-03-17 13:29:57, Nikolay Borisov wrote: > Commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O > during memory allocation") added the memalloc_noio_(save|restore) functions > to enable people to modify the MM behavior by disbaling I/O during memory > allocation. This was further extended in Fixes: 934f3072c17c ("mm: clear > __GFP_FS when PF_MEMALLOC_NOIO is set"). memalloc_noio_* functions prevent > allocation paths recursing back into the filesystem without explicitly > changing the flags for every allocation site. However, lockdep hasn't been > keeping up with the changes and it entirely misses handling the memalloc_noio > adjustments. Instead, it is left to the callers of __lockdep_trace_alloc to > call the functino after they have shaven the respective GFP flags. I would just add that this might lead to false positives and past the example you have encountered. > Let's fix this by making lockdep explicitly do the shaving of respective > GFP flags. > > Fixes: 934f3072c17c ("mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set") > Signed-off-by: Nikolay Borisov Acked-by: Michal Hocko > --- > kernel/locking/lockdep.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > Changes since v2: > * Incorporate Michal's suggestion of using memalloc_noio_flags explicitly. > * Tune the commit message to make the problem statement a bit more > descriptive. > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 9812e5dd409e..565506c9e99c 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -2861,6 +2861,8 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags) > if (unlikely(!debug_locks)) > return; > > + gfp_mask = memalloc_noio_flags(gfp_mask); > + > /* no reclaim without waiting on it */ > if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) > return; > @@ -3852,7 +3854,7 @@ EXPORT_SYMBOL_GPL(lock_unpin_lock); > > void lockdep_set_current_reclaim_state(gfp_t gfp_mask) > { > - current->lockdep_reclaim_gfp = gfp_mask; > + current->lockdep_reclaim_gfp = memalloc_noio_flags(gfp_mask); > } > > void lockdep_clear_current_reclaim_state(void) > -- > 2.7.4 -- Michal Hocko SUSE Labs