From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752276AbdCAJrw (ORCPT ); Wed, 1 Mar 2017 04:47:52 -0500 Received: from merlin.infradead.org ([205.233.59.134]:39530 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751291AbdCAJrr (ORCPT ); Wed, 1 Mar 2017 04:47:47 -0500 Date: Wed, 1 Mar 2017 10:46:57 +0100 From: Peter Zijlstra To: Nikolay Borisov Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, ming.lei@canonical.com, minchan@kernel.org, mel@csn.ul.ie Subject: Re: [PATCH v2] lockdep: Teach lockdep about memalloc_noio_save Message-ID: <20170301094657.GC6515@twins.programming.kicks-ass.net> References: <1488354506-23774-1-git-send-email-nborisov@suse.com> <1488355140-24528-1-git-send-email-nborisov@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1488355140-24528-1-git-send-email-nborisov@suse.com> 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 Wed, Mar 01, 2017 at 09:59:00AM +0200, 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 prevents allocation paths recursing back into the filesystem > without explicitly changing the flags for every allocation site. Yet, lockdep > not being aware of that is prone to showing false positives. Fix this > by teaching it that the presence of PF_MEMALLOC_NOIO flag mean we are not > going to issue any I/O I'm not up to date on the specific, but GFP_IO is separate from GFP_FS. And MEMALLOC_NOIO only clears GFP_IO but leaves GFP_FS set. Therefore I think your change is wrong, but I might have overlooked a detail. Added original authors to Cc to clarify. > Signed-off-by: Nikolay Borisov > --- > kernel/locking/lockdep.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > > Turned out there was another place where RELCAIM_FS was being set, fix it > by using the memalloc_noio_flags when setting ->lockdep_reclaim_gfp flags. > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 9812e5dd409e..87cf9910e66f 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -2866,7 +2866,8 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags) > return; > > /* this guy won't enter reclaim */ > - if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC)) > + if (((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC)) || > + curr->flags & PF_MEMALLOC_NOIO) > return; > > /* We're only interested __GFP_FS allocations for now */ > @@ -3852,7 +3853,7 @@ 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 >