From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751254AbcGNOAV (ORCPT ); Thu, 14 Jul 2016 10:00:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58776 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751115AbcGNOAT (ORCPT ); Thu, 14 Jul 2016 10:00:19 -0400 Date: Thu, 14 Jul 2016 10:00:16 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Michal Hocko cc: Ondrej Kozina , Jerome Marchand , Stanislav Kozina , linux-mm@kvack.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: System freezes after OOM In-Reply-To: <20160714125129.GA12289@dhcp22.suse.cz> Message-ID: References: <57837CEE.1010609@redhat.com> <9be09452-de7f-d8be-fd5d-4a80d1cd1ba3@redhat.com> <20160712064905.GA14586@dhcp22.suse.cz> <20160713111006.GF28723@dhcp22.suse.cz> <20160714125129.GA12289@dhcp22.suse.cz> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 14 Jul 2016 14:00:18 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 14 Jul 2016, Michal Hocko wrote: > On Wed 13-07-16 11:02:15, Mikulas Patocka wrote: > > > diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c > > > index 4f3cb3554944..0b806810efab 100644 > > > --- a/drivers/md/dm-crypt.c > > > +++ b/drivers/md/dm-crypt.c > > > @@ -1392,11 +1392,14 @@ static void kcryptd_async_done(struct crypto_async_request *async_req, > > > static void kcryptd_crypt(struct work_struct *work) > > > { > > > struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work); > > > + unsigned int pflags = current->flags; > > > > > > + current->flags |= PF_LESS_THROTTLE; > > > if (bio_data_dir(io->base_bio) == READ) > > > kcryptd_crypt_read_convert(io); > > > else > > > kcryptd_crypt_write_convert(io); > > > + tsk_restore_flags(current, pflags, PF_LESS_THROTTLE); > > > } > > > > > > static void kcryptd_queue_crypt(struct dm_crypt_io *io) > > > > ^^^ That fixes just one specific case - but there may be other threads > > doing mempool allocations in the device mapper subsystem - and you would > > need to mark all of them. > > Now that I am thinking about it some more. Are there any mempool users > which would actually want to be throttled? I would expect mempool users > are necessary to push IO through and throttle them sounds like a bad > decision in the first place but there might be other mempool users which > could cause issues. Anyway how about setting PF_LESS_THROTTLE > unconditionally inside mempool_alloc? Something like the following: > > diff --git a/mm/mempool.c b/mm/mempool.c > index 8f65464da5de..e21fb632983f 100644 > --- a/mm/mempool.c > +++ b/mm/mempool.c > @@ -310,7 +310,8 @@ EXPORT_SYMBOL(mempool_resize); > */ > void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > { > - void *element; > + unsigned int pflags = current->flags; > + void *element = NULL; > unsigned long flags; > wait_queue_t wait; > gfp_t gfp_temp; > @@ -327,6 +328,12 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > > gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO); > > + /* > + * Make sure that the allocation doesn't get throttled during the > + * reclaim > + */ > + if (gfpflags_allow_blocking(gfp_mask)) > + current->flags |= PF_LESS_THROTTLE; > repeat_alloc: > if (likely(pool->curr_nr)) { > /* > @@ -339,7 +346,7 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > > element = pool->alloc(gfp_temp, pool->pool_data); > if (likely(element != NULL)) > - return element; > + goto out; > > spin_lock_irqsave(&pool->lock, flags); > if (likely(pool->curr_nr)) { > @@ -352,7 +359,7 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > * for debugging. > */ > kmemleak_update_trace(element); > - return element; > + goto out; > } > > /* > @@ -369,7 +376,7 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > /* We must not sleep if !__GFP_DIRECT_RECLAIM */ > if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) { > spin_unlock_irqrestore(&pool->lock, flags); > - return NULL; > + goto out; > } > > /* Let's wait for someone else to return an element to @pool */ > @@ -386,6 +393,10 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) > > finish_wait(&pool->wait, &wait); > goto repeat_alloc; > +out: > + if (gfpflags_allow_blocking(gfp_mask)) > + tsk_restore_flags(current, pflags, PF_LESS_THROTTLE); > + return element; > } > EXPORT_SYMBOL(mempool_alloc); > But it needs other changes to honor the PF_LESS_THROTTLE flag: static int current_may_throttle(void) { return !(current->flags & PF_LESS_THROTTLE) || current->backing_dev_info == NULL || bdi_write_congested(current->backing_dev_info); } --- if you set PF_LESS_THROTTLE, current_may_throttle may still return true if one of the other conditions is met. shrink_zone_memcg calls throttle_vm_writeout without checking PF_LESS_THROTTLE at all. Mikulas