From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 04/10] mm, memcg: fix corruption on 64-bit divisor in memory.high throttling Date: Sat, 21 Mar 2020 18:22:20 -0700 Message-ID: <20200322012220.Y-EvF7Agt%akpm@linux-foundation.org> References: <20200321181954.c0564dfd5514cd742b534884@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:41124 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726859AbgCVBWV (ORCPT ); Sat, 21 Mar 2020 21:22:21 -0400 In-Reply-To: <20200321181954.c0564dfd5514cd742b534884@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, chris@chrisdown.name, guro@fb.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@kernel.org, mm-commits@vger.kernel.org, natechancellor@gmail.com, stable@vger.kernel.org, tj@kernel.org, torvalds@linux-foundation.org From: Chris Down Subject: mm, memcg: fix corruption on 64-bit divisor in memory.high throttling 0e4b01df8659 had a bunch of fixups to use the right division method. However, it seems that after all that it still wasn't right -- div_u64 takes a 32-bit divisor. The headroom is still large (2^32 pages), so on mundane systems you won't hit this, but this should definitely be fixed. Link: http://lkml.kernel.org/r/80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.name Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Signed-off-by: Chris Down Reported-by: Johannes Weiner Acked-by: Johannes Weiner Cc: Tejun Heo Cc: Roman Gushchin Cc: Michal Hocko Cc: Nathan Chancellor Cc: [5.4.x+] Signed-off-by: Andrew Morton --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/memcontrol.c~mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling +++ a/mm/memcontrol.c @@ -2339,7 +2339,7 @@ void mem_cgroup_handle_over_high(void) */ clamped_high = max(high, 1UL); - overage = div_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, + overage = div64_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, clamped_high); penalty_jiffies = ((u64)overage * overage * HZ) _