From: Chris Down chris@chrisdown.name 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... Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Signed-off-by: Chris Down chris@chrisdown.name Reported-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Tejun Heo tj@kernel.org Cc: Roman Gushchin guro@fb.com Cc: Michal Hocko mhocko@kernel.org Cc: Nathan Chancellor natechancellor@gmail.com Cc: stable@vger.kernel.org [5.4.x+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
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) _