From f56ce412a59d7d938b81de8878faef128812482c Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 19 Aug 2021 19:04:21 -0700 Subject: mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim We've noticed occasional OOM killing when memory.low settings are in effect for cgroups. This is unexpected and undesirable as memory.low is supposed to express non-OOMing memory priorities between cgroups. The reason for this is proportional memory.low reclaim. When cgroups are below their memory.low threshold, reclaim passes them over in the first round, and then retries if it couldn't find pages anywhere else. But when cgroups are slightly above their memory.low setting, page scan force is scaled down and diminished in proportion to the overage, to the point where it can cause reclaim to fail as well - only in that case we currently don't retry, and instead trigger OOM. To fix this, hook proportional reclaim into the same retry logic we have in place for when cgroups are skipped entirely. This way if reclaim fails and some cgroups were scanned with diminished pressure, we'll try another full-force cycle before giving up and OOMing. [akpm@linux-foundation.org: coding-style fixes] Link: https://lkml.kernel.org/r/20210817180506.220056-1-hannes@cmpxchg.org Fixes: 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim") Signed-off-by: Johannes Weiner Reported-by: Leon Yang Reviewed-by: Rik van Riel Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Chris Down Acked-by: Michal Hocko Cc: [5.4+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index bfe5c486f4ad..24797929d8a1 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -612,12 +612,15 @@ static inline bool mem_cgroup_disabled(void) return !cgroup_subsys_enabled(memory_cgrp_subsys); } -static inline unsigned long mem_cgroup_protection(struct mem_cgroup *root, - struct mem_cgroup *memcg, - bool in_low_reclaim) +static inline void mem_cgroup_protection(struct mem_cgroup *root, + struct mem_cgroup *memcg, + unsigned long *min, + unsigned long *low) { + *min = *low = 0; + if (mem_cgroup_disabled()) - return 0; + return; /* * There is no reclaim protection applied to a targeted reclaim. @@ -653,13 +656,10 @@ static inline unsigned long mem_cgroup_protection(struct mem_cgroup *root, * */ if (root == memcg) - return 0; - - if (in_low_reclaim) - return READ_ONCE(memcg->memory.emin); + return; - return max(READ_ONCE(memcg->memory.emin), - READ_ONCE(memcg->memory.elow)); + *min = READ_ONCE(memcg->memory.emin); + *low = READ_ONCE(memcg->memory.elow); } void mem_cgroup_calculate_protection(struct mem_cgroup *root, @@ -1147,11 +1147,12 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm, { } -static inline unsigned long mem_cgroup_protection(struct mem_cgroup *root, - struct mem_cgroup *memcg, - bool in_low_reclaim) +static inline void mem_cgroup_protection(struct mem_cgroup *root, + struct mem_cgroup *memcg, + unsigned long *min, + unsigned long *low) { - return 0; + *min = *low = 0; } static inline void mem_cgroup_calculate_protection(struct mem_cgroup *root, -- cgit v1.2.3 From a7cb5d23eaea148f8582229846f8dfff192f05c3 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 19 Aug 2021 19:04:30 -0700 Subject: kfence: fix is_kfence_address() for addresses below KFENCE_POOL_SIZE Originally the addr != NULL check was meant to take care of the case where __kfence_pool == NULL (KFENCE is disabled). However, this does not work for addresses where addr > 0 && addr < KFENCE_POOL_SIZE. This can be the case on NULL-deref where addr > 0 && addr < PAGE_SIZE or any other faulting access with addr < KFENCE_POOL_SIZE. While the kernel would likely crash, the stack traces and report might be confusing due to double faults upon KFENCE's attempt to unprotect such an address. Fix it by just checking that __kfence_pool != NULL instead. Link: https://lkml.kernel.org/r/20210818130300.2482437-1-elver@google.com Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Marco Elver Reported-by: Kuan-Ying Lee Acked-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: [5.12+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kfence.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/kfence.h b/include/linux/kfence.h index a70d1ea03532..3fe6dd8a18c1 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -51,10 +51,11 @@ extern atomic_t kfence_allocation_gate; static __always_inline bool is_kfence_address(const void *addr) { /* - * The non-NULL check is required in case the __kfence_pool pointer was - * never initialized; keep it in the slow-path after the range-check. + * The __kfence_pool != NULL check is required to deal with the case + * where __kfence_pool == NULL && addr < KFENCE_POOL_SIZE. Keep it in + * the slow-path after the range-check! */ - return unlikely((unsigned long)((char *)addr - __kfence_pool) < KFENCE_POOL_SIZE && addr); + return unlikely((unsigned long)((char *)addr - __kfence_pool) < KFENCE_POOL_SIZE && __kfence_pool); } /** -- cgit v1.2.3