From: Waiman Long <longman@redhat.com> To: Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@kernel.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com> Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Waiman Long <longman@redhat.com> Subject: [PATCH v3 2/2] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Date: Wed, 5 May 2021 11:46:13 -0400 [thread overview] Message-ID: <20210505154613.17214-3-longman@redhat.com> (raw) In-Reply-To: <20210505154613.17214-1-longman@redhat.com> There are currently two problems in the way the objcg pointer array (memcg_data) in the page structure is being allocated and freed. On its allocation, it is possible that the allocated objcg pointer array comes from the same slab that requires memory accounting. If this happens, the slab will never become empty again as there is at least one object left (the obj_cgroup array) in the slab. When it is freed, the objcg pointer array object may be the last one in its slab and hence causes kfree() to be called again. With the right workload, the slab cache may be set up in a way that allows the recursive kfree() calling loop to nest deep enough to cause a kernel stack overflow and panic the system. One way to solve this problem is to split the kmalloc-<n> caches (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n> (KMALLOC_NORMAL) caches for non-accounted objects only and a new set of kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All the other caches can still allow a mix of accounted and non-accounted objects. With this change, all the objcg pointer array objects will come from KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So both the recursive kfree() problem and non-freeable slab problem are gone. Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have mixed accounted and unaccounted objects, this will slightly reduce the number of objcg pointer arrays that need to be allocated and save a bit of memory. The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() will include the newly added caches without change. Suggested-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Waiman Long <longman@redhat.com> --- include/linux/slab.h | 42 ++++++++++++++++++++++++++++++++++-------- mm/slab_common.c | 23 +++++++++++++++-------- 2 files changed, 49 insertions(+), 16 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index 0c97d788762c..f2d9ebc34f5c 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -305,9 +305,16 @@ static inline void __check_heap_object(const void *ptr, unsigned long n, /* * Whenever changing this, take care of that kmalloc_type() and * create_kmalloc_caches() still work as intended. + * + * KMALLOC_NORMAL is for non-accounted objects only whereas KMALLOC_CGROUP + * is for accounted objects only. All the other kmem caches can have both + * accounted and non-accounted objects. */ enum kmalloc_cache_type { KMALLOC_NORMAL = 0, +#ifdef CONFIG_MEMCG_KMEM + KMALLOC_CGROUP, +#endif KMALLOC_RECLAIM, #ifdef CONFIG_ZONE_DMA KMALLOC_DMA, @@ -315,28 +322,47 @@ enum kmalloc_cache_type { NR_KMALLOC_TYPES }; +#ifndef CONFIG_MEMCG_KMEM +#define KMALLOC_CGROUP KMALLOC_NORMAL +#endif +#ifndef CONFIG_ZONE_DMA +#define KMALLOC_DMA KMALLOC_NORMAL +#endif + #ifndef CONFIG_SLOB extern struct kmem_cache * kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1]; +/* + * Define gfp bits that should not be set for KMALLOC_NORMAL. + */ +#define KMALLOC_NOT_NORMAL_BITS \ + (__GFP_RECLAIMABLE | \ + (IS_ENABLED(CONFIG_ZONE_DMA) ? __GFP_DMA : 0) | \ + (IS_ENABLED(CONFIG_MEMCG_KMEM) ? __GFP_ACCOUNT : 0)) + static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) { -#ifdef CONFIG_ZONE_DMA /* * The most common case is KMALLOC_NORMAL, so test for it * with a single branch for both flags. */ - if (likely((flags & (__GFP_DMA | __GFP_RECLAIMABLE)) == 0)) + if (likely((flags & KMALLOC_NOT_NORMAL_BITS) == 0)) return KMALLOC_NORMAL; /* - * At least one of the flags has to be set. If both are, __GFP_DMA - * is more important. + * At least one of the flags has to be set. Their priorities in + * decreasing order are: + * 1) __GFP_DMA + * 2) __GFP_RECLAIMABLE + * 3) __GFP_ACCOUNT */ - return flags & __GFP_DMA ? KMALLOC_DMA : KMALLOC_RECLAIM; -#else - return flags & __GFP_RECLAIMABLE ? KMALLOC_RECLAIM : KMALLOC_NORMAL; -#endif + if (IS_ENABLED(CONFIG_ZONE_DMA) && (flags & __GFP_DMA)) + return KMALLOC_DMA; + if (!IS_ENABLED(CONFIG_MEMCG_KMEM) || (flags & __GFP_RECLAIMABLE)) + return KMALLOC_RECLAIM; + else + return KMALLOC_CGROUP; } /* diff --git a/mm/slab_common.c b/mm/slab_common.c index f8833d3e5d47..d750e3ba7af5 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -727,21 +727,25 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) } #ifdef CONFIG_ZONE_DMA -#define INIT_KMALLOC_INFO(__size, __short_size) \ -{ \ - .name[KMALLOC_NORMAL] = "kmalloc-" #__short_size, \ - .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size, \ - .name[KMALLOC_DMA] = "dma-kmalloc-" #__short_size, \ - .size = __size, \ -} +#define KMALLOC_DMA_NAME(sz) .name[KMALLOC_DMA] = "dma-kmalloc-" #sz, +#else +#define KMALLOC_DMA_NAME(sz) +#endif + +#ifdef CONFIG_MEMCG_KMEM +#define KMALLOC_CGROUP_NAME(sz) .name[KMALLOC_CGROUP] = "kmalloc-cg-" #sz, #else +#define KMALLOC_CGROUP_NAME(sz) +#endif + #define INIT_KMALLOC_INFO(__size, __short_size) \ { \ .name[KMALLOC_NORMAL] = "kmalloc-" #__short_size, \ .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size, \ + KMALLOC_CGROUP_NAME(__short_size) \ + KMALLOC_DMA_NAME(__short_size) \ .size = __size, \ } -#endif /* * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time. @@ -847,6 +851,9 @@ void __init create_kmalloc_caches(slab_flags_t flags) int i; enum kmalloc_cache_type type; + /* + * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined + */ for (type = KMALLOC_NORMAL; type <= KMALLOC_RECLAIM; type++) { for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) { if (!kmalloc_caches[type][i]) -- 2.18.1
WARNING: multiple messages have this Message-ID (diff)
From: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, Pekka Enberg <penberg-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Joonsoo Kim <iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org>, Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Subject: [PATCH v3 2/2] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Date: Wed, 5 May 2021 11:46:13 -0400 [thread overview] Message-ID: <20210505154613.17214-3-longman@redhat.com> (raw) In-Reply-To: <20210505154613.17214-1-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> There are currently two problems in the way the objcg pointer array (memcg_data) in the page structure is being allocated and freed. On its allocation, it is possible that the allocated objcg pointer array comes from the same slab that requires memory accounting. If this happens, the slab will never become empty again as there is at least one object left (the obj_cgroup array) in the slab. When it is freed, the objcg pointer array object may be the last one in its slab and hence causes kfree() to be called again. With the right workload, the slab cache may be set up in a way that allows the recursive kfree() calling loop to nest deep enough to cause a kernel stack overflow and panic the system. One way to solve this problem is to split the kmalloc-<n> caches (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n> (KMALLOC_NORMAL) caches for non-accounted objects only and a new set of kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All the other caches can still allow a mix of accounted and non-accounted objects. With this change, all the objcg pointer array objects will come from KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So both the recursive kfree() problem and non-freeable slab problem are gone. Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have mixed accounted and unaccounted objects, this will slightly reduce the number of objcg pointer arrays that need to be allocated and save a bit of memory. The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() will include the newly added caches without change. Suggested-by: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org> Signed-off-by: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> --- include/linux/slab.h | 42 ++++++++++++++++++++++++++++++++++-------- mm/slab_common.c | 23 +++++++++++++++-------- 2 files changed, 49 insertions(+), 16 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index 0c97d788762c..f2d9ebc34f5c 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -305,9 +305,16 @@ static inline void __check_heap_object(const void *ptr, unsigned long n, /* * Whenever changing this, take care of that kmalloc_type() and * create_kmalloc_caches() still work as intended. + * + * KMALLOC_NORMAL is for non-accounted objects only whereas KMALLOC_CGROUP + * is for accounted objects only. All the other kmem caches can have both + * accounted and non-accounted objects. */ enum kmalloc_cache_type { KMALLOC_NORMAL = 0, +#ifdef CONFIG_MEMCG_KMEM + KMALLOC_CGROUP, +#endif KMALLOC_RECLAIM, #ifdef CONFIG_ZONE_DMA KMALLOC_DMA, @@ -315,28 +322,47 @@ enum kmalloc_cache_type { NR_KMALLOC_TYPES }; +#ifndef CONFIG_MEMCG_KMEM +#define KMALLOC_CGROUP KMALLOC_NORMAL +#endif +#ifndef CONFIG_ZONE_DMA +#define KMALLOC_DMA KMALLOC_NORMAL +#endif + #ifndef CONFIG_SLOB extern struct kmem_cache * kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1]; +/* + * Define gfp bits that should not be set for KMALLOC_NORMAL. + */ +#define KMALLOC_NOT_NORMAL_BITS \ + (__GFP_RECLAIMABLE | \ + (IS_ENABLED(CONFIG_ZONE_DMA) ? __GFP_DMA : 0) | \ + (IS_ENABLED(CONFIG_MEMCG_KMEM) ? __GFP_ACCOUNT : 0)) + static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) { -#ifdef CONFIG_ZONE_DMA /* * The most common case is KMALLOC_NORMAL, so test for it * with a single branch for both flags. */ - if (likely((flags & (__GFP_DMA | __GFP_RECLAIMABLE)) == 0)) + if (likely((flags & KMALLOC_NOT_NORMAL_BITS) == 0)) return KMALLOC_NORMAL; /* - * At least one of the flags has to be set. If both are, __GFP_DMA - * is more important. + * At least one of the flags has to be set. Their priorities in + * decreasing order are: + * 1) __GFP_DMA + * 2) __GFP_RECLAIMABLE + * 3) __GFP_ACCOUNT */ - return flags & __GFP_DMA ? KMALLOC_DMA : KMALLOC_RECLAIM; -#else - return flags & __GFP_RECLAIMABLE ? KMALLOC_RECLAIM : KMALLOC_NORMAL; -#endif + if (IS_ENABLED(CONFIG_ZONE_DMA) && (flags & __GFP_DMA)) + return KMALLOC_DMA; + if (!IS_ENABLED(CONFIG_MEMCG_KMEM) || (flags & __GFP_RECLAIMABLE)) + return KMALLOC_RECLAIM; + else + return KMALLOC_CGROUP; } /* diff --git a/mm/slab_common.c b/mm/slab_common.c index f8833d3e5d47..d750e3ba7af5 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -727,21 +727,25 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags) } #ifdef CONFIG_ZONE_DMA -#define INIT_KMALLOC_INFO(__size, __short_size) \ -{ \ - .name[KMALLOC_NORMAL] = "kmalloc-" #__short_size, \ - .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size, \ - .name[KMALLOC_DMA] = "dma-kmalloc-" #__short_size, \ - .size = __size, \ -} +#define KMALLOC_DMA_NAME(sz) .name[KMALLOC_DMA] = "dma-kmalloc-" #sz, +#else +#define KMALLOC_DMA_NAME(sz) +#endif + +#ifdef CONFIG_MEMCG_KMEM +#define KMALLOC_CGROUP_NAME(sz) .name[KMALLOC_CGROUP] = "kmalloc-cg-" #sz, #else +#define KMALLOC_CGROUP_NAME(sz) +#endif + #define INIT_KMALLOC_INFO(__size, __short_size) \ { \ .name[KMALLOC_NORMAL] = "kmalloc-" #__short_size, \ .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size, \ + KMALLOC_CGROUP_NAME(__short_size) \ + KMALLOC_DMA_NAME(__short_size) \ .size = __size, \ } -#endif /* * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time. @@ -847,6 +851,9 @@ void __init create_kmalloc_caches(slab_flags_t flags) int i; enum kmalloc_cache_type type; + /* + * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined + */ for (type = KMALLOC_NORMAL; type <= KMALLOC_RECLAIM; type++) { for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) { if (!kmalloc_caches[type][i]) -- 2.18.1
next prev parent reply other threads:[~2021-05-05 15:47 UTC|newest] Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-05 15:46 [PATCH v3 0/2] mm: memcg/slab: Fix objcg pointer array handling problem Waiman Long 2021-05-05 15:46 ` Waiman Long 2021-05-05 15:46 ` [PATCH v3 1/2] mm: memcg/slab: Properly set up gfp flags for objcg pointer array Waiman Long 2021-05-05 15:46 ` Waiman Long 2021-05-05 16:09 ` Shakeel Butt 2021-05-05 16:09 ` Shakeel Butt 2021-05-05 16:09 ` Shakeel Butt 2021-05-05 16:46 ` Roman Gushchin 2021-05-05 16:46 ` Roman Gushchin 2021-05-05 15:46 ` Waiman Long [this message] 2021-05-05 15:46 ` [PATCH v3 2/2] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Waiman Long 2021-05-05 16:06 ` Vlastimil Babka 2021-05-05 16:06 ` Vlastimil Babka 2021-05-05 16:31 ` Waiman Long 2021-05-05 16:31 ` Waiman Long 2021-05-05 16:17 ` Shakeel Butt 2021-05-05 16:17 ` Shakeel Butt 2021-05-05 16:17 ` Shakeel Butt 2021-05-05 16:31 ` Waiman Long 2021-05-05 16:31 ` Waiman Long 2021-05-05 17:30 ` Roman Gushchin 2021-05-05 17:30 ` Roman Gushchin 2021-05-05 18:02 ` Vlastimil Babka 2021-05-05 18:02 ` Vlastimil Babka 2021-05-05 18:18 ` Roman Gushchin 2021-05-05 18:18 ` Roman Gushchin 2021-05-05 18:31 ` Waiman Long 2021-05-05 18:31 ` Waiman Long 2021-05-05 18:38 ` Roman Gushchin 2021-05-05 18:38 ` Roman Gushchin 2021-05-05 18:56 ` Waiman Long 2021-05-05 18:56 ` Waiman Long 2021-05-05 18:32 ` Roman Gushchin 2021-05-05 18:32 ` Roman Gushchin 2021-05-05 21:29 ` Vlastimil Babka 2021-05-05 21:29 ` Vlastimil Babka 2021-05-05 22:19 ` Roman Gushchin 2021-05-05 22:19 ` Roman Gushchin 2021-05-05 23:06 ` Waiman Long 2021-05-05 23:06 ` Waiman Long 2021-05-05 18:11 ` Waiman Long 2021-05-05 18:11 ` Waiman Long 2021-05-05 18:22 ` Roman Gushchin 2021-05-05 18:22 ` Roman Gushchin 2021-05-05 18:54 ` Waiman Long 2021-05-05 18:54 ` Waiman Long
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