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authorWaiman Long <longman@redhat.com>2021-06-28 19:37:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-29 10:53:49 -0700
commit494c1dfe855ec1f70f89552fce5eadf4a1717552 (patch)
tree1f75eb40a47f81a9133fd096a48feb4776fde9d7 /mm/slab_common.c
parent41eb5df1cbc9b302fc263ad7c9f38cfc38b4df61 (diff)
mm: memcg/slab: create a new set of kmalloc-cg-<n> caches
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 unaccounted 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 unaccounted 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. On the other hand, creating a new set of kmalloc caches does have the effect of reducing cache utilization. So it is properly a wash. 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. [vbabka@suse.cz: don't create kmalloc-cg caches with cgroup.memory=nokmem] Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com [akpm@linux-foundation.org: un-fat-finger v5 delta creation] [longman@redhat.com: disable cache merging for KMALLOC_NORMAL caches] Link: https://lkml.kernel.org/r/20210505200610.13943-4-longman@redhat.com Link: https://lkml.kernel.org/r/20210512145107.6208-1-longman@redhat.com Link: https://lkml.kernel.org/r/20210505200610.13943-3-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <guro@fb.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> [longman@redhat.com: fix for CONFIG_ZONE_DMA=n] Suggested-by: Roman Gushchin <guro@fb.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab_common.c')
-rw-r--r--mm/slab_common.c32
1 files changed, 23 insertions, 9 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 6c0db9f9bd8a..db3f356bf725 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -738,21 +738,25 @@ 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.
@@ -838,8 +842,15 @@ void __init setup_kmalloc_cache_index_table(void)
static void __init
new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
{
- if (type == KMALLOC_RECLAIM)
+ if (type == KMALLOC_RECLAIM) {
flags |= SLAB_RECLAIM_ACCOUNT;
+ } else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
+ if (cgroup_memory_nokmem) {
+ kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
+ return;
+ }
+ flags |= SLAB_ACCOUNT;
+ }
kmalloc_caches[type][idx] = create_kmalloc_cache(
kmalloc_info[idx].name[type],
@@ -857,6 +868,9 @@ 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])