From: Alexey Dobriyan adobriyan@gmail.com
/* * cpu_partial determined the maximum number of objects * kept in the per cpu partial lists of a processor. */
Can't be negative.
I hit a real issue that it will result in a large number of memory leak. Because Freeing slabs are in interrupt context. So it can trigger this issue. put_cpu_partial can be interrupted more than once. due to a union struct of lru and pobjects in struct page, when other core handles page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will result in pobjects being a negative value(0xdead0000). Therefore, a large number of slabs will be added to per_cpu partial list.
I had posted the issue to community before. The detailed issue description is as follows.
Link: https://www.spinics.net/lists/kernel/msg2870979.html
After applying the patch, The issue is fixed. So the patch is a effective bugfix. It should go into stable.
Signed-off-by: Alexey Dobriyan adobriyan@gmail.com Acked-by: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: zhong jiang zhongjiang@huawei.com --- include/linux/slub_def.h | 3 ++- mm/slub.c | 6 +++--- 2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index 3388511..9b681f2 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -67,7 +67,8 @@ struct kmem_cache { int size; /* The size of an object including meta data */ int object_size; /* The size of an object without meta data */ int offset; /* Free pointer offset. */ - int cpu_partial; /* Number of per cpu partial objects to keep around */ + /* Number of per cpu partial objects to keep around */ + unsigned int cpu_partial; struct kmem_cache_order_objects oo;
/* Allocation and freeing of slabs */ diff --git a/mm/slub.c b/mm/slub.c index 2284c43..c33b0e1 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1661,7 +1661,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n, { struct page *page, *page2; void *object = NULL; - int available = 0; + unsigned int available = 0; int objects;
/* @@ -4674,10 +4674,10 @@ static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf) static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf, size_t length) { - unsigned long objects; + unsigned int objects; int err;
- err = kstrtoul(buf, 10, &objects); + err = kstrtouint(buf, 10, &objects); if (err) return err; if (objects && !kmem_cache_has_cpu_partial(s))