Commit 0647398a authored by Catalin Marinas's avatar Catalin Marinas Committed by Linus Torvalds
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mm: kmemleak: simple memory allocation pool for kmemleak objects 

Add a memory pool for struct kmemleak_object in case the normal
kmem_cache_alloc() fails under the gfp constraints passed by the caller.
The mem_pool[] array size is currently fixed at 16000.

We are not using the existing mempool kernel API since this requires
the slab allocator to be available (for pool->elements allocation).  A
subsequent kmemleak patch will replace the static early log buffer with
the pool allocation introduced here and this functionality is required
to be available before the slab was initialised.

Link: http://lkml.kernel.org/r/20190812160642.52134-3-catalin.marinas@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dba82d94

mm/kmemleak.c

+52 −2
Original line number Diff line number Diff line
@@ -180,11 +180,17 @@ struct kmemleak_object { 
#define HEX_ASCII		1

/* max number of lines to be printed */

#define HEX_MAX_LINES		2

/* memory pool size */

#define MEM_POOL_SIZE		16000



/* the list of all allocated objects */

static LIST_HEAD(object_list);

/* the list of gray-colored objects (see color_gray comment below) */

static LIST_HEAD(gray_list);

/* memory pool allocation */

static struct kmemleak_object mem_pool[MEM_POOL_SIZE];

static int mem_pool_free_count = ARRAY_SIZE(mem_pool);

static LIST_HEAD(mem_pool_free_list);

/* search tree for object boundaries */

static struct rb_root object_tree_root = RB_ROOT;

/* rw_lock protecting the access to object_list and object_tree_root */
@@ -451,6 +457,50 @@ static int get_object(struct kmemleak_object *object) 
	return atomic_inc_not_zero(&object->use_count);

}



/*

 * Memory pool allocation and freeing. kmemleak_lock must not be held.

 */

static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)

{

	unsigned long flags;

	struct kmemleak_object *object;



	/* try the slab allocator first */

	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));

	if (object)

		return object;



	/* slab allocation failed, try the memory pool */

	write_lock_irqsave(&kmemleak_lock, flags);

	object = list_first_entry_or_null(&mem_pool_free_list,

					  typeof(*object), object_list);

	if (object)

		list_del(&object->object_list);

	else if (mem_pool_free_count)

		object = &mem_pool[--mem_pool_free_count];

	write_unlock_irqrestore(&kmemleak_lock, flags);



	return object;

}



/*

 * Return the object to either the slab allocator or the memory pool.

 */

static void mem_pool_free(struct kmemleak_object *object)

{

	unsigned long flags;



	if (object < mem_pool || object >= mem_pool + ARRAY_SIZE(mem_pool)) {

		kmem_cache_free(object_cache, object);

		return;

	}



	/* add the object to the memory pool free list */

	write_lock_irqsave(&kmemleak_lock, flags);

	list_add(&object->object_list, &mem_pool_free_list);

	write_unlock_irqrestore(&kmemleak_lock, flags);

}



/*

 * RCU callback to free a kmemleak_object.

 */
@@ -469,7 +519,7 @@ static void free_object_rcu(struct rcu_head *rcu) 
		hlist_del(&area->node);

		kmem_cache_free(scan_area_cache, area);

	}

	kmem_cache_free(object_cache, object);

	mem_pool_free(object);

}



/*
@@ -552,7 +602,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, 
	struct rb_node **link, *rb_parent;

	unsigned long untagged_ptr;



	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));

	object = mem_pool_alloc(gfp);

	if (!object) {

		pr_warn("Cannot allocate a kmemleak_object structure\n");

		kmemleak_disable();

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