Commit 617f8e4d authored by Sidhartha Kumar's avatar Sidhartha Kumar Committed by Andrew Morton
Browse files

maple_tree: add test to replicate low memory race conditions 

Add new callback fields to the userspace implementation of struct
kmem_cache.  This allows for executing callback functions in order to
further test low memory scenarios where node allocation is retried.

This callback can help test race conditions by calling a function when a
low memory event is tested.

Link: https://lkml.kernel.org/r/20240812190543.71967-2-sidhartha.kumar@oracle.com


Signed-off-by: default avatarSidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e1b8b883

lib/maple_tree.c

+13 −0
Original line number Diff line number Diff line
@@ -7005,6 +7005,19 @@ void mt_set_non_kernel(unsigned int val) 
	kmem_cache_set_non_kernel(maple_node_cache, val);

}



extern void kmem_cache_set_callback(struct kmem_cache *cachep,

		void (*callback)(void *));

void mt_set_callback(void (*callback)(void *))

{

	kmem_cache_set_callback(maple_node_cache, callback);

}



extern void kmem_cache_set_private(struct kmem_cache *cachep, void *private);

void mt_set_private(void *private)

{

	kmem_cache_set_private(maple_node_cache, private);

}



extern unsigned long kmem_cache_get_alloc(struct kmem_cache *);

unsigned long mt_get_alloc_size(void)

{

tools/testing/radix-tree/maple.c

+63 −0
Original line number Diff line number Diff line
@@ -36224,6 +36224,65 @@ static noinline void __init check_mtree_dup(struct maple_tree *mt) 








extern void test_kmem_cache_bulk(void);

















/* callback function used for check_nomem_writer_race() */









static void writer2(void *maple_tree)









{









	struct maple_tree *mt = (struct maple_tree *)maple_tree;









	MA_STATE(mas, mt, 6, 10);

















	mtree_lock(mas.tree);









	mas_store(&mas, xa_mk_value(0xC));









	mas_destroy(&mas);









	mtree_unlock(mas.tree);









}

















/*









 * check_nomem_writer_race() - test a possible race in the mas_nomem() path









 * @mt: The tree to build.









 *









 * There is a possible race condition in low memory conditions when mas_nomem()









 * gives up its lock. A second writer can chagne the entry that the primary









 * writer executing the mas_nomem() path is modifying. This test recreates this









 * scenario to ensure we are handling it correctly.









 */









static void check_nomem_writer_race(struct maple_tree *mt)









{









	MA_STATE(mas, mt, 0, 5);

















	mt_set_non_kernel(0);









	/* setup root with 2 values with NULL in between */









	mtree_store_range(mt, 0, 5, xa_mk_value(0xA), GFP_KERNEL);









	mtree_store_range(mt, 6, 10, NULL, GFP_KERNEL);









	mtree_store_range(mt, 11, 15, xa_mk_value(0xB), GFP_KERNEL);

















	/* setup writer 2 that will trigger the race condition */









	mt_set_private(mt);









	mt_set_callback(writer2);

















	mtree_lock(mt);









	/* erase 0-5 */









	mas_erase(&mas);

















	/* index 6-10 should retain the value from writer 2 */









	check_load(mt, 6, xa_mk_value(0xC));









	mtree_unlock(mt);

















	/* test for the same race but with mas_store_gfp() */









	mtree_store_range(mt, 0, 5, xa_mk_value(0xA), GFP_KERNEL);









	mtree_store_range(mt, 6, 10, NULL, GFP_KERNEL);

















	mas_set_range(&mas, 0, 5);









	mtree_lock(mt);









	mas_store_gfp(&mas, NULL, GFP_KERNEL);

















	/* ensure write made by writer 2 is retained */









	check_load(mt, 6, xa_mk_value(0xC));

















	mt_set_private(NULL);









	mt_set_callback(NULL);









	mtree_unlock(mt);









}

















void farmer_tests(void)









{









	struct maple_node *node;








@@ -36257,6 +36316,10 @@ void farmer_tests(void)







	check_dfs_preorder(&tree);









	mtree_destroy(&tree);

















	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE | MT_FLAGS_USE_RCU);









	check_nomem_writer_race(&tree);









	mtree_destroy(&tree);

















	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);









	check_prealloc(&tree);









	mtree_destroy(&tree);

























tools/testing/shared/linux.c



+25
−1






























Original line number
Diff line number
Diff line







@@ -26,8 +26,21 @@ struct kmem_cache {







	unsigned int non_kernel;









	unsigned long nr_allocated;









	unsigned long nr_tallocated;









	bool exec_callback;









	void (*callback)(void *);









	void *private;









};



















void kmem_cache_set_callback(struct kmem_cache *cachep, void (*callback)(void *))









{









	cachep->callback = callback;









}



















void kmem_cache_set_private(struct kmem_cache *cachep, void *private)









{









	cachep->private = private;









}



















void kmem_cache_set_non_kernel(struct kmem_cache *cachep, unsigned int val)









{









	cachep->non_kernel = val;








@@ -58,9 +71,17 @@ void *kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru,







{









	void *p;



















	if (cachep->exec_callback) {









		if (cachep->callback)









			cachep->callback(cachep->private);









		cachep->exec_callback = false;









	}



















	if (!(gfp & __GFP_DIRECT_RECLAIM)) {









		if (!cachep->non_kernel)









		if (!cachep->non_kernel) {









			cachep->exec_callback = true;









			return NULL;









		}



















		cachep->non_kernel--;









	}








@@ -223,6 +244,9 @@ kmem_cache_create(const char *name, unsigned int size, unsigned int align,







	ret->objs = NULL;









	ret->ctor = ctor;









	ret->non_kernel = 0;









	ret->exec_callback = false;









	ret->callback = NULL;









	ret->private = NULL;









	return ret;









}