From 90e9f6a66c78fdf3c2e5884ffe97bfc2736863c2 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 30 Jan 2020 22:11:57 -0800 Subject: [PATCH] mm/slub.c: avoid slub allocation while holding list_lock If we are already under list_lock, don't call kmalloc(). Otherwise we will run into a deadlock because kmalloc() also tries to grab the same lock. Fix the problem by using a static bitmap instead. WARNING: possible recursive locking detected -------------------------------------------- mount-encrypted/4921 is trying to acquire lock: (&(&n->list_lock)->rlock){-.-.}, at: ___slab_alloc+0x104/0x437 but task is already holding lock: (&(&n->list_lock)->rlock){-.-.}, at: __kmem_cache_shutdown+0x81/0x3cb other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&n->list_lock)->rlock); lock(&(&n->list_lock)->rlock); *** DEADLOCK *** Link: http://lkml.kernel.org/r/20191108193958.205102-2-yuzhao@google.com Signed-off-by: Yu Zhao Acked-by: Kirill A. Shutemov Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Tetsuo Handa Cc: Yu Zhao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slub.c | 88 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 47 insertions(+), 41 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 0ab92ec8c2a6..17dc00e33115 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -439,19 +439,38 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page, } #ifdef CONFIG_SLUB_DEBUG +static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)]; +static DEFINE_SPINLOCK(object_map_lock); + /* * Determine a map of object in use on a page. * * Node listlock must be held to guarantee that the page does * not vanish from under us. */ -static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map) +static unsigned long *get_map(struct kmem_cache *s, struct page *page) { void *p; void *addr = page_address(page); + VM_BUG_ON(!irqs_disabled()); + + spin_lock(&object_map_lock); + + bitmap_zero(object_map, page->objects); + for (p = page->freelist; p; p = get_freepointer(s, p)) - set_bit(slab_index(p, s, addr), map); + set_bit(slab_index(p, s, addr), object_map); + + return object_map; +} + +static void put_map(unsigned long *map) +{ + VM_BUG_ON(map != object_map); + lockdep_assert_held(&object_map_lock); + + spin_unlock(&object_map_lock); } static inline unsigned int size_from_object(struct kmem_cache *s) @@ -3675,13 +3694,12 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, #ifdef CONFIG_SLUB_DEBUG void *addr = page_address(page); void *p; - unsigned long *map = bitmap_zalloc(page->objects, GFP_ATOMIC); - if (!map) - return; + unsigned long *map; + slab_err(s, page, text, s->name); slab_lock(page); - get_map(s, page, map); + map = get_map(s, page); for_each_object(p, s, addr, page->objects) { if (!test_bit(slab_index(p, s, addr), map)) { @@ -3689,8 +3707,9 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, print_tracking(s, p); } } + put_map(map); + slab_unlock(page); - bitmap_free(map); #endif } @@ -4384,19 +4403,19 @@ static int count_total(struct page *page) #endif #ifdef CONFIG_SLUB_DEBUG -static void validate_slab(struct kmem_cache *s, struct page *page, - unsigned long *map) +static void validate_slab(struct kmem_cache *s, struct page *page) { void *p; void *addr = page_address(page); + unsigned long *map; + + slab_lock(page); if (!check_slab(s, page) || !on_freelist(s, page, NULL)) - return; + goto unlock; /* Now we know that a valid freelist exists */ - bitmap_zero(map, page->objects); - - get_map(s, page, map); + map = get_map(s, page); for_each_object(p, s, addr, page->objects) { u8 val = test_bit(slab_index(p, s, addr), map) ? SLUB_RED_INACTIVE : SLUB_RED_ACTIVE; @@ -4404,18 +4423,13 @@ static void validate_slab(struct kmem_cache *s, struct page *page, if (!check_object(s, page, p, val)) break; } -} - -static void validate_slab_slab(struct kmem_cache *s, struct page *page, - unsigned long *map) -{ - slab_lock(page); - validate_slab(s, page, map); + put_map(map); +unlock: slab_unlock(page); } static int validate_slab_node(struct kmem_cache *s, - struct kmem_cache_node *n, unsigned long *map) + struct kmem_cache_node *n) { unsigned long count = 0; struct page *page; @@ -4424,7 +4438,7 @@ static int validate_slab_node(struct kmem_cache *s, spin_lock_irqsave(&n->list_lock, flags); list_for_each_entry(page, &n->partial, slab_list) { - validate_slab_slab(s, page, map); + validate_slab(s, page); count++; } if (count != n->nr_partial) @@ -4435,7 +4449,7 @@ static int validate_slab_node(struct kmem_cache *s, goto out; list_for_each_entry(page, &n->full, slab_list) { - validate_slab_slab(s, page, map); + validate_slab(s, page); count++; } if (count != atomic_long_read(&n->nr_slabs)) @@ -4452,15 +4466,11 @@ static long validate_slab_cache(struct kmem_cache *s) int node; unsigned long count = 0; struct kmem_cache_node *n; - unsigned long *map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL); - - if (!map) - return -ENOMEM; flush_all(s); for_each_kmem_cache_node(s, node, n) - count += validate_slab_node(s, n, map); - bitmap_free(map); + count += validate_slab_node(s, n); + return count; } /* @@ -4590,18 +4600,17 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, } static void process_slab(struct loc_track *t, struct kmem_cache *s, - struct page *page, enum track_item alloc, - unsigned long *map) + struct page *page, enum track_item alloc) { void *addr = page_address(page); void *p; + unsigned long *map; - bitmap_zero(map, page->objects); - get_map(s, page, map); - + map = get_map(s, page); for_each_object(p, s, addr, page->objects) if (!test_bit(slab_index(p, s, addr), map)) add_location(t, s, get_track(s, p, alloc)); + put_map(map); } static int list_locations(struct kmem_cache *s, char *buf, @@ -4612,11 +4621,9 @@ static int list_locations(struct kmem_cache *s, char *buf, struct loc_track t = { 0, 0, NULL }; int node; struct kmem_cache_node *n; - unsigned long *map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL); - if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), - GFP_KERNEL)) { - bitmap_free(map); + if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), + GFP_KERNEL)) { return sprintf(buf, "Out of memory\n"); } /* Push back cpu slabs */ @@ -4631,9 +4638,9 @@ static int list_locations(struct kmem_cache *s, char *buf, spin_lock_irqsave(&n->list_lock, flags); list_for_each_entry(page, &n->partial, slab_list) - process_slab(&t, s, page, alloc, map); + process_slab(&t, s, page, alloc); list_for_each_entry(page, &n->full, slab_list) - process_slab(&t, s, page, alloc, map); + process_slab(&t, s, page, alloc); spin_unlock_irqrestore(&n->list_lock, flags); } @@ -4682,7 +4689,6 @@ static int list_locations(struct kmem_cache *s, char *buf, } free_loc_track(&t); - bitmap_free(map); if (!t.count) len += sprintf(buf, "No data\n"); return len; -- GitLab