From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-mm@kvack.org
Cc: Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [RFC] SLUB: list_slab_objects() looks like a miss-merge
Date: Thu, 18 Jun 2020 11:46:23 +0200 [thread overview]
Message-ID: <20200618094623.ef7wrsyrnrsfm7as@linutronix.de> (raw)
Hi,
I stumbled over the following:
| static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
| {
…
| unsigned long *map = NULL;
|
| #ifdef CONFIG_SLUB_DEBUG
| map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
| #endif
…
| } else {
| list_slab_objects(s, page,
| "Objects remaining in %s on __kmem_cache_shutdown()",
| map);
| }
| }
…
| #ifdef CONFIG_SLUB_DEBUG
| bitmap_free(map);
| #endif
…
| }
so map gets allocated, passed to list_slab_objects() and then freed at
end. Haven't notices where `map' is set but maybe it is just a buffer
used in list_slab_objects().
And then there is this:
| static void list_slab_objects(struct kmem_cache *s, struct page *page,
| const char *text, unsigned long *map)
| {
| #ifdef CONFIG_SLUB_DEBUG
| void *addr = page_address(page);
| void *p;
|
| if (!map)
| return;
No map, return. Okay.
| slab_err(s, page, text, s->name);
| slab_lock(page);
|
| map = get_map(s, page);
and here `map' gets overwritten, correct? But it gets initialized. And it also
acquires `object_map_lock'.
| for_each_object(p, s, addr, page->objects) {
|
| if (!test_bit(slab_index(p, s, addr), map)) {
| pr_err("INFO: Object 0x%p @offset=%tu\n", p, p - addr);
| print_tracking(s, p);
| }
| }
and here I would expect to unlock `object_map_lock'.
| slab_unlock(page);
| #endif
| }
Is this a miss-merge of some kind? I would revert commit
aa456c7aebb14 ("slub: remove kmalloc under list_lock from list_slab_objects() V2")
by doing this:
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
deleted file mode 100644
index e69de29bb2d1d..0000000000000
diff --git a/mm/slub.c b/mm/slub.c
index b8f798b50d44d..72195cafbb503 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3766,15 +3766,13 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
}
static void list_slab_objects(struct kmem_cache *s, struct page *page,
- const char *text, unsigned long *map)
+ const char *text)
{
#ifdef CONFIG_SLUB_DEBUG
void *addr = page_address(page);
+ unsigned long *map;
void *p;
- if (!map)
- return;
-
slab_err(s, page, text, s->name);
slab_lock(page);
@@ -3786,6 +3784,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
print_tracking(s, p);
}
}
+ put_map(map);
slab_unlock(page);
#endif
}
@@ -3799,11 +3798,6 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
{
LIST_HEAD(discard);
struct page *page, *h;
- unsigned long *map = NULL;
-
-#ifdef CONFIG_SLUB_DEBUG
- map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
-#endif
BUG_ON(irqs_disabled());
spin_lock_irq(&n->list_lock);
@@ -3813,16 +3807,11 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
list_add(&page->slab_list, &discard);
} else {
list_slab_objects(s, page,
- "Objects remaining in %s on __kmem_cache_shutdown()",
- map);
+ "Objects remaining in %s on __kmem_cache_shutdown()");
}
}
spin_unlock_irq(&n->list_lock);
-#ifdef CONFIG_SLUB_DEBUG
- bitmap_free(map);
-#endif
-
list_for_each_entry_safe(page, h, &discard, slab_list)
discard_slab(s, page);
}
Is there something I'm missing? This is completely untested of course.
Sebastian
next reply other threads:[~2020-06-18 9:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 9:46 Sebastian Andrzej Siewior [this message]
2020-06-18 15:03 ` [RFC] SLUB: list_slab_objects() looks like a miss-merge Christopher Lameter
2020-06-18 20:12 ` [PATCH 1/2] slub: Cure list_slab_objects() from double fix Sebastian Andrzej Siewior
2020-06-18 20:12 ` [PATCH 2/2] slub: Drop lockdep_assert_held() from put_map() Sebastian Andrzej Siewior
2020-06-18 21:02 ` [RFC] SLUB: list_slab_objects() looks like a miss-merge Yu Zhao
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