[Patch net-next] ila: make lockdep happy again

[Patch net-next] ila: make lockdep happy again

[Cong Wang]

Previously, alloc_ila_locks() and bucket_table_alloc() call
spin_lock_init() separately, therefore they have two different
lock names and lock class keys. However, after commit b893281715ab
("ila: Call library function alloc_bucket_locks") they both call
helper alloc_bucket_spinlocks() which now only has one lock
name and lock class key. This causes a few bogus lockdep warnings
as reported by syzbot.

Fix this by making alloc_bucket_locks() a macro and pass declaration
name as lock name and a static lock class key inside the macro.

Fixes: b893281715ab ("ila: Call library function alloc_bucket_locks")
Reported-by: <syzbot+b66a5a554991a8ed027c@syzkaller.appspotmail.com>
Cc: Tom Herbert <tom@quantonium.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 include/linux/spinlock.h | 17 ++++++++++++++---
 lib/bucket_locks.c       | 11 +++++++----
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index fd57888d4942..a81040719fb9 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -432,9 +432,20 @@ extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
 #define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
 		__cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
 
-int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
-			   size_t max_size, unsigned int cpu_mult,
-			   gfp_t gfp);
+int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
+			     size_t max_size, unsigned int cpu_mult,
+			     gfp_t gfp, const char *name,
+			     struct lock_class_key *key);
+
+#define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp)    \
+	({								     \
+		static struct lock_class_key key;			     \
+		int ret;						     \
+									     \
+		ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size,   \
+					       cpu_mult, gfp, #locks, &key); \
+		ret;							     \
+	})
 
 void free_bucket_spinlocks(spinlock_t *locks);
 
diff --git a/lib/bucket_locks.c b/lib/bucket_locks.c
index ade3ce6c4af6..64b92e1dbace 100644
--- a/lib/bucket_locks.c
+++ b/lib/bucket_locks.c
@@ -11,8 +11,9 @@
  * to a power of 2 to be suitable as a hash table.
  */
 
-int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
-			   size_t max_size, unsigned int cpu_mult, gfp_t gfp)
+int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
+			     size_t max_size, unsigned int cpu_mult, gfp_t gfp,
+			     const char *name, struct lock_class_key *key)
 {
 	spinlock_t *tlocks = NULL;
 	unsigned int i, size;
@@ -33,8 +34,10 @@ int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
 		tlocks = kvmalloc_array(size, sizeof(spinlock_t), gfp);
 		if (!tlocks)
 			return -ENOMEM;
-		for (i = 0; i < size; i++)
+		for (i = 0; i < size; i++) {
 			spin_lock_init(&tlocks[i]);
+			lockdep_init_map(&tlocks[i].dep_map, name, key, 0);
+		}
 	}
 
 	*locks = tlocks;
@@ -42,7 +45,7 @@ int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
 
 	return 0;
 }
-EXPORT_SYMBOL(alloc_bucket_spinlocks);
+EXPORT_SYMBOL(__alloc_bucket_spinlocks);
 
 void free_bucket_spinlocks(spinlock_t *locks)
 {
-- 
2.14.4

Re: [Patch net-next] ila: make lockdep happy again

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue, 14 Aug 2018 15:21:31 -0700

> Previously, alloc_ila_locks() and bucket_table_alloc() call
> spin_lock_init() separately, therefore they have two different
> lock names and lock class keys. However, after commit b893281715ab
> ("ila: Call library function alloc_bucket_locks") they both call
> helper alloc_bucket_spinlocks() which now only has one lock
> name and lock class key. This causes a few bogus lockdep warnings
> as reported by syzbot.
> 
> Fix this by making alloc_bucket_locks() a macro and pass declaration
> name as lock name and a static lock class key inside the macro.
> 
> Fixes: b893281715ab ("ila: Call library function alloc_bucket_locks")
> Reported-by: <syzbot+b66a5a554991a8ed027c@syzkaller.appspotmail.com>
> Cc: Tom Herbert <tom@quantonium.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied, thank you.