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Commit 182fd64b authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep() 



There currently are two mechanisms gating active ref lockdep
annotations - KERNFS_LOCKDEP flag and KERNFS_ACTIVE_REF type mask.
The former disables lockdep annotations in kernfs_get/put_active()
while the latter disables all of kernfs_deactivate().

While KERNFS_ACTIVE_REF also behaves as an optimization to skip the
deactivation step for non-file nodes, the benefit is marginal and it
needlessly diverges code paths.  Let's drop KERNFS_ACTIVE_REF.

While at it, add a test helper kernfs_lockdep() to test KERNFS_LOCKDEP
flag so that it's more convenient and the related code can be compiled
out when not enabled.

v2: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
    KERNFS_LOCKDEP flag").  As the earlier patch already added
    KERNFS_LOCKDEP tests to kernfs_deactivate(), those additions are
    dropped from this patch and the existing ones are simply converted
    to kernfs_lockdep().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 988cd7af

fs/kernfs/dir.c

+13 −7
Original line number Diff line number Diff line
@@ -22,6 +22,15 @@ DEFINE_MUTEX(kernfs_mutex); 


#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)



static bool kernfs_lockdep(struct kernfs_node *kn)

{

#ifdef CONFIG_DEBUG_LOCK_ALLOC

	return kn->flags & KERNFS_LOCKDEP;

#else

	return false;

#endif

}



/**

 *	kernfs_name_hash

 *	@name: Null terminated string to hash
@@ -144,7 +153,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn) 
	if (!atomic_inc_unless_negative(&kn->active))

		return NULL;



	if (kn->flags & KERNFS_LOCKDEP)

	if (kernfs_lockdep(kn))

		rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);

	return kn;

}
@@ -164,7 +173,7 @@ void kernfs_put_active(struct kernfs_node *kn) 
	if (unlikely(!kn))

		return;



	if (kn->flags & KERNFS_LOCKDEP)

	if (kernfs_lockdep(kn))

		rwsem_release(&kn->dep_map, 1, _RET_IP_);

	v = atomic_dec_return(&kn->active);

	if (likely(v != KN_DEACTIVATED_BIAS))
@@ -190,16 +199,13 @@ static void kernfs_deactivate(struct kernfs_node *kn) 
	lockdep_assert_held(&kernfs_mutex);

	BUG_ON(!(kn->flags & KERNFS_REMOVED));



	if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))

		return;



	/* only the first invocation on @kn should deactivate it */

	if (atomic_read(&kn->active) >= 0)

		atomic_add(KN_DEACTIVATED_BIAS, &kn->active);



	mutex_unlock(&kernfs_mutex);



	if (kn->flags & KERNFS_LOCKDEP) {

	if (kernfs_lockdep(kn)) {

		rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);

		if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)

			lock_contended(&kn->dep_map, _RET_IP_);
@@ -209,7 +215,7 @@ static void kernfs_deactivate(struct kernfs_node *kn) 
	wait_event(root->deactivate_waitq,

		   atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);



	if (kn->flags & KERNFS_LOCKDEP) {

	if (kernfs_lockdep(kn)) {

		lock_acquired(&kn->dep_map, _RET_IP_);

		rwsem_release(&kn->dep_map, 1, _RET_IP_);

	}

include/linux/kernfs.h

+0 −1
Original line number Diff line number Diff line
@@ -35,7 +35,6 @@ enum kernfs_node_type { 
};



#define KERNFS_TYPE_MASK	0x000f

#define KERNFS_ACTIVE_REF	KERNFS_FILE

#define KERNFS_FLAG_MASK	~KERNFS_TYPE_MASK



enum kernfs_node_flag {