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Commit 0890147f authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman
Browse files

Revert "kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()" 



This reverts commit a69d001c.

Tejun writes:
        I'm sorry but can you please revert the whole series?
        get_active() waiting while a node is deactivated has potential
        to lead to deadlock and that deactivate/reactivate interface is
        something fundamentally flawed and that cgroup will have to work
        with the remove_self() like everybody else.  IOW, I think the
        first posting was correct.

Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 798c75a0

fs/kernfs/dir.c

+11 −20
Original line number Diff line number Diff line
@@ -22,15 +22,6 @@ 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
@@ -147,7 +138,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn) 
	if (!atomic_inc_unless_negative(&kn->active))

		return NULL;



	if (kernfs_lockdep(kn))

	if (kn->flags & KERNFS_LOCKDEP)

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

	return kn;

}
@@ -167,7 +158,7 @@ void kernfs_put_active(struct kernfs_node *kn) 
	if (unlikely(!kn))

		return;



	if (kernfs_lockdep(kn))

	if (kn->flags & KERNFS_LOCKDEP)

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

	v = atomic_dec_return(&kn->active);

	if (likely(v != KN_DEACTIVATED_BIAS))
@@ -188,22 +179,22 @@ static void kernfs_deactivate(struct kernfs_node *kn) 


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



	atomic_add(KN_DEACTIVATED_BIAS, &kn->active);

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

		return;



	if (kernfs_lockdep(kn)) {

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



	atomic_add(KN_DEACTIVATED_BIAS, &kn->active);



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

		lock_contended(&kn->dep_map, _RET_IP_);

	}



	wait_event(root->deactivate_waitq,

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



	if (kernfs_lockdep(kn)) {

	lock_acquired(&kn->dep_map, _RET_IP_);

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

}

}



/**

 * kernfs_get - get a reference count on a kernfs_node

include/linux/kernfs.h

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 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 {