kernfs: make kernfs_get_active() block if the node is deactivated but not removed (895a068a) · Commits · 戴 / test

Currently, kernfs_get_active() fails if the target node is deactivated. This is fine as a node always gets removed after deactivation; however, we're gonna add reactivation so the assumption won't hold. It'd be incorrect for kernfs_get_active() to fail for a node which was deactivated only temporarily. This patch makes kernfs_get_active() block if the node is deactivated but not removed. If the node gets reactivated (not yet implemented), it will be retried and succeed. If the node gets removed, it will be woken up and fail. Signed-off-by:

Tejun Heo <tj@kernel.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/dir.c

+21 −4

Original line number	Diff line number	Diff line
		@@ -149,12 +149,25 @@ struct kernfs_node kernfs_get_active(struct kernfs_node kn)
		if (unlikely(!kn))
		return NULL;

		if (!atomic_inc_unless_negative(&kn->active))
		return NULL;

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

		/*
		* Try to obtain an active ref. If @kn is deactivated, we block
		* till either it's reactivated or killed.
		*/
		do {
		if (atomic_inc_unless_negative(&kn->active))
		return kn;

		wait_event(kernfs_root(kn)->deactivate_waitq,
		atomic_read(&kn->active) >= 0 \|\|
		RB_EMPTY_NODE(&kn->rb));
		} while (!RB_EMPTY_NODE(&kn->rb));

		if (kernfs_lockdep(kn))
		rwsem_release(&kn->dep_map, 1, _RET_IP_);
		return NULL;
		}

		/**
		@@ -786,6 +799,7 @@ static void __kernfs_deactivate(struct kernfs_node *kn)

		static void __kernfs_remove(struct kernfs_node *kn)
		{
		struct kernfs_root *root = kernfs_root(kn);
		struct kernfs_node *pos;

		lockdep_assert_held(&kernfs_mutex);
		@@ -837,6 +851,9 @@ static void __kernfs_remove(struct kernfs_node *kn)

		kernfs_put(pos);
		} while (pos != kn);

		/* some nodes killed, kick get_active waiters */
		wake_up_all(&root->deactivate_waitq);
		}

		/**

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