fs_pin: Allow for the possibility that m_list or s_list go unused. (820f9f14) · Commits · 戴 / test

This is needed to support lazily umounting locked mounts. Because the entire unmounted subtree needs to stay together until there are no users with references to any part of the subtree. To support this guarantee that the fs_pin m_list and s_list nodes are initialized by initializing them in init_fs_pin allowing for the possibility that pin_insert_group does not touch them. Further use hlist_del_init in pin_remove so that there is a hlist_unhashed test before the list we attempt to update the previous list item. Signed-off-by:

"Eric W. Biederman" <ebiederm@xmission.com>

fs/fs_pin.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -9,8 +9,8 @@ static DEFINE_SPINLOCK(pin_lock);
	void pin_remove(struct fs_pin *pin)		void pin_remove(struct fs_pin *pin)
	{		{
	spin_lock(&pin_lock);		spin_lock(&pin_lock);
	hlist_del(&pin->m_list);		hlist_del_init(&pin->m_list);
	hlist_del(&pin->s_list);		hlist_del_init(&pin->s_list);
	spin_unlock(&pin_lock);		spin_unlock(&pin_lock);
	spin_lock_irq(&pin->wait.lock);		spin_lock_irq(&pin->wait.lock);
	pin->done = 1;		pin->done = 1;

include/linux/fs_pin.h

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -13,6 +13,8 @@ struct vfsmount;
	static inline void init_fs_pin(struct fs_pin p, void (kill)(struct fs_pin *))		static inline void init_fs_pin(struct fs_pin p, void (kill)(struct fs_pin *))
	{		{
	init_waitqueue_head(&p->wait);		init_waitqueue_head(&p->wait);
			INIT_HLIST_NODE(&p->s_list);
			INIT_HLIST_NODE(&p->m_list);
	p->kill = kill;		p->kill = kill;
	}		}

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