Commit 2fd26970 authored by Imran Khan's avatar Imran Khan Committed by Greg Kroah-Hartman
Browse files

Revert "kernfs: Change kernfs_notify_list to llist." 



This reverts commit b8f35fa1.

This is causing regression due to same kernfs_node getting
added multiple times in kernfs_notify_list so revert it until
safe way of using llist in this context is found.

Reported-by: default avatarNathan Chancellor <nathan@kernel.org>
Reported-by: default avatarMichael Walle <michael@walle.cc>
Reported-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: default avatarImran Khan <imran.f.khan@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220705201026.2487665-1-imran.f.khan@oracle.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 72b5d5ae

fs/kernfs/file.c

+27 −20
Original line number Diff line number Diff line
@@ -25,16 +25,18 @@ struct kernfs_open_node { 
	struct list_head	files; /* goes through kernfs_open_file.list */

};



/**

 * attribute_to_node - get kernfs_node object corresponding to a kernfs attribute

 * @ptr:	&struct kernfs_elem_attr

 * @type:	struct kernfs_node

 * @member:	name of member (i.e attr)

/*

 * kernfs_notify() may be called from any context and bounces notifications

 * through a work item.  To minimize space overhead in kernfs_node, the

 * pending queue is implemented as a singly linked list of kernfs_nodes.

 * The list is terminated with the self pointer so that whether a

 * kernfs_node is on the list or not can be determined by testing the next

 * pointer for NULL.

 */

#define attribute_to_node(ptr, type, member)	\

	container_of(ptr, type, member)

#define KERNFS_NOTIFY_EOL			((void *)&kernfs_notify_list)



static LLIST_HEAD(kernfs_notify_list);

static DEFINE_SPINLOCK(kernfs_notify_lock);

static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;



static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn)

{
@@ -909,16 +911,18 @@ static void kernfs_notify_workfn(struct work_struct *work) 
	struct kernfs_node *kn;

	struct kernfs_super_info *info;

	struct kernfs_root *root;

	struct llist_node *free;

	struct kernfs_elem_attr *attr;

repeat:

	/* pop one off the notify_list */

	free = llist_del_first(&kernfs_notify_list);

	if (free == NULL)

	spin_lock_irq(&kernfs_notify_lock);

	kn = kernfs_notify_list;

	if (kn == KERNFS_NOTIFY_EOL) {

		spin_unlock_irq(&kernfs_notify_lock);

		return;

	}

	kernfs_notify_list = kn->attr.notify_next;

	kn->attr.notify_next = NULL;

	spin_unlock_irq(&kernfs_notify_lock);



	attr = llist_entry(free, struct kernfs_elem_attr, notify_next);

	kn = attribute_to_node(attr, struct kernfs_node, attr);

	root = kernfs_root(kn);

	/* kick fsnotify */

	down_write(&root->kernfs_rwsem);
@@ -974,14 +978,12 @@ static void kernfs_notify_workfn(struct work_struct *work) 
void kernfs_notify(struct kernfs_node *kn)

{

	static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);

	unsigned long flags;

	struct kernfs_open_node *on;



	if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))

		return;



	/* Because we are using llist for kernfs_notify_list */

	WARN_ON_ONCE(in_nmi());



	/* kick poll immediately */

	rcu_read_lock();

	on = rcu_dereference(kn->attr.open);
@@ -992,10 +994,15 @@ void kernfs_notify(struct kernfs_node *kn) 
	rcu_read_unlock();



	/* schedule work to kick fsnotify */

	spin_lock_irqsave(&kernfs_notify_lock, flags);

	if (!kn->attr.notify_next) {

		kernfs_get(kn);

	llist_add(&kn->attr.notify_next, &kernfs_notify_list);

		kn->attr.notify_next = kernfs_notify_list;

		kernfs_notify_list = kn;

		schedule_work(&kernfs_notify_work);

	}

	spin_unlock_irqrestore(&kernfs_notify_lock, flags);

}

EXPORT_SYMBOL_GPL(kernfs_notify);



const struct file_operations kernfs_file_fops = {

include/linux/kernfs.h

+1 −1
Original line number Diff line number Diff line
@@ -173,7 +173,7 @@ struct kernfs_elem_attr { 
	const struct kernfs_ops	*ops;

	struct kernfs_open_node __rcu	*open;

	loff_t			size;

	struct llist_node	notify_next;	/* for kernfs_notify() */

	struct kernfs_node	*notify_next;	/* for kernfs_notify() */

};



/*