Commit bd900901 authored by Imran Khan's avatar Imran Khan Committed by Greg Kroah-Hartman
Browse files

kernfs: Remove reference counting for kernfs_open_node. 



The decision to free kernfs_open_node object in kernfs_put_open_node can
be taken based on whether kernfs_open_node->files list is empty or not. As
far as kernfs_drain_open_files is concerned it can't overlap with
kernfs_fops_open and hence can check for ->attr.open optimistically
(if ->attr.open is NULL) or under kernfs_open_file_mutex (if it needs to
traverse the ->files list.) Thus kernfs_drain_open_files can work w/o ref
counting involved kernfs_open_node as well.
So remove ->refcnt and modify the above mentioned users accordingly.

Suggested by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: default avatarImran Khan <imran.f.khan@oracle.com>
Link: https://lore.kernel.org/r/20220324103040.584491-2-imran.f.khan@oracle.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6423d295

fs/kernfs/file.c

+9 −14
Original line number Diff line number Diff line
@@ -33,7 +33,6 @@ static DEFINE_SPINLOCK(kernfs_open_node_lock); 
static DEFINE_MUTEX(kernfs_open_file_mutex);



struct kernfs_open_node {

	atomic_t		refcnt;

	atomic_t		event;

	wait_queue_head_t	poll;

	struct list_head	files; /* goes through kernfs_open_file.list */
@@ -530,10 +529,8 @@ static int kernfs_get_open_node(struct kernfs_node *kn, 
	}



	on = kn->attr.open;

	if (on) {

		atomic_inc(&on->refcnt);

	if (on)

		list_add_tail(&of->list, &on->files);

	}



	spin_unlock_irq(&kernfs_open_node_lock);

	mutex_unlock(&kernfs_open_file_mutex);
@@ -548,7 +545,6 @@ static int kernfs_get_open_node(struct kernfs_node *kn, 
	if (!new_on)

		return -ENOMEM;



	atomic_set(&new_on->refcnt, 0);

	atomic_set(&new_on->event, 1);

	init_waitqueue_head(&new_on->poll);

	INIT_LIST_HEAD(&new_on->files);
@@ -557,11 +553,12 @@ static int kernfs_get_open_node(struct kernfs_node *kn, 


/**

 *	kernfs_put_open_node - put kernfs_open_node

 *	@kn: target kernfs_nodet

 *	@kn: target kernfs_node

 *	@of: associated kernfs_open_file

 *

 *	Put @kn->attr.open and unlink @of from the files list.  If

 *	reference count reaches zero, disassociate and free it.

 *	list of associated open files becomes empty, disassociate and

 *	free kernfs_open_node.

 *

 *	LOCKING:

 *	None.
@@ -578,7 +575,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn, 
	if (of)

		list_del(&of->list);



	if (atomic_dec_and_test(&on->refcnt))

	if (list_empty(&on->files))

		kn->attr.open = NULL;

	else

		on = NULL;
@@ -768,15 +765,15 @@ void kernfs_drain_open_files(struct kernfs_node *kn) 
	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))

		return;



	spin_lock_irq(&kernfs_open_node_lock);

	on = kn->attr.open;

	if (on)

		atomic_inc(&on->refcnt);

	spin_unlock_irq(&kernfs_open_node_lock);

	if (!on)

		return;



	mutex_lock(&kernfs_open_file_mutex);

	if (!kn->attr.open) {

		mutex_unlock(&kernfs_open_file_mutex);

		return;

	}



	list_for_each_entry(of, &on->files, list) {

		struct inode *inode = file_inode(of->file);
@@ -789,8 +786,6 @@ void kernfs_drain_open_files(struct kernfs_node *kn) 
	}



	mutex_unlock(&kernfs_open_file_mutex);



	kernfs_put_open_node(kn, NULL);

}



/*