locks: avoid taking global lock if possible when waking up blocked waiters

 * the order they blocked. The documentation doesn't require this but

 * it seems like the reasonable thing to do.

 *

 * Must be called with file_lock_lock held!

 * Must be called with both the i_lock and file_lock_lock held. The fl_block

 * list itself is protected by the file_lock_list, but by ensuring that the

 * i_lock is also held on insertions we can avoid taking the file_lock_lock

 * in some cases when we see that the fl_block list is empty.

 */

static void __locks_insert_block(struct file_lock *blocker,

					struct file_lock *waiter)

 */

static void locks_wake_up_blocks(struct file_lock *blocker)

{

	/*

	 * Avoid taking global lock if list is empty. This is safe since new

	 * blocked requests are only added to the list under the i_lock, and

	 * the i_lock is always held here. Note that removal from the fl_block

	 * list does not require the i_lock, so we must recheck list_empty()

	 * after acquiring the file_lock_lock.

	 */

	if (list_empty(&blocker->fl_block))

		return;

	spin_lock(&file_lock_lock);

	while (!list_empty(&blocker->fl_block)) {

		struct file_lock *waiter;