On Thu 31-01-13 15:57:26, Andrew Morton wrote:

On Thu, 31 Jan 2013 22:49:49 +0100
Jan Kara [off-list ref] wrote:

quoted

Implement range locking using interval tree.

...

+void range_lock(struct range_lock_tree *tree, struct range_lock *lock)
+{
+	struct interval_tree_node *node;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tree->lock, flags);
+	node = interval_tree_iter_first(&tree->root, lock->node.start,
+					lock->node.last);
+	while (node) {
+		lock->blocking_ranges++;
+		node = interval_tree_iter_next(node, lock->node.start,
+					       lock->node.last);
+	}
+	interval_tree_insert(&lock->node, &tree->root);
+	/* Do we need to go to sleep? */
+	while (lock->blocking_ranges) {
+		lock->task = current;
+		__set_current_state(TASK_UNINTERRUPTIBLE);
+		spin_unlock_irqrestore(&tree->lock, flags);
+		schedule();
+		spin_lock_irqsave(&tree->lock, flags);
+	}
+	spin_unlock_irqrestore(&tree->lock, flags);
+}

...

+void range_unlock(struct range_lock_tree *tree, struct range_lock *lock)
+{
+	struct interval_tree_node *node;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tree->lock, flags);
+	interval_tree_remove(&lock->node, &tree->root);
+	node = interval_tree_iter_first(&tree->root, lock->node.start,
+					lock->node.last);
+	while (node) {
+		range_lock_unblock((struct range_lock *)node);
+		node = interval_tree_iter_next(node, lock->node.start,
+					       lock->node.last);
+	}
+	spin_unlock_irqrestore(&tree->lock, flags);
+}

What are the worst-case interrupt-off durations here?

  Good question. In theory, it could be relatively long, e.g. when there
are lots of DIOs in flight against a range which is locked. I'll do some
measurements to get some idea.
 

I note that the new exported functions in this patchset are
refreshingly free of documentation ;)

  They are *so* obvious ;) Point taken... Thanks for review.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR

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