+enum ocfs2_la_event {
+ OCFS2_LA_EVENT_SLIDE, /* Normal window slide. */
+ OCFS2_LA_EVENT_FRAGMENTED, /* The global bitmap has
+ * enough bits theoretically
+ * free, but a contiguous
+ * allocation could not be
+ * found. */
+ OCFS2_LA_EVENT_ENOSPC, /* Global bitmap doesn't have
+ * enough bits free to satisfy
+ * our request. */
+};
+#define OCFS2_LA_ENABLE_INTERVAL (30 * HZ)
+/*
+ * Given an event, calculate the size of our next local alloc window.
+ *
+ * This should always be called under i_mutex of the local alloc inode
+ * so that local alloc disabling doesn't race with processes trying to
+ * use the allocator.
+ *
+ * Returns the state which the local alloc was left in. This value can
+ * be ignored by some paths.
+ */
+static int ocfs2_recalc_la_window(struct ocfs2_super *osb,
+ enum ocfs2_la_event event)
+{
+ unsigned int bits;
+ int state;
+
+ spin_lock(&osb->osb_lock);
+ if (osb->local_alloc_state == OCFS2_LA_DISABLED) {
+ WARN_ON_ONCE(osb->local_alloc_state == OCFS2_LA_DISABLED);
+ goto out_unlock;
+ }
+
+ /*
+ * ENOSPC and fragmentation are treated similarly for now.
+ */
+ if (event == OCFS2_LA_EVENT_ENOSPC ||
+ event == OCFS2_LA_EVENT_FRAGMENTED) {
+ /*
+ * We ran out of contiguous space in the primary
+ * bitmap. Drastically reduce the number of bits used
+ * by local alloc until we have to disable it.
+ */
+ bits = osb->local_alloc_bits >> 1;
+ if (bits > ocfs2_megabytes_to_clusters(osb->sb, 1)) {
+ /*
+ * By setting state to THROTTLED, we'll keep
+ * the number of local alloc bits used down
+ * until an event occurs which would give us
+ * reason to assume the bitmap situation might
+ * have changed.
+ */
+ osb->local_alloc_state = OCFS2_LA_THROTTLED;
+ osb->local_alloc_bits = bits;
+ } else {
+ osb->local_alloc_state = OCFS2_LA_DISABLED;
+ }
+ queue_delayed_work(ocfs2_wq, &osb->la_enable_wq,
+ OCFS2_LA_ENABLE_INTERVAL);
+ goto out_unlock;
+ }
+
+ /*
+ * Don't increase the size of the local alloc window until we
+ * know we might be able to fulfill the request. Otherwise, we
+ * risk bouncing around the global bitmap during periods of
+ * low space.
+ */
+ if (osb->local_alloc_state != OCFS2_LA_THROTTLED)
+ osb->local_alloc_bits = osb->local_alloc_default_bits;
+
+out_unlock:
+ state = osb->local_alloc_state;
+ spin_unlock(&osb->osb_lock);
+
+ return state;
+}
+