From d35a117e4b46921c79eb7628e197231e949b176a Mon Sep 17 00:00:00 2001
From: Zdenek Kabelac <zkabelac@redhat.com>
Date: Mon, 3 Oct 2011 18:39:17 +0000
Subject: [PATCH] Add simple function for lookup of some free device_id

Initial simple implementation for finding some free device_id.
---
 lib/metadata/metadata.h   |  3 +++
 lib/metadata/thin_manip.c | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/lib/metadata/metadata.h b/lib/metadata/metadata.h
index e984ba83d..d1b1b1f33 100644
--- a/lib/metadata/metadata.h
+++ b/lib/metadata/metadata.h
@@ -374,6 +374,9 @@ struct lv_segment *find_seg_by_le(const struct logical_volume *lv, uint32_t le);
 /* Find pool LV segment given a thin pool data or metadata segment. */
 struct lv_segment *find_pool_seg(const struct lv_segment *seg);
 
+/* Find some unused device_id for thin pool LV segment. */
+uint32_t get_free_pool_device_id(struct lv_segment *thin_pool_seg);
+
 /*
  * Remove a dev_dir if present.
  */
diff --git a/lib/metadata/thin_manip.c b/lib/metadata/thin_manip.c
index 2412db6c3..ead121816 100644
--- a/lib/metadata/thin_manip.c
+++ b/lib/metadata/thin_manip.c
@@ -80,3 +80,40 @@ struct lv_segment *find_pool_seg(const struct lv_segment *seg)
 
         return pool_seg;
 }
+
+/*
+ * Find a free device_id for given thin_pool segment.
+ *
+ * \return
+ * Free device id, or 0 if free device_id is not found.
+ *
+ * FIXME: Improve naive search and keep the value cached
+ * and updated during VG lifetime (so no const for lv_segment)
+ */
+uint32_t get_free_pool_device_id(struct lv_segment *thin_pool_seg)
+{
+	uint32_t dev_id, max_id = 0;
+	struct dm_list *h;
+
+	if (!seg_is_thin_pool(thin_pool_seg)) {
+		log_error("Segment in %s is not a thin pool segment.",
+			  pool_seg->lv->name);
+		return 0;
+	}
+
+	dm_list_iterate(h, &thin_pool_seg->lv->segs_using_this_lv) {
+		dev_id = dm_list_item(h, struct seg_list)->seg->device_id;
+		if (dev_id > max_id)
+			max_id = dev_id;
+	}
+
+	if (++max_id >= (1 << 24)) {
+		// FIXME: try to find empty holes....
+		log_error("Free device_id exhausted...");
+		return 0;
+	}
+
+	log_debug("Found free pool device_id %u.", max_id);
+
+	return max_id;
+}
-- 
2.43.5