1 files changed, 74 insertions, 7 deletions

diff --git a/btrfs-convert.c b/btrfs-convert.c
index 856fac60..f78bfbf4 100644
--- a/btrfs-convert.c
+++ b/btrfs-convert.c
@@ -1928,6 +1928,57 @@ static int convert_open_fs(const char *devname,
 }
 
 /*
+ * Helper for expand and merge extent_cache for wipe_one_reserved_range() to
+ * handle wiping a range that exists in cache.
+ */
+static int _expand_extent_cache(struct cache_tree *tree,
+				struct cache_extent *entry,
+				u64 min_stripe_size, int backward)
+{
+	struct cache_extent *ce;
+	int diff;
+
+	if (entry->size >= min_stripe_size)
+		return 0;
+	diff = min_stripe_size - entry->size;
+
+	if (backward) {
+		ce = prev_cache_extent(entry);
+		if (!ce)
+			goto expand_back;
+		if (ce->start + ce->size >= entry->start - diff) {
+			/* Directly merge with previous extent */
+			ce->size = entry->start + entry->size - ce->start;
+			remove_cache_extent(tree, entry);
+			free(entry);
+			return 0;
+		}
+expand_back:
+		/* No overlap, normal extent */
+		if (entry->start < diff) {
+			error("cannot find space for data chunk layout");
+			return -ENOSPC;
+		}
+		entry->start -= diff;
+		entry->size += diff;
+		return 0;
+	}
+	ce = next_cache_extent(entry);
+	if (!ce)
+		goto expand_after;
+	if (entry->start + entry->size + diff >= ce->start) {
+		/* Directly merge with next extent */
+		entry->size = ce->start + ce->size - entry->start;
+		remove_cache_extent(tree, ce);
+		free(ce);
+		return 0;
+	}
+expand_after:
+	entry->size += diff;
+	return 0;
+}
+
+/*
  * Remove one reserve range from given cache tree
  * if min_stripe_size is non-zero, it will ensure for split case,
  * all its split cache extent is no smaller than @min_strip_size / 2.
@@ -1986,21 +2037,37 @@ static int wipe_one_reserved_range(struct cache_tree *tree,
 		 * |-------cache-----|
 		 *	|-wipe-|
 		 */
+		u64 old_start = cache->start;
 		u64 old_len = cache->size;
 		u64 insert_start = start + len;
 		u64 insert_len;
 
 		cache->size = start - cache->start;
-		if (ensure_size)
-			cache->size = max(cache->size, min_stripe_size);
-		cache->start = start - cache->size;
+		/* Expand the leading half part if needed */
+		if (ensure_size && cache->size < min_stripe_size) {
+			ret = _expand_extent_cache(tree, cache,
+					min_stripe_size, 1);
+			if (ret < 0)
+				return ret;
+		}
 
 		/* And insert the new one */
-		insert_len = old_len - start - len;
-		if (ensure_size)
-			insert_len = max(insert_len, min_stripe_size);
-
+		insert_len = old_start + old_len - start - len;
 		ret = add_merge_cache_extent(tree, insert_start, insert_len);
+		if (ret < 0)
+			return ret;
+
+		/* Expand the last half part if needed */
+		if (ensure_size && insert_len < min_stripe_size) {
+			cache = lookup_cache_extent(tree, insert_start,
+						    insert_len);
+			if (!cache || cache->start != insert_start ||
+			    cache->size != insert_len)
+				return -ENOENT;
+			ret = _expand_extent_cache(tree, cache,
+					min_stripe_size, 0);
+		}
+
 		return ret;
 	}
 	/*