1 files changed, 32 insertions, 7 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index dd0c8e560ef6..a47ee0ad57f7 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -1425,6 +1425,28 @@ static void nilfs_btree_shrink(struct nilfs_bmap *btree,
 	path[level].bp_bh = NULL;
 }
 
+/**
+ * nilfs_btree_discard - discard the last node for the mapping transformation
+ * @btree: bmap struct of btree
+ * @path: array of nilfs_btree_path struct
+ * @level: level of the B-tree node being operated on
+ * @keyp: argument for passing a key (unused)
+ * @ptrp: argument for passing a pointer (unused)
+ */
+static void nilfs_btree_discard(struct nilfs_bmap *btree,
+				struct nilfs_btree_path *path, int level,
+				__u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *root = nilfs_btree_get_root(btree);
+
+	nilfs_btree_node_delete(root, 0, NULL, NULL,
+				NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	nilfs_btree_node_set_level(root, level);
+
+	nilfs_btnode_delete(path[level].bp_bh);
+	path[level].bp_bh = NULL;
+}
+
 static void nilfs_btree_nop(struct nilfs_bmap *btree,
 			    struct nilfs_btree_path *path,
 			    int level, __u64 *keyp, __u64 *ptrp)
@@ -1435,7 +1457,7 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      int *levelp,
 				      struct nilfs_bmap_stats *stats,
-				      struct inode *dat)
+				      struct inode *dat, bool deform)
 {
 	struct buffer_head *bh;
 	struct nilfs_btree_node *node, *parent, *sib;
@@ -1522,15 +1544,17 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
 			if (nilfs_btree_node_get_nchildren(node) - 1 <=
 			    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
 				path[level].bp_op = nilfs_btree_shrink;
-				stats->bs_nblocks += 2;
-				level++;
-				path[level].bp_op = nilfs_btree_nop;
-				goto shrink_root_child;
+			} else if (deform) {
+				path[level].bp_op = nilfs_btree_discard;
 			} else {
 				path[level].bp_op = nilfs_btree_do_delete;
 				stats->bs_nblocks++;
 				goto out;
 			}
+			stats->bs_nblocks += 2;
+			level++;
+			path[level].bp_op = nilfs_btree_nop;
+			goto shrink_root_child;
 		}
 	}
 
@@ -1581,7 +1605,7 @@ static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,
 		nilfs_bmap_set_dirty(btree);
 }
 
-static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
+static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key, bool deform)
 
 {
 	struct nilfs_btree_path *path;
@@ -1601,7 +1625,8 @@ static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
 
 	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
 
-	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);
+	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat,
+			deform);
 	if (ret < 0)
 		goto out;
 	nilfs_btree_commit_delete(btree, path, level, dat);