f2fs: use radix_tree for ino management

For better ino management, this patch replaces the data structure from list
to radix tree.

Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index b6fa6ec..4454caa 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -456,6 +456,7 @@
 	wait_queue_head_t cp_wait;
 
 	/* for inode management */
+	struct radix_tree_root ino_root[MAX_INO_ENTRY];	/* ino entry array */
 	spinlock_t ino_lock[MAX_INO_ENTRY];		/* for ino entry lock */
 	struct list_head ino_list[MAX_INO_ENTRY];	/* inode list head */