nilfs2: remove own inode hash used for GC

This uses inode hash function that vfs provides instead of the own
hash table for caching gc inodes.  This finally removes the own inode
hash from nilfs.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index f785a7b..c7ecd0c 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -81,7 +81,6 @@
  * @ns_sufile: segusage file inode
  * @ns_gc_dat: shadow inode of the DAT file inode for GC
  * @ns_gc_inodes: dummy inodes to keep live blocks
- * @ns_gc_inodes_h: hash list to keep dummy inode holding live blocks
  * @ns_blocksize_bits: bit length of block size
  * @ns_blocksize: block size
  * @ns_nsegments: number of segments in filesystem
@@ -165,9 +164,8 @@
 	struct inode	       *ns_sufile;
 	struct inode	       *ns_gc_dat;
 
-	/* GC inode list and hash table head */
+	/* GC inode list */
 	struct list_head	ns_gc_inodes;
-	struct hlist_head      *ns_gc_inodes_h;
 
 	/* Disk layout information (static) */
 	unsigned int		ns_blocksize_bits;
@@ -182,9 +180,6 @@
 	u32			ns_crc_seed;
 };
 
-#define NILFS_GCINODE_HASH_BITS		8
-#define NILFS_GCINODE_HASH_SIZE		(1<<NILFS_GCINODE_HASH_BITS)
-
 #define THE_NILFS_FNS(bit, name)					\
 static inline void set_nilfs_##name(struct the_nilfs *nilfs)		\
 {									\