ocfs2: Store dir index records inline

Allow us to store a small number of directory index records in the
ocfs2_dx_root_block. This saves us a disk read on small to medium sized
directories (less than about 250 entries). The inline root is automatically
turned into a root block with extents if the directory size increases beyond
it's capacity.
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Acked-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/dir.h

@@ -37,6 +37,8 @@ struct ocfs2_dir_lookup_result {
 	struct ocfs2_dir_entry		*dl_entry;	/* Target dirent in
 							 * unindexed leaf */
 
+	struct buffer_head		*dl_dx_root_bh;	/* Root of indexed
+							 * tree */
 	struct buffer_head		*dl_dx_leaf_bh;	/* Indexed leaf block */
 	struct ocfs2_dx_entry		*dl_dx_entry;	/* Target dx_entry in
 							 * indexed leaf */

fs/ocfs2/journal.h

@@ -458,6 +458,16 @@ static inline int ocfs2_rename_credits(struct super_block *sb)
 #define OCFS2_DX_ROOT_REMOVE_CREDITS (OCFS2_INODE_UPDATE_CREDITS +	\
 				      OCFS2_SUBALLOC_FREE)
 
+static inline int ocfs2_calc_dxi_expand_credits(struct super_block *sb)
+{
+	int credits = 1 + OCFS2_SUBALLOC_ALLOC;
+
+	credits += ocfs2_clusters_to_blocks(sb, 1);
+	credits += ocfs2_quota_trans_credits(sb);
+
+	return credits;
+}
+
 /*
  * Please note that the caller must make sure that root_el is the root
  * of extent tree. So for an inode, it should be &fe->id2.i_list. Otherwise

fs/ocfs2/namei.c

@@ -321,10 +321,8 @@ static int ocfs2_mknod(struct inode *dir,
 		want_clusters += 1;
 
 		/* Dir indexing requires extra space as well */
-		if (ocfs2_supports_indexed_dirs(osb)) {
-			want_clusters++;
+		if (ocfs2_supports_indexed_dirs(osb))
 			want_meta++;
-		}
 	}
 
 	status = ocfs2_reserve_new_metadata_blocks(osb, want_meta, &meta_ac);

fs/ocfs2/ocfs2_fs.h

@@ -815,6 +815,8 @@ struct ocfs2_dx_entry_list {
 							 * length de_num_used */
 };
 
+#define OCFS2_DX_FLAG_INLINE	0x01
+
 /*
  * A directory indexing block. Each indexed directory has one of these,
  * pointed to by ocfs2_dinode.
@@ -835,13 +837,21 @@ struct ocfs2_dx_root_block {
 						 * extent block */
 	__le32		dr_clusters;		/* Clusters allocated
 						 * to the indexed tree. */
-	__le32		dr_reserved1;
+	__u8		dr_flags;		/* OCFS2_DX_FLAG_* flags */
+	__u8		dr_reserved0;
+	__le16		dr_reserved1;
 	__le64		dr_dir_blkno;		/* Pointer to parent inode */
 	__le64		dr_reserved2;
 	__le64		dr_reserved3[16];
-	struct ocfs2_extent_list	dr_list; /* Keep this aligned to 128
-						  * bits for maximum space
-						  * efficiency. */
+	union {
+		struct ocfs2_extent_list dr_list; /* Keep this aligned to 128
+						   * bits for maximum space
+						   * efficiency. */
+		struct ocfs2_dx_entry_list dr_entries; /* In-root-block list of
+							* entries. We grow out
+							* to extents if this
+							* gets too big. */
+	};
 };
 
 /*
@@ -1228,6 +1238,16 @@ static inline int ocfs2_dx_entries_per_leaf(struct super_block *sb)
 	return size / sizeof(struct ocfs2_dx_entry);
 }
 
+static inline int ocfs2_dx_entries_per_root(struct super_block *sb)
+{
+	int size;
+
+	size = sb->s_blocksize -
+		offsetof(struct ocfs2_dx_root_block, dr_entries.de_entries);
+
+	return size / sizeof(struct ocfs2_dx_entry);
+}
+
 static inline u16 ocfs2_local_alloc_size(struct super_block *sb)
 {
 	u16 size;