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>

1 files changed, 24 insertions, 4 deletions

diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index 036eb03950a3..1d1c54ea5bc4 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/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;