ocfs2: Add a name indexed b-tree to directory inodes

This patch makes use of Ocfs2's flexible btree code to add an additional
tree to directory inodes. The new tree stores an array of small,
fixed-length records in each leaf block. Each record stores a hash value,
and pointer to a block in the traditional (unindexed) directory tree where a
dirent with the given name hash resides. Lookup exclusively uses this tree
to find dirents, thus providing us with constant time name lookups.

Some of the hashing code was copied from ext3. Unfortunately, it has lots of
unfixed checkpatch errors. I left that as-is so that tracking changes would
be easier.

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Acked-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 99 insertions, 3 deletions

diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index 2332ef740f4f..036eb03950a3 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -66,6 +66,8 @@
 #define OCFS2_GROUP_DESC_SIGNATURE      "GROUP01"
 #define OCFS2_XATTR_BLOCK_SIGNATURE     "XATTR01"
 #define OCFS2_DIR_TRAILER_SIGNATURE     "DIRTRL1"
+#define OCFS2_DX_ROOT_SIGNATURE         "DXDIR01"
+#define OCFS2_DX_LEAF_SIGNATURE         "DXLEAF1"
 
 /* Compatibility flags */
 #define OCFS2_HAS_COMPAT_FEATURE(sb,mask)                       \
@@ -151,6 +153,9 @@
 /* Support for extended attributes */
 #define OCFS2_FEATURE_INCOMPAT_XATTR            0x0200
 
+/* Support for indexed directores */
+#define OCFS2_FEATURE_INCOMPAT_INDEXED_DIRS     0x0400
+
 /* Metadata checksum and error correction */
 #define OCFS2_FEATURE_INCOMPAT_META_ECC         0x0800
 
@@ -628,8 +633,9 @@ struct ocfs2_super_block {
 /*B8*/  __le16 s_xattr_inline_size;     /* extended attribute inline size
                                            for this fs*/
         __le16 s_reserved0;
-        __le32 s_reserved1;
-/*C0*/  __le64 s_reserved2[16];         /* Fill out superblock */
+        __le32 s_dx_seed[3];            /* seed[0-2] for dx dir hash.
+                                         * s_uuid_hash serves as seed[3]. */
+/*C0*/  __le64 s_reserved2[15];         /* Fill out superblock */
 /*140*/
 
         /*
@@ -705,7 +711,8 @@ struct ocfs2_dinode {
         __le16 i_dyn_features;
         __le64 i_xattr_loc;
 /*80*/  struct ocfs2_block_check i_check;       /* Error checking */
-/*88*/  __le64 i_reserved2[6];
+/*88*/  __le64 i_dx_root;               /* Pointer to dir index root block */
+        __le64 i_reserved2[5];
 /*B8*/  union {
                 __le64 i_pad1;          /* Generic way to refer to this
                                            64bit union */
@@ -781,6 +788,75 @@ struct ocfs2_dir_block_trailer {
 /*40*/
 };
 
+ /*
+ * A directory entry in the indexed tree. We don't store the full name here,
+ * but instead provide a pointer to the full dirent in the unindexed tree.
+ *
+ * We also store name_len here so as to reduce the number of leaf blocks we
+ * need to search in case of collisions.
+ */
+struct ocfs2_dx_entry {
+        __le32          dx_major_hash;  /* Used to find logical
+                                         * cluster in index */
+        __le32          dx_minor_hash;  /* Lower bits used to find
+                                         * block in cluster */
+        __le64          dx_dirent_blk;  /* Physical block in unindexed
+                                         * tree holding this dirent. */
+};
+
+struct ocfs2_dx_entry_list {
+        __le32          de_reserved;
+        __le16          de_count;       /* Maximum number of entries
+                                         * possible in de_entries */
+        __le16          de_num_used;    /* Current number of
+                                         * de_entries entries */
+        struct  ocfs2_dx_entry          de_entries[0];  /* Indexed dir entries
+                                                         * in a packed array of
+                                                         * length de_num_used */
+};
+
+/*
+ * A directory indexing block. Each indexed directory has one of these,
+ * pointed to by ocfs2_dinode.
+ *
+ * This block stores an indexed btree root, and a set of free space
+ * start-of-list pointers.
+ */
+struct ocfs2_dx_root_block {
+        __u8            dr_signature[8];        /* Signature for verification */
+        struct ocfs2_block_check dr_check;      /* Error checking */
+        __le16          dr_suballoc_slot;       /* Slot suballocator this
+                                                 * block belongs to. */
+        __le16          dr_suballoc_bit;        /* Bit offset in suballocator
+                                                 * block group */
+        __le32          dr_fs_generation;       /* Must match super block */
+        __le64          dr_blkno;               /* Offset on disk, in blocks */
+        __le64          dr_last_eb_blk;         /* Pointer to last
+                                                 * extent block */
+        __le32          dr_clusters;            /* Clusters allocated
+                                                 * to the indexed tree. */
+        __le32          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. */
+};
+
+/*
+ * The header of a leaf block in the indexed tree.
+ */
+struct ocfs2_dx_leaf {
+        __u8            dl_signature[8];/* Signature for verification */
+        struct ocfs2_block_check dl_check;      /* Error checking */
+        __le64          dl_blkno;       /* Offset on disk, in blocks */
+        __le32          dl_fs_generation;/* Must match super block */
+        __le32          dl_reserved0;
+        __le64          dl_reserved1;
+        struct ocfs2_dx_entry_list      dl_list;
+};
+
 /*
  * On disk allocator group structure for OCFS2
  */
@@ -1112,6 +1188,16 @@ static inline int ocfs2_extent_recs_per_inode_with_xattr(
         return size / sizeof(struct ocfs2_extent_rec);
 }
 
+static inline int ocfs2_extent_recs_per_dx_root(struct super_block *sb)
+{
+        int size;
+
+        size = sb->s_blocksize -
+                offsetof(struct ocfs2_dx_root_block, dr_list.l_recs);
+
+        return size / sizeof(struct ocfs2_extent_rec);
+}
+
 static inline int ocfs2_chain_recs_per_inode(struct super_block *sb)
 {
         int size;
@@ -1132,6 +1218,16 @@ static inline u16 ocfs2_extent_recs_per_eb(struct super_block *sb)
         return size / sizeof(struct ocfs2_extent_rec);
 }
 
+static inline int ocfs2_dx_entries_per_leaf(struct super_block *sb)
+{
+        int size;
+
+        size = sb->s_blocksize -
+                offsetof(struct ocfs2_dx_leaf, dl_list.de_entries);
+
+        return size / sizeof(struct ocfs2_dx_entry);
+}
+
 static inline u16 ocfs2_local_alloc_size(struct super_block *sb)
 {
         u16 size;