ctree.h

   1 #ifndef __CTREE__
   2 #define __CTREE__
   3
   4 #define CTREE_BLOCKSIZE 1024
   5
   6 /*
   7  * the key defines the order in the tree, and so it also defines (optimal)
   8  * block layout.  objectid corresonds to the inode number.  The flags
   9  * tells us things about the object, and is a kind of stream selector.
  10  * so for a given inode, keys with flags of 1 might refer to the inode
  11  * data, flags of 2 may point to file data in the btree and flags == 3
  12  * may point to extents.
  13  *
  14  * offset is the starting byte offset for this key in the stream.
  15  */
  16 struct key {
  17         u64 objectid;
  18         u32 flags;
  19         u64 offset;
  20 } __attribute__ ((__packed__));
  21
  22 /*
  23  * every tree block (leaf or node) starts with this header.
  24  */
  25 struct header {
  26         u64 fsid[2]; /* FS specific uuid */
  27         u64 blocknr; /* which block this node is supposed to live in */
  28         u64 parentid; /* objectid of the tree root */
  29         u32 csum;
  30         u32 ham;
  31         u16 nritems;
  32         u16 flags;
  33         /* generation flags to be added */
  34 } __attribute__ ((__packed__));
  35
  36 #define NODEPTRS_PER_BLOCK ((CTREE_BLOCKSIZE - sizeof(struct header)) / \
  37                             (sizeof(struct key) + sizeof(u64)))
  38
  39 #define MAX_LEVEL 8
  40 #define node_level(f) ((f) & (MAX_LEVEL-1))
  41 #define is_leaf(f) (node_level(f) == 0)
  42
  43 struct tree_buffer;
  44
  45 /*
  46  * in ram representation of the tree.  extent_root is used for all allocations
  47  * and for the extent tree extent_root root.  current_insert is used
  48  * only for the extent tree.
  49  */
  50 struct ctree_root {
  51         struct tree_buffer *node;
  52         struct ctree_root *extent_root;
  53         struct key current_insert;
  54         int fp;
  55         struct radix_tree_root cache_radix;
  56 };
  57
  58 /*
  59  * describes a tree on disk
  60  */
  61 struct ctree_root_info {
  62         u64 fsid[2]; /* FS specific uuid */
  63         u64 blocknr; /* blocknr of this block */
  64         u64 objectid; /* inode number of this root */
  65         u64 tree_root; /* the tree root block */
  66         u32 csum;
  67         u32 ham;
  68         u64 snapuuid[2]; /* root specific uuid */
  69 } __attribute__ ((__packed__));
  70
  71 /*
  72  * the super block basically lists the main trees of the FS
  73  * it currently lacks any block count etc etc
  74  */
  75 struct ctree_super_block {
  76         struct ctree_root_info root_info;
  77         struct ctree_root_info extent_info;
  78 } __attribute__ ((__packed__));
  79
  80 /*
  81  * A leaf is full of items.  The exact type of item is defined by
  82  * the key flags parameter.  offset and size tell us where to find
  83  * the item in the leaf (relative to the start of the data area)
  84  */
  85 struct item {
  86         struct key key;
  87         u16 offset;
  88         u16 size;
  89 } __attribute__ ((__packed__));
  90
  91 /*
  92  * leaves have an item area and a data area:
  93  * [item0, item1....itemN] [free space] [dataN...data1, data0]
  94  *
  95  * The data is separate from the items to get the keys closer together
  96  * during searches.
  97  */
  98 #define LEAF_DATA_SIZE (CTREE_BLOCKSIZE - sizeof(struct header))
  99 struct leaf {
 100         struct header header;
 101         union {
 102                 struct item items[LEAF_DATA_SIZE/sizeof(struct item)];
 103                 u8 data[CTREE_BLOCKSIZE-sizeof(struct header)];
 104         };
 105 } __attribute__ ((__packed__));
 106
 107 /*
 108  * all non-leaf blocks are nodes, they hold only keys and pointers to
 109  * other blocks
 110  */
 111 struct node {
 112         struct header header;
 113         struct key keys[NODEPTRS_PER_BLOCK];
 114         u64 blockptrs[NODEPTRS_PER_BLOCK];
 115 } __attribute__ ((__packed__));
 116
 117 /*
 118  * items in the extent btree are used to record the objectid of the
 119  * owner of the block and the number of references
 120  */
 121 struct extent_item {
 122         u32 refs;
 123         u64 owner;
 124 } __attribute__ ((__packed__));
 125
 126 /*
 127  * ctree_paths remember the path taken from the root down to the leaf.
 128  * level 0 is always the leaf, and nodes[1...MAX_LEVEL] will point
 129  * to any other levels that are present.
 130  *
 131  * The slots array records the index of the item or block pointer
 132  * used while walking the tree.
 133  */
 134 struct ctree_path {
 135         struct tree_buffer *nodes[MAX_LEVEL];
 136         int slots[MAX_LEVEL];
 137 };
 138
 139 struct tree_buffer *alloc_free_block(struct ctree_root *root);
 140 int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks);
 141 int search_slot(struct ctree_root *root, struct key *key, struct ctree_path *p, int ins_len);
 142 void release_path(struct ctree_root *root, struct ctree_path *p);
 143 void init_path(struct ctree_path *p);
 144 int del_item(struct ctree_root *root, struct ctree_path *path);
 145 int insert_item(struct ctree_root *root, struct key *key, void *data, int data_size);
 146 int next_leaf(struct ctree_root *root, struct ctree_path *path);
 147 int leaf_free_space(struct leaf *leaf);
 148 #endif