fs/btrfs/ctree.h

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