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 tree_buffer *commit_root;
  55         struct ctree_root *extent_root;
  56         struct key current_insert;
  57         int fp;
  58         struct radix_tree_root cache_radix;
  59         struct radix_tree_root pinned_radix;
  60         struct list_head trans;
  61         struct list_head cache;
  62         int cache_size;
  63 };
  64
  65 /*
  66  * describes a tree on disk
  67  */
  68 struct ctree_root_info {
  69         u64 fsid[2]; /* FS specific uuid */
  70         u64 blocknr; /* blocknr of this block */
  71         u64 objectid; /* inode number of this root */
  72         u64 tree_root; /* the tree root block */
  73         u32 csum;
  74         u32 ham;
  75         u64 snapuuid[2]; /* root specific uuid */
  76 } __attribute__ ((__packed__));
  77
  78 /*
  79  * the super block basically lists the main trees of the FS
  80  * it currently lacks any block count etc etc
  81  */
  82 struct ctree_super_block {
  83         struct ctree_root_info root_info;
  84         struct ctree_root_info extent_info;
  85 } __attribute__ ((__packed__));
  86
  87 /*
  88  * A leaf is full of items.  The exact type of item is defined by
  89  * the key flags parameter.  offset and size tell us where to find
  90  * the item in the leaf (relative to the start of the data area)
  91  */
  92 struct item {
  93         struct key key;
  94         u16 offset;
  95         u16 size;
  96 } __attribute__ ((__packed__));
  97
  98 /*
  99  * leaves have an item area and a data area:
 100  * [item0, item1....itemN] [free space] [dataN...data1, data0]
 101  *
 102  * The data is separate from the items to get the keys closer together
 103  * during searches.
 104  */
 105 #define LEAF_DATA_SIZE (CTREE_BLOCKSIZE - sizeof(struct header))
 106 struct leaf {
 107         struct header header;
 108         union {
 109                 struct item items[LEAF_DATA_SIZE/sizeof(struct item)];
 110                 u8 data[CTREE_BLOCKSIZE-sizeof(struct header)];
 111         };
 112 } __attribute__ ((__packed__));
 113
 114 /*
 115  * all non-leaf blocks are nodes, they hold only keys and pointers to
 116  * other blocks
 117  */
 118 struct node {
 119         struct header header;
 120         struct key keys[NODEPTRS_PER_BLOCK];
 121         u64 blockptrs[NODEPTRS_PER_BLOCK];
 122 } __attribute__ ((__packed__));
 123
 124 /*
 125  * items in the extent btree are used to record the objectid of the
 126  * owner of the block and the number of references
 127  */
 128 struct extent_item {
 129         u32 refs;
 130         u64 owner;
 131 } __attribute__ ((__packed__));
 132
 133 /*
 134  * ctree_paths remember the path taken from the root down to the leaf.
 135  * level 0 is always the leaf, and nodes[1...MAX_LEVEL] will point
 136  * to any other levels that are present.
 137  *
 138  * The slots array records the index of the item or block pointer
 139  * used while walking the tree.
 140  */
 141 struct ctree_path {
 142         struct tree_buffer *nodes[MAX_LEVEL];
 143         int slots[MAX_LEVEL];
 144 };
 145
 146 struct tree_buffer *alloc_free_block(struct ctree_root *root);
 147 int btrfs_inc_ref(struct ctree_root *root, struct tree_buffer *buf);
 148 int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks);
 149 int search_slot(struct ctree_root *root, struct key *key, struct ctree_path *p, int ins_len, int cow);
 150 void release_path(struct ctree_root *root, struct ctree_path *p);
 151 void init_path(struct ctree_path *p);
 152 int del_item(struct ctree_root *root, struct ctree_path *path);
 153 int insert_item(struct ctree_root *root, struct key *key, void *data, int data_size);
 154 int next_leaf(struct ctree_root *root, struct ctree_path *path);
 155 int leaf_free_space(struct leaf *leaf);
 156 int btrfs_drop_snapshot(struct ctree_root *root, struct tree_buffer *snap);
 157 int btrfs_finish_extent_commit(struct ctree_root *root);
 158 #endif