Btrfs: Add backing store, memory management

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -0,0 +1,62 @@
+#ifndef __CTREE__
+#define __CTREE__
+
+#define CTREE_BLOCKSIZE 4096
+
+struct key {
+	u64 objectid;
+	u32 flags;
+	u64 offset;
+} __attribute__ ((__packed__));
+
+struct header {
+	u64 fsid[2]; /* FS specific uuid */
+	u64 blocknr;
+	u64 parentid;
+	u32 csum;
+	u32 ham;
+	u16 nritems;
+	u16 flags;
+} __attribute__ ((__packed__));
+
+#define NODEPTRS_PER_BLOCK ((CTREE_BLOCKSIZE - sizeof(struct header)) / \
+			    (sizeof(struct key) + sizeof(u64)))
+
+#define LEVEL_BITS 3
+#define MAX_LEVEL (1 << LEVEL_BITS)
+#define node_level(f) ((f) & (MAX_LEVEL-1))
+#define is_leaf(f) (node_level(f) == 0)
+
+struct tree_buffer;
+struct ctree_root {
+	struct tree_buffer *node;
+	int fp;
+	struct radix_tree_root cache_radix;
+};
+
+struct item {
+	struct key key;
+	u16 offset;
+	u16 size;
+} __attribute__ ((__packed__));
+
+#define LEAF_DATA_SIZE (CTREE_BLOCKSIZE - sizeof(struct header))
+struct leaf {
+	struct header header;
+	union {
+		struct item items[LEAF_DATA_SIZE/sizeof(struct item)];
+		u8 data[CTREE_BLOCKSIZE-sizeof(struct header)];
+	};
+} __attribute__ ((__packed__));
+
+struct node {
+	struct header header;
+	struct key keys[NODEPTRS_PER_BLOCK];
+	u64 blockptrs[NODEPTRS_PER_BLOCK];
+} __attribute__ ((__packed__));
+
+struct ctree_path {
+	struct tree_buffer *nodes[MAX_LEVEL];
+	int slots[MAX_LEVEL];
+};
+#endif