---

yaml
---
r: 128247
b: refs/heads/master
c: fec577f
h: refs/heads/master
i:
  128245: efbf2c6
  128243: 4b8400f
  128239: e9a39c5
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 97571fd0c939be8ae9cb57a8c57430a244ce13ae
+refs/heads/master: fec577fb7f516e0d12ff821b1af272fd754e120a

trunk/fs/btrfs/Makefile

@@ -6,11 +6,17 @@ objects = ctree.o disk-io.o radix-tree.o mkfs.o extent-tree.o print-tree.o
 #.c.o:
 #	$(CC) $(CFLAGS) -c $<
 
-ctree : $(objects)
-	gcc $(CFLAGS) -o ctree $(objects)
+all: tester debug-tree
+
+debug-tree: $(objects) debug-tree.o
+	gcc $(CFLAGS) -o debug-tree $(objects) debug-tree.o
+
+tester: $(objects) random-test.o
+	gcc $(CFLAGS) -o tester $(objects) random-test.o
 
 $(objects) : $(headers)
 
 clean :
 	rm ctree *.o
 
+

trunk/fs/btrfs/ctree.c

@@ -1047,14 +1047,14 @@ int next_leaf(struct ctree_root *root, struct ctree_path *path)
 	return 0;
 }
 
+/* some sample code to insert,search & delete items */
+#if 0
 /* for testing only */
 int next_key(int i, int max_key) {
 	return rand() % max_key;
 	//return i;
 }
-
 int main() {
-	struct ctree_root *root;
 	struct key ins;
 	struct key last = { (u64)-1, 0, 0};
 	char *buf;
@@ -1066,6 +1066,7 @@ int main() {
 	int tree_size = 0;
 	struct ctree_path path;
 	struct ctree_super_block super;
+	struct ctree_root *root;
 
 	radix_tree_init();
 
@@ -1207,3 +1208,4 @@ int main() {
 	close_ctree(root);
 	return 0;
 }
+#endif

trunk/fs/btrfs/ctree.h

@@ -1,22 +1,36 @@
 #ifndef __CTREE__
 #define __CTREE__
 
-#define CTREE_BLOCKSIZE 4096
+#define CTREE_BLOCKSIZE 1024
 
+/*
+ * the key defines the order in the tree, and so it also defines (optimal)
+ * block layout.  objectid corresonds to the inode number.  The flags
+ * tells us things about the object, and is a kind of stream selector.
+ * so for a given inode, keys with flags of 1 might refer to the inode
+ * data, flags of 2 may point to file data in the btree and flags == 3
+ * may point to extents.
+ *
+ * offset is the starting byte offset for this key in the stream.
+ */
 struct key {
 	u64 objectid;
 	u32 flags;
 	u64 offset;
 } __attribute__ ((__packed__));
 
+/*
+ * every tree block (leaf or node) starts with this header.
+ */
 struct header {
 	u64 fsid[2]; /* FS specific uuid */
-	u64 blocknr;
-	u64 parentid;
+	u64 blocknr; /* which block this node is supposed to live in */
+	u64 parentid; /* objectid of the tree root */
 	u32 csum;
 	u32 ham;
 	u16 nritems;
 	u16 flags;
+	/* generation flags to be added */
 } __attribute__ ((__packed__));
 
 #define NODEPTRS_PER_BLOCK ((CTREE_BLOCKSIZE - sizeof(struct header)) / \
@@ -28,6 +42,11 @@ struct header {
 
 struct tree_buffer;
 
+/*
+ * in ram representation of the tree.  extent_root is used for all allocations
+ * and for the extent tree extent_root root.  current_insert is used
+ * only for the extent tree.
+ */
 struct ctree_root {
 	struct tree_buffer *node;
 	struct ctree_root *extent_root;
@@ -36,27 +55,46 @@ struct ctree_root {
 	struct radix_tree_root cache_radix;
 };
 
+/*
+ * describes a tree on disk
+ */
 struct ctree_root_info {
 	u64 fsid[2]; /* FS specific uuid */
 	u64 blocknr; /* blocknr of this block */
 	u64 objectid; /* inode number of this root */
-	u64 tree_root; /* the tree root */
+	u64 tree_root; /* the tree root block */
 	u32 csum;
 	u32 ham;
 	u64 snapuuid[2]; /* root specific uuid */
 } __attribute__ ((__packed__));
 
+/*
+ * the super block basically lists the main trees of the FS
+ * it currently lacks any block count etc etc
+ */
 struct ctree_super_block {
 	struct ctree_root_info root_info;
 	struct ctree_root_info extent_info;
 } __attribute__ ((__packed__));
 
+/*
+ * A leaf is full of items.  The exact type of item is defined by
+ * the key flags parameter.  offset and size tell us where to find
+ * the item in the leaf (relative to the start of the data area)
+ */
 struct item {
 	struct key key;
 	u16 offset;
 	u16 size;
 } __attribute__ ((__packed__));
 
+/*
+ * leaves have an item area and a data area:
+ * [item0, item1....itemN] [free space] [dataN...data1, data0]
+ *
+ * The data is separate from the items to get the keys closer together
+ * during searches.
+ */
 #define LEAF_DATA_SIZE (CTREE_BLOCKSIZE - sizeof(struct header))
 struct leaf {
 	struct header header;
@@ -66,17 +104,33 @@ struct leaf {
 	};
 } __attribute__ ((__packed__));
 
+/*
+ * all non-leaf blocks are nodes, they hold only keys and pointers to
+ * other blocks
+ */
 struct node {
 	struct header header;
 	struct key keys[NODEPTRS_PER_BLOCK];
 	u64 blockptrs[NODEPTRS_PER_BLOCK];
 } __attribute__ ((__packed__));
 
+/*
+ * items in the extent btree are used to record the objectid of the
+ * owner of the block and the number of references
+ */
 struct extent_item {
 	u32 refs;
 	u64 owner;
 } __attribute__ ((__packed__));
 
+/*
+ * ctree_paths remember the path taken from the root down to the leaf.
+ * level 0 is always the leaf, and nodes[1...MAX_LEVEL] will point
+ * to any other levels that are present.
+ *
+ * The slots array records the index of the item or block pointer
+ * used while walking the tree.
+ */
 struct ctree_path {
 	struct tree_buffer *nodes[MAX_LEVEL];
 	int slots[MAX_LEVEL];

trunk/fs/btrfs/debug-tree.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "kerncompat.h"
+#include "radix-tree.h"
+#include "ctree.h"
+#include "disk-io.h"
+#include "print-tree.h"
+
+int main() {
+	struct ctree_super_block super;
+	struct ctree_root *root;
+	radix_tree_init();
+	root = open_ctree("dbfile", &super);
+	printf("root tree\n");
+	print_tree(root, root->node);
+	printf("map tree\n");
+	print_tree(root->extent_root, root->extent_root->node);
+	return 0;
+}