Commit 3768f368 authored by Chris Mason's avatar Chris Mason Committed by David Woodhouse
Browse files

Btrfs: Change the super to point to a tree of trees to enable persistent snapshots 



Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent eaee50e8

fs/btrfs/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -2,7 +2,8 @@ 
CC=gcc

CFLAGS = -g -Wall

headers = radix-tree.h ctree.h disk-io.h kerncompat.h print-tree.h list.h

objects = ctree.o disk-io.o radix-tree.o mkfs.o extent-tree.o print-tree.o

objects = ctree.o disk-io.o radix-tree.o mkfs.o extent-tree.o print-tree.o \

	  root-tree.o



# if you don't have sparse installed, use ls instead

CHECKFLAGS=-D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise \

fs/btrfs/TODO

+1 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
* make a real mkfs and superblock

* Do checksumming

* Define FS objects in terms of different item types

* add inode tree

* Add block mapping tree (simple dm layer)

* Add simple tree locking (semaphore per tree)

* Make allocator smarter

fs/btrfs/ctree.h

+107 −16
Original line number Diff line number Diff line
@@ -4,8 +4,13 @@ 
#include "list.h"

#include "kerncompat.h"



#define BTRFS_MAGIC "_BtRfS_M"

#define BTRFS_BLOCKSIZE 1024



#define BTRFS_ROOT_TREE_OBJECTID 1

#define BTRFS_EXTENT_TREE_OBJECTID 2

#define BTRFS_FS_TREE_OBJECTID 3



/*

 * the key defines the order in the tree, and so it also defines (optimal)

 * block layout.  objectid corresonds to the inode number.  The flags
@@ -36,7 +41,7 @@ struct btrfs_key { 
 * every tree block (leaf or node) starts with this header.

 */

struct btrfs_header {

	__le64 fsid[2]; /* FS specific uuid */

	u8 fsid[16]; /* FS specific uuid */

	__le64 blocknr; /* which block this node is supposed to live in */

	__le64 parentid; /* objectid of the tree root */

	__le32 csum;
@@ -52,6 +57,14 @@ struct btrfs_header { 


struct btrfs_buffer;



struct btrfs_root_item {

	__le64 blocknr;

	__le32 flags;

	__le64 block_limit;

	__le64 blocks_used;

	__le32 refs;

};



/*

 * 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
@@ -61,6 +74,7 @@ struct btrfs_root { 
	struct btrfs_buffer *node;

	struct btrfs_buffer *commit_root;

	struct btrfs_root *extent_root;

	struct btrfs_root *tree_root;

	struct btrfs_key current_insert;

	struct btrfs_key last_insert;

	int fp;
@@ -69,28 +83,25 @@ struct btrfs_root { 
	struct list_head trans;

	struct list_head cache;

	int cache_size;

	int ref_cows;

	struct btrfs_root_item root_item;

	struct btrfs_key root_key;

};



/*

 * describes a tree on disk

 */

struct btrfs_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 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 btrfs_super_block {

	struct btrfs_root_info root_info;

	struct btrfs_root_info extent_info;

	u8 fsid[16];    /* FS specific uuid */

	__le64 blocknr; /* this block number */

	__le32 csum;

	__le64 magic;

	__le16 blocksize;

	__le64 generation;

	__le64 root;

	__le64 total_blocks;

	__le64 blocks_used;

} __attribute__ ((__packed__));



/*
@@ -317,6 +328,79 @@ static inline int btrfs_is_leaf(struct btrfs_node *n) 
	return (btrfs_header_level(&n->header) == 0);

}



static inline u64 btrfs_root_blocknr(struct btrfs_root_item *item)

{

	return le64_to_cpu(item->blocknr);

}



static inline void btrfs_set_root_blocknr(struct btrfs_root_item *item, u64 val)

{

	item->blocknr = cpu_to_le64(val);

}



static inline u32 btrfs_root_refs(struct btrfs_root_item *item)

{

	return le32_to_cpu(item->refs);

}



static inline void btrfs_set_root_refs(struct btrfs_root_item *item, u32 val)

{

	item->refs = cpu_to_le32(val);

}



static inline u64 btrfs_super_blocknr(struct btrfs_super_block *s)

{

	return le64_to_cpu(s->blocknr);

}



static inline void btrfs_set_super_blocknr(struct btrfs_super_block *s, u64 val)

{

	s->blocknr = cpu_to_le64(val);

}



static inline u64 btrfs_super_root(struct btrfs_super_block *s)

{

	return le64_to_cpu(s->root);

}



static inline void btrfs_set_super_root(struct btrfs_super_block *s, u64 val)

{

	s->root = cpu_to_le64(val);

}



static inline u64 btrfs_super_total_blocks(struct btrfs_super_block *s)

{

	return le64_to_cpu(s->total_blocks);

}



static inline void btrfs_set_super_total_blocks(struct btrfs_super_block *s,

						u64 val)

{

	s->total_blocks = cpu_to_le64(val);

}



static inline u64 btrfs_super_blocks_used(struct btrfs_super_block *s)

{

	return le64_to_cpu(s->blocks_used);

}



static inline void btrfs_set_super_blocks_used(struct btrfs_super_block *s,

						u64 val)

{

	s->blocks_used = cpu_to_le64(val);

}



static inline u16 btrfs_super_blocksize(struct btrfs_super_block *s)

{

	return le16_to_cpu(s->blocksize);

}



static inline void btrfs_set_super_blocksize(struct btrfs_super_block *s,

						u16 val)

{

	s->blocksize = cpu_to_le16(val);

}



struct btrfs_buffer *btrfs_alloc_free_block(struct btrfs_root *root);

int btrfs_inc_ref(struct btrfs_root *root, struct btrfs_buffer *buf);

int btrfs_free_extent(struct btrfs_root *root, u64 blocknr, u64 num_blocks);
@@ -331,4 +415,11 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path); 
int btrfs_leaf_free_space(struct btrfs_leaf *leaf);

int btrfs_drop_snapshot(struct btrfs_root *root, struct btrfs_buffer *snap);

int btrfs_finish_extent_commit(struct btrfs_root *root);

int btrfs_del_root(struct btrfs_root *root, struct btrfs_key *key);

int btrfs_insert_root(struct btrfs_root *root, struct btrfs_key *key,

		      struct btrfs_root_item *item);

int btrfs_update_root(struct btrfs_root *root, struct btrfs_key *key,

		      struct btrfs_root_item *item);

int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,

			struct btrfs_root_item *item, struct btrfs_key *key);

#endif

fs/btrfs/debug-tree.c

+3 −1
Original line number Diff line number Diff line
@@ -11,9 +11,11 @@ int main(int ac, char **av) { 
	struct btrfs_root *root;

	radix_tree_init();

	root = open_ctree("dbfile", &super);

	printf("root tree\n");

	printf("fs tree\n");

	btrfs_print_tree(root, root->node);

	printf("map tree\n");

	btrfs_print_tree(root->extent_root, root->extent_root->node);

	printf("root tree\n");

	btrfs_print_tree(root->tree_root, root->tree_root->node);

	return 0;

}

fs/btrfs/disk-io.c

+107 −28
Original line number Diff line number Diff line
@@ -154,41 +154,96 @@ static int __commit_transaction(struct btrfs_root *root) 
	return ret;

}



static int commit_extent_and_tree_roots(struct btrfs_root *tree_root,

					struct btrfs_root *extent_root)

{

	int ret;

	u64 old_extent_block;



	while(1) {

		old_extent_block = btrfs_root_blocknr(&extent_root->root_item);

		if (old_extent_block == extent_root->node->blocknr)

			break;

		btrfs_set_root_blocknr(&extent_root->root_item,

				       extent_root->node->blocknr);

		ret = btrfs_update_root(tree_root,

					&extent_root->root_key,

					&extent_root->root_item);

		BUG_ON(ret);

	}

	__commit_transaction(extent_root);

	__commit_transaction(tree_root);

	return 0;

}



int btrfs_commit_transaction(struct btrfs_root *root,

			     struct btrfs_super_block *s)

{

	int ret = 0;

	struct btrfs_buffer *snap = root->commit_root;

	struct btrfs_key snap_key;



	ret = __commit_transaction(root);

	if (!ret && root != root->extent_root)

		ret = __commit_transaction(root->extent_root);

	BUG_ON(ret);

	if (root->commit_root != root->node) {

		struct btrfs_buffer *snap = root->commit_root;



	if (root->commit_root == root->node)

		return 0;



	memcpy(&snap_key, &root->root_key, sizeof(snap_key));

	root->root_key.offset++;



	btrfs_set_root_blocknr(&root->root_item, root->node->blocknr);

	ret = btrfs_insert_root(root->tree_root, &root->root_key,

				&root->root_item);

	BUG_ON(ret);



	ret = commit_extent_and_tree_roots(root->tree_root, root->extent_root);

	BUG_ON(ret);



        write_ctree_super(root, s);

	btrfs_finish_extent_commit(root->extent_root);

	btrfs_finish_extent_commit(root->tree_root);



	root->commit_root = root->node;

	root->node->count++;

	ret = btrfs_drop_snapshot(root, snap);

	BUG_ON(ret);

		// btrfs_block_release(root, snap);

	}

        write_ctree_super(root, s);

	btrfs_finish_extent_commit(root);



	ret = btrfs_del_root(root->tree_root, &snap_key);

	BUG_ON(ret);



	return ret;

}



static int __setup_root(struct btrfs_root *root, struct btrfs_root *extent_root,

			struct btrfs_root_info *info, int fp)

static int __setup_root(struct btrfs_root *root, u64 objectid, int fp)

{

	INIT_LIST_HEAD(&root->trans);

	INIT_LIST_HEAD(&root->cache);

	root->cache_size = 0;

	root->fp = fp;

	root->node = NULL;

	root->extent_root = extent_root;

	root->commit_root = NULL;

	root->node = read_tree_block(root, info->tree_root);

	memset(&root->current_insert, 0, sizeof(root->current_insert));

	memset(&root->last_insert, 0, sizeof(root->last_insert));

	memset(&root->root_key, 0, sizeof(root->root_key));

	memset(&root->root_item, 0, sizeof(root->root_item));

	return 0;

}



static int find_and_setup_root(struct btrfs_root *tree_root, u64 objectid,

			struct btrfs_root *root, int fp)

{

	int ret;



	__setup_root(root, objectid, fp);

	ret = btrfs_find_last_root(tree_root, objectid,

				   &root->root_item, &root->root_key);

	BUG_ON(ret);



	root->node = read_tree_block(root,

				     btrfs_root_blocknr(&root->root_item));

	root->ref_cows = 0;

	BUG_ON(!root->node);

	return 0;

}
@@ -196,9 +251,19 @@ struct btrfs_root *open_ctree(char *filename, struct btrfs_super_block *super) 
{

	struct btrfs_root *root = malloc(sizeof(struct btrfs_root));

	struct btrfs_root *extent_root = malloc(sizeof(struct btrfs_root));

	struct btrfs_root *tree_root = malloc(sizeof(struct btrfs_root));

	int fp;

	int ret;



	root->extent_root = extent_root;

	root->tree_root = tree_root;



	extent_root->extent_root = extent_root;

	extent_root->tree_root = tree_root;



	tree_root->extent_root = extent_root;

	tree_root->tree_root = tree_root;



	fp = open(filename, O_CREAT | O_RDWR, 0600);

	if (fp < 0) {

		free(root);
@@ -208,11 +273,14 @@ struct btrfs_root *open_ctree(char *filename, struct btrfs_super_block *super) 
	INIT_RADIX_TREE(&root->pinned_radix, GFP_KERNEL);

	INIT_RADIX_TREE(&extent_root->pinned_radix, GFP_KERNEL);

	INIT_RADIX_TREE(&extent_root->cache_radix, GFP_KERNEL);

	INIT_RADIX_TREE(&tree_root->pinned_radix, GFP_KERNEL);

	INIT_RADIX_TREE(&tree_root->cache_radix, GFP_KERNEL);



	ret = pread(fp, super, sizeof(struct btrfs_super_block),

		     BTRFS_SUPER_INFO_OFFSET(BTRFS_BLOCKSIZE));

	if (ret == 0 || super->root_info.tree_root == 0) {

	if (ret == 0 || btrfs_super_root(super) == 0) {

		printf("making new FS!\n");

		ret = mkfs(fp);

		ret = mkfs(fp, 0, BTRFS_BLOCKSIZE);

		if (ret)

			return NULL;

		ret = pread(fp, super, sizeof(struct btrfs_super_block),
@@ -221,24 +289,29 @@ struct btrfs_root *open_ctree(char *filename, struct btrfs_super_block *super) 
			return NULL;

	}

	BUG_ON(ret < 0);

	__setup_root(root, extent_root, &super->root_info, fp);

	__setup_root(extent_root, extent_root, &super->extent_info, fp);



	__setup_root(tree_root, BTRFS_ROOT_TREE_OBJECTID, fp);

	tree_root->node = read_tree_block(tree_root, btrfs_super_root(super));

	BUG_ON(!tree_root->node);



	ret = find_and_setup_root(tree_root, BTRFS_EXTENT_TREE_OBJECTID,

				  extent_root, fp);

	BUG_ON(ret);



	ret = find_and_setup_root(tree_root, BTRFS_FS_TREE_OBJECTID,

				  root, fp);

	BUG_ON(ret);



	root->commit_root = root->node;

	root->node->count++;

	root->ref_cows = 1;

	return root;

}



static int __update_root(struct btrfs_root *root, struct btrfs_root_info *info)

{

	info->tree_root = root->node->blocknr;

	return 0;

}



int write_ctree_super(struct btrfs_root *root, struct btrfs_super_block *s)

{

	int ret;

	__update_root(root, &s->root_info);

	__update_root(root->extent_root, &s->extent_info);

	btrfs_set_super_root(s, root->tree_root->node->blocknr);

	ret = pwrite(root->fp, s, sizeof(*s),

		     BTRFS_SUPER_INFO_OFFSET(BTRFS_BLOCKSIZE));

	if (ret != sizeof(*s)) {
@@ -260,19 +333,25 @@ static int drop_cache(struct btrfs_root *root) 
}

int close_ctree(struct btrfs_root *root, struct btrfs_super_block *s)

{

	int ret;

	btrfs_commit_transaction(root, s);

	__commit_transaction(root->extent_root);

	ret = commit_extent_and_tree_roots(root->tree_root, root->extent_root);

	BUG_ON(ret);

	write_ctree_super(root, s);

	drop_cache(root->extent_root);

	drop_cache(root->tree_root);

	drop_cache(root);

	BUG_ON(!list_empty(&root->trans));

	BUG_ON(!list_empty(&root->extent_root->trans));

	BUG_ON(!list_empty(&root->tree_root->trans));



	close(root->fp);

	if (root->node)

		btrfs_block_release(root, root->node);

	if (root->extent_root->node)

		btrfs_block_release(root->extent_root, root->extent_root->node);

	if (root->tree_root->node)

		btrfs_block_release(root->tree_root, root->tree_root->node);

	btrfs_block_release(root, root->commit_root);

	free(root);

	printf("on close %d blocks are allocated\n", allocated_blocks);