Btrfs: Add backing store, memory management

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

fs/btrfs/Makefile

 
-ctree: ctree.o
-	gcc -g -O2 -Wall -o ctree ctree.c
+CFLAGS= -g -Wall
+
+.c.o:
+	$(CC) $(CFLAGS) -c $<
+
+ctree: ctree.o disk-io.h ctree.h disk-io.o radix-tree.o radix-tree.h
+	gcc $(CFLAGS) -o ctree ctree.o disk-io.o radix-tree.o
 
 clean:
-	rm ctree ctree.o
+	rm ctree *.o
 

fs/btrfs/ctree.h

+#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

fs/btrfs/disk-io.c

+#define _XOPEN_SOURCE 500
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "kerncompat.h"
+#include "radix-tree.h"
+#include "ctree.h"
+#include "disk-io.h"
+
+static int allocated_blocks = 0;
+
+struct ctree_header {
+	u64 root_block;
+} __attribute__ ((__packed__));
+
+static int get_free_block(struct ctree_root *root, u64 *block)
+{
+	struct stat st;
+	int ret;
+
+	st.st_size = 0;
+	ret = fstat(root->fp, &st);
+	if (st.st_size > sizeof(struct ctree_header)) {
+		*block = (st.st_size -
+			sizeof(struct ctree_header)) / CTREE_BLOCKSIZE;
+	} else {
+		*block = 0;
+	}
+	ret = ftruncate(root->fp, sizeof(struct ctree_header) + (*block + 1) *
+			CTREE_BLOCKSIZE);
+	return ret;
+}
+
+struct tree_buffer *alloc_tree_block(struct ctree_root *root, u64 blocknr)
+{
+	struct tree_buffer *buf;
+	int ret;
+	buf = malloc(sizeof(struct tree_buffer));
+	if (!buf)
+		return buf;
+	allocated_blocks++;
+	buf->blocknr = blocknr;
+	buf->count = 1;
+	radix_tree_preload(GFP_KERNEL);
+	ret = radix_tree_insert(&root->cache_radix, blocknr, buf);
+	radix_tree_preload_end();
+	if (ret) {
+		free(buf);
+		return NULL;
+	}
+	return buf;
+}
+
+struct tree_buffer *alloc_free_block(struct ctree_root *root)
+{
+	u64 free_block;
+	int ret;
+	struct tree_buffer * buf;
+	ret = get_free_block(root, &free_block);
+	if (ret) {
+		BUG();
+		return NULL;
+	}
+	buf = alloc_tree_block(root, free_block);
+	if (!buf)
+		BUG();
+	return buf;
+}
+
+struct tree_buffer *read_tree_block(struct ctree_root *root, u64 blocknr)
+{
+	loff_t offset = blocknr * CTREE_BLOCKSIZE + sizeof(struct ctree_header);
+	struct tree_buffer *buf;
+	int ret;
+
+	buf = radix_tree_lookup(&root->cache_radix, blocknr);
+	if (buf) {
+		buf->count++;
+		if (buf->blocknr != blocknr)
+			BUG();
+		if (buf->blocknr != buf->node.header.blocknr)
+			BUG();
+		return buf;
+	}
+	buf = alloc_tree_block(root, blocknr);
+	if (!buf)
+		return NULL;
+	ret = pread(root->fp, &buf->node, CTREE_BLOCKSIZE, offset);
+	if (ret != CTREE_BLOCKSIZE) {
+		free(buf);
+		return NULL;
+	}
+	if (buf->blocknr != buf->node.header.blocknr)
+		BUG();
+	return buf;
+}
+
+int write_tree_block(struct ctree_root *root, struct tree_buffer *buf)
+{
+	u64 blocknr = buf->blocknr;
+	loff_t offset = blocknr * CTREE_BLOCKSIZE + sizeof(struct ctree_header);
+	int ret;
+
+	if (buf->blocknr != buf->node.header.blocknr)
+		BUG();
+	ret = pwrite(root->fp, &buf->node, CTREE_BLOCKSIZE, offset);
+	if (ret != CTREE_BLOCKSIZE)
+		return ret;
+	if (buf == root->node)
+		return update_root_block(root);
+	return 0;
+}
+
+struct ctree_root *open_ctree(char *filename)
+{
+	struct ctree_root *root = malloc(sizeof(struct ctree_root));
+	int fp;
+	u64 root_block;
+	int ret;
+
+	fp = open(filename, O_CREAT | O_RDWR);
+	if (fp < 0) {
+		free(root);
+		return NULL;
+	}
+	root->fp = fp;
+	INIT_RADIX_TREE(&root->cache_radix, GFP_KERNEL);
+	ret = pread(fp, &root_block, sizeof(u64), 0);
+	if (ret == sizeof(u64)) {
+		printf("reading root node at block %lu\n", root_block);
+		root->node = read_tree_block(root, root_block);
+	} else
+		root->node = NULL;
+	return root;
+}
+
+int close_ctree(struct ctree_root *root)
+{
+	close(root->fp);
+	if (root->node)
+		tree_block_release(root, root->node);
+	free(root);
+	printf("on close %d blocks are allocated\n", allocated_blocks);
+	return 0;
+}
+
+int update_root_block(struct ctree_root *root)
+{
+	int ret;
+	u64 root_block = root->node->blocknr;
+
+	ret = pwrite(root->fp, &root_block, sizeof(u64), 0);
+	if (ret != sizeof(u64))
+		return ret;
+	return 0;
+}
+
+void tree_block_release(struct ctree_root *root, struct tree_buffer *buf)
+{
+	buf->count--;
+	if (buf->count == 0) {
+		if (!radix_tree_lookup(&root->cache_radix, buf->blocknr))
+			BUG();
+		radix_tree_delete(&root->cache_radix, buf->blocknr);
+		memset(buf, 0, sizeof(*buf));
+		free(buf);
+		BUG_ON(allocated_blocks == 0);
+		allocated_blocks--;
+	}
+}
+

fs/btrfs/disk-io.h

+#ifndef __DISKIO__
+#define __DISKIO__
+
+struct tree_buffer {
+	u64 blocknr;
+	int count;
+	union {
+		struct node node;
+		struct leaf leaf;
+	};
+};
+
+struct tree_buffer *read_tree_block(struct ctree_root *root, u64 blocknr);
+int write_tree_block(struct ctree_root *root, struct tree_buffer *buf);
+struct ctree_root *open_ctree(char *filename);
+int close_ctree(struct ctree_root *root);
+void tree_block_release(struct ctree_root *root, struct tree_buffer *buf);
+struct tree_buffer *alloc_free_block(struct ctree_root *root);
+int update_root_block(struct ctree_root *root);
+
+#endif

fs/btrfs/kerncompat.h

@@ -6,6 +6,7 @@
 #define BITS_PER_LONG 64
 #define __GFP_BITS_SHIFT 20
 #define __GFP_BITS_MASK ((int)((1 << __GFP_BITS_SHIFT) - 1))
+#define GFP_KERNEL 0
 #define __read_mostly
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 #define __force

fs/btrfs/radix-tree.h

+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2, or (at
+ * your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#ifndef _LINUX_RADIX_TREE_H
+#define _LINUX_RADIX_TREE_H
+
+#define RADIX_TREE_MAX_TAGS 2
+
+/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
+struct radix_tree_root {
+	unsigned int		height;
+	gfp_t			gfp_mask;
+	struct radix_tree_node	*rnode;
+};
+
+#define RADIX_TREE_INIT(mask)	{					\
+	.height = 0,							\
+	.gfp_mask = (mask),						\
+	.rnode = NULL,							\
+}
+
+#define RADIX_TREE(name, mask) \
+	struct radix_tree_root name = RADIX_TREE_INIT(mask)
+
+#define INIT_RADIX_TREE(root, mask)					\
+do {									\
+	(root)->height = 0;						\
+	(root)->gfp_mask = (mask);					\
+	(root)->rnode = NULL;						\
+} while (0)
+
+int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
+void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
+void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
+void *radix_tree_delete(struct radix_tree_root *, unsigned long);
+unsigned int
+radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
+			unsigned long first_index, unsigned int max_items);
+int radix_tree_preload(gfp_t gfp_mask);
+void radix_tree_init(void);
+void *radix_tree_tag_set(struct radix_tree_root *root,
+			unsigned long index, unsigned int tag);
+void *radix_tree_tag_clear(struct radix_tree_root *root,
+			unsigned long index, unsigned int tag);
+int radix_tree_tag_get(struct radix_tree_root *root,
+			unsigned long index, unsigned int tag);
+unsigned int
+radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
+		unsigned long first_index, unsigned int max_items,
+		unsigned int tag);
+int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
+
+static inline void radix_tree_preload_end(void)
+{
+	preempt_enable();
+}
+
+#endif /* _LINUX_RADIX_TREE_H */