Btrfs: Add backing store, memory management

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

1 files changed, 174 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
new file mode 100644
index 00000000000..8d51a07051d
--- /dev/null
+++ b/fs/btrfs/disk-io.c
@@ -0,0 +1,174 @@
+#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--;
+	}
+}
+