Btrfs: Add backing store, memory management
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
new file mode 100644
index 0000000..8d51a07
--- /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--;
+ }
+}
+
