diff -ur btrfs-progs-0.20.rc1.20121017git91d9eec.old/disk-io.c btrfs-progs-0.20.rc1.20121017git91d9eec/disk-io.c
--- btrfs-progs-0.20.rc1.20121017git91d9eec.old/disk-io.c	2013-02-13 11:04:05.361458311 +0000
+++ btrfs-progs-0.20.rc1.20121017git91d9eec/disk-io.c	2013-02-13 11:04:22.513377018 +0000
@@ -634,6 +634,9 @@
 	if (sb_bytenr == 0)
 		sb_bytenr = BTRFS_SUPER_INFO_OFFSET;
 
+	/* try to drop all the caches */
+	posix_fadvise(fp, 0, 0, POSIX_FADV_DONTNEED);
+
 	ret = btrfs_scan_one_device(fp, path, &fs_devices,
 				    &total_devs, sb_bytenr);
 
@@ -1083,6 +1086,10 @@
 	list = &fs_info->fs_devices->devices;
 	list_for_each_safe(next, tmp, list) {
 		device = list_entry(next, struct btrfs_device, dev_list);
+		if (device->fd) {
+			fsync(device->fd);
+			posix_fadvise(device->fd, 0, 0, POSIX_FADV_DONTNEED);
+		}
 		close(device->fd);
 		list_del(&device->dev_list);
 		free(device->name);
diff -ur btrfs-progs-0.20.rc1.20121017git91d9eec.old/disk-io.c.orig btrfs-progs-0.20.rc1.20121017git91d9eec/disk-io.c.orig
--- btrfs-progs-0.20.rc1.20121017git91d9eec.old/disk-io.c.orig	2012-10-05 01:35:31.000000000 +0100
+++ btrfs-progs-0.20.rc1.20121017git91d9eec/disk-io.c.orig	2013-02-13 11:04:05.361458311 +0000
@@ -458,8 +458,10 @@
 	u64 blocknr = btrfs_super_log_root(disk_super);
 	struct btrfs_root *log_root = malloc(sizeof(struct btrfs_root));
 
-	if (blocknr == 0)
+	if (blocknr == 0) {
+		free(log_root);
 		return 0;
+	}
 
 	blocksize = btrfs_level_size(tree_root,
 			     btrfs_super_log_root_level(disk_super));
@@ -622,7 +624,7 @@
 	struct btrfs_root *chunk_root = malloc(sizeof(struct btrfs_root));
 	struct btrfs_root *dev_root = malloc(sizeof(struct btrfs_root));
 	struct btrfs_root *csum_root = malloc(sizeof(struct btrfs_root));
-	struct btrfs_fs_info *fs_info = malloc(sizeof(*fs_info));
+	struct btrfs_fs_info *fs_info = malloc(sizeof(struct btrfs_fs_info));
 	int ret;
 	struct btrfs_super_block *disk_super;
 	struct btrfs_fs_devices *fs_devices = NULL;
@@ -646,7 +648,7 @@
 			goto out;
 	}
 
-	memset(fs_info, 0, sizeof(*fs_info));
+	memset(fs_info, 0, sizeof(struct btrfs_fs_info));
 	fs_info->tree_root = tree_root;
 	fs_info->extent_root = extent_root;
 	fs_info->chunk_root = chunk_root;
@@ -1075,15 +1077,19 @@
 {
 	struct list_head *list;
 	struct list_head *next;
+	struct list_head *tmp;
 	struct btrfs_device *device;
 
-	return 0;
-
 	list = &fs_info->fs_devices->devices;
-	list_for_each(next, list) {
+	list_for_each_safe(next, tmp, list) {
 		device = list_entry(next, struct btrfs_device, dev_list);
 		close(device->fd);
+		list_del(&device->dev_list);
+		free(device->name);
+		free(device->label);
+		free(device);
 	}
+	free(fs_info->fs_devices);
 	return 0;
 }
 
@@ -1133,12 +1139,14 @@
 	extent_io_tree_cleanup(&fs_info->pinned_extents);
 	extent_io_tree_cleanup(&fs_info->pending_del);
 	extent_io_tree_cleanup(&fs_info->extent_ins);
+	btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
 	free(fs_info->tree_root);
 	free(fs_info->extent_root);
 	free(fs_info->chunk_root);
 	free(fs_info->dev_root);
 	free(fs_info->csum_root);
+	free(fs_info->log_root_tree);
 	free(fs_info);
 
 	return 0;
diff -ur btrfs-progs-0.20.rc1.20121017git91d9eec.old/volumes.c btrfs-progs-0.20.rc1.20121017git91d9eec/volumes.c
--- btrfs-progs-0.20.rc1.20121017git91d9eec.old/volumes.c	2013-02-13 11:04:05.411458074 +0000
+++ btrfs-progs-0.20.rc1.20121017git91d9eec/volumes.c	2013-02-13 11:04:22.514377013 +0000
@@ -176,6 +176,8 @@
 			goto fail;
 		}
 
+		posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
+
 		if (device->devid == fs_devices->latest_devid)
 			fs_devices->latest_bdev = fd;
 		if (device->devid == fs_devices->lowest_devid)