@@ -868,6 +868,15 @@ static int read_data_extent(struct metadump_struct *md,
return 0;
}
+static int get_dev_fd(struct btrfs_root *root)
+{
+ struct btrfs_device *dev;
+
+ dev = list_first_entry(&root->fs_info->fs_devices->devices,
+ struct btrfs_device, dev_list);
+ return dev->fd;
+}
+
static int flush_pending(struct metadump_struct *md, int done)
{
struct async_work *async = NULL;
@@ -904,6 +913,24 @@ static int flush_pending(struct metadump_struct *md, int done)
}
}
+ /*
+ * Balance can make the mapping not cover the super block, so
+ * just copy directly from one of the devices.
+ */
+ if (start == BTRFS_SUPER_INFO_OFFSET) {
+ int fd = get_dev_fd(md->root);
+
+ ret = pread64(fd, async->buffer, size, start);
+ if (ret < size) {
+ free(async->buffer);
+ free(async);
+ fprintf(stderr, "Error reading superblock\n");
+ return -EIO;
+ }
+ size = 0;
+ ret = 0;
+ }
+
while (!md->data && size > 0) {
u64 this_read = min(blocksize, size);
eb = read_tree_block(md->root, start, this_read, 0);
When btrfs-image makes a metadump it'll map all the blocks from their logical address to their physical. This works out fine with the exception of the super block, which is the physical offset. Normally this just works, but if the user has balanced their fs it'll either crash btrfs-image or it'll copy some completely arbitrary data. This forces btrfs-image to read the super directly from the disk. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> --- btrfs-image.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)