Hi,
I want to read the complete CSUM-Tree from userspace. I tried it via the
ioctl. This is what the code looks like:
struct btrfs_sv2_args sv2_args;
int fd = open(filename, O_RDONLY);
sv2_args.key.tree_id = BTRFS_CSUM_TREE_OBJECTID;
sv2_args.key.min_objectid = 0;
sv2_args.key.max_objectid = -1;
sv2_args.key.min_offset = 0;
sv2_args.key.max_offset = -1;
sv2_args.key.min_transid = 0;
sv2_args.key.max_transid = -1;
sv2_args.key.min_type = BTRFS_CSUM_ITEM_KEY;
sv2_args.key.max_type = BTRFS_CSUM_ITEM_KEY;
sv2_args.key.nr_items = -1;
sv2_args.buf_size = sizeof(sv2_args.buf);
ioctl(fd, BTRFS_IOC_TREE_SEARCH_V2, &sv2_args);
But the device is not small and I hit the limit of the
btrfs_sv2_args.buf which seems to be 16 MB.
How can I get the *complete* CSUM-Tree?
Limiting to offset does not work (My first idea was to do it this way
and get it in chunks).
Limiting to a single transid does not work as well because even one
transid is larger than the limit.
Kernel is 4.15.
Any help would be appreciated.
Best Regards
Tobias
