On 31.10.2017 06:03, Qu Wenruo wrote:
> For key type BTRFS_UUID_KEY_SUBVOL or BTRFS_UUID_KEY_RECEIVED_SUBVOL the
> key objectid and key offset are just half of the UUID.
>
> However we just print the key as %llu, which is converted from little
> endian, not byte order for UUID, nor the traditional 36 bytes human
> readable uuid format.
>
> Although true engineer can easily convert it in their brain, but to
> make it easier for search, output the result UUID using the 36 chars format.
>
> Cc: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> Inspired by UUID related work from Misono.
> ---
> print-tree.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/print-tree.c b/print-tree.c
> index 3c585e31f1fc..687f871db302 100644
> --- a/print-tree.c
> +++ b/print-tree.c
> @@ -803,14 +803,25 @@ void btrfs_print_key(struct btrfs_disk_key *disk_key)
> }
> }
>
> -static void print_uuid_item(struct extent_buffer *l, unsigned long offset,
> - u32 item_size)
> +static void print_uuid_item(struct extent_buffer *l, int slot,
> + unsigned long offset, u32 item_size)
> {
> + struct btrfs_key key;
> + char uuid_str[BTRFS_UUID_UNPARSED_SIZE];
> + u8 uuid[BTRFS_UUID_SIZE];
> +
> + /* Reassemble the uuid from key.objecitd and key.offset */
> + btrfs_item_key_to_cpu(l, &key, slot);
> + put_unaligned_le64(key.objectid, uuid);
> + put_unaligned_le64(key.offset, uuid + sizeof(u64));
I don't think this will work on a BE system. Because
btrfs_item_key_to_cpu take the LE representation on-disk and turns it
into a cpu representation which might very well be BE. And then you
essentially reverse it by using put_unaligned_le64 for x86 it works fine
due to it being a LE system.
> + uuid_unparse(uuid, uuid_str);
> +
> if (item_size & (sizeof(u64) - 1)) {
> printf("btrfs: uuid item with illegal size %lu!\n",
> (unsigned long)item_size);
> return;
> }
> + printf("\t\tuuid %s\n", uuid_str);
> while (item_size) {
> __le64 subvol_id;
>
> @@ -1297,7 +1308,7 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *eb)
> break;
> case BTRFS_UUID_KEY_SUBVOL:
> case BTRFS_UUID_KEY_RECEIVED_SUBVOL:
> - print_uuid_item(eb, btrfs_item_ptr_offset(eb, i),
> + print_uuid_item(eb, i, btrfs_item_ptr_offset(eb, i),
> btrfs_item_size_nr(eb, i));
> break;
> case BTRFS_STRING_ITEM_KEY: {
>
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