BTRFS device stats tabular view broken

[linux4life798]

It seems as though the tabular mode (-T) of the device stats sub-command seems to be broken. The tabular view shows zero errors, but the normal mode shows many read/write errors for one drive. Luckily, the "check" (-c) mode still seems to work correctly.

Checkout this example:

someuser@nas:~$ sudo btrfs device stats /var/hdd
[/dev/mapper/sdc_crypt].write_io_errs    0
[/dev/mapper/sdc_crypt].read_io_errs     0
[/dev/mapper/sdc_crypt].flush_io_errs    0
[/dev/mapper/sdc_crypt].corruption_errs  0
[/dev/mapper/sdc_crypt].generation_errs  0
[/dev/mapper/sdd_crypt].write_io_errs    0
[/dev/mapper/sdd_crypt].read_io_errs     0
[/dev/mapper/sdd_crypt].flush_io_errs    0
[/dev/mapper/sdd_crypt].corruption_errs  0
[/dev/mapper/sdd_crypt].generation_errs  0
[/dev/mapper/sdb_crypt].write_io_errs    0
[/dev/mapper/sdb_crypt].read_io_errs     0
[/dev/mapper/sdb_crypt].flush_io_errs    0
[/dev/mapper/sdb_crypt].corruption_errs  0
[/dev/mapper/sdb_crypt].generation_errs  0
[/dev/mapper/sda_crypt].write_io_errs    17876972
[/dev/mapper/sda_crypt].read_io_errs     8890703
[/dev/mapper/sda_crypt].flush_io_errs    15
[/dev/mapper/sda_crypt].corruption_errs  3
[/dev/mapper/sda_crypt].generation_errs  0

someuser@nas:~$ sudo btrfs device stats -T /var/hdd
Id Path                  Write errors Read errors Flush errors Corruption errors Generation errors
-- --------------------- ------------ ----------- ------------ ----------------- -----------------
 1 /dev/mapper/sdc_crypt            0           0            0                 0                 0
 2 /dev/mapper/sdd_crypt            0           0            0                 0                 0
 3 /dev/mapper/sdb_crypt            0           0            0                 0                 0
 4 /dev/mapper/sda_crypt            0           0            0                 0                 0

someuser@nas:~$ sudo btrfs device stats /var/hdd
[/dev/mapper/sdc_crypt].write_io_errs    0
[/dev/mapper/sdc_crypt].read_io_errs     0
[/dev/mapper/sdc_crypt].flush_io_errs    0
[/dev/mapper/sdc_crypt].corruption_errs  0
[/dev/mapper/sdc_crypt].generation_errs  0
[/dev/mapper/sdd_crypt].write_io_errs    0
[/dev/mapper/sdd_crypt].read_io_errs     0
[/dev/mapper/sdd_crypt].flush_io_errs    0
[/dev/mapper/sdd_crypt].corruption_errs  0
[/dev/mapper/sdd_crypt].generation_errs  0
[/dev/mapper/sdb_crypt].write_io_errs    0
[/dev/mapper/sdb_crypt].read_io_errs     0
[/dev/mapper/sdb_crypt].flush_io_errs    0
[/dev/mapper/sdb_crypt].corruption_errs  0
[/dev/mapper/sdb_crypt].generation_errs  0
[/dev/mapper/sda_crypt].write_io_errs    17876972
[/dev/mapper/sda_crypt].read_io_errs     8890703
[/dev/mapper/sda_crypt].flush_io_errs    15
[/dev/mapper/sda_crypt].corruption_errs  3
[/dev/mapper/sda_crypt].generation_errs  0

Reproduction:

1. Remove one hard drive from a mirrored BTRFS filesystem
2. Run a scrub to generate some IO errors for teh removed disk
3. Run sudo btrfs device stats /mount-point to see correct errors count
4. Run sudo btrfs device stats -T /mount-point to see incorrect errors count