Hello there,

I'm trying to figure out what the `btrfs scrub` output means. 
Specifically, I get an error summary that reports "no errors found" and 
then a warning, saying "errors detected during scrubbing, corrected". 
Checking dmesg didn't reveal anything obvious to me.

I'm using Marc Merlin's scrub script [1] but get the same behaviour when 
initiating a scrub directly.

Attached you will find the output of the script (`output.txt`) and a 
filtered (`dmesg | grep -i btrfs`) dmesg log (`dmesg.txt`).

My specs:

```
$ uname -a
Linux venus 5.3.0-40-generic #32~18.04.1-Ubuntu SMP Mon Feb 3 14:05:59 
UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

$ btrfs --version # compiled from source
btrfs-progs v5.4.1

$ sudo btrfs fi show
Label: none  uuid: 7b39ba35-352a-4b76-9f33-79a05c7a1e1b
	Total devices 2 FS bytes used 426.41GiB
	devid    1 size 878.99GiB used 436.06GiB path /dev/sda5
	devid    2 size 894.25GiB used 436.06GiB path /dev/sdb

Label: 'storage'  uuid: cb041791-3931-429d-a249-d9fd4f2ba081
	Total devices 1 FS bytes used 728.32GiB
	devid    1 size 831.51GiB used 738.09GiB path /dev/sdc3

Label: 'snow'  uuid: 1ef734b2-5dc0-4349-8b5b-e4ba46e2f165
	Total devices 1 FS bytes used 761.16GiB
	devid    1 size 931.51GiB used 766.02GiB path 
/dev/mapper/luks-726a8c1f-e8f2-4d59-91d5-a0b52b43cb5e

Label: 'akasha'  uuid: 265cdb90-5b04-42a4-a40b-7ac9d2f9b881
	Total devices 1 FS bytes used 1.86TiB
	devid    1 size 2.73TiB used 1.89TiB path 
/dev/mapper/luks-aff1ccef-a303-470c-9eb3-27fdb97b544d

$ sudo btrfs fi df /
Data, RAID1: total=430.00GiB, used=422.39GiB
System, RAID1: total=64.00MiB, used=96.00KiB
Metadata, RAID1: total=6.00GiB, used=4.00GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

$ sudo btrfs fi df /media/josh/storage
Data, single: total=724.01GiB, used=722.89GiB
System, DUP: total=40.00MiB, used=96.00KiB
Metadata, DUP: total=7.00GiB, used=5.43GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

$ sudo btrfs fi df /media/josh/snow
Data, single: total=760.01GiB, used=759.11GiB
System, DUP: total=8.00MiB, used=96.00KiB
Metadata, DUP: total=3.00GiB, used=2.05GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

$ sudo btrfs fi df /media/josh/akasha
Data, single: total=1.83TiB, used=1.83TiB
System, DUP: total=40.00MiB, used=256.00KiB
Metadata, DUP: total=32.00GiB, used=28.27GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
```

I also tried getting help on Reddit [2] before coming here. Feel free to 
check out that thread.

Would appreciate some insight. Thanks in advance!

Josh

P.S.: This is my first time using a mailing list. I apologize if I'm 
doing this wrong and appreciate pointers on etiquette and best practices.

[1] http://marc.merlins.org/linux/scripts/btrfs-scrub
[2] 
https://www.reddit.com/r/btrfs/comments/f089hh/confused_about_scrub_output/