Still seeing high autodefrag IO with kernel 5.16.5

[Benjamin Xiao <ben.r.xiao@gmail.com>]

Hello all,

Even after the defrag patches that landed in 5.16.5, I am still seeing 
lots of cpu usage and disk writes to my SSD when autodefrag is enabled. 
I kinda expected slightly more IO during writes compared to 5.15, but 
what I am actually seeing is massive amounts of btrfs-cleaner i/o even 
when no programs are actively writing to the disk.

I can reproduce it quite reliably on my 2TB Btrfs Steam library 
partition. In my case, I was downloading Strange Brigade, which is a 
roughly 25GB download and 33.65GB on disk. Somewhere during the 
download, iostat will start reporting disk writes around 300 MB/s, even 
though Steam itself reports disk usage of 40-45MB/s. After the download 
finishes and nothing else is being written to disk, I still see around 
90-150MB/s worth of disk writes. Checking in iotop, I can see btrfs 
cleaner and other btrfs processes writing a lot of data.

I left it running for a while to see if it was just some maintenance 
tasks that Btrfs needed to do, but it just kept going. I tried to 
reboot, but it actually prevented me from properly rebooting. After 
systemd timed out, my system finally shutdown.

Here are my mount options:
rw,relatime,compress-force=zstd:2,ssd,autodefrag,space_cache=v2,subvolid=5,subvol=/

I've disabled autodefrag again for now to save my SSD, but just wanted 
to say that there is still an issue. Have the defrag issues been fully 
fixed or are there more patches incoming despite what Reddit and 
Phoronix say? XD

Thanks!
Ben