Re: Simple quota unsafe? RIP: 0010:__btrfs_free_extent.isra.0+0xc41/0x1020 [btrfs] / do_free_extent_accounting:2999: errno=-2 No such entry

[Boris Burkov <boris@bur.io>]

On Thu, Apr 16, 2026 at 02:47:14PM -0700, Marc MERLIN wrote:
> On Thu, Apr 16, 2026 at 02:36:32PM -0700, Boris Burkov wrote:
> > On Thu, Apr 16, 2026 at 10:21:44AM -0700, Marc MERLIN wrote:
> > > No help needed, just showing it happened overnight with balance and squota in 6.19
> > > on my laptop. It looks like squota and balance are simply not compatible until the
> > > fix for squota, lands.
> > > Now that I know more, I rescued the FS and removed squota on my own and it's good again.
> > > 
> > > It looks pretty clear that btrfs balance seems to trigger the bug in
> > > squota:
> > 
> > Thank you for the additional report, this is helpful. I am attempting to
> > reproduce directly with balance to be sure I've got everything.
> > 
> > One question just to be extra careful:
> > In all these situations, were you ever manually managing either the
> > subvolumes or the qgroups? e.g., when, if ever, where you deleting
> > qgroups and / or subvols?
> 
> All 3 filesystems this happened on were btrfs receive recipients, so
> that created snapshots nightly (when it crashed each time).
> Also after btrfs receive, my script deletes the oldest backup that rolls
> out the rotation.
> Then I also have some amount btrfs-snaps that makes hourly/daily/weekly
> snapshots
> 
> So yes, multiple per day per subvolume multipled by many subvolume
> (10-ish)

Just to be extra clear as it is relevant for fully understanding the
repro-space, are you managing these purely with receive / subvol delete
commands? Did you ever delete a qgroup that was straggling around or add
automation to do that (btrfs qgroup destroy <qgid>) or did you ever
disable/enable squotas besides the first time?

Were all the squota enables on existing fs-es?

> 
> I have squotas still running on a single host but I turned off btrfs
> balance nightly cronjob as well as btrfs scrub, and it has not crashed
> yet (it's a 20TB+ backup recipient built from scratch, I woudl love for
> squotas to work on it)
> 
> Marc
> -- 
> "A mouse is a device used to point at the xterm you want to type in" - A.S.R.
>  
> Home page: http://marc.merlins.org/                       | PGP 7F55D5F27AAF9D08