Re: Regression in: [PATCH 4/4] btrfs: qgroup: account shared subtree during snapshot delete

[Mark Fasheh <mfasheh@suse.de>]

On Mon, Nov 02, 2015 at 06:46:06AM +0100, Stefan Priebe wrote:
> Am 02.11.2015 um 02:34 schrieb Qu Wenruo:
> >
> >
> >Stefan Priebe wrote on 2015/11/01 21:49 +0100:
> >>Hi,
> >>
> >>this one: http://www.spinics.net/lists/linux-btrfs/msg47377.html
> >>
> >>adds a regression to my test systems with very large disks (30tb and
> >>50tb).
> >>
> >>btrfs balance is super slow afterwards while heavily making use of cp
> >>--reflink=always on big files (200gb - 500gb).
> >>
> >>Sorry didn't know how to correctly reply to that "old" message.
> >>
> >>Greets,
> >>Stefan
> >>--
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> >
> >Thanks for the testing.
> >
> >Are you using qgroup or just doing normal balance with qgroup disabled?
> 
> just doing normal balance with qgroup disabled.

Then that patch is very unlikely to be your actual problem as it won't be
doing anything (ok some kmalloc/free of a very tiny object) since qgroups
are disabled.

Also, btrfs had working subtree accounting in that code for the last N
releases (doing the same exact thing) and it only changed for the one
release that Qu's rework was in (which lazily tore it out).
	--Mark

--
Mark Fasheh