From: Alexandru Moise <00moses.alexander00@gmail.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: clm@fb.com, jbacik@fb.com, dsterba@suse.com,
linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] btrfs: Remove unneeded cast to s64 for qgroup rfer state
Date: Mon, 31 Aug 2015 09:32:52 +0300 [thread overview]
Message-ID: <20150831063252.GA3537@gmail.com> (raw)
In-Reply-To: <55E3B191.7030800@cn.fujitsu.com>
On Mon, Aug 31, 2015 at 09:44:49AM +0800, Qu Wenruo wrote:
> >> >From the perspective of users, qgroup's referenced or exclusive
> >> is negative,but user can not continue to write data! a workaround
> >> way is to cast u64 to s64 when doing qgroup reservation
> >
> >I am unable to reproduce this problem without his modification.
> >I could be wrong in reverting this, so I'm gonna CC Wang as well so
> >he is aware of this patch.
>
> The cast is a workaround for a quite old qgroup bug, which will
> cause excl/rfer overflow to minus.
>
> The remove of cast rfer/exel now is OK, as qgroup keeps maturing,
> especially after 4.2-rc1 rfer/exel will keep sane under most case
> (exception will be qgroup reassign and subvolume deletion, but will
> not case minus value even under than case).
rfer/exel and reserved are all of type unsigned int, how exactly would
they overflow to minus?
>
> But I'm not a fan to remove it now.
> As qgroup still has a known huge bug for the qg->reserved part, we
> are aware of it and working on it actively.
Can you tell me more about this known huge bug and how you can
reproduce it using the present implementation?
next prev parent reply other threads:[~2015-08-31 6:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-29 11:45 [PATCH] btrfs: Remove unneeded cast to s64 for qgroup rfer state Alexandru Moise
2015-08-31 1:44 ` Qu Wenruo
2015-08-31 6:32 ` Alexandru Moise [this message]
2015-08-31 6:51 ` Qu Wenruo
2015-08-31 6:56 ` Alexandru Moise
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