This is due to the implicit type cast in the compiler, when
st->f_blocks < (used_bytes/st->f_bsize),
the minus should be a negative ,but the compiler take it as an unsigned value
Fix is proposed in https://github.com/ceph/ceph/pull/3451
Xiaoxi
-----Original Message-----
From: ceph-devel-owner@xxxxxxxxxxxxxxx [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Nelson
Sent: Wednesday, January 21, 2015 10:13 PM
To: Blinick, Stephen L; Ceph Development
Subject: Re: Memstore issue on v0.91
On 01/21/2015 01:48 AM, Blinick, Stephen L wrote:
> Moved to 0.91 yesterday and ran into some issues, with a Memstore OSD of default size. After a few hundred K OPS client gets a FULL message and the avail space looks like:
>
> [root@cephtestnode0 bmpa]# rados df
> pool name KB objects clones degraded unfound rd rd KB wr wr KB
> rbd 0 0 0 0 0 0 0 0 0
> testmemstore 1505052 376263 0 0 0 0 0 376263 1505052
> total used 1494247 376263
> total avail 18014398508987737
> total space 1000000
>
> I was looking at pull request #2836 and found a case where there could be an unsigned int underflow in MemStore.cc:statfs:
>
> st->f_bfree = st->f_bavail = MAX((st->f_blocks - used_bytes /
> st->f_bsize), 0);
>
> But that wasn't the final issue.. I put some asserts where used_bytes could underflow as well and didn't catch anything. I will keep digging but wanted to find out if anyone else was seeing the issue as well.
FWIW, I hit this yesterday too. I hadn't started debugging it yet though. Looks like you are farther along than I am, thanks Stephen! :)
>
> Thanks,
>
> Stephen
>
>
>
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