[sheepdog] [PATCH 6/6] sheep: clear bit in vdi_deleted if vdi is created

[Liu Yuan]

On Tue, Mar 17, 2015 at 02:59:12PM +0900, Hitoshi Mitake wrote:
> At Tue, 17 Mar 2015 13:54:16 +0800,
> Liu Yuan wrote:
> > 
> > On Tue, Mar 17, 2015 at 01:40:51PM +0800, Liu Yuan wrote:
> > > On Tue, Mar 17, 2015 at 01:32:44PM +0800, Liu Yuan wrote:
> > > > On Tue, Mar 17, 2015 at 01:16:00PM +0800, Liu Yuan wrote:
> > > > > On Tue, Mar 17, 2015 at 02:03:03PM +0900, Hitoshi Mitake wrote:
> > > > > > At Tue, 17 Mar 2015 13:58:08 +0900,
> > > > > > Hitoshi Mitake wrote:
> > > > > > > 
> > > > > > > At Tue, 17 Mar 2015 13:51:48 +0900,
> > > > > > > Hitoshi Mitake wrote:
> > > > > > > > 
> > > > > > > > At Tue, 17 Mar 2015 12:42:35 +0800,
> > > > > > > > Liu Yuan wrote:
> > > > > > > > > 
> > > > > > > > > On Mon, Mar 16, 2015 at 08:49:34PM +0800, Liu Yuan wrote:
> > > > > > > > > > From: Liu Yuan <liuyuan at cmss.chinamobile.com>
> > > > > > > > > > 
> > > > > > > > > > This patch fixes following problem:
> > > > > > > > > > 
> > > > > > > > > > $ dog vdi create test 100M
> > > > > > > > > > $ dog vdi delete test
> > > > > > > > > > $ dog vdi create test 200M
> > > > > > > > > > $ dog vdi list # expect show test, but nothing shows out.
> > > > > > > > > > 
> > > > > > > > > > Which was brought by
> > > > > > > > > > 
> > > > > > > > > > *commit f68feab7edc0ded86701a2e902d85616b24942ab
> > > > > > > > > > *Author: Saeki Masaki <saeki.masaki at po.ntts.co.jp>
> > > > > > > > > > *Date:   Wed Nov 26 10:50:46 2014 +0900
> > > > > > > > > > 
> > > > > > > > > >     sheep/dog: introduce new bitmap for delete vdi
> > > > > > > > > > 
> > > > > > > > > > Cc: Saeki Masaki <saeki.masaki at po.ntts.co.jp>
> > > > > > > > > > Signed-off-by: Liu Yuan <liuyuan at cmss.chinamobile.com>
> > > > > > > > > > ---
> > > > > > > > > >  sheep/ops.c | 7 +++++--
> > > > > > > > > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > > > > > > > > > 
> > > > > > > > > > diff --git a/sheep/ops.c b/sheep/ops.c
> > > > > > > > > > index 8a0f77c..464ae0b 100644
> > > > > > > > > > --- a/sheep/ops.c
> > > > > > > > > > +++ b/sheep/ops.c
> > > > > > > > > > @@ -130,11 +130,14 @@ static int post_cluster_new_vdi(const struct sd_req *req, struct sd_rsp *rsp,
> > > > > > > > > >  	unsigned long nr = rsp->vdi.vdi_id;
> > > > > > > > > >  	int ret = rsp->result;
> > > > > > > > > >  
> > > > > > > > > > -	sd_info("req->vdi.base_vdi_id: %x, rsp->vdi.vdi_id: %x", req->vdi.base_vdi_id, rsp->vdi.vdi_id);
> > > > > > > > > > +	sd_info("req->vdi.base_vdi_id: %x, rsp->vdi.vdi_id: %x",
> > > > > > > > > > +		req->vdi.base_vdi_id, rsp->vdi.vdi_id);
> > > > > > > > > >  
> > > > > > > > > >  	sd_debug("done %d %lx", ret, nr);
> > > > > > > > > > -	if (ret == SD_RES_SUCCESS)
> > > > > > > > > > +	if (ret == SD_RES_SUCCESS) {
> > > > > > > > > >  		atomic_set_bit(nr, sys->vdi_inuse);
> > > > > > > > > > +		atomic_clear_bit(nr, sys->vdi_deleted);
> > > > > > > > > > +	}
> > > > > > > > > >  
> > > > > > > > > >  	return ret;
> > > > > > > > > >  }
> > > > > > > > > > -- 
> > > > > > > > > > 1.9.1
> > > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > At least this patch fixes a real problem and should be applied, Hitoshi?
> > > > > > > > > 
> > > > > > > > > Yuan
> > > > > > > > 
> > > > > > > > Applied this one, thanks.
> > > > > > > 
> > > > > > > On the second thought, this problem cannot happen on the current
> > > > > > > master. It is caused by the old invalid recycling. So I'll revert
> > > > > > > it, OK?
> > > > > > > # seems that there's no patches after this one, I'll simply rebase and
> > > > > > > # update forcibly
> > > > > > 
> > > > > > Removed this one, sorry for confusion.
> > > > > 
> > > > > Current master actually have this problem because bit in vdi_deleted never get
> > > > > cleared.
> > > > 
> > > > If you disable vid_gc(), this problem will show up. This patch actually fix a
> > > > broader bug. For every newly created vid, either fresh, snapshot, clone, we
> > > > should clear it in vdi_deleted.
> > > 
> > > The master dosen't have this problem because we don't reuse vid. If gc is
> > > disabled, we should logically first clear the bit in the deleted because we
> > > actually create a new one. This will prevent any future bugs and will allow our
> > > in-house patch, which reuse vid as old algorithm work correctly.
> > > 
> > 
> > The master just work-around this problem and hide it, no? If we set bit in
> > vdi_inuse but this bit is also set in vdi_deleted too, isn't a bug? Or am I
> > missing something?
> 
> If the situation can arise, it would be a bug. But current master
> doesn't allow it because every bit of vdi_deleted must be 0 if
> corresponding vdi_inuse is 0. And if they become 1 once, they will
> never back to 0.

Does this mean, even if we disable new algorithm, current master will never work
as old algorithm?

Thanks,
Yuan