[sheepdog] [PATCH] sheep: fix confused comments of vdi_snapshot()

[Hitoshi Mitake]

At Thu, 23 Apr 2015 19:15:00 +0800,
Yu Yang wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Hitoshi Mitake [mailto:mitake.hitoshi at gmail.com] On Behalf Of Hitoshi
> > Mitake
> > Sent: Thursday, April 23, 2015 5:28 PM
> > To: Yu Yang
> > Cc: sheepdog at lists.wpkg.org
> > Subject: Re: [sheepdog] [PATCH] sheep: fix confused comments of
> > vdi_snapshot()
> > 
> > At Thu, 23 Apr 2015 16:03:49 +0800,
> > Yu Yang wrote:
> > >
> > > From: Yu Yang <yuyang at cmss.chinamobile.com>
> > >
> > > fix the confused comments between snapid and vid for vdi_snapshot().
> > >
> > > Signed-off-by: Yu Yang <yuyang at cmss.chinamobile.com>
> > > ---
> > >  sheep/vdi.c |    4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/sheep/vdi.c b/sheep/vdi.c
> > > index 63e578d..b35a763 100644
> > > --- a/sheep/vdi.c
> > > +++ b/sheep/vdi.c
> > > @@ -1572,8 +1572,8 @@ int vdi_create(const struct vdi_iocb *iocb, uint32_t
> > *new_vid)
> > >   * 2. rollback create (base_vid != current_vid)
> > >   *
> > >   * This function expects SUCCESS returned from vdi_lookup().  Both rollback
> > and
> > > - * snap create started with current working VDI's snap_id + 1. Working VDI
> > > - * always has the highest snapid.
> > > + * snap creation starts with current working VDI's vid + 1. Working VDI
> > > + * always has the highest vid and its snapid is 0.
> > 
> > Sorry, I missed to point a possibility of vid overflow. Working VDI doesn't
> > have the highest VID always.
> > 
> > And the snapid of working VDI is always highest. It is simply incremented.
> > 
> > Could you fix them?
> > 
> > Thanks,
> > Hitoshi
> > 
> 
> I know when vid is overflow it's not the highest, 
> but you said the snapid of working VDI is always the highest ?
> I find it is always ZERO, or I misunderstand of working VDI which can be
> read/write ?

You can check the snapid field with
$ dog vdi object dump-inode <inode object path>

It will show that working VDIs have largest snapid (working VDIs have
higher VIDs).

# anyway, the field doesn't seem to be used currently

Thanks,
Hitoshi

> 
> Thanks
> Yang
> 
> > >   */
> > >  int vdi_snapshot(const struct vdi_iocb *iocb, uint32_t *new_vid)
> > >  {
> > > --
> > > 1.7.9.5
> > >
> > >
> > > --
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> > > sheepdog at lists.wpkg.org
> > > https://lists.wpkg.org/mailman/listinfo/sheepdog
> 
> 
> 
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