Re: [PATCH 3/3] pmem: Use the poison list to expose badblocks

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Wed, 2015-12-23 at 12:28 -0800, Dan Williams wrote:
> On Sun, Dec 20, 2015 at 1:18 AM,  <vishal@kernel.org> wrote:
> > From: Vishal Verma <vishal.l.verma@intel.com>
> > 
> > Enable the gendisk badblocks feature for pmem namespaces.
> > If the pmem namespace being created has any known poison associated
> > with
> > its physical address space, convert the poison ranges to bad sectors
> > exposed using the badblocks interface.
> > 
> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> > ---
> >  drivers/nvdimm/pmem.c | 124
> > ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 124 insertions(+)
> > 
> > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> > index 8ee7989..462570f 100644
> > --- a/drivers/nvdimm/pmem.c
> > +++ b/drivers/nvdimm/pmem.c
> [..]
> > @@ -196,6 +311,15 @@ static int pmem_attach_disk(struct device *dev,
> >         set_capacity(disk, (pmem->size - pmem->data_offset) / 512);
> >         pmem->pmem_disk = disk;
> > 
> > +       ret = disk_alloc_badblocks(disk);
> > +       if (ret)
> > +               return ret;
> 
> I think we should skip allocating a bad block list in the case we find
> no poison.  Then we can do a simple "if (disk->bb)" to check if there
> are any bad blocks.

Sounds good - I'll move this allocation into the (what will be a core)
routine that traverses the list, and make it such that we allocate
disk->bb iff a poison entry is found for _this_ pmem range.

It will mean a check at every list node, but that shouldn't matter as
this is just init-time overhead.

	-Vishal