On 07/26, Dan Williams wrote:
> On Tue, Jul 26, 2016 at 2:24 PM, Verma, Vishal L
> <vishal.l.ve...@intel.com> wrote:
> > On Tue, 2016-07-26 at 14:58 -0600, Vishal Verma wrote:
> >> On 07/26, Linda Knippers wrote:
> >> >
> >> > My system has 4 8G NVDIMMs and I have them configured in different
> >> > ways, as you can
> >> > see from the ndctl output:
> >> >
> >> > $ ndctl list
> >> > [
> >> > {
> >> > "dev":"namespace3.0",
> >> > "mode":"raw",
> >> > "size":8589934592,
> >> > "blockdev":"pmem3"
> >> > },
> >> > {
> >> > "dev":"namespace2.0",
> >> > "mode":"memory",
> >> > "size":8587837440,
> >> > "uuid":"2567d762-68ae-486b-a6eb-2d3ab1b9dca9",
> >> > "blockdev":"pmem2"
> >> > },
> >> > {
> >> > "dev":"namespace1.0",
> >> > "mode":"sector",
> >> > "uuid":"44fb474e-7db8-4438-ad95-05ecb9f2075e",
> >> > "sector_size":4096,
> >> > "blockdev":"pmem1s"
> >> > },
> >> > {
> >> > "dev":"namespace0.0",
> >> > "mode":"memory",
> >> > "size":8453619712,
> >> > "uuid":"933ed54b-5b64-47f1-8409-c88f7c846522",
> >> > "blockdev":"pmem0"
> >> > }
> >> > ]
> >> >
> >> > The two memory namespaces have different sizes because one is --
> >> > map=dev and the other is --map=mem.
> >> > It would be nice if the map option was displayed but my question is
> >> > about the size value for the
> >> > btt device, or lack of one.
> >> >
> >> > All the namespaces show a size except for the btt. The btt only
> >> > shows a sector size. There
> >> > is no size value exposed by the btt sysfs information, which is
> >> > probably why it's not in ndctl.
> >> >
> >> > I know the size can be gotten from the block device but it looks
> >> > like an omission here.
> >> > Is this a bug or a feature?
> >>
> >> Probably an omission :)
> >> This patch should expose a size attribute in sysfs:
> >>
> >> $ cat /sys/bus/nd/devices/btt7.0/size
> >> 32440320
> >>
> >> I can look at the 'ndctl list' enabling too if this looks good.
> >>
> >> 8<------
> >>
> >> From fb119bf4380d1d65d82754e581bbd41161c2100f Mon Sep 17 00:00:00 2001
> >> From: Vishal Verma <vishal.l.ve...@intel.com>
> >> Date: Tue, 26 Jul 2016 14:54:39 -0600
> >> Subject: [PATCH] nvdimm, btt: add a size attribute for BTTs
> >>
> >> To be consistent with other namespaces, expose a 'size' attribute for
> >> BTT devices also.
> >>
> >> Cc: Dan Williams <dan.j.willi...@intel.com>
> >> Reported-by: Linda Knippers <linda.knipp...@hpe.com>
> >> Signed-off-by: Vishal Verma <vishal.l.ve...@intel.com>
> >> ---
> >> drivers/nvdimm/btt.c | 1 +
> >> drivers/nvdimm/btt_devs.c | 15 +++++++++++++++
> >> drivers/nvdimm/nd.h | 1 +
> >> 3 files changed, 17 insertions(+)
> >>
> >> diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
> >> index 68a7c3c..71ce0dc 100644
> >> --- a/drivers/nvdimm/btt.c
> >> +++ b/drivers/nvdimm/btt.c
> >> @@ -1270,6 +1270,7 @@ static int btt_blk_init(struct btt *btt)
> >> }
> >> }
> >> set_capacity(btt->btt_disk, btt->nlba * btt->sector_size >>
> >> 9);
> >> + btt->nd_btt->size = btt->nlba * btt->sector_size;
> >
> > Blargh, I think I was a bit hasty; I think this should be:
> >
> > + btt->nd_btt->size = btt->nlba * (u64)btt->sector_size;
> >
> > Right? (I always get bit by integer promotion rules...)
>
> ...but at this point we're identical to what the block layer is
> reporting. The other 'size' attributes are communicating the raw
> byte-aligned capacity of the namespace minus local driver overhead.
Wouldn't we want to be identical to what the block layer is reporting?
The only difference would come from removing any sub-sector capacity in
our case - is that information useful/desirable? I'd think being
consistent with the block layer reporting makes most sense..
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