linux-kernel - RE: [PATCH v2] libnvdimm, pmem: Add sysfs notifications to badblocks

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Date:   Sat, 1 Jul 2017 00:41:32 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     Vishal L Verma <vishal.l.verma@...el.com>,
        "Knippers, Linda" <linda.knippers@....com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] libnvdimm, pmem: Add sysfs notifications to badblocks

> > Sysfs "badblocks" information may be updated during run-time that:
> >  - MCE, SCI, and sysfs "scrub" may add new bad blocks
> >  - Writes and ioctl() may clear bad blocks
> >
> > Add support to send sysfs notifications to sysfs "badblocks" file
> > under region and pmem directories when their badblocks information
> > is re-evaluated (but is not necessarily changed) during run-time.
> >
> > Signed-off-by: Toshi Kani <toshi.kani@....com>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Vishal Verma <vishal.l.verma@...el.com>
> > Cc: Linda Knippers <linda.knippers@....com>
> > ---
> > v2: Send notifications for the clearing case
> > ---
> >  drivers/nvdimm/bus.c    |    3 +++
> >  drivers/nvdimm/nd.h     |    1 +
> >  drivers/nvdimm/pmem.c   |   14 ++++++++++++++
> >  drivers/nvdimm/pmem.h   |    1 +
> >  drivers/nvdimm/region.c |   12 ++++++++++--
> >  5 files changed, 29 insertions(+), 2 deletions(-)
> >
> [..]
> > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> > index c544d46..6c14c72 100644
> > --- a/drivers/nvdimm/pmem.c
> > +++ b/drivers/nvdimm/pmem.c
> [..]
> > @@ -377,6 +379,13 @@ static int pmem_attach_disk(struct device *dev,
> >
> >         revalidate_disk(disk);
> >
> > +       pmem->bb_state = sysfs_get_dirent(disk_to_dev(disk)->kobj.sd,
> > +                                         "badblocks");
> > +       if (pmem->bb_state)
> > +               sysfs_put(pmem->bb_state);
> 
> Sorry I missed this on the first review, but this looks broken. We
> need to hold the reference for as long as we might trigger
> notifications, so the sysfs_put() should wait until
> pmem_release_disk().

I see.
 
> [..]
> > diff --git a/drivers/nvdimm/region.c b/drivers/nvdimm/region.c
> > index 869a886..ca94029 100644
> > --- a/drivers/nvdimm/region.c
> > +++ b/drivers/nvdimm/region.c
> > @@ -58,10 +58,16 @@ static int nd_region_probe(struct device *dev)
> >
> >                 if (devm_init_badblocks(dev, &nd_region->bb))
> >                         return -ENODEV;
> > +               nd_region->bb_state = sysfs_get_dirent(nd_region->dev.kobj.sd,
> > +                                                      "badblocks");
> > +               if (nd_region->bb_state)
> > +                       sysfs_put(nd_region->bb_state);
> 
> ...same here. This should wait until we tear down the region.
> 
> I'll take a look at an incremental fix patch.

Thanks Dan!
-Toshi