libnvdimm, region: Fail badblocks listing for inactive regions

While experimenting with region driver loading the following backtrace
was triggered:

 INFO: trying to register non-static key.
 the code is fine but needs lockdep annotation.
 turning off the locking correctness validator.
 [..]
 Call Trace:
  dump_stack+0x85/0xcb
  register_lock_class+0x571/0x580
  ? __lock_acquire+0x2ba/0x1310
  ? kernfs_seq_start+0x2a/0x80
  __lock_acquire+0xd4/0x1310
  ? dev_attr_show+0x1c/0x50
  ? __lock_acquire+0x2ba/0x1310
  ? kernfs_seq_start+0x2a/0x80
  ? lock_acquire+0x9e/0x1a0
  lock_acquire+0x9e/0x1a0
  ? dev_attr_show+0x1c/0x50
  badblocks_show+0x70/0x190
  ? dev_attr_show+0x1c/0x50
  dev_attr_show+0x1c/0x50

This results from a missing successful call to devm_init_badblocks()
from nd_region_probe(). Block attempts to show badblocks while the
region is not enabled.

Fixes: 6a6bef90425e ("libnvdimm: add mechanism to publish badblocks...")
Cc: <stable@vger.kernel.org>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index fa37afcd43ff..174a418cb171 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -560,10 +560,17 @@ static ssize_t region_badblocks_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
         struct nd_region *nd_region = to_nd_region(dev);
+        ssize_t rc;
 
-        return badblocks_show(&nd_region->bb, buf, 0);
-}
+        device_lock(dev);
+        if (dev->driver)
+                rc = badblocks_show(&nd_region->bb, buf, 0);
+        else
+                rc = -ENXIO;
+        device_unlock(dev);
 
+        return rc;
+}
 static DEVICE_ATTR(badblocks, 0444, region_badblocks_show, NULL);
 
 static ssize_t resource_show(struct device *dev,