Merge tag 'libnvdimm-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm updates from Dan Williams:

 - Improve the efficiency and performance of reading nvdimm-namespace
   labels. Reduce the amount of label data read at driver load time by a
   few orders of magnitude. Reduce heavyweight call-outs to
   platform-firmware routines.

 - Handle media errors located in the 'struct page' array stored on a
   persistent memory namespace. Let the kernel clear these errors rather
   than an awkward userspace workaround.

 - Fix Address Range Scrub (ARS) completion tracking. Correct occasions
   where the kernel indicates completion of ARS before submission.

 - Fix asynchronous device registration reference counting.

 - Add support for reporting an nvdimm dirty-shutdown-count via sysfs.

 - Fix various small libnvdimm core and uapi issues.

* tag 'libnvdimm-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (21 commits)
  acpi, nfit: Further restrict userspace ARS start requests
  acpi, nfit: Fix Address Range Scrub completion tracking
  UAPI: ndctl: Remove use of PAGE_SIZE
  UAPI: ndctl: Fix g++-unsupported initialisation in headers
  tools/testing/nvdimm: Populate dirty shutdown data
  acpi, nfit: Collect shutdown status
  acpi, nfit: Introduce nfit_mem flags
  libnvdimm, label: Fix sparse warning
  nvdimm: Use namespace index data to reduce number of label reads needed
  nvdimm: Split label init out from the logic for getting config data
  nvdimm: Remove empty if statement
  nvdimm: Clarify comment in sizeof_namespace_index
  nvdimm: Sanity check labeloff
  libnvdimm, dimm: Maximize label transfer size
  libnvdimm, pmem: Fix badblocks population for 'raw' namespaces
  libnvdimm, namespace: Drop the repeat assignment for variable dev->parent
  libnvdimm, region: Fail badblocks listing for inactive regions
  libnvdimm, pfn: during init, clear errors in the metadata area
  libnvdimm: Set device node in nd_device_register
  libnvdimm: Hold reference on parent while scheduling async init
  ...

11 files changed, 251 insertions, 63 deletions

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 8aae6dcc839f..f1fb39921236 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -54,12 +54,6 @@ static int to_nd_device_type(struct device *dev)
 
 static int nvdimm_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
-	/*
-	 * Ensure that region devices always have their numa node set as
-	 * early as possible.
-	 */
-	if (is_nd_region(dev))
-		set_dev_node(dev, to_nd_region(dev)->numa_node);
 	return add_uevent_var(env, "MODALIAS=" ND_DEVICE_MODALIAS_FMT,
 			to_nd_device_type(dev));
 }
@@ -488,6 +482,8 @@ static void nd_async_device_register(void *d, async_cookie_t cookie)
 		put_device(dev);
 	}
 	put_device(dev);
+	if (dev->parent)
+		put_device(dev->parent);
 }
 
 static void nd_async_device_unregister(void *d, async_cookie_t cookie)
@@ -506,7 +502,19 @@ void __nd_device_register(struct device *dev)
 {
 	if (!dev)
 		return;
+
+	/*
+	 * Ensure that region devices always have their NUMA node set as
+	 * early as possible. This way we are able to make certain that
+	 * any memory associated with the creation and the creation
+	 * itself of the region is associated with the correct node.
+	 */
+	if (is_nd_region(dev))
+		set_dev_node(dev, to_nd_region(dev)->numa_node);
+
 	dev->bus = &nvdimm_bus_type;
+	if (dev->parent)
+		get_device(dev->parent);
 	get_device(dev);
 	async_schedule_domain(nd_async_device_register, dev,
 			&nd_async_domain);
diff --git a/drivers/nvdimm/dimm.c b/drivers/nvdimm/dimm.c
index 6c8fb7590838..9899c97138a3 100644
--- a/drivers/nvdimm/dimm.c
+++ b/drivers/nvdimm/dimm.c
@@ -75,7 +75,7 @@ static int nvdimm_probe(struct device *dev)
 	 * DIMM capacity. We fail the dimm probe to prevent regions from
 	 * attempting to parse the label area.
 	 */
-	rc = nvdimm_init_config_data(ndd);
+	rc = nd_label_data_init(ndd);
 	if (rc == -EACCES)
 		nvdimm_set_locked(dev);
 	if (rc)
@@ -84,10 +84,6 @@ static int nvdimm_probe(struct device *dev)
 	dev_dbg(dev, "config data size: %d\n", ndd->nsarea.config_size);
 
 	nvdimm_bus_lock(dev);
-	ndd->ns_current = nd_label_validate(ndd);
-	ndd->ns_next = nd_label_next_nsindex(ndd->ns_current);
-	nd_label_copy(ndd, to_next_namespace_index(ndd),
-			to_current_namespace_index(ndd));
 	if (ndd->ns_current >= 0) {
 		rc = nd_label_reserve_dpa(ndd);
 		if (rc == 0)
diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 863cabc35215..6c3de2317390 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -85,56 +85,48 @@ int nvdimm_init_nsarea(struct nvdimm_drvdata *ndd)
 	return cmd_rc;
 }
 
-int nvdimm_init_config_data(struct nvdimm_drvdata *ndd)
+int nvdimm_get_config_data(struct nvdimm_drvdata *ndd, void *buf,
+			   size_t offset, size_t len)
 {
 	struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
+	struct nvdimm_bus_descriptor *nd_desc = nvdimm_bus->nd_desc;
 	int rc = validate_dimm(ndd), cmd_rc = 0;
 	struct nd_cmd_get_config_data_hdr *cmd;
-	struct nvdimm_bus_descriptor *nd_desc;
-	u32 max_cmd_size, config_size;
-	size_t offset;
+	size_t max_cmd_size, buf_offset;
 
 	if (rc)
 		return rc;
 
-	if (ndd->data)
-		return 0;
-
-	if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0
-			|| ndd->nsarea.config_size < ND_LABEL_MIN_SIZE) {
-		dev_dbg(ndd->dev, "failed to init config data area: (%d:%d)\n",
-				ndd->nsarea.max_xfer, ndd->nsarea.config_size);
+	if (offset + len > ndd->nsarea.config_size)
 		return -ENXIO;
-	}
 
-	ndd->data = kvmalloc(ndd->nsarea.config_size, GFP_KERNEL);
-	if (!ndd->data)
-		return -ENOMEM;
-
-	max_cmd_size = min_t(u32, PAGE_SIZE, ndd->nsarea.max_xfer);
-	cmd = kzalloc(max_cmd_size + sizeof(*cmd), GFP_KERNEL);
+	max_cmd_size = min_t(u32, len, ndd->nsarea.max_xfer);
+	cmd = kvzalloc(max_cmd_size + sizeof(*cmd), GFP_KERNEL);
 	if (!cmd)
 		return -ENOMEM;
 
-	nd_desc = nvdimm_bus->nd_desc;
-	for (config_size = ndd->nsarea.config_size, offset = 0;
-			config_size; config_size -= cmd->in_length,
-			offset += cmd->in_length) {
-		cmd->in_length = min(config_size, max_cmd_size);
-		cmd->in_offset = offset;
+	for (buf_offset = 0; len;
+	     len -= cmd->in_length, buf_offset += cmd->in_length) {
+		size_t cmd_size;
+
+		cmd->in_offset = offset + buf_offset;
+		cmd->in_length = min(max_cmd_size, len);
+
+		cmd_size = sizeof(*cmd) + cmd->in_length;
+
 		rc = nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
-				ND_CMD_GET_CONFIG_DATA, cmd,
-				cmd->in_length + sizeof(*cmd), &cmd_rc);
+				ND_CMD_GET_CONFIG_DATA, cmd, cmd_size, &cmd_rc);
 		if (rc < 0)
 			break;
 		if (cmd_rc < 0) {
 			rc = cmd_rc;
 			break;
 		}
-		memcpy(ndd->data + offset, cmd->out_buf, cmd->in_length);
+
+		/* out_buf should be valid, copy it into our output buffer */
+		memcpy(buf + buf_offset, cmd->out_buf, cmd->in_length);
 	}
-	dev_dbg(ndd->dev, "len: %zu rc: %d\n", offset, rc);
-	kfree(cmd);
+	kvfree(cmd);
 
 	return rc;
 }
@@ -151,15 +143,11 @@ int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
 	if (rc)
 		return rc;
 
-	if (!ndd->data)
-		return -ENXIO;
-
 	if (offset + len > ndd->nsarea.config_size)
 		return -ENXIO;
 
-	max_cmd_size = min_t(u32, PAGE_SIZE, len);
-	max_cmd_size = min_t(u32, max_cmd_size, ndd->nsarea.max_xfer);
-	cmd = kzalloc(max_cmd_size + sizeof(*cmd) + sizeof(u32), GFP_KERNEL);
+	max_cmd_size = min_t(u32, len, ndd->nsarea.max_xfer);
+	cmd = kvzalloc(max_cmd_size + sizeof(*cmd) + sizeof(u32), GFP_KERNEL);
 	if (!cmd)
 		return -ENOMEM;
 
@@ -183,7 +171,7 @@ int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
 			break;
 		}
 	}
-	kfree(cmd);
+	kvfree(cmd);
 
 	return rc;
 }
diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
index 1d28cd656536..750dbaa6ce82 100644
--- a/drivers/nvdimm/label.c
+++ b/drivers/nvdimm/label.c
@@ -75,7 +75,8 @@ size_t sizeof_namespace_index(struct nvdimm_drvdata *ndd)
 	/*
 	 * Per UEFI 2.7, the minimum size of the Label Storage Area is large
 	 * enough to hold 2 index blocks and 2 labels.  The minimum index
-	 * block size is 256 bytes, and the minimum label size is 256 bytes.
+	 * block size is 256 bytes. The label size is 128 for namespaces
+	 * prior to version 1.2 and at minimum 256 for version 1.2 and later.
 	 */
 	nslot = nvdimm_num_label_slots(ndd);
 	space = ndd->nsarea.config_size - nslot * sizeof_namespace_label(ndd);
@@ -183,6 +184,13 @@ static int __nd_label_validate(struct nvdimm_drvdata *ndd)
 					__le64_to_cpu(nsindex[i]->otheroff));
 			continue;
 		}
+		if (__le64_to_cpu(nsindex[i]->labeloff)
+				!= 2 * sizeof_namespace_index(ndd)) {
+			dev_dbg(dev, "nsindex%d labeloff: %#llx invalid\n",
+					i, (unsigned long long)
+					__le64_to_cpu(nsindex[i]->labeloff));
+			continue;
+		}
 
 		size = __le64_to_cpu(nsindex[i]->mysize);
 		if (size > sizeof_namespace_index(ndd)
@@ -227,7 +235,7 @@ static int __nd_label_validate(struct nvdimm_drvdata *ndd)
 	return -1;
 }
 
-int nd_label_validate(struct nvdimm_drvdata *ndd)
+static int nd_label_validate(struct nvdimm_drvdata *ndd)
 {
 	/*
 	 * In order to probe for and validate namespace index blocks we
@@ -250,12 +258,12 @@ int nd_label_validate(struct nvdimm_drvdata *ndd)
 	return -1;
 }
 
-void nd_label_copy(struct nvdimm_drvdata *ndd, struct nd_namespace_index *dst,
-		struct nd_namespace_index *src)
+static void nd_label_copy(struct nvdimm_drvdata *ndd,
+			  struct nd_namespace_index *dst,
+			  struct nd_namespace_index *src)
 {
-	if (dst && src)
-		/* pass */;
-	else
+	/* just exit if either destination or source is NULL */
+	if (!dst || !src)
 		return;
 
 	memcpy(dst, src, sizeof_namespace_index(ndd));
@@ -410,6 +418,128 @@ int nd_label_reserve_dpa(struct nvdimm_drvdata *ndd)
 	return 0;
 }
 
+int nd_label_data_init(struct nvdimm_drvdata *ndd)
+{
+	size_t config_size, read_size, max_xfer, offset;
+	struct nd_namespace_index *nsindex;
+	unsigned int i;
+	int rc = 0;
+	u32 nslot;
+
+	if (ndd->data)
+		return 0;
+
+	if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0) {
+		dev_dbg(ndd->dev, "failed to init config data area: (%u:%u)\n",
+			ndd->nsarea.max_xfer, ndd->nsarea.config_size);
+		return -ENXIO;
+	}
+
+	/*
+	 * We need to determine the maximum index area as this is the section
+	 * we must read and validate before we can start processing labels.
+	 *
+	 * If the area is too small to contain the two indexes and 2 labels
+	 * then we abort.
+	 *
+	 * Start at a label size of 128 as this should result in the largest
+	 * possible namespace index size.
+	 */
+	ndd->nslabel_size = 128;
+	read_size = sizeof_namespace_index(ndd) * 2;
+	if (!read_size)
+		return -ENXIO;
+
+	/* Allocate config data */
+	config_size = ndd->nsarea.config_size;
+	ndd->data = kvzalloc(config_size, GFP_KERNEL);
+	if (!ndd->data)
+		return -ENOMEM;
+
+	/*
+	 * We want to guarantee as few reads as possible while conserving
+	 * memory. To do that we figure out how much unused space will be left
+	 * in the last read, divide that by the total number of reads it is
+	 * going to take given our maximum transfer size, and then reduce our
+	 * maximum transfer size based on that result.
+	 */
+	max_xfer = min_t(size_t, ndd->nsarea.max_xfer, config_size);
+	if (read_size < max_xfer) {
+		/* trim waste */
+		max_xfer -= ((max_xfer - 1) - (config_size - 1) % max_xfer) /
+			    DIV_ROUND_UP(config_size, max_xfer);
+		/* make certain we read indexes in exactly 1 read */
+		if (max_xfer < read_size)
+			max_xfer = read_size;
+	}
+
+	/* Make our initial read size a multiple of max_xfer size */
+	read_size = min(DIV_ROUND_UP(read_size, max_xfer) * max_xfer,
+			config_size);
+
+	/* Read the index data */
+	rc = nvdimm_get_config_data(ndd, ndd->data, 0, read_size);
+	if (rc)
+		goto out_err;
+
+	/* Validate index data, if not valid assume all labels are invalid */
+	ndd->ns_current = nd_label_validate(ndd);
+	if (ndd->ns_current < 0)
+		return 0;
+
+	/* Record our index values */
+	ndd->ns_next = nd_label_next_nsindex(ndd->ns_current);
+
+	/* Copy "current" index on top of the "next" index */
+	nsindex = to_current_namespace_index(ndd);
+	nd_label_copy(ndd, to_next_namespace_index(ndd), nsindex);
+
+	/* Determine starting offset for label data */
+	offset = __le64_to_cpu(nsindex->labeloff);
+	nslot = __le32_to_cpu(nsindex->nslot);
+
+	/* Loop through the free list pulling in any active labels */
+	for (i = 0; i < nslot; i++, offset += ndd->nslabel_size) {
+		size_t label_read_size;
+
+		/* zero out the unused labels */
+		if (test_bit_le(i, nsindex->free)) {
+			memset(ndd->data + offset, 0, ndd->nslabel_size);
+			continue;
+		}
+
+		/* if we already read past here then just continue */
+		if (offset + ndd->nslabel_size <= read_size)
+			continue;
+
+		/* if we haven't read in a while reset our read_size offset */
+		if (read_size < offset)
+			read_size = offset;
+
+		/* determine how much more will be read after this next call. */
+		label_read_size = offset + ndd->nslabel_size - read_size;
+		label_read_size = DIV_ROUND_UP(label_read_size, max_xfer) *
+				  max_xfer;
+
+		/* truncate last read if needed */
+		if (read_size + label_read_size > config_size)
+			label_read_size = config_size - read_size;
+
+		/* Read the label data */
+		rc = nvdimm_get_config_data(ndd, ndd->data + read_size,
+					    read_size, label_read_size);
+		if (rc)
+			goto out_err;
+
+		/* push read_size to next read offset */
+		read_size += label_read_size;
+	}
+
+	dev_dbg(ndd->dev, "len: %zu rc: %d\n", offset, rc);
+out_err:
+	return rc;
+}
+
 int nd_label_active_count(struct nvdimm_drvdata *ndd)
 {
 	struct nd_namespace_index *nsindex;
diff --git a/drivers/nvdimm/label.h b/drivers/nvdimm/label.h
index 18bbe183b3a9..e9a2ad3c2150 100644
--- a/drivers/nvdimm/label.h
+++ b/drivers/nvdimm/label.h
@@ -138,9 +138,7 @@ static inline int nd_label_next_nsindex(int index)
 }
 
 struct nvdimm_drvdata;
-int nd_label_validate(struct nvdimm_drvdata *ndd);
-void nd_label_copy(struct nvdimm_drvdata *ndd, struct nd_namespace_index *dst,
-		struct nd_namespace_index *src);
+int nd_label_data_init(struct nvdimm_drvdata *ndd);
 size_t sizeof_namespace_index(struct nvdimm_drvdata *ndd);
 int nd_label_active_count(struct nvdimm_drvdata *ndd);
 struct nd_namespace_label *nd_label_active(struct nvdimm_drvdata *ndd, int n);
diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 4a4266250c28..681af3a8fd62 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -2099,7 +2099,6 @@ static struct device *nd_namespace_pmem_create(struct nd_region *nd_region)
 		return NULL;
 	}
 	dev_set_name(dev, "namespace%d.%d", nd_region->id, nspm->id);
-	dev->parent = &nd_region->dev;
 	dev->groups = nd_namespace_attribute_groups;
 	nd_namespace_pmem_set_resource(nd_region, nspm, 0);
 
diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
index ac68072fb8cd..182258f64417 100644
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -14,7 +14,6 @@
 #define __ND_CORE_H__
 #include <linux/libnvdimm.h>
 #include <linux/device.h>
-#include <linux/libnvdimm.h>
 #include <linux/sizes.h>
 #include <linux/mutex.h>
 #include <linux/nd.h>
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 98317e7ce5b5..e79cc8e5c114 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -241,6 +241,8 @@ struct nvdimm_drvdata *to_ndd(struct nd_mapping *nd_mapping);
 int nvdimm_check_config_data(struct device *dev);
 int nvdimm_init_nsarea(struct nvdimm_drvdata *ndd);
 int nvdimm_init_config_data(struct nvdimm_drvdata *ndd);
+int nvdimm_get_config_data(struct nvdimm_drvdata *ndd, void *buf,
+			   size_t offset, size_t len);
 int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
 		void *buf, size_t len);
 long nvdimm_clear_poison(struct device *dev, phys_addr_t phys,
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 3f7ad5bc443e..24c64090169e 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -361,6 +361,65 @@ struct device *nd_pfn_create(struct nd_region *nd_region)
 	return dev;
 }
 
+/*
+ * nd_pfn_clear_memmap_errors() clears any errors in the volatile memmap
+ * space associated with the namespace. If the memmap is set to DRAM, then
+ * this is a no-op. Since the memmap area is freshly initialized during
+ * probe, we have an opportunity to clear any badblocks in this area.
+ */
+static int nd_pfn_clear_memmap_errors(struct nd_pfn *nd_pfn)
+{
+	struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
+	struct nd_namespace_common *ndns = nd_pfn->ndns;
+	void *zero_page = page_address(ZERO_PAGE(0));
+	struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
+	int num_bad, meta_num, rc, bb_present;
+	sector_t first_bad, meta_start;
+	struct nd_namespace_io *nsio;
+
+	if (nd_pfn->mode != PFN_MODE_PMEM)
+		return 0;
+
+	nsio = to_nd_namespace_io(&ndns->dev);
+	meta_start = (SZ_4K + sizeof(*pfn_sb)) >> 9;
+	meta_num = (le64_to_cpu(pfn_sb->dataoff) >> 9) - meta_start;
+
+	do {
+		unsigned long zero_len;
+		u64 nsoff;
+
+		bb_present = badblocks_check(&nd_region->bb, meta_start,
+				meta_num, &first_bad, &num_bad);
+		if (bb_present) {
+			dev_dbg(&nd_pfn->dev, "meta: %x badblocks at %lx\n",
+					num_bad, first_bad);
+			nsoff = ALIGN_DOWN((nd_region->ndr_start
+					+ (first_bad << 9)) - nsio->res.start,
+					PAGE_SIZE);
+			zero_len = ALIGN(num_bad << 9, PAGE_SIZE);
+			while (zero_len) {
+				unsigned long chunk = min(zero_len, PAGE_SIZE);
+
+				rc = nvdimm_write_bytes(ndns, nsoff, zero_page,
+							chunk, 0);
+				if (rc)
+					break;
+
+				zero_len -= chunk;
+				nsoff += chunk;
+			}
+			if (rc) {
+				dev_err(&nd_pfn->dev,
+					"error clearing %x badblocks at %lx\n",
+					num_bad, first_bad);
+				return rc;
+			}
+		}
+	} while (bb_present);
+
+	return 0;
+}
+
 int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 {
 	u64 checksum, offset;
@@ -477,7 +536,7 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 		return -ENXIO;
 	}
 
-	return 0;
+	return nd_pfn_clear_memmap_errors(nd_pfn);
 }
 EXPORT_SYMBOL(nd_pfn_validate);
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index a75d10c23d80..0e39e3d1846f 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -421,9 +421,11 @@ static int pmem_attach_disk(struct device *dev,
 		addr = devm_memremap_pages(dev, &pmem->pgmap);
 		pmem->pfn_flags |= PFN_MAP;
 		memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
-	} else
+	} else {
 		addr = devm_memremap(dev, pmem->phys_addr,
 				pmem->size, ARCH_MEMREMAP_PMEM);
+		memcpy(&bb_res, &nsio->res, sizeof(bb_res));
+	}
 
 	/*
 	 * At release time the queue must be frozen before
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,