libnvdimm, dax: introduce device-dax infrastructure

Device DAX is the device-centric analogue of Filesystem DAX
(CONFIG_FS_DAX).  It allows persistent memory ranges to be allocated and
mapped without need of an intervening file system.  This initial
infrastructure arranges for a libnvdimm pfn-device to be represented as
a different device-type so that it can be attached to a driver other
than the pmem driver.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

11 files changed, 261 insertions, 34 deletions

diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index 53c11621d5b1..7c8a3bf07884 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -88,4 +88,17 @@ config NVDIMM_PFN
 
           Select Y if unsure
 
+config NVDIMM_DAX
+        bool "NVDIMM DAX: Raw access to persistent memory"
+        default LIBNVDIMM
+        depends on NVDIMM_PFN
+        help
+          Support raw device dax access to a persistent memory
+          namespace.  For environments that want to hard partition
+          peristent memory, this capability provides a mechanism to
+          sub-divide a namespace into character devices that can only be
+          accessed via DAX (mmap(2)).
+
+          Select Y if unsure
+
 endif
diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
index ea84d3c4e8e5..909554c3f955 100644
--- a/drivers/nvdimm/Makefile
+++ b/drivers/nvdimm/Makefile
@@ -23,3 +23,4 @@ libnvdimm-y += label.o
 libnvdimm-$(CONFIG_ND_CLAIM) += claim.o
 libnvdimm-$(CONFIG_BTT) += btt_devs.o
 libnvdimm-$(CONFIG_NVDIMM_PFN) += pfn_devs.o
+libnvdimm-$(CONFIG_NVDIMM_DAX) += dax_devs.o
diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 19f822d7f652..97589e3cb852 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -40,6 +40,8 @@ static int to_nd_device_type(struct device *dev)
                 return ND_DEVICE_REGION_PMEM;
         else if (is_nd_blk(dev))
                 return ND_DEVICE_REGION_BLK;
+        else if (is_nd_dax(dev))
+                return ND_DEVICE_DAX_PMEM;
         else if (is_nd_pmem(dev->parent) || is_nd_blk(dev->parent))
                 return nd_region_to_nstype(to_nd_region(dev->parent));
 
@@ -246,6 +248,8 @@ static void nd_async_device_unregister(void *d, async_cookie_t cookie)
 
 void __nd_device_register(struct device *dev)
 {
+        if (!dev)
+                return;
         dev->bus = &nvdimm_bus_type;
         get_device(dev);
         async_schedule_domain(nd_async_device_register, dev,
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index 6bbd0a36994a..5f53db59a058 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -85,6 +85,8 @@ static bool is_idle(struct device *dev, struct nd_namespace_common *ndns)
                 seed = nd_region->btt_seed;
         else if (is_nd_pfn(dev))
                 seed = nd_region->pfn_seed;
+        else if (is_nd_dax(dev))
+                seed = nd_region->dax_seed;
 
         if (seed == dev || ndns || dev->driver)
                 return false;
diff --git a/drivers/nvdimm/dax_devs.c b/drivers/nvdimm/dax_devs.c
new file mode 100644
index 000000000000..f90f7549e7f4
--- /dev/null
+++ b/drivers/nvdimm/dax_devs.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright(c) 2013-2016 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/device.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include "nd-core.h"
+#include "nd.h"
+
+static void nd_dax_release(struct device *dev)
+{
+        struct nd_region *nd_region = to_nd_region(dev->parent);
+        struct nd_dax *nd_dax = to_nd_dax(dev);
+        struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
+
+        dev_dbg(dev, "%s\n", __func__);
+        nd_detach_ndns(dev, &nd_pfn->ndns);
+        ida_simple_remove(&nd_region->dax_ida, nd_pfn->id);
+        kfree(nd_pfn->uuid);
+        kfree(nd_dax);
+}
+
+static struct device_type nd_dax_device_type = {
+        .name = "nd_dax",
+        .release = nd_dax_release,
+};
+
+bool is_nd_dax(struct device *dev)
+{
+        return dev ? dev->type == &nd_dax_device_type : false;
+}
+EXPORT_SYMBOL(is_nd_dax);
+
+struct nd_dax *to_nd_dax(struct device *dev)
+{
+        struct nd_dax *nd_dax = container_of(dev, struct nd_dax, nd_pfn.dev);
+
+        WARN_ON(!is_nd_dax(dev));
+        return nd_dax;
+}
+EXPORT_SYMBOL(to_nd_dax);
+
+static const struct attribute_group *nd_dax_attribute_groups[] = {
+        &nd_pfn_attribute_group,
+        &nd_device_attribute_group,
+        &nd_numa_attribute_group,
+        NULL,
+};
+
+static struct nd_dax *nd_dax_alloc(struct nd_region *nd_region)
+{
+        struct nd_pfn *nd_pfn;
+        struct nd_dax *nd_dax;
+        struct device *dev;
+
+        nd_dax = kzalloc(sizeof(*nd_dax), GFP_KERNEL);
+        if (!nd_dax)
+                return NULL;
+
+        nd_pfn = &nd_dax->nd_pfn;
+        nd_pfn->id = ida_simple_get(&nd_region->dax_ida, 0, 0, GFP_KERNEL);
+        if (nd_pfn->id < 0) {
+                kfree(nd_dax);
+                return NULL;
+        }
+
+        dev = &nd_pfn->dev;
+        dev_set_name(dev, "dax%d.%d", nd_region->id, nd_pfn->id);
+        dev->groups = nd_dax_attribute_groups;
+        dev->type = &nd_dax_device_type;
+        dev->parent = &nd_region->dev;
+
+        return nd_dax;
+}
+
+struct device *nd_dax_create(struct nd_region *nd_region)
+{
+        struct device *dev = NULL;
+        struct nd_dax *nd_dax;
+
+        if (!is_nd_pmem(&nd_region->dev))
+                return NULL;
+
+        nd_dax = nd_dax_alloc(nd_region);
+        if (nd_dax)
+                dev = nd_pfn_devinit(&nd_dax->nd_pfn, NULL);
+        __nd_device_register(dev);
+        return dev;
+}
diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index e5ad5162bf34..c5e3196c45b0 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -1288,6 +1288,8 @@ static ssize_t mode_show(struct device *dev,
                 mode = "safe";
         else if (claim && is_nd_pfn(claim))
                 mode = "memory";
+        else if (claim && is_nd_dax(claim))
+                mode = "dax";
         else if (!claim && pmem_should_map_pages(dev))
                 mode = "memory";
         else
@@ -1379,14 +1381,17 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
 {
         struct nd_btt *nd_btt = is_nd_btt(dev) ? to_nd_btt(dev) : NULL;
         struct nd_pfn *nd_pfn = is_nd_pfn(dev) ? to_nd_pfn(dev) : NULL;
+        struct nd_dax *nd_dax = is_nd_dax(dev) ? to_nd_dax(dev) : NULL;
         struct nd_namespace_common *ndns = NULL;
         resource_size_t size;
 
-        if (nd_btt || nd_pfn) {
+        if (nd_btt || nd_pfn || nd_dax) {
                 if (nd_btt)
                         ndns = nd_btt->ndns;
                 else if (nd_pfn)
                         ndns = nd_pfn->ndns;
+                else if (nd_dax)
+                        ndns = nd_dax->nd_pfn.ndns;
 
                 if (!ndns)
                         return ERR_PTR(-ENODEV);
@@ -1779,6 +1784,18 @@ void nd_region_create_blk_seed(struct nd_region *nd_region)
                 nd_device_register(nd_region->ns_seed);
 }
 
+void nd_region_create_dax_seed(struct nd_region *nd_region)
+{
+        WARN_ON(!is_nvdimm_bus_locked(&nd_region->dev));
+        nd_region->dax_seed = nd_dax_create(nd_region);
+        /*
+         * Seed creation failures are not fatal, provisioning is simply
+         * disabled until memory becomes available
+         */
+        if (!nd_region->dax_seed)
+                dev_err(&nd_region->dev, "failed to create dax namespace\n");
+}
+
 void nd_region_create_pfn_seed(struct nd_region *nd_region)
 {
         WARN_ON(!is_nvdimm_bus_locked(&nd_region->dev));
diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
index 1d1500f3d8b5..cb65308c0329 100644
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -54,6 +54,7 @@ struct nd_region;
 void nd_region_create_blk_seed(struct nd_region *nd_region);
 void nd_region_create_btt_seed(struct nd_region *nd_region);
 void nd_region_create_pfn_seed(struct nd_region *nd_region);
+void nd_region_create_dax_seed(struct nd_region *nd_region);
 void nd_region_disable(struct nvdimm_bus *nvdimm_bus, struct device *dev);
 int nvdimm_bus_create_ndctl(struct nvdimm_bus *nvdimm_bus);
 void nvdimm_bus_destroy_ndctl(struct nvdimm_bus *nvdimm_bus);
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 6c36509662e4..46910b8f32b1 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -101,10 +101,12 @@ struct nd_region {
         struct ida ns_ida;
         struct ida btt_ida;
         struct ida pfn_ida;
+        struct ida dax_ida;
         unsigned long flags;
         struct device *ns_seed;
         struct device *btt_seed;
         struct device *pfn_seed;
+        struct device *dax_seed;
         u16 ndr_mappings;
         u64 ndr_size;
         u64 ndr_start;
@@ -161,6 +163,10 @@ struct nd_pfn {
         struct nd_namespace_common *ndns;
 };
 
+struct nd_dax {
+        struct nd_pfn nd_pfn;
+};
+
 enum nd_async_mode {
         ND_SYNC,
         ND_ASYNC,
@@ -224,7 +230,10 @@ struct nd_pfn *to_nd_pfn(struct device *dev);
 int nd_pfn_probe(struct device *dev, struct nd_namespace_common *ndns);
 bool is_nd_pfn(struct device *dev);
 struct device *nd_pfn_create(struct nd_region *nd_region);
+struct device *nd_pfn_devinit(struct nd_pfn *nd_pfn,
+                struct nd_namespace_common *ndns);
 int nd_pfn_validate(struct nd_pfn *nd_pfn);
+extern struct attribute_group nd_pfn_attribute_group;
 #else
 static inline int nd_pfn_probe(struct device *dev,
                 struct nd_namespace_common *ndns)
@@ -248,6 +257,22 @@ static inline int nd_pfn_validate(struct nd_pfn *nd_pfn)
 }
 #endif
 
+struct nd_dax *to_nd_dax(struct device *dev);
+#if IS_ENABLED(CONFIG_NVDIMM_DAX)
+bool is_nd_dax(struct device *dev);
+struct device *nd_dax_create(struct nd_region *nd_region);
+#else
+static inline bool is_nd_dax(struct device *dev)
+{
+        return false;
+}
+
+static inline struct device *nd_dax_create(struct nd_region *nd_region)
+{
+        return NULL;
+}
+#endif
+
 struct nd_region *to_nd_region(struct device *dev);
 int nd_region_to_nstype(struct nd_region *nd_region);
 int nd_region_register_namespaces(struct nd_region *nd_region, int *err);
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index e8693fe65e49..6ade2eb7615d 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -1,5 +1,5 @@
 /*
- * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ * Copyright(c) 2013-2016 Intel Corporation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of version 2 of the GNU General Public License as
@@ -54,10 +54,29 @@ struct nd_pfn *to_nd_pfn(struct device *dev)
 }
 EXPORT_SYMBOL(to_nd_pfn);
 
+static struct nd_pfn *to_nd_pfn_safe(struct device *dev)
+{
+        /*
+         * pfn device attributes are re-used by dax device instances, so we
+         * need to be careful to correct device-to-nd_pfn conversion.
+         */
+        if (is_nd_pfn(dev))
+                return to_nd_pfn(dev);
+
+        if (is_nd_dax(dev)) {
+                struct nd_dax *nd_dax = to_nd_dax(dev);
+
+                return &nd_dax->nd_pfn;
+        }
+
+        WARN_ON(1);
+        return NULL;
+}
+
 static ssize_t mode_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
 
         switch (nd_pfn->mode) {
         case PFN_MODE_RAM:
@@ -72,7 +91,7 @@ static ssize_t mode_show(struct device *dev,
 static ssize_t mode_store(struct device *dev,
                 struct device_attribute *attr, const char *buf, size_t len)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc = 0;
 
         device_lock(dev);
@@ -106,7 +125,7 @@ static DEVICE_ATTR_RW(mode);
 static ssize_t align_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
 
         return sprintf(buf, "%lx\n", nd_pfn->align);
 }
@@ -134,7 +153,7 @@ static ssize_t __align_store(struct nd_pfn *nd_pfn, const char *buf)
 static ssize_t align_store(struct device *dev,
                 struct device_attribute *attr, const char *buf, size_t len)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         device_lock(dev);
@@ -152,7 +171,7 @@ static DEVICE_ATTR_RW(align);
 static ssize_t uuid_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
 
         if (nd_pfn->uuid)
                 return sprintf(buf, "%pUb\n", nd_pfn->uuid);
@@ -162,7 +181,7 @@ static ssize_t uuid_show(struct device *dev,
 static ssize_t uuid_store(struct device *dev,
                 struct device_attribute *attr, const char *buf, size_t len)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         device_lock(dev);
@@ -178,7 +197,7 @@ static DEVICE_ATTR_RW(uuid);
 static ssize_t namespace_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         nvdimm_bus_lock(dev);
@@ -191,7 +210,7 @@ static ssize_t namespace_show(struct device *dev,
 static ssize_t namespace_store(struct device *dev,
                 struct device_attribute *attr, const char *buf, size_t len)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         device_lock(dev);
@@ -209,7 +228,7 @@ static DEVICE_ATTR_RW(namespace);
 static ssize_t resource_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         device_lock(dev);
@@ -235,7 +254,7 @@ static DEVICE_ATTR_RO(resource);
 static ssize_t size_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
-        struct nd_pfn *nd_pfn = to_nd_pfn(dev);
+        struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
         ssize_t rc;
 
         device_lock(dev);
@@ -270,7 +289,7 @@ static struct attribute *nd_pfn_attributes[] = {
         NULL,
 };
 
-static struct attribute_group nd_pfn_attribute_group = {
+struct attribute_group nd_pfn_attribute_group = {
         .attrs = nd_pfn_attributes,
 };
 
@@ -281,15 +300,31 @@ static const struct attribute_group *nd_pfn_attribute_groups[] = {
         NULL,
 };
 
-static struct device *__nd_pfn_create(struct nd_region *nd_region,
+struct device *nd_pfn_devinit(struct nd_pfn *nd_pfn,
                 struct nd_namespace_common *ndns)
 {
-        struct nd_pfn *nd_pfn;
-        struct device *dev;
+        struct device *dev = &nd_pfn->dev;
 
-        /* we can only create pages for contiguous ranged of pmem */
-        if (!is_nd_pmem(&nd_region->dev))
+        if (!nd_pfn)
+                return NULL;
+
+        nd_pfn->mode = PFN_MODE_NONE;
+        nd_pfn->align = HPAGE_SIZE;
+        dev = &nd_pfn->dev;
+        device_initialize(&nd_pfn->dev);
+        if (ndns && !__nd_attach_ndns(&nd_pfn->dev, ndns, &nd_pfn->ndns)) {
+                dev_dbg(&ndns->dev, "%s failed, already claimed by %s\n",
+                                __func__, dev_name(ndns->claim));
+                put_device(dev);
                 return NULL;
+        }
+        return dev;
+}
+
+static struct nd_pfn *nd_pfn_alloc(struct nd_region *nd_region)
+{
+        struct nd_pfn *nd_pfn;
+        struct device *dev;
 
         nd_pfn = kzalloc(sizeof(*nd_pfn), GFP_KERNEL);
         if (!nd_pfn)
@@ -301,29 +336,27 @@ static struct device *__nd_pfn_create(struct nd_region *nd_region,
                 return NULL;
         }
 
-        nd_pfn->mode = PFN_MODE_NONE;
-        nd_pfn->align = HPAGE_SIZE;
         dev = &nd_pfn->dev;
         dev_set_name(dev, "pfn%d.%d", nd_region->id, nd_pfn->id);
-        dev->parent = &nd_region->dev;
-        dev->type = &nd_pfn_device_type;
         dev->groups = nd_pfn_attribute_groups;
-        device_initialize(&nd_pfn->dev);
-        if (ndns && !__nd_attach_ndns(&nd_pfn->dev, ndns, &nd_pfn->ndns)) {
-                dev_dbg(&ndns->dev, "%s failed, already claimed by %s\n",
-                                __func__, dev_name(ndns->claim));
-                put_device(dev);
-                return NULL;
-        }
-        return dev;
+        dev->type = &nd_pfn_device_type;
+        dev->parent = &nd_region->dev;
+
+        return nd_pfn;
 }
 
 struct device *nd_pfn_create(struct nd_region *nd_region)
 {
-        struct device *dev = __nd_pfn_create(nd_region, NULL);
+        struct nd_pfn *nd_pfn;
+        struct device *dev;
+
+        if (!is_nd_pmem(&nd_region->dev))
+                return NULL;
+
+        nd_pfn = nd_pfn_alloc(nd_region);
+        dev = nd_pfn_devinit(nd_pfn, NULL);
 
-        if (dev)
-                __nd_device_register(dev);
+        __nd_device_register(dev);
         return dev;
 }
 
@@ -423,7 +456,8 @@ int nd_pfn_probe(struct device *dev, struct nd_namespace_common *ndns)
                 return -ENODEV;
 
         nvdimm_bus_lock(&ndns->dev);
-        pfn_dev = __nd_pfn_create(nd_region, ndns);
+        nd_pfn = nd_pfn_alloc(nd_region);
+        pfn_dev = nd_pfn_devinit(nd_pfn, ndns);
         nvdimm_bus_unlock(&ndns->dev);
         if (!pfn_dev)
                 return -ENOMEM;
diff --git a/drivers/nvdimm/region.c b/drivers/nvdimm/region.c
index 4b7715e29cff..05a912359939 100644
--- a/drivers/nvdimm/region.c
+++ b/drivers/nvdimm/region.c
@@ -54,6 +54,7 @@ static int nd_region_probe(struct device *dev)
 
         nd_region->btt_seed = nd_btt_create(nd_region);
         nd_region->pfn_seed = nd_pfn_create(nd_region);
+        nd_region->dax_seed = nd_dax_create(nd_region);
         if (err == 0)
                 return 0;
 
@@ -86,6 +87,7 @@ static int nd_region_remove(struct device *dev)
         nd_region->ns_seed = NULL;
         nd_region->btt_seed = NULL;
         nd_region->pfn_seed = NULL;
+        nd_region->dax_seed = NULL;
         dev_set_drvdata(dev, NULL);
         nvdimm_bus_unlock(dev);
 
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 139bf71ca549..9e1b054e0e61 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -306,6 +306,23 @@ static ssize_t pfn_seed_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(pfn_seed);
 
+static ssize_t dax_seed_show(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct nd_region *nd_region = to_nd_region(dev);
+        ssize_t rc;
+
+        nvdimm_bus_lock(dev);
+        if (nd_region->dax_seed)
+                rc = sprintf(buf, "%s\n", dev_name(nd_region->dax_seed));
+        else
+                rc = sprintf(buf, "\n");
+        nvdimm_bus_unlock(dev);
+
+        return rc;
+}
+static DEVICE_ATTR_RO(dax_seed);
+
 static ssize_t read_only_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
@@ -335,6 +352,7 @@ static struct attribute *nd_region_attributes[] = {
         &dev_attr_mappings.attr,
         &dev_attr_btt_seed.attr,
         &dev_attr_pfn_seed.attr,
+        &dev_attr_dax_seed.attr,
         &dev_attr_read_only.attr,
         &dev_attr_set_cookie.attr,
         &dev_attr_available_size.attr,
@@ -353,6 +371,9 @@ static umode_t region_visible(struct kobject *kobj, struct attribute *a, int n)
         if (!is_nd_pmem(dev) && a == &dev_attr_pfn_seed.attr)
                 return 0;
 
+        if (!is_nd_pmem(dev) && a == &dev_attr_dax_seed.attr)
+                return 0;
+
         if (a != &dev_attr_set_cookie.attr
                         && a != &dev_attr_available_size.attr)
                 return a->mode;
@@ -441,6 +462,13 @@ static void nd_region_notify_driver_action(struct nvdimm_bus *nvdimm_bus,
                         nd_region_create_pfn_seed(nd_region);
                 nvdimm_bus_unlock(dev);
         }
+        if (is_nd_dax(dev) && probe) {
+                nd_region = to_nd_region(dev->parent);
+                nvdimm_bus_lock(dev);
+                if (nd_region->dax_seed == dev)
+                        nd_region_create_dax_seed(nd_region);
+                nvdimm_bus_unlock(dev);
+        }
 }
 
 void nd_region_probe_success(struct nvdimm_bus *nvdimm_bus, struct device *dev)
@@ -718,6 +746,7 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
         ida_init(&nd_region->ns_ida);
         ida_init(&nd_region->btt_ida);
         ida_init(&nd_region->pfn_ida);
+        ida_init(&nd_region->dax_ida);
         dev = &nd_region->dev;
         dev_set_name(dev, "region%d", nd_region->id);
         dev->parent = &nvdimm_bus->dev;