Merge branch 'for-4.12/dax' into libnvdimm-for-next

8 files changed, 619 insertions, 319 deletions

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 9e95bf94eb13..b7053eafd88e 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -1,8 +1,13 @@
-menuconfig DEV_DAX
+menuconfig DAX
 	tristate "DAX: direct access to differentiated memory"
+	select SRCU
 	default m if NVDIMM_DAX
+
+if DAX
+
+config DEV_DAX
+	tristate "Device DAX: direct access mapping device"
 	depends on TRANSPARENT_HUGEPAGE
-	select SRCU
 	help
 	  Support raw access to differentiated (persistence, bandwidth,
 	  latency...) memory via an mmap(2) capable character
@@ -11,7 +16,6 @@ menuconfig DEV_DAX
 	  baseline memory pool.  Mappings of a /dev/daxX.Y device impose
 	  restrictions that make the mapping behavior deterministic.
 
-if DEV_DAX
 
 config DEV_DAX_PMEM
 	tristate "PMEM DAX: direct access to persistent memory"
diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
index 27c54e38478a..dc7422530462 100644
--- a/drivers/dax/Makefile
+++ b/drivers/dax/Makefile
@@ -1,4 +1,7 @@
-obj-$(CONFIG_DEV_DAX) += dax.o
+obj-$(CONFIG_DAX) += dax.o
+obj-$(CONFIG_DEV_DAX) += device_dax.o
 obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
 
+dax-y := super.o
 dax_pmem-y := pmem.o
+device_dax-y := device.o
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index b1cd7a8e5ab9..b6fc4f04636d 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -38,22 +38,18 @@ struct dax_region {
 };
 
 /**
- * struct dax_dev - subdivision of a dax region
+ * struct dev_dax - instance data for a subdivision of a dax region
  * @region - parent region
- * @inode - inode
- * @dev - device backing the character device
- * @cdev - core chardev data
- * @alive - !alive + srcu grace period == no new mappings can be established
+ * @dax_dev - core dax functionality
+ * @dev - device core
  * @id - child id in the region
  * @num_resources - number of physical address extents in this device
  * @res - array of physical address ranges
  */
-struct dax_dev {
+struct dev_dax {
 	struct dax_region *region;
-	struct inode *inode;
+	struct dax_device *dax_dev;
 	struct device dev;
-	struct cdev cdev;
-	bool alive;
 	int id;
 	int num_resources;
 	struct resource res[0];
diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
index ddd829ab58c0..f9e5feea742c 100644
--- a/drivers/dax/dax.h
+++ b/drivers/dax/dax.h
@@ -1,5 +1,5 @@
 /*
- * Copyright(c) 2016 Intel Corporation. All rights reserved.
+ * Copyright(c) 2016 - 2017 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
@@ -12,14 +12,7 @@
  */
 #ifndef __DAX_H__
 #define __DAX_H__
-struct device;
-struct dax_dev;
-struct resource;
-struct dax_region;
-void dax_region_put(struct dax_region *dax_region);
-struct dax_region *alloc_dax_region(struct device *parent,
-		int region_id, struct resource *res, unsigned int align,
-		void *addr, unsigned long flags);
-struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
-		struct resource *res, int count);
+struct dax_device;
+struct dax_device *inode_dax(struct inode *inode);
+struct inode *dax_inode(struct dax_device *dax_dev);
 #endif /* __DAX_H__ */
diff --git a/drivers/dax/device-dax.h b/drivers/dax/device-dax.h
new file mode 100644
index 000000000000..fdcd9769ffde
--- /dev/null
+++ b/drivers/dax/device-dax.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright(c) 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.
+ */
+#ifndef __DEVICE_DAX_H__
+#define __DEVICE_DAX_H__
+struct device;
+struct dev_dax;
+struct resource;
+struct dax_region;
+void dax_region_put(struct dax_region *dax_region);
+struct dax_region *alloc_dax_region(struct device *parent,
+		int region_id, struct resource *res, unsigned int align,
+		void *addr, unsigned long flags);
+struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
+		struct resource *res, int count);
+#endif /* __DEVICE_DAX_H__ */
diff --git a/drivers/dax/dax.c b/drivers/dax/device.c
index 5e8302d3a89c..006e657dfcb9 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/device.c
@@ -1,5 +1,5 @@
 /*
- * Copyright(c) 2016 Intel Corporation. All rights reserved.
+ * Copyright(c) 2016 - 2017 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
@@ -13,10 +13,7 @@
 #include <linux/pagemap.h>
 #include <linux/module.h>
 #include <linux/device.h>
-#include <linux/magic.h>
-#include <linux/mount.h>
 #include <linux/pfn_t.h>
-#include <linux/hash.h>
 #include <linux/cdev.h>
 #include <linux/slab.h>
 #include <linux/dax.h>
@@ -25,16 +22,7 @@
 #include "dax-private.h"
 #include "dax.h"
 
-static dev_t dax_devt;
-DEFINE_STATIC_SRCU(dax_srcu);
 static struct class *dax_class;
-static DEFINE_IDA(dax_minor_ida);
-static int nr_dax = CONFIG_NR_DEV_DAX;
-module_param(nr_dax, int, S_IRUGO);
-static struct vfsmount *dax_mnt;
-static struct kmem_cache *dax_cache __read_mostly;
-static struct super_block *dax_superblock __read_mostly;
-MODULE_PARM_DESC(nr_dax, "max number of device-dax instances");
 
 /*
  * Rely on the fact that drvdata is set before the attributes are
@@ -87,117 +75,6 @@ static const struct attribute_group *dax_region_attribute_groups[] = {
 	NULL,
 };
 
-static struct inode *dax_alloc_inode(struct super_block *sb)
-{
-	return kmem_cache_alloc(dax_cache, GFP_KERNEL);
-}
-
-static void dax_i_callback(struct rcu_head *head)
-{
-	struct inode *inode = container_of(head, struct inode, i_rcu);
-
-	kmem_cache_free(dax_cache, inode);
-}
-
-static void dax_destroy_inode(struct inode *inode)
-{
-	call_rcu(&inode->i_rcu, dax_i_callback);
-}
-
-static const struct super_operations dax_sops = {
-	.statfs = simple_statfs,
-	.alloc_inode = dax_alloc_inode,
-	.destroy_inode = dax_destroy_inode,
-	.drop_inode = generic_delete_inode,
-};
-
-static struct dentry *dax_mount(struct file_system_type *fs_type,
-		int flags, const char *dev_name, void *data)
-{
-	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
-}
-
-static struct file_system_type dax_type = {
-	.name = "dax",
-	.mount = dax_mount,
-	.kill_sb = kill_anon_super,
-};
-
-static int dax_test(struct inode *inode, void *data)
-{
-	return inode->i_cdev == data;
-}
-
-static int dax_set(struct inode *inode, void *data)
-{
-	inode->i_cdev = data;
-	return 0;
-}
-
-static struct inode *dax_inode_get(struct cdev *cdev, dev_t devt)
-{
-	struct inode *inode;
-
-	inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
-			dax_test, dax_set, cdev);
-
-	if (!inode)
-		return NULL;
-
-	if (inode->i_state & I_NEW) {
-		inode->i_mode = S_IFCHR;
-		inode->i_flags = S_DAX;
-		inode->i_rdev = devt;
-		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
-		unlock_new_inode(inode);
-	}
-	return inode;
-}
-
-static void init_once(void *inode)
-{
-	inode_init_once(inode);
-}
-
-static int dax_inode_init(void)
-{
-	int rc;
-
-	dax_cache = kmem_cache_create("dax_cache", sizeof(struct inode), 0,
-			(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
-			 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
-			init_once);
-	if (!dax_cache)
-		return -ENOMEM;
-
-	rc = register_filesystem(&dax_type);
-	if (rc)
-		goto err_register_fs;
-
-	dax_mnt = kern_mount(&dax_type);
-	if (IS_ERR(dax_mnt)) {
-		rc = PTR_ERR(dax_mnt);
-		goto err_mount;
-	}
-	dax_superblock = dax_mnt->mnt_sb;
-
-	return 0;
-
- err_mount:
-	unregister_filesystem(&dax_type);
- err_register_fs:
-	kmem_cache_destroy(dax_cache);
-
-	return rc;
-}
-
-static void dax_inode_exit(void)
-{
-	kern_unmount(dax_mnt);
-	unregister_filesystem(&dax_type);
-	kmem_cache_destroy(dax_cache);
-}
-
 static void dax_region_free(struct kref *kref)
 {
 	struct dax_region *dax_region;
@@ -266,47 +143,47 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 }
 EXPORT_SYMBOL_GPL(alloc_dax_region);
 
-static struct dax_dev *to_dax_dev(struct device *dev)
+static struct dev_dax *to_dev_dax(struct device *dev)
 {
-	return container_of(dev, struct dax_dev, dev);
+	return container_of(dev, struct dev_dax, dev);
 }
 
 static ssize_t size_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
-	struct dax_dev *dax_dev = to_dax_dev(dev);
+	struct dev_dax *dev_dax = to_dev_dax(dev);
 	unsigned long long size = 0;
 	int i;
 
-	for (i = 0; i < dax_dev->num_resources; i++)
-		size += resource_size(&dax_dev->res[i]);
+	for (i = 0; i < dev_dax->num_resources; i++)
+		size += resource_size(&dev_dax->res[i]);
 
 	return sprintf(buf, "%llu\n", size);
 }
 static DEVICE_ATTR_RO(size);
 
-static struct attribute *dax_device_attributes[] = {
+static struct attribute *dev_dax_attributes[] = {
 	&dev_attr_size.attr,
 	NULL,
 };
 
-static const struct attribute_group dax_device_attribute_group = {
-	.attrs = dax_device_attributes,
+static const struct attribute_group dev_dax_attribute_group = {
+	.attrs = dev_dax_attributes,
 };
 
 static const struct attribute_group *dax_attribute_groups[] = {
-	&dax_device_attribute_group,
+	&dev_dax_attribute_group,
 	NULL,
 };
 
-static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
+static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
 		const char *func)
 {
-	struct dax_region *dax_region = dax_dev->region;
-	struct device *dev = &dax_dev->dev;
+	struct dax_region *dax_region = dev_dax->region;
+	struct device *dev = &dev_dax->dev;
 	unsigned long mask;
 
-	if (!dax_dev->alive)
+	if (!dax_alive(dev_dax->dax_dev))
 		return -ENXIO;
 
 	/* prevent private mappings from being established */
@@ -341,23 +218,23 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 }
 
 /* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
-__weak phys_addr_t dax_pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
+__weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
 		unsigned long size)
 {
 	struct resource *res;
 	phys_addr_t phys;
 	int i;
 
-	for (i = 0; i < dax_dev->num_resources; i++) {
-		res = &dax_dev->res[i];
+	for (i = 0; i < dev_dax->num_resources; i++) {
+		res = &dev_dax->res[i];
 		phys = pgoff * PAGE_SIZE + res->start;
 		if (phys >= res->start && phys <= res->end)
 			break;
 		pgoff -= PHYS_PFN(resource_size(res));
 	}
 
-	if (i < dax_dev->num_resources) {
-		res = &dax_dev->res[i];
+	if (i < dev_dax->num_resources) {
+		res = &dev_dax->res[i];
 		if (phys + size - 1 <= res->end)
 			return phys;
 	}
@@ -365,28 +242,29 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
 	return -1;
 }
 
-static int __dax_dev_pte_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
+static int __dev_dax_pte_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
 {
-	struct device *dev = &dax_dev->dev;
+	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	int rc = VM_FAULT_SIGBUS;
 	phys_addr_t phys;
 	pfn_t pfn;
 	unsigned int fault_size = PAGE_SIZE;
 
-	if (check_vma(dax_dev, vmf->vma, __func__))
+	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;
 
-	dax_region = dax_dev->region;
+	dax_region = dev_dax->region;
 	if (dax_region->align > PAGE_SIZE) {
-		dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+		dev_dbg(dev, "%s: alignment (%#x) > fault size (%#x)\n",
+			__func__, dax_region->align, fault_size);
 		return VM_FAULT_SIGBUS;
 	}
 
 	if (fault_size != dax_region->align)
 		return VM_FAULT_SIGBUS;
 
-	phys = dax_pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
+	phys = dax_pgoff_to_phys(dev_dax, vmf->pgoff, PAGE_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "%s: pgoff_to_phys(%#lx) failed\n", __func__,
 				vmf->pgoff);
@@ -405,28 +283,29 @@ static int __dax_dev_pte_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 	return VM_FAULT_NOPAGE;
 }
 
-static int __dax_dev_pmd_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
+static int __dev_dax_pmd_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
 {
 	unsigned long pmd_addr = vmf->address & PMD_MASK;
-	struct device *dev = &dax_dev->dev;
+	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	pgoff_t pgoff;
 	pfn_t pfn;
 	unsigned int fault_size = PMD_SIZE;
 
-	if (check_vma(dax_dev, vmf->vma, __func__))
+	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;
 
-	dax_region = dax_dev->region;
+	dax_region = dev_dax->region;
 	if (dax_region->align > PMD_SIZE) {
-		dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+		dev_dbg(dev, "%s: alignment (%#x) > fault size (%#x)\n",
+			__func__, dax_region->align, fault_size);
 		return VM_FAULT_SIGBUS;
 	}
 
 	/* dax pmd mappings require pfn_t_devmap() */
 	if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
-		dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+		dev_dbg(dev, "%s: region lacks devmap flags\n", __func__);
 		return VM_FAULT_SIGBUS;
 	}
 
@@ -441,7 +320,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 
 	pgoff = linear_page_index(vmf->vma, pmd_addr);
-	phys = dax_pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
+	phys = dax_pgoff_to_phys(dev_dax, pgoff, PMD_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "%s: pgoff_to_phys(%#lx) failed\n", __func__,
 				pgoff);
@@ -455,10 +334,10 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 }
 
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
-static int __dax_dev_pud_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
+static int __dev_dax_pud_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
 {
 	unsigned long pud_addr = vmf->address & PUD_MASK;
-	struct device *dev = &dax_dev->dev;
+	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	pgoff_t pgoff;
@@ -466,18 +345,19 @@ static int __dax_dev_pud_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 	unsigned int fault_size = PUD_SIZE;
 
 
-	if (check_vma(dax_dev, vmf->vma, __func__))
+	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;
 
-	dax_region = dax_dev->region;
+	dax_region = dev_dax->region;
 	if (dax_region->align > PUD_SIZE) {
-		dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+		dev_dbg(dev, "%s: alignment (%#x) > fault size (%#x)\n",
+			__func__, dax_region->align, fault_size);
 		return VM_FAULT_SIGBUS;
 	}
 
 	/* dax pud mappings require pfn_t_devmap() */
 	if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
-		dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+		dev_dbg(dev, "%s: region lacks devmap flags\n", __func__);
 		return VM_FAULT_SIGBUS;
 	}
 
@@ -492,7 +372,7 @@ static int __dax_dev_pud_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 
 	pgoff = linear_page_index(vmf->vma, pud_addr);
-	phys = dax_pgoff_to_phys(dax_dev, pgoff, PUD_SIZE);
+	phys = dax_pgoff_to_phys(dev_dax, pgoff, PUD_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "%s: pgoff_to_phys(%#lx) failed\n", __func__,
 				pgoff);
@@ -505,65 +385,71 @@ static int __dax_dev_pud_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
 			vmf->flags & FAULT_FLAG_WRITE);
 }
 #else
-static int __dax_dev_pud_fault(struct dax_dev *dax_dev, struct vm_fault *vmf)
+static int __dev_dax_pud_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
 {
 	return VM_FAULT_FALLBACK;
 }
 #endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 
-static int dax_dev_huge_fault(struct vm_fault *vmf,
+static int dev_dax_huge_fault(struct vm_fault *vmf,
 		enum page_entry_size pe_size)
 {
 	int rc, id;
 	struct file *filp = vmf->vma->vm_file;
-	struct dax_dev *dax_dev = filp->private_data;
+	struct dev_dax *dev_dax = filp->private_data;
 
-	dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
+	dev_dbg(&dev_dax->dev, "%s: %s: %s (%#lx - %#lx) size = %d\n", __func__,
 			current->comm, (vmf->flags & FAULT_FLAG_WRITE)
 			? "write" : "read",
-			vmf->vma->vm_start, vmf->vma->vm_end);
+			vmf->vma->vm_start, vmf->vma->vm_end, pe_size);
 
-	id = srcu_read_lock(&dax_srcu);
+	id = dax_read_lock();
 	switch (pe_size) {
 	case PE_SIZE_PTE:
-		rc = __dax_dev_pte_fault(dax_dev, vmf);
+		rc = __dev_dax_pte_fault(dev_dax, vmf);
 		break;
 	case PE_SIZE_PMD:
-		rc = __dax_dev_pmd_fault(dax_dev, vmf);
+		rc = __dev_dax_pmd_fault(dev_dax, vmf);
 		break;
 	case PE_SIZE_PUD:
-		rc = __dax_dev_pud_fault(dax_dev, vmf);
+		rc = __dev_dax_pud_fault(dev_dax, vmf);
 		break;
 	default:
-		return VM_FAULT_FALLBACK;
+		rc = VM_FAULT_SIGBUS;
 	}
-	srcu_read_unlock(&dax_srcu, id);
+	dax_read_unlock(id);
 
 	return rc;
 }
 
-static int dax_dev_fault(struct vm_fault *vmf)
+static int dev_dax_fault(struct vm_fault *vmf)
 {
-	return dax_dev_huge_fault(vmf, PE_SIZE_PTE);
+	return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
 }
 
-static const struct vm_operations_struct dax_dev_vm_ops = {
-	.fault = dax_dev_fault,
-	.huge_fault = dax_dev_huge_fault,
+static const struct vm_operations_struct dax_vm_ops = {
+	.fault = dev_dax_fault,
+	.huge_fault = dev_dax_huge_fault,
 };
 
 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
 {
-	struct dax_dev *dax_dev = filp->private_data;
-	int rc;
+	struct dev_dax *dev_dax = filp->private_data;
+	int rc, id;
 
-	dev_dbg(&dax_dev->dev, "%s\n", __func__);
+	dev_dbg(&dev_dax->dev, "%s\n", __func__);
 
-	rc = check_vma(dax_dev, vma, __func__);
+	/*
+	 * We lock to check dax_dev liveness and will re-check at
+	 * fault time.
+	 */
+	id = dax_read_lock();
+	rc = check_vma(dev_dax, vma, __func__);
+	dax_read_unlock(id);
 	if (rc)
 		return rc;
 
-	vma->vm_ops = &dax_dev_vm_ops;
+	vma->vm_ops = &dax_vm_ops;
 	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
 	return 0;
 }
@@ -574,13 +460,13 @@ static unsigned long dax_get_unmapped_area(struct file *filp,
 		unsigned long flags)
 {
 	unsigned long off, off_end, off_align, len_align, addr_align, align;
-	struct dax_dev *dax_dev = filp ? filp->private_data : NULL;
+	struct dev_dax *dev_dax = filp ? filp->private_data : NULL;
 	struct dax_region *dax_region;
 
-	if (!dax_dev || addr)
+	if (!dev_dax || addr)
 		goto out;
 
-	dax_region = dax_dev->region;
+	dax_region = dev_dax->region;
 	align = dax_region->align;
 	off = pgoff << PAGE_SHIFT;
 	off_end = off + len;
@@ -605,14 +491,15 @@ static unsigned long dax_get_unmapped_area(struct file *filp,
 
 static int dax_open(struct inode *inode, struct file *filp)
 {
-	struct dax_dev *dax_dev;
+	struct dax_device *dax_dev = inode_dax(inode);
+	struct inode *__dax_inode = dax_inode(dax_dev);
+	struct dev_dax *dev_dax = dax_get_private(dax_dev);
 
-	dax_dev = container_of(inode->i_cdev, struct dax_dev, cdev);
-	dev_dbg(&dax_dev->dev, "%s\n", __func__);
-	inode->i_mapping = dax_dev->inode->i_mapping;
-	inode->i_mapping->host = dax_dev->inode;
+	dev_dbg(&dev_dax->dev, "%s\n", __func__);
+	inode->i_mapping = __dax_inode->i_mapping;
+	inode->i_mapping->host = __dax_inode;
 	filp->f_mapping = inode->i_mapping;
-	filp->private_data = dax_dev;
+	filp->private_data = dev_dax;
 	inode->i_flags = S_DAX;
 
 	return 0;
@@ -620,9 +507,9 @@ static int dax_open(struct inode *inode, struct file *filp)
 
 static int dax_release(struct inode *inode, struct file *filp)
 {
-	struct dax_dev *dax_dev = filp->private_data;
+	struct dev_dax *dev_dax = filp->private_data;
 
-	dev_dbg(&dax_dev->dev, "%s\n", __func__);
+	dev_dbg(&dev_dax->dev, "%s\n", __func__);
 	return 0;
 }
 
@@ -635,51 +522,54 @@ static const struct file_operations dax_fops = {
 	.mmap = dax_mmap,
 };
 
-static void dax_dev_release(struct device *dev)
+static void dev_dax_release(struct device *dev)
 {
-	struct dax_dev *dax_dev = to_dax_dev(dev);
-	struct dax_region *dax_region = dax_dev->region;
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	struct dax_device *dax_dev = dev_dax->dax_dev;
 
-	ida_simple_remove(&dax_region->ida, dax_dev->id);
-	ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
+	ida_simple_remove(&dax_region->ida, dev_dax->id);
 	dax_region_put(dax_region);
-	iput(dax_dev->inode);
-	kfree(dax_dev);
+	put_dax(dax_dev);
+	kfree(dev_dax);
+}
+
+static void kill_dev_dax(struct dev_dax *dev_dax)
+{
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+	struct inode *inode = dax_inode(dax_dev);
+
+	kill_dax(dax_dev);
+	unmap_mapping_range(inode->i_mapping, 0, 0, 1);
 }
 
-static void unregister_dax_dev(void *dev)
+static void unregister_dev_dax(void *dev)
 {
-	struct dax_dev *dax_dev = to_dax_dev(dev);
-	struct cdev *cdev = &dax_dev->cdev;
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+	struct inode *inode = dax_inode(dax_dev);
+	struct cdev *cdev = inode->i_cdev;
 
 	dev_dbg(dev, "%s\n", __func__);
 
-	/*
-	 * Note, rcu is not protecting the liveness of dax_dev, rcu is
-	 * ensuring that any fault handlers that might have seen
-	 * dax_dev->alive == true, have completed.  Any fault handlers
-	 * that start after synchronize_srcu() has started will abort
-	 * upon seeing dax_dev->alive == false.
-	 */
-	dax_dev->alive = false;
-	synchronize_srcu(&dax_srcu);
-	unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
-	cdev_del(cdev);
-	device_unregister(dev);
+	kill_dev_dax(dev_dax);
+	cdev_device_del(cdev, dev);
+	put_device(dev);
 }
 
-struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
+struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
 		struct resource *res, int count)
 {
 	struct device *parent = dax_region->dev;
-	struct dax_dev *dax_dev;
-	int rc = 0, minor, i;
+	struct dax_device *dax_dev;
+	struct dev_dax *dev_dax;
+	struct inode *inode;
 	struct device *dev;
 	struct cdev *cdev;
-	dev_t dev_t;
+	int rc = 0, i;
 
-	dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
-	if (!dax_dev)
+	dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL);
+	if (!dev_dax)
 		return ERR_PTR(-ENOMEM);
 
 	for (i = 0; i < count; i++) {
@@ -689,115 +579,79 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
 			rc = -EINVAL;
 			break;
 		}
-		dax_dev->res[i].start = res[i].start;
-		dax_dev->res[i].end = res[i].end;
+		dev_dax->res[i].start = res[i].start;
+		dev_dax->res[i].end = res[i].end;
 	}
 
 	if (i < count)
 		goto err_id;
 
-	dax_dev->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
-	if (dax_dev->id < 0) {
-		rc = dax_dev->id;
+	dev_dax->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
+	if (dev_dax->id < 0) {
+		rc = dev_dax->id;
 		goto err_id;
 	}
 
-	minor = ida_simple_get(&dax_minor_ida, 0, 0, GFP_KERNEL);
-	if (minor < 0) {
-		rc = minor;
-		goto err_minor;
-	}
-
-	dev_t = MKDEV(MAJOR(dax_devt), minor);
-	dev = &dax_dev->dev;
-	dax_dev->inode = dax_inode_get(&dax_dev->cdev, dev_t);
-	if (!dax_dev->inode) {
-		rc = -ENOMEM;
-		goto err_inode;
-	}
+	/*
+	 * No 'host' or dax_operations since there is no access to this
+	 * device outside of mmap of the resulting character device.
+	 */
+	dax_dev = alloc_dax(dev_dax, NULL, NULL);
+	if (!dax_dev)
+		goto err_dax;
 
-	/* device_initialize() so cdev can reference kobj parent */
+	/* from here on we're committed to teardown via dax_dev_release() */
+	dev = &dev_dax->dev;
 	device_initialize(dev);
 
-	cdev = &dax_dev->cdev;
+	inode = dax_inode(dax_dev);
+	cdev = inode->i_cdev;
 	cdev_init(cdev, &dax_fops);
 	cdev->owner = parent->driver->owner;
-	cdev->kobj.parent = &dev->kobj;
-	rc = cdev_add(&dax_dev->cdev, dev_t, 1);
-	if (rc)
-		goto err_cdev;
 
-	/* from here on we're committed to teardown via dax_dev_release() */
-	dax_dev->num_resources = count;
-	dax_dev->alive = true;
-	dax_dev->region = dax_region;
+	dev_dax->num_resources = count;
+	dev_dax->dax_dev = dax_dev;
+	dev_dax->region = dax_region;
 	kref_get(&dax_region->kref);
 
-	dev->devt = dev_t;
+	dev->devt = inode->i_rdev;
 	dev->class = dax_class;
 	dev->parent = parent;
 	dev->groups = dax_attribute_groups;
-	dev->release = dax_dev_release;
-	dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
-	rc = device_add(dev);
+	dev->release = dev_dax_release;
+	dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id);
+
+	rc = cdev_device_add(cdev, dev);
 	if (rc) {
+		kill_dev_dax(dev_dax);
 		put_device(dev);
 		return ERR_PTR(rc);
 	}
 
-	rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
+	rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
 	if (rc)
 		return ERR_PTR(rc);
 
-	return dax_dev;
+	return dev_dax;
 
- err_cdev:
-	iput(dax_dev->inode);
- err_inode:
-	ida_simple_remove(&dax_minor_ida, minor);
- err_minor:
-	ida_simple_remove(&dax_region->ida, dax_dev->id);
+ err_dax:
+	ida_simple_remove(&dax_region->ida, dev_dax->id);
  err_id:
-	kfree(dax_dev);
+	kfree(dev_dax);
 
 	return ERR_PTR(rc);
 }
-EXPORT_SYMBOL_GPL(devm_create_dax_dev);
+EXPORT_SYMBOL_GPL(devm_create_dev_dax);
 
 static int __init dax_init(void)
 {
-	int rc;
-
-	rc = dax_inode_init();
-	if (rc)
-		return rc;
-
-	nr_dax = max(nr_dax, 256);
-	rc = alloc_chrdev_region(&dax_devt, 0, nr_dax, "dax");
-	if (rc)
-		goto err_chrdev;
-
 	dax_class = class_create(THIS_MODULE, "dax");
-	if (IS_ERR(dax_class)) {
-		rc = PTR_ERR(dax_class);
-		goto err_class;
-	}
-
-	return 0;
-
- err_class:
-	unregister_chrdev_region(dax_devt, nr_dax);
- err_chrdev:
-	dax_inode_exit();
-	return rc;
+	return PTR_ERR_OR_ZERO(dax_class);
 }
 
 static void __exit dax_exit(void)
 {
 	class_destroy(dax_class);
-	unregister_chrdev_region(dax_devt, nr_dax);
-	ida_destroy(&dax_minor_ida);
-	dax_inode_exit();
 }
 
 MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 033f49b31fdc..d4ca19bd74eb 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -16,7 +16,7 @@
 #include <linux/pfn_t.h>
 #include "../nvdimm/pfn.h"
 #include "../nvdimm/nd.h"
-#include "dax.h"
+#include "device-dax.h"
 
 struct dax_pmem {
 	struct device *dev;
@@ -61,8 +61,8 @@ static int dax_pmem_probe(struct device *dev)
 	int rc;
 	void *addr;
 	struct resource res;
-	struct dax_dev *dax_dev;
 	struct nd_pfn_sb *pfn_sb;
+	struct dev_dax *dev_dax;
 	struct dax_pmem *dax_pmem;
 	struct nd_region *nd_region;
 	struct nd_namespace_io *nsio;
@@ -130,12 +130,12 @@ static int dax_pmem_probe(struct device *dev)
 		return -ENOMEM;
 
 	/* TODO: support for subdividing a dax region... */
-	dax_dev = devm_create_dax_dev(dax_region, &res, 1);
+	dev_dax = devm_create_dev_dax(dax_region, &res, 1);
 
-	/* child dax_dev instances now own the lifetime of the dax_region */
+	/* child dev_dax instances now own the lifetime of the dax_region */
 	dax_region_put(dax_region);
 
-	return PTR_ERR_OR_ZERO(dax_dev);
+	return PTR_ERR_OR_ZERO(dev_dax);
 }
 
 static struct nd_device_driver dax_pmem_driver = {
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
new file mode 100644
index 000000000000..465dcd7317d5
--- /dev/null
+++ b/drivers/dax/super.c
@@ -0,0 +1,425 @@
+/*
+ * Copyright(c) 2017 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/pagemap.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/magic.h>
+#include <linux/cdev.h>
+#include <linux/hash.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+
+static int nr_dax = CONFIG_NR_DEV_DAX;
+module_param(nr_dax, int, S_IRUGO);
+MODULE_PARM_DESC(nr_dax, "max number of dax device instances");
+
+static dev_t dax_devt;
+DEFINE_STATIC_SRCU(dax_srcu);
+static struct vfsmount *dax_mnt;
+static DEFINE_IDA(dax_minor_ida);
+static struct kmem_cache *dax_cache __read_mostly;
+static struct super_block *dax_superblock __read_mostly;
+
+#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
+static struct hlist_head dax_host_list[DAX_HASH_SIZE];
+static DEFINE_SPINLOCK(dax_host_lock);
+
+int dax_read_lock(void)
+{
+	return srcu_read_lock(&dax_srcu);
+}
+EXPORT_SYMBOL_GPL(dax_read_lock);
+
+void dax_read_unlock(int id)
+{
+	srcu_read_unlock(&dax_srcu, id);
+}
+EXPORT_SYMBOL_GPL(dax_read_unlock);
+
+/**
+ * struct dax_device - anchor object for dax services
+ * @inode: core vfs
+ * @cdev: optional character interface for "device dax"
+ * @host: optional name for lookups where the device path is not available
+ * @private: dax driver private data
+ * @alive: !alive + rcu grace period == no new operations / mappings
+ */
+struct dax_device {
+	struct hlist_node list;
+	struct inode inode;
+	struct cdev cdev;
+	const char *host;
+	void *private;
+	bool alive;
+	const struct dax_operations *ops;
+};
+
+/**
+ * dax_direct_access() - translate a device pgoff to an absolute pfn
+ * @dax_dev: a dax_device instance representing the logical memory range
+ * @pgoff: offset in pages from the start of the device to translate
+ * @nr_pages: number of consecutive pages caller can handle relative to @pfn
+ * @kaddr: output parameter that returns a virtual address mapping of pfn
+ * @pfn: output parameter that returns an absolute pfn translation of @pgoff
+ *
+ * Return: negative errno if an error occurs, otherwise the number of
+ * pages accessible at the device relative @pgoff.
+ */
+long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
+		void **kaddr, pfn_t *pfn)
+{
+	long avail;
+
+	/*
+	 * The device driver is allowed to sleep, in order to make the
+	 * memory directly accessible.
+	 */
+	might_sleep();
+
+	if (!dax_dev)
+		return -EOPNOTSUPP;
+
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+
+	if (nr_pages < 0)
+		return nr_pages;
+
+	avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
+			kaddr, pfn);
+	if (!avail)
+		return -ERANGE;
+	return min(avail, nr_pages);
+}
+EXPORT_SYMBOL_GPL(dax_direct_access);
+
+bool dax_alive(struct dax_device *dax_dev)
+{
+	lockdep_assert_held(&dax_srcu);
+	return dax_dev->alive;
+}
+EXPORT_SYMBOL_GPL(dax_alive);
+
+static int dax_host_hash(const char *host)
+{
+	return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
+}
+
+/*
+ * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
+ * that any fault handlers or operations that might have seen
+ * dax_alive(), have completed.  Any operations that start after
+ * synchronize_srcu() has run will abort upon seeing !dax_alive().
+ */
+void kill_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+
+	dax_dev->alive = false;
+
+	synchronize_srcu(&dax_srcu);
+
+	spin_lock(&dax_host_lock);
+	hlist_del_init(&dax_dev->list);
+	spin_unlock(&dax_host_lock);
+
+	dax_dev->private = NULL;
+}
+EXPORT_SYMBOL_GPL(kill_dax);
+
+static struct inode *dax_alloc_inode(struct super_block *sb)
+{
+	struct dax_device *dax_dev;
+
+	dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL);
+	return &dax_dev->inode;
+}
+
+static struct dax_device *to_dax_dev(struct inode *inode)
+{
+	return container_of(inode, struct dax_device, inode);
+}
+
+static void dax_i_callback(struct rcu_head *head)
+{
+	struct inode *inode = container_of(head, struct inode, i_rcu);
+	struct dax_device *dax_dev = to_dax_dev(inode);
+
+	kfree(dax_dev->host);
+	dax_dev->host = NULL;
+	ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
+	kmem_cache_free(dax_cache, dax_dev);
+}
+
+static void dax_destroy_inode(struct inode *inode)
+{
+	struct dax_device *dax_dev = to_dax_dev(inode);
+
+	WARN_ONCE(dax_dev->alive,
+			"kill_dax() must be called before final iput()\n");
+	call_rcu(&inode->i_rcu, dax_i_callback);
+}
+
+static const struct super_operations dax_sops = {
+	.statfs = simple_statfs,
+	.alloc_inode = dax_alloc_inode,
+	.destroy_inode = dax_destroy_inode,
+	.drop_inode = generic_delete_inode,
+};
+
+static struct dentry *dax_mount(struct file_system_type *fs_type,
+		int flags, const char *dev_name, void *data)
+{
+	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
+}
+
+static struct file_system_type dax_fs_type = {
+	.name = "dax",
+	.mount = dax_mount,
+	.kill_sb = kill_anon_super,
+};
+
+static int dax_test(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	return inode->i_rdev == devt;
+}
+
+static int dax_set(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	inode->i_rdev = devt;
+	return 0;
+}
+
+static struct dax_device *dax_dev_get(dev_t devt)
+{
+	struct dax_device *dax_dev;
+	struct inode *inode;
+
+	inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
+			dax_test, dax_set, &devt);
+
+	if (!inode)
+		return NULL;
+
+	dax_dev = to_dax_dev(inode);
+	if (inode->i_state & I_NEW) {
+		dax_dev->alive = true;
+		inode->i_cdev = &dax_dev->cdev;
+		inode->i_mode = S_IFCHR;
+		inode->i_flags = S_DAX;
+		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+		unlock_new_inode(inode);
+	}
+
+	return dax_dev;
+}
+
+static void dax_add_host(struct dax_device *dax_dev, const char *host)
+{
+	int hash;
+
+	/*
+	 * Unconditionally init dax_dev since it's coming from a
+	 * non-zeroed slab cache
+	 */
+	INIT_HLIST_NODE(&dax_dev->list);
+	dax_dev->host = host;
+	if (!host)
+		return;
+
+	hash = dax_host_hash(host);
+	spin_lock(&dax_host_lock);
+	hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
+	spin_unlock(&dax_host_lock);
+}
+
+struct dax_device *alloc_dax(void *private, const char *__host,
+		const struct dax_operations *ops)
+{
+	struct dax_device *dax_dev;
+	const char *host;
+	dev_t devt;
+	int minor;
+
+	host = kstrdup(__host, GFP_KERNEL);
+	if (__host && !host)
+		return NULL;
+
+	minor = ida_simple_get(&dax_minor_ida, 0, nr_dax, GFP_KERNEL);
+	if (minor < 0)
+		goto err_minor;
+
+	devt = MKDEV(MAJOR(dax_devt), minor);
+	dax_dev = dax_dev_get(devt);
+	if (!dax_dev)
+		goto err_dev;
+
+	dax_add_host(dax_dev, host);
+	dax_dev->ops = ops;
+	dax_dev->private = private;
+	return dax_dev;
+
+ err_dev:
+	ida_simple_remove(&dax_minor_ida, minor);
+ err_minor:
+	kfree(host);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(alloc_dax);
+
+void put_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+	iput(&dax_dev->inode);
+}
+EXPORT_SYMBOL_GPL(put_dax);
+
+/**
+ * dax_get_by_host() - temporary lookup mechanism for filesystem-dax
+ * @host: alternate name for the device registered by a dax driver
+ */
+struct dax_device *dax_get_by_host(const char *host)
+{
+	struct dax_device *dax_dev, *found = NULL;
+	int hash, id;
+
+	if (!host)
+		return NULL;
+
+	hash = dax_host_hash(host);
+
+	id = dax_read_lock();
+	spin_lock(&dax_host_lock);
+	hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
+		if (!dax_alive(dax_dev)
+				|| strcmp(host, dax_dev->host) != 0)
+			continue;
+
+		if (igrab(&dax_dev->inode))
+			found = dax_dev;
+		break;
+	}
+	spin_unlock(&dax_host_lock);
+	dax_read_unlock(id);
+
+	return found;
+}
+EXPORT_SYMBOL_GPL(dax_get_by_host);
+
+/**
+ * inode_dax: convert a public inode into its dax_dev
+ * @inode: An inode with i_cdev pointing to a dax_dev
+ *
+ * Note this is not equivalent to to_dax_dev() which is for private
+ * internal use where we know the inode filesystem type == dax_fs_type.
+ */
+struct dax_device *inode_dax(struct inode *inode)
+{
+	struct cdev *cdev = inode->i_cdev;
+
+	return container_of(cdev, struct dax_device, cdev);
+}
+EXPORT_SYMBOL_GPL(inode_dax);
+
+struct inode *dax_inode(struct dax_device *dax_dev)
+{
+	return &dax_dev->inode;
+}
+EXPORT_SYMBOL_GPL(dax_inode);
+
+void *dax_get_private(struct dax_device *dax_dev)
+{
+	return dax_dev->private;
+}
+EXPORT_SYMBOL_GPL(dax_get_private);
+
+static void init_once(void *_dax_dev)
+{
+	struct dax_device *dax_dev = _dax_dev;
+	struct inode *inode = &dax_dev->inode;
+
+	inode_init_once(inode);
+}
+
+static int __dax_fs_init(void)
+{
+	int rc;
+
+	dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
+			(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
+			 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+			init_once);
+	if (!dax_cache)
+		return -ENOMEM;
+
+	rc = register_filesystem(&dax_fs_type);
+	if (rc)
+		goto err_register_fs;
+
+	dax_mnt = kern_mount(&dax_fs_type);
+	if (IS_ERR(dax_mnt)) {
+		rc = PTR_ERR(dax_mnt);
+		goto err_mount;
+	}
+	dax_superblock = dax_mnt->mnt_sb;
+
+	return 0;
+
+ err_mount:
+	unregister_filesystem(&dax_fs_type);
+ err_register_fs:
+	kmem_cache_destroy(dax_cache);
+
+	return rc;
+}
+
+static void __dax_fs_exit(void)
+{
+	kern_unmount(dax_mnt);
+	unregister_filesystem(&dax_fs_type);
+	kmem_cache_destroy(dax_cache);
+}
+
+static int __init dax_fs_init(void)
+{
+	int rc;
+
+	rc = __dax_fs_init();
+	if (rc)
+		return rc;
+
+	nr_dax = max(nr_dax, 256);
+	rc = alloc_chrdev_region(&dax_devt, 0, nr_dax, "dax");
+	if (rc)
+		__dax_fs_exit();
+	return rc;
+}
+
+static void __exit dax_fs_exit(void)
+{
+	unregister_chrdev_region(dax_devt, nr_dax);
+	ida_destroy(&dax_minor_ida);
+	__dax_fs_exit();
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+subsys_initcall(dax_fs_init);
+module_exit(dax_fs_exit);