Merge branch 'for-4.9/dax' into libnvdimm-for-next

7 files changed, 365 insertions, 233 deletions

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index cedab7572de3..daadd20aa936 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -23,4 +23,9 @@ config DEV_DAX_PMEM
 
 	  Say Y if unsure
 
+config NR_DEV_DAX
+	int "Maximum number of Device-DAX instances"
+	default 32768
+	range 256 2147483647
+
 endif
diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index 29f600f2c447..0e499bfca41c 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -13,15 +13,25 @@
 #include <linux/pagemap.h>
 #include <linux/module.h>
 #include <linux/device.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>
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include "dax.h"
 
-static int dax_major;
+static dev_t dax_devt;
 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");
 
 /**
  * struct dax_region - mapping infrastructure for dax devices
@@ -48,7 +58,7 @@ struct dax_region {
  * struct dax_dev - subdivision of a dax region
  * @region - parent region
  * @dev - device backing the character device
- * @kref - enable this data to be tracked in filp->private_data
+ * @cdev - core chardev data
  * @alive - !alive + rcu grace period == no new mappings can be established
  * @id - child id in the region
  * @num_resources - number of physical address extents in this device
@@ -56,41 +66,139 @@ struct dax_region {
  */
 struct dax_dev {
 	struct dax_region *region;
-	struct device *dev;
-	struct kref kref;
+	struct inode *inode;
+	struct device dev;
+	struct cdev cdev;
 	bool alive;
 	int id;
 	int num_resources;
 	struct resource res[0];
 };
 
-static void dax_region_free(struct kref *kref)
+static struct inode *dax_alloc_inode(struct super_block *sb)
 {
-	struct dax_region *dax_region;
+	return kmem_cache_alloc(dax_cache, GFP_KERNEL);
+}
 
-	dax_region = container_of(kref, struct dax_region, kref);
-	kfree(dax_region);
+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);
 }
 
-void dax_region_put(struct dax_region *dax_region)
+static void dax_destroy_inode(struct inode *inode)
 {
-	kref_put(&dax_region->kref, dax_region_free);
+	call_rcu(&inode->i_rcu, dax_i_callback);
 }
-EXPORT_SYMBOL_GPL(dax_region_put);
 
-static void dax_dev_free(struct kref *kref)
+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)
 {
-	struct dax_dev *dax_dev;
+	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
+}
 
-	dax_dev = container_of(kref, struct dax_dev, kref);
-	dax_region_put(dax_dev->region);
-	kfree(dax_dev);
+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_dev_put(struct dax_dev *dax_dev)
+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;
+
+	dax_region = container_of(kref, struct dax_region, kref);
+	kfree(dax_region);
+}
+
+void dax_region_put(struct dax_region *dax_region)
 {
-	kref_put(&dax_dev->kref, dax_dev_free);
+	kref_put(&dax_region->kref, dax_region_free);
 }
+EXPORT_SYMBOL_GPL(dax_region_put);
 
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 		struct resource *res, unsigned int align, void *addr,
@@ -98,8 +206,11 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 {
 	struct dax_region *dax_region;
 
-	dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
+	if (!IS_ALIGNED(res->start, align)
+			|| !IS_ALIGNED(resource_size(res), align))
+		return NULL;
 
+	dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
 	if (!dax_region)
 		return NULL;
 
@@ -116,10 +227,15 @@ 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)
+{
+	return container_of(dev, struct dax_dev, dev);
+}
+
 static ssize_t size_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
-	struct dax_dev *dax_dev = dev_get_drvdata(dev);
+	struct dax_dev *dax_dev = to_dax_dev(dev);
 	unsigned long long size = 0;
 	int i;
 
@@ -144,180 +260,11 @@ static const struct attribute_group *dax_attribute_groups[] = {
 	NULL,
 };
 
-static void unregister_dax_dev(void *_dev)
-{
-	struct device *dev = _dev;
-	struct dax_dev *dax_dev = dev_get_drvdata(dev);
-	struct dax_region *dax_region = dax_dev->region;
-
-	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_rcu() has started will abort
-	 * upon seeing dax_dev->alive == false.
-	 */
-	dax_dev->alive = false;
-	synchronize_rcu();
-
-	get_device(dev);
-	device_unregister(dev);
-	ida_simple_remove(&dax_region->ida, dax_dev->id);
-	ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
-	put_device(dev);
-	dax_dev_put(dax_dev);
-}
-
-int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
-		int count)
-{
-	struct device *parent = dax_region->dev;
-	struct dax_dev *dax_dev;
-	struct device *dev;
-	int rc, minor;
-	dev_t dev_t;
-
-	dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
-	if (!dax_dev)
-		return -ENOMEM;
-	memcpy(dax_dev->res, res, sizeof(*res) * count);
-	dax_dev->num_resources = count;
-	kref_init(&dax_dev->kref);
-	dax_dev->alive = true;
-	dax_dev->region = dax_region;
-	kref_get(&dax_region->kref);
-
-	dax_dev->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
-	if (dax_dev->id < 0) {
-		rc = dax_dev->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(dax_major, minor);
-	dev = device_create_with_groups(dax_class, parent, dev_t, dax_dev,
-			dax_attribute_groups, "dax%d.%d", dax_region->id,
-			dax_dev->id);
-	if (IS_ERR(dev)) {
-		rc = PTR_ERR(dev);
-		goto err_create;
-	}
-	dax_dev->dev = dev;
-
-	rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
-	if (rc)
-		return rc;
-
-	return 0;
-
- err_create:
-	ida_simple_remove(&dax_minor_ida, minor);
- err_minor:
-	ida_simple_remove(&dax_region->ida, dax_dev->id);
- err_id:
-	dax_dev_put(dax_dev);
-
-	return rc;
-}
-EXPORT_SYMBOL_GPL(devm_create_dax_dev);
-
-/* return an unmapped area aligned to the dax region specified alignment */
-static unsigned long dax_dev_get_unmapped_area(struct file *filp,
-		unsigned long addr, unsigned long len, unsigned long pgoff,
-		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 dax_region *dax_region;
-
-	if (!dax_dev || addr)
-		goto out;
-
-	dax_region = dax_dev->region;
-	align = dax_region->align;
-	off = pgoff << PAGE_SHIFT;
-	off_end = off + len;
-	off_align = round_up(off, align);
-
-	if ((off_end <= off_align) || ((off_end - off_align) < align))
-		goto out;
-
-	len_align = len + align;
-	if ((off + len_align) < off)
-		goto out;
-
-	addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
-			pgoff, flags);
-	if (!IS_ERR_VALUE(addr_align)) {
-		addr_align += (off - addr_align) & (align - 1);
-		return addr_align;
-	}
- out:
-	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
-}
-
-static int __match_devt(struct device *dev, const void *data)
-{
-	const dev_t *devt = data;
-
-	return dev->devt == *devt;
-}
-
-static struct device *dax_dev_find(dev_t dev_t)
-{
-	return class_find_device(dax_class, NULL, &dev_t, __match_devt);
-}
-
-static int dax_dev_open(struct inode *inode, struct file *filp)
-{
-	struct dax_dev *dax_dev = NULL;
-	struct device *dev;
-
-	dev = dax_dev_find(inode->i_rdev);
-	if (!dev)
-		return -ENXIO;
-
-	device_lock(dev);
-	dax_dev = dev_get_drvdata(dev);
-	if (dax_dev) {
-		dev_dbg(dev, "%s\n", __func__);
-		filp->private_data = dax_dev;
-		kref_get(&dax_dev->kref);
-		inode->i_flags = S_DAX;
-	}
-	device_unlock(dev);
-
-	if (!dax_dev) {
-		put_device(dev);
-		return -ENXIO;
-	}
-	return 0;
-}
-
-static int dax_dev_release(struct inode *inode, struct file *filp)
-{
-	struct dax_dev *dax_dev = filp->private_data;
-	struct device *dev = dax_dev->dev;
-
-	dev_dbg(dax_dev->dev, "%s\n", __func__);
-	dax_dev_put(dax_dev);
-	put_device(dev);
-
-	return 0;
-}
-
 static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 		const char *func)
 {
 	struct dax_region *dax_region = dax_dev->region;
-	struct device *dev = dax_dev->dev;
+	struct device *dev = &dax_dev->dev;
 	unsigned long mask;
 
 	if (!dax_dev->alive)
@@ -382,7 +329,7 @@ static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 		struct vm_fault *vmf)
 {
 	unsigned long vaddr = (unsigned long) vmf->virtual_address;
-	struct device *dev = dax_dev->dev;
+	struct device *dev = &dax_dev->dev;
 	struct dax_region *dax_region;
 	int rc = VM_FAULT_SIGBUS;
 	phys_addr_t phys;
@@ -422,7 +369,7 @@ static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	struct file *filp = vma->vm_file;
 	struct dax_dev *dax_dev = filp->private_data;
 
-	dev_dbg(dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
+	dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 			current->comm, (vmf->flags & FAULT_FLAG_WRITE)
 			? "write" : "read", vma->vm_start, vma->vm_end);
 	rcu_read_lock();
@@ -437,7 +384,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
 		unsigned int flags)
 {
 	unsigned long pmd_addr = addr & PMD_MASK;
-	struct device *dev = dax_dev->dev;
+	struct device *dev = &dax_dev->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	pgoff_t pgoff;
@@ -479,7 +426,7 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	struct file *filp = vma->vm_file;
 	struct dax_dev *dax_dev = filp->private_data;
 
-	dev_dbg(dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
+	dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 			current->comm, (flags & FAULT_FLAG_WRITE)
 			? "write" : "read", vma->vm_start, vma->vm_end);
 
@@ -490,81 +437,257 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 	return rc;
 }
 
-static void dax_dev_vm_open(struct vm_area_struct *vma)
-{
-	struct file *filp = vma->vm_file;
-	struct dax_dev *dax_dev = filp->private_data;
-
-	dev_dbg(dax_dev->dev, "%s\n", __func__);
-	kref_get(&dax_dev->kref);
-}
-
-static void dax_dev_vm_close(struct vm_area_struct *vma)
-{
-	struct file *filp = vma->vm_file;
-	struct dax_dev *dax_dev = filp->private_data;
-
-	dev_dbg(dax_dev->dev, "%s\n", __func__);
-	dax_dev_put(dax_dev);
-}
-
 static const struct vm_operations_struct dax_dev_vm_ops = {
 	.fault = dax_dev_fault,
 	.pmd_fault = dax_dev_pmd_fault,
-	.open = dax_dev_vm_open,
-	.close = dax_dev_vm_close,
 };
 
-static int dax_dev_mmap(struct file *filp, struct vm_area_struct *vma)
+static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct dax_dev *dax_dev = filp->private_data;
 	int rc;
 
-	dev_dbg(dax_dev->dev, "%s\n", __func__);
+	dev_dbg(&dax_dev->dev, "%s\n", __func__);
 
 	rc = check_vma(dax_dev, vma, __func__);
 	if (rc)
 		return rc;
 
-	kref_get(&dax_dev->kref);
 	vma->vm_ops = &dax_dev_vm_ops;
 	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
 	return 0;
+}
+
+/* return an unmapped area aligned to the dax region specified alignment */
+static unsigned long dax_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		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 dax_region *dax_region;
+
+	if (!dax_dev || addr)
+		goto out;
+
+	dax_region = dax_dev->region;
+	align = dax_region->align;
+	off = pgoff << PAGE_SHIFT;
+	off_end = off + len;
+	off_align = round_up(off, align);
+
+	if ((off_end <= off_align) || ((off_end - off_align) < align))
+		goto out;
+
+	len_align = len + align;
+	if ((off + len_align) < off)
+		goto out;
 
+	addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
+			pgoff, flags);
+	if (!IS_ERR_VALUE(addr_align)) {
+		addr_align += (off - addr_align) & (align - 1);
+		return addr_align;
+	}
+ out:
+	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+
+static int dax_open(struct inode *inode, struct file *filp)
+{
+	struct dax_dev *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;
+	filp->f_mapping = inode->i_mapping;
+	filp->private_data = dax_dev;
+	inode->i_flags = S_DAX;
+
+	return 0;
+}
+
+static int dax_release(struct inode *inode, struct file *filp)
+{
+	struct dax_dev *dax_dev = filp->private_data;
+
+	dev_dbg(&dax_dev->dev, "%s\n", __func__);
+	return 0;
 }
 
 static const struct file_operations dax_fops = {
 	.llseek = noop_llseek,
 	.owner = THIS_MODULE,
-	.open = dax_dev_open,
-	.release = dax_dev_release,
-	.get_unmapped_area = dax_dev_get_unmapped_area,
-	.mmap = dax_dev_mmap,
+	.open = dax_open,
+	.release = dax_release,
+	.get_unmapped_area = dax_get_unmapped_area,
+	.mmap = dax_mmap,
 };
 
+static void dax_dev_release(struct device *dev)
+{
+	struct dax_dev *dax_dev = to_dax_dev(dev);
+	struct dax_region *dax_region = dax_dev->region;
+
+	ida_simple_remove(&dax_region->ida, dax_dev->id);
+	ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
+	dax_region_put(dax_region);
+	iput(dax_dev->inode);
+	kfree(dax_dev);
+}
+
+static void unregister_dax_dev(void *dev)
+{
+	struct dax_dev *dax_dev = to_dax_dev(dev);
+	struct cdev *cdev = &dax_dev->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_rcu() has started will abort
+	 * upon seeing dax_dev->alive == false.
+	 */
+	dax_dev->alive = false;
+	synchronize_rcu();
+	unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
+	cdev_del(cdev);
+	device_unregister(dev);
+}
+
+struct dax_dev *devm_create_dax_dev(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 device *dev;
+	struct cdev *cdev;
+	dev_t dev_t;
+
+	dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
+	if (!dax_dev)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < count; i++) {
+		if (!IS_ALIGNED(res[i].start, dax_region->align)
+				|| !IS_ALIGNED(resource_size(&res[i]),
+					dax_region->align)) {
+			rc = -EINVAL;
+			break;
+		}
+		dax_dev->res[i].start = res[i].start;
+		dax_dev->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;
+		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;
+	}
+
+	/* device_initialize() so cdev can reference kobj parent */
+	device_initialize(dev);
+
+	cdev = &dax_dev->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;
+	kref_get(&dax_region->kref);
+
+	dev->devt = dev_t;
+	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);
+	if (rc) {
+		put_device(dev);
+		return ERR_PTR(rc);
+	}
+
+	rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
+	if (rc)
+		return ERR_PTR(rc);
+
+	return dax_dev;
+
+ 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_id:
+	kfree(dax_dev);
+
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(devm_create_dax_dev);
+
 static int __init dax_init(void)
 {
 	int rc;
 
-	rc = register_chrdev(0, "dax", &dax_fops);
-	if (rc < 0)
+	rc = dax_inode_init();
+	if (rc)
 		return rc;
-	dax_major = 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)) {
-		unregister_chrdev(dax_major, "dax");
-		return PTR_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;
 }
 
 static void __exit dax_exit(void)
 {
 	class_destroy(dax_class);
-	unregister_chrdev(dax_major, "dax");
+	unregister_chrdev_region(dax_devt, nr_dax);
 	ida_destroy(&dax_minor_ida);
+	dax_inode_exit();
 }
 
 MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
index d8b8f1f25054..ddd829ab58c0 100644
--- a/drivers/dax/dax.h
+++ b/drivers/dax/dax.h
@@ -13,12 +13,13 @@
 #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);
-int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
-		int count);
+struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
+		struct resource *res, int count);
 #endif /* __DAX_H__ */
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 1f01e98c83c7..9630d8837ba9 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -24,7 +24,7 @@ struct dax_pmem {
 	struct completion cmp;
 };
 
-struct dax_pmem *to_dax_pmem(struct percpu_ref *ref)
+static struct dax_pmem *to_dax_pmem(struct percpu_ref *ref)
 {
 	return container_of(ref, struct dax_pmem, ref);
 }
@@ -61,6 +61,7 @@ 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 dax_pmem *dax_pmem;
 	struct nd_region *nd_region;
@@ -126,12 +127,12 @@ static int dax_pmem_probe(struct device *dev)
 		return -ENOMEM;
 
 	/* TODO: support for subdividing a dax region... */
-	rc = devm_create_dax_dev(dax_region, &res, 1);
+	dax_dev = devm_create_dax_dev(dax_region, &res, 1);
 
 	/* child dax_dev instances now own the lifetime of the dax_region */
 	dax_region_put(dax_region);
 
-	return rc;
+	return PTR_ERR_OR_ZERO(dax_dev);
 }
 
 static struct nd_device_driver dax_pmem_driver = {
diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index 124c2432ac9c..8b2b740d6679 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -89,7 +89,7 @@ config NVDIMM_PFN
 	  Select Y if unsure
 
 config NVDIMM_DAX
-	bool "NVDIMM DAX: Raw access to persistent memory"
+	tristate "NVDIMM DAX: Raw access to persistent memory"
 	default LIBNVDIMM
 	depends on NVDIMM_PFN
 	help
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 6edd825231c5..44a240c4bb65 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -406,6 +406,7 @@ void cd_forget(struct inode *inode)
 	spin_lock(&cdev_lock);
 	list_del_init(&inode->i_devices);
 	inode->i_cdev = NULL;
+	inode->i_mapping = &inode->i_data;
 	spin_unlock(&cdev_lock);
 }
 
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index e398beac67b8..9bd559472c92 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -65,6 +65,7 @@
 #define V9FS_MAGIC		0x01021997
 
 #define BDEVFS_MAGIC            0x62646576
+#define DAXFS_MAGIC             0x64646178
 #define BINFMTFS_MAGIC          0x42494e4d
 #define DEVPTS_SUPER_MAGIC	0x1cd1
 #define FUTEXFS_SUPER_MAGIC	0xBAD1DEA