drivers/dax/device.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright(c) 2016-2018 Intel Corporation. All rights reserved. */
 #include <linux/memremap.h>
 #include <linux/pagemap.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/pfn_t.h>
 #include <linux/cdev.h>
 #include <linux/slab.h>
 #include <linux/dax.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include "dax-private.h"
 #include "bus.h"

 static struct dev_dax *ref_to_dev_dax(struct percpu_ref *ref)
 {
 	return container_of(ref, struct dev_dax, ref);
 }

 static void dev_dax_percpu_release(struct percpu_ref *ref)
 {
 	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

 	dev_dbg(&dev_dax->dev, "%s\n", __func__);
 	complete(&dev_dax->cmp);
 }

 static void dev_dax_percpu_exit(struct percpu_ref *ref)
 {
 	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

 	dev_dbg(&dev_dax->dev, "%s\n", __func__);
 	wait_for_completion(&dev_dax->cmp);
 	percpu_ref_exit(ref);
 }

 static void dev_dax_percpu_kill(struct percpu_ref *data)
 {
 	struct percpu_ref *ref = data;
 	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

 	dev_dbg(&dev_dax->dev, "%s\n", __func__);
 	percpu_ref_kill(ref);
 }

 static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
 		const char *func)
 {
 	struct dax_region *dax_region = dev_dax->region;
 	struct device *dev = &dev_dax->dev;
 	unsigned long mask;

 	if (!dax_alive(dev_dax->dax_dev))
 		return -ENXIO;

 	/* prevent private mappings from being established */
 	if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
 		dev_info_ratelimited(dev,
 				"%s: %s: fail, attempted private mapping\n",
 				current->comm, func);
 		return -EINVAL;
 	}

 	mask = dax_region->align - 1;
 	if (vma->vm_start & mask || vma->vm_end & mask) {
 		dev_info_ratelimited(dev,
 				"%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
 				current->comm, func, vma->vm_start, vma->vm_end,
 				mask);
 		return -EINVAL;
 	}

 	if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) == PFN_DEV
 			&& (vma->vm_flags & VM_DONTCOPY) == 0) {
 		dev_info_ratelimited(dev,
 				"%s: %s: fail, dax range requires MADV_DONTFORK\n",
 				current->comm, func);
 		return -EINVAL;
 	}

 	if (!vma_is_dax(vma)) {
 		dev_info_ratelimited(dev,
 				"%s: %s: fail, vma is not DAX capable\n",
 				current->comm, func);
 		return -EINVAL;
 	}

 	return 0;
 }

 /* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
 __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
 		unsigned long size)
 {
 	struct resource *res = &dev_dax->region->res;
 	phys_addr_t phys;

 	phys = pgoff * PAGE_SIZE + res->start;
 	if (phys >= res->start && phys <= res->end) {
 		if (phys + size - 1 <= res->end)
 			return phys;
 	}

 	return -1;
 }

 static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
 				struct vm_fault *vmf, pfn_t *pfn)
 {
 	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	unsigned int fault_size = PAGE_SIZE;

 	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;

 	dax_region = dev_dax->region;
 	if (dax_region->align > PAGE_SIZE) {
 		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
 			dax_region->align, fault_size);
 		return VM_FAULT_SIGBUS;
 	}

 	if (fault_size != dax_region->align)
 		return VM_FAULT_SIGBUS;

 	phys = dax_pgoff_to_phys(dev_dax, vmf->pgoff, PAGE_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", vmf->pgoff);
 		return VM_FAULT_SIGBUS;
 	}

 	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

 	return vmf_insert_mixed(vmf->vma, vmf->address, *pfn);
 }

 static vm_fault_t __dev_dax_pmd_fault(struct dev_dax *dev_dax,
 				struct vm_fault *vmf, pfn_t *pfn)
 {
 	unsigned long pmd_addr = vmf->address & PMD_MASK;
 	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	pgoff_t pgoff;
 	unsigned int fault_size = PMD_SIZE;

 	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;

 	dax_region = dev_dax->region;
 	if (dax_region->align > PMD_SIZE) {
 		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
 			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, "region lacks devmap flags\n");
 		return VM_FAULT_SIGBUS;
 	}

 	if (fault_size < dax_region->align)
 		return VM_FAULT_SIGBUS;
 	else if (fault_size > dax_region->align)
 		return VM_FAULT_FALLBACK;

 	/* if we are outside of the VMA */
 	if (pmd_addr < vmf->vma->vm_start ||
 			(pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
 		return VM_FAULT_SIGBUS;

 	pgoff = linear_page_index(vmf->vma, pmd_addr);
 	phys = dax_pgoff_to_phys(dev_dax, pgoff, PMD_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
 		return VM_FAULT_SIGBUS;
 	}

 	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

 	return vmf_insert_pfn_pmd(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
 }

 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
 				struct vm_fault *vmf, pfn_t *pfn)
 {
 	unsigned long pud_addr = vmf->address & PUD_MASK;
 	struct device *dev = &dev_dax->dev;
 	struct dax_region *dax_region;
 	phys_addr_t phys;
 	pgoff_t pgoff;
 	unsigned int fault_size = PUD_SIZE;


 	if (check_vma(dev_dax, vmf->vma, __func__))
 		return VM_FAULT_SIGBUS;

 	dax_region = dev_dax->region;
 	if (dax_region->align > PUD_SIZE) {
 		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
 			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, "region lacks devmap flags\n");
 		return VM_FAULT_SIGBUS;
 	}

 	if (fault_size < dax_region->align)
 		return VM_FAULT_SIGBUS;
 	else if (fault_size > dax_region->align)
 		return VM_FAULT_FALLBACK;

 	/* if we are outside of the VMA */
 	if (pud_addr < vmf->vma->vm_start ||
 			(pud_addr + PUD_SIZE) > vmf->vma->vm_end)
 		return VM_FAULT_SIGBUS;

 	pgoff = linear_page_index(vmf->vma, pud_addr);
 	phys = dax_pgoff_to_phys(dev_dax, pgoff, PUD_SIZE);
 	if (phys == -1) {
 		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
 		return VM_FAULT_SIGBUS;
 	}

 	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

 	return vmf_insert_pfn_pud(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
 }
 #else
 static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
 				struct vm_fault *vmf, pfn_t *pfn)
 {
 	return VM_FAULT_FALLBACK;
 }
 #endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */

 static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
 		enum page_entry_size pe_size)
 {
 	struct file *filp = vmf->vma->vm_file;
 	unsigned long fault_size;
 	vm_fault_t rc = VM_FAULT_SIGBUS;
 	int id;
 	pfn_t pfn;
 	struct dev_dax *dev_dax = filp->private_data;

 	dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) size = %d\n", current->comm,
 			(vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
 			vmf->vma->vm_start, vmf->vma->vm_end, pe_size);

 	id = dax_read_lock();
 	switch (pe_size) {
 	case PE_SIZE_PTE:
 		fault_size = PAGE_SIZE;
 		rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
 		break;
 	case PE_SIZE_PMD:
 		fault_size = PMD_SIZE;
 		rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
 		break;
 	case PE_SIZE_PUD:
 		fault_size = PUD_SIZE;
 		rc = __dev_dax_pud_fault(dev_dax, vmf, &pfn);
 		break;
 	default:
 		rc = VM_FAULT_SIGBUS;
 	}

 	if (rc == VM_FAULT_NOPAGE) {
 		unsigned long i;
 		pgoff_t pgoff;

 		/*
 		 * In the device-dax case the only possibility for a
 		 * VM_FAULT_NOPAGE result is when device-dax capacity is
 		 * mapped. No need to consider the zero page, or racing
 		 * conflicting mappings.
 		 */
 		pgoff = linear_page_index(vmf->vma, vmf->address
 				& ~(fault_size - 1));
 		for (i = 0; i < fault_size / PAGE_SIZE; i++) {
 			struct page *page;

 			page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
 			if (page->mapping)
 				continue;
 			page->mapping = filp->f_mapping;
 			page->index = pgoff + i;
 		}
 	}
 	dax_read_unlock(id);

 	return rc;
 }

 static vm_fault_t dev_dax_fault(struct vm_fault *vmf)
 {
 	return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
 }

 static int dev_dax_split(struct vm_area_struct *vma, unsigned long addr)
 {
 	struct file *filp = vma->vm_file;
 	struct dev_dax *dev_dax = filp->private_data;
 	struct dax_region *dax_region = dev_dax->region;

 	if (!IS_ALIGNED(addr, dax_region->align))
 		return -EINVAL;
 	return 0;
 }

 static unsigned long dev_dax_pagesize(struct vm_area_struct *vma)
 {
 	struct file *filp = vma->vm_file;
 	struct dev_dax *dev_dax = filp->private_data;
 	struct dax_region *dax_region = dev_dax->region;

 	return dax_region->align;
 }

 static const struct vm_operations_struct dax_vm_ops = {
 	.fault = dev_dax_fault,
 	.huge_fault = dev_dax_huge_fault,
 	.split = dev_dax_split,
 	.pagesize = dev_dax_pagesize,
 };

 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct dev_dax *dev_dax = filp->private_data;
 	int rc, id;

 	dev_dbg(&dev_dax->dev, "trace\n");

 	/*
 	 * 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_vm_ops;
 	vma->vm_flags |= 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 dev_dax *dev_dax = filp ? filp->private_data : NULL;
 	struct dax_region *dax_region;

 	if (!dev_dax || addr)
 		goto out;

 	dax_region = dev_dax->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 const struct address_space_operations dev_dax_aops = {
 	.set_page_dirty		= noop_set_page_dirty,
 	.invalidatepage		= noop_invalidatepage,
 };

 static int dax_open(struct inode *inode, struct file *filp)
 {
 	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);

 	dev_dbg(&dev_dax->dev, "trace\n");
 	inode->i_mapping = __dax_inode->i_mapping;
 	inode->i_mapping->host = __dax_inode;
 	inode->i_mapping->a_ops = &dev_dax_aops;
 	filp->f_mapping = inode->i_mapping;
 	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
 	filp->private_data = dev_dax;
 	inode->i_flags = S_DAX;

 	return 0;
 }

 static int dax_release(struct inode *inode, struct file *filp)
 {
 	struct dev_dax *dev_dax = filp->private_data;

 	dev_dbg(&dev_dax->dev, "trace\n");
 	return 0;
 }

 static const struct file_operations dax_fops = {
 	.llseek = noop_llseek,
 	.owner = THIS_MODULE,
 	.open = dax_open,
 	.release = dax_release,
 	.get_unmapped_area = dax_get_unmapped_area,
 	.mmap = dax_mmap,
 	.mmap_supported_flags = MAP_SYNC,
 };

 static void dev_dax_cdev_del(void *cdev)
 {
 	cdev_del(cdev);
 }

 static void dev_dax_kill(void *dev_dax)
 {
 	kill_dev_dax(dev_dax);
 }

 int dev_dax_probe(struct device *dev)
 {
 	struct dev_dax *dev_dax = to_dev_dax(dev);
 	struct dax_device *dax_dev = dev_dax->dax_dev;
 	struct resource *res = &dev_dax->region->res;
 	struct inode *inode;
 	struct cdev *cdev;
 	void *addr;
 	int rc;

 	/* 1:1 map region resource range to device-dax instance range */
 	if (!devm_request_mem_region(dev, res->start, resource_size(res),
 				dev_name(dev))) {
 		dev_warn(dev, "could not reserve region %pR\n", res);
 		return -EBUSY;
 	}

 	init_completion(&dev_dax->cmp);
 	rc = percpu_ref_init(&dev_dax->ref, dev_dax_percpu_release, 0,
 			GFP_KERNEL);
 	if (rc)
 		return rc;

 	dev_dax->pgmap.ref = &dev_dax->ref;
 	dev_dax->pgmap.kill = dev_dax_percpu_kill;
 	dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
 	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);

 	inode = dax_inode(dax_dev);
 	cdev = inode->i_cdev;
 	cdev_init(cdev, &dax_fops);
 	if (dev->class) {
 		/* for the CONFIG_DEV_DAX_PMEM_COMPAT case */
 		cdev->owner = dev->parent->driver->owner;
 	} else
 		cdev->owner = dev->driver->owner;
 	cdev_set_parent(cdev, &dev->kobj);
 	rc = cdev_add(cdev, dev->devt, 1);
 	if (rc)
 		return rc;

 	rc = devm_add_action_or_reset(dev, dev_dax_cdev_del, cdev);
 	if (rc)
 		return rc;

 	run_dax(dax_dev);
 	return devm_add_action_or_reset(dev, dev_dax_kill, dev_dax);
 }
 EXPORT_SYMBOL_GPL(dev_dax_probe);

 static int dev_dax_remove(struct device *dev)
 {
 	/* all probe actions are unwound by devm */
 	return 0;
 }

 static struct dax_device_driver device_dax_driver = {
 	.drv = {
 		.probe = dev_dax_probe,
 		.remove = dev_dax_remove,
 	},
 	.match_always = 1,
 };

 static int __init dax_init(void)
 {
 	return dax_driver_register(&device_dax_driver);
 }

 static void __exit dax_exit(void)
 {
 	dax_driver_unregister(&device_dax_driver);
 }

 MODULE_AUTHOR("Intel Corporation");
 MODULE_LICENSE("GPL v2");
 module_init(dax_init);
 module_exit(dax_exit);
 MODULE_ALIAS_DAX_DEVICE(0);
	// SPDX-License-Identifier: GPL-2.0
	/* Copyright(c) 2016-2018 Intel Corporation. All rights reserved. */
	#include <linux/memremap.h>
	#include <linux/pagemap.h>
	#include <linux/module.h>
	#include <linux/device.h>
	#include <linux/pfn_t.h>
	#include <linux/cdev.h>
	#include <linux/slab.h>
	#include <linux/dax.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/mman.h>
	#include "dax-private.h"
	#include "bus.h"

	static struct dev_dax ref_to_dev_dax(struct percpu_ref ref)
	{
	return container_of(ref, struct dev_dax, ref);
	}

	static void dev_dax_percpu_release(struct percpu_ref *ref)
	{
	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

	dev_dbg(&dev_dax->dev, "%s\n", __func__);
	complete(&dev_dax->cmp);
	}

	static void dev_dax_percpu_exit(struct percpu_ref *ref)
	{
	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

	dev_dbg(&dev_dax->dev, "%s\n", __func__);
	wait_for_completion(&dev_dax->cmp);
	percpu_ref_exit(ref);
	}

	static void dev_dax_percpu_kill(struct percpu_ref *data)
	{
	struct percpu_ref *ref = data;
	struct dev_dax *dev_dax = ref_to_dev_dax(ref);

	dev_dbg(&dev_dax->dev, "%s\n", __func__);
	percpu_ref_kill(ref);
	}

	static int check_vma(struct dev_dax dev_dax, struct vm_area_struct vma,
	const char *func)
	{
	struct dax_region *dax_region = dev_dax->region;
	struct device *dev = &dev_dax->dev;
	unsigned long mask;

	if (!dax_alive(dev_dax->dax_dev))
	return -ENXIO;

	/* prevent private mappings from being established */
	if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
	dev_info_ratelimited(dev,
	"%s: %s: fail, attempted private mapping\n",
	current->comm, func);
	return -EINVAL;
	}

	mask = dax_region->align - 1;
	if (vma->vm_start & mask \|\| vma->vm_end & mask) {
	dev_info_ratelimited(dev,
	"%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
	current->comm, func, vma->vm_start, vma->vm_end,
	mask);
	return -EINVAL;
	}

	if ((dax_region->pfn_flags & (PFN_DEV\|PFN_MAP)) == PFN_DEV
	&& (vma->vm_flags & VM_DONTCOPY) == 0) {
	dev_info_ratelimited(dev,
	"%s: %s: fail, dax range requires MADV_DONTFORK\n",
	current->comm, func);
	return -EINVAL;
	}

	if (!vma_is_dax(vma)) {
	dev_info_ratelimited(dev,
	"%s: %s: fail, vma is not DAX capable\n",
	current->comm, func);
	return -EINVAL;
	}

	return 0;
	}

	/* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
	__weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
	unsigned long size)
	{
	struct resource *res = &dev_dax->region->res;
	phys_addr_t phys;

	phys = pgoff * PAGE_SIZE + res->start;
	if (phys >= res->start && phys <= res->end) {
	if (phys + size - 1 <= res->end)
	return phys;
	}

	return -1;
	}

	static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
	struct vm_fault vmf, pfn_t pfn)
	{
	struct device *dev = &dev_dax->dev;
	struct dax_region *dax_region;
	phys_addr_t phys;
	unsigned int fault_size = PAGE_SIZE;

	if (check_vma(dev_dax, vmf->vma, __func__))
	return VM_FAULT_SIGBUS;

	dax_region = dev_dax->region;
	if (dax_region->align > PAGE_SIZE) {
	dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
	dax_region->align, fault_size);
	return VM_FAULT_SIGBUS;
	}

	if (fault_size != dax_region->align)
	return VM_FAULT_SIGBUS;

	phys = dax_pgoff_to_phys(dev_dax, vmf->pgoff, PAGE_SIZE);
	if (phys == -1) {
	dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", vmf->pgoff);
	return VM_FAULT_SIGBUS;
	}

	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

	return vmf_insert_mixed(vmf->vma, vmf->address, *pfn);
	}

	static vm_fault_t __dev_dax_pmd_fault(struct dev_dax *dev_dax,
	struct vm_fault vmf, pfn_t pfn)
	{
	unsigned long pmd_addr = vmf->address & PMD_MASK;
	struct device *dev = &dev_dax->dev;
	struct dax_region *dax_region;
	phys_addr_t phys;
	pgoff_t pgoff;
	unsigned int fault_size = PMD_SIZE;

	if (check_vma(dev_dax, vmf->vma, __func__))
	return VM_FAULT_SIGBUS;

	dax_region = dev_dax->region;
	if (dax_region->align > PMD_SIZE) {
	dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
	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, "region lacks devmap flags\n");
	return VM_FAULT_SIGBUS;
	}

	if (fault_size < dax_region->align)
	return VM_FAULT_SIGBUS;
	else if (fault_size > dax_region->align)
	return VM_FAULT_FALLBACK;

	/* if we are outside of the VMA */
	if (pmd_addr < vmf->vma->vm_start \|\|
	(pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
	return VM_FAULT_SIGBUS;

	pgoff = linear_page_index(vmf->vma, pmd_addr);
	phys = dax_pgoff_to_phys(dev_dax, pgoff, PMD_SIZE);
	if (phys == -1) {
	dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
	return VM_FAULT_SIGBUS;
	}

	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

	return vmf_insert_pfn_pmd(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
	}

	#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
	static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
	struct vm_fault vmf, pfn_t pfn)
	{
	unsigned long pud_addr = vmf->address & PUD_MASK;
	struct device *dev = &dev_dax->dev;
	struct dax_region *dax_region;
	phys_addr_t phys;
	pgoff_t pgoff;
	unsigned int fault_size = PUD_SIZE;


	if (check_vma(dev_dax, vmf->vma, __func__))
	return VM_FAULT_SIGBUS;

	dax_region = dev_dax->region;
	if (dax_region->align > PUD_SIZE) {
	dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
	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, "region lacks devmap flags\n");
	return VM_FAULT_SIGBUS;
	}

	if (fault_size < dax_region->align)
	return VM_FAULT_SIGBUS;
	else if (fault_size > dax_region->align)
	return VM_FAULT_FALLBACK;

	/* if we are outside of the VMA */
	if (pud_addr < vmf->vma->vm_start \|\|
	(pud_addr + PUD_SIZE) > vmf->vma->vm_end)
	return VM_FAULT_SIGBUS;

	pgoff = linear_page_index(vmf->vma, pud_addr);
	phys = dax_pgoff_to_phys(dev_dax, pgoff, PUD_SIZE);
	if (phys == -1) {
	dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
	return VM_FAULT_SIGBUS;
	}

	*pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

	return vmf_insert_pfn_pud(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
	}
	#else
	static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
	struct vm_fault vmf, pfn_t pfn)
	{
	return VM_FAULT_FALLBACK;
	}
	#endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */

	static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
	enum page_entry_size pe_size)
	{
	struct file *filp = vmf->vma->vm_file;
	unsigned long fault_size;
	vm_fault_t rc = VM_FAULT_SIGBUS;
	int id;
	pfn_t pfn;
	struct dev_dax *dev_dax = filp->private_data;

	dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) size = %d\n", current->comm,
	(vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
	vmf->vma->vm_start, vmf->vma->vm_end, pe_size);

	id = dax_read_lock();
	switch (pe_size) {
	case PE_SIZE_PTE:
	fault_size = PAGE_SIZE;
	rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
	break;
	case PE_SIZE_PMD:
	fault_size = PMD_SIZE;
	rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
	break;
	case PE_SIZE_PUD:
	fault_size = PUD_SIZE;
	rc = __dev_dax_pud_fault(dev_dax, vmf, &pfn);
	break;
	default:
	rc = VM_FAULT_SIGBUS;
	}

	if (rc == VM_FAULT_NOPAGE) {
	unsigned long i;
	pgoff_t pgoff;

	/*
	* In the device-dax case the only possibility for a
	* VM_FAULT_NOPAGE result is when device-dax capacity is
	* mapped. No need to consider the zero page, or racing
	* conflicting mappings.
	*/
	pgoff = linear_page_index(vmf->vma, vmf->address
	& ~(fault_size - 1));
	for (i = 0; i < fault_size / PAGE_SIZE; i++) {
	struct page *page;

	page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
	if (page->mapping)
	continue;
	page->mapping = filp->f_mapping;
	page->index = pgoff + i;
	}
	}
	dax_read_unlock(id);

	return rc;
	}

	static vm_fault_t dev_dax_fault(struct vm_fault *vmf)
	{
	return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
	}

	static int dev_dax_split(struct vm_area_struct *vma, unsigned long addr)
	{
	struct file *filp = vma->vm_file;
	struct dev_dax *dev_dax = filp->private_data;
	struct dax_region *dax_region = dev_dax->region;

	if (!IS_ALIGNED(addr, dax_region->align))
	return -EINVAL;
	return 0;
	}

	static unsigned long dev_dax_pagesize(struct vm_area_struct *vma)
	{
	struct file *filp = vma->vm_file;
	struct dev_dax *dev_dax = filp->private_data;
	struct dax_region *dax_region = dev_dax->region;

	return dax_region->align;
	}

	static const struct vm_operations_struct dax_vm_ops = {
	.fault = dev_dax_fault,
	.huge_fault = dev_dax_huge_fault,
	.split = dev_dax_split,
	.pagesize = dev_dax_pagesize,
	};

	static int dax_mmap(struct file filp, struct vm_area_struct vma)
	{
	struct dev_dax *dev_dax = filp->private_data;
	int rc, id;

	dev_dbg(&dev_dax->dev, "trace\n");

	/*
	* 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_vm_ops;
	vma->vm_flags \|= 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 dev_dax *dev_dax = filp ? filp->private_data : NULL;
	struct dax_region *dax_region;

	if (!dev_dax \|\| addr)
	goto out;

	dax_region = dev_dax->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 const struct address_space_operations dev_dax_aops = {
	.set_page_dirty = noop_set_page_dirty,
	.invalidatepage = noop_invalidatepage,
	};

	static int dax_open(struct inode inode, struct file filp)
	{
	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);

	dev_dbg(&dev_dax->dev, "trace\n");
	inode->i_mapping = __dax_inode->i_mapping;
	inode->i_mapping->host = __dax_inode;
	inode->i_mapping->a_ops = &dev_dax_aops;
	filp->f_mapping = inode->i_mapping;
	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
	filp->private_data = dev_dax;
	inode->i_flags = S_DAX;

	return 0;
	}

	static int dax_release(struct inode inode, struct file filp)
	{
	struct dev_dax *dev_dax = filp->private_data;

	dev_dbg(&dev_dax->dev, "trace\n");
	return 0;
	}

	static const struct file_operations dax_fops = {
	.llseek = noop_llseek,
	.owner = THIS_MODULE,
	.open = dax_open,
	.release = dax_release,
	.get_unmapped_area = dax_get_unmapped_area,
	.mmap = dax_mmap,
	.mmap_supported_flags = MAP_SYNC,
	};

	static void dev_dax_cdev_del(void *cdev)
	{
	cdev_del(cdev);
	}

	static void dev_dax_kill(void *dev_dax)
	{
	kill_dev_dax(dev_dax);
	}

	int dev_dax_probe(struct device *dev)
	{
	struct dev_dax *dev_dax = to_dev_dax(dev);
	struct dax_device *dax_dev = dev_dax->dax_dev;
	struct resource *res = &dev_dax->region->res;
	struct inode *inode;
	struct cdev *cdev;
	void *addr;
	int rc;

	/* 1:1 map region resource range to device-dax instance range */
	if (!devm_request_mem_region(dev, res->start, resource_size(res),
	dev_name(dev))) {
	dev_warn(dev, "could not reserve region %pR\n", res);
	return -EBUSY;
	}

	init_completion(&dev_dax->cmp);
	rc = percpu_ref_init(&dev_dax->ref, dev_dax_percpu_release, 0,
	GFP_KERNEL);
	if (rc)
	return rc;

	dev_dax->pgmap.ref = &dev_dax->ref;
	dev_dax->pgmap.kill = dev_dax_percpu_kill;
	dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
	if (IS_ERR(addr))
	return PTR_ERR(addr);

	inode = dax_inode(dax_dev);
	cdev = inode->i_cdev;
	cdev_init(cdev, &dax_fops);
	if (dev->class) {
	/* for the CONFIG_DEV_DAX_PMEM_COMPAT case */
	cdev->owner = dev->parent->driver->owner;
	} else
	cdev->owner = dev->driver->owner;
	cdev_set_parent(cdev, &dev->kobj);
	rc = cdev_add(cdev, dev->devt, 1);
	if (rc)
	return rc;

	rc = devm_add_action_or_reset(dev, dev_dax_cdev_del, cdev);
	if (rc)
	return rc;

	run_dax(dax_dev);
	return devm_add_action_or_reset(dev, dev_dax_kill, dev_dax);
	}
	EXPORT_SYMBOL_GPL(dev_dax_probe);

	static int dev_dax_remove(struct device *dev)
	{
	/* all probe actions are unwound by devm */
	return 0;
	}

	static struct dax_device_driver device_dax_driver = {
	.drv = {
	.probe = dev_dax_probe,
	.remove = dev_dax_remove,
	},
	.match_always = 1,
	};

	static int __init dax_init(void)
	{
	return dax_driver_register(&device_dax_driver);
	}

	static void __exit dax_exit(void)
	{
	dax_driver_unregister(&device_dax_driver);
	}

	MODULE_AUTHOR("Intel Corporation");
	MODULE_LICENSE("GPL v2");
	module_init(dax_init);
	module_exit(dax_exit);
	MODULE_ALIAS_DAX_DEVICE(0);