2 files changed, 323 insertions, 0 deletions

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 86ffbaa891ad..cedab7572de3 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -1,6 +1,7 @@
 menuconfig DEV_DAX
         tristate "DAX: direct access to differentiated memory"
         default m if NVDIMM_DAX
+        depends on TRANSPARENT_HUGEPAGE
         help
           Support raw access to differentiated (persistence, bandwidth,
           latency...) memory via an mmap(2) capable character
diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index 4c22a40f2335..b891a129b275 100644
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -49,6 +49,7 @@ struct dax_region {
  * @region - parent region
  * @dev - device backing the character device
  * @kref - enable this data to be tracked in filp->private_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
  * @res - array of physical address ranges
@@ -57,6 +58,7 @@ struct dax_dev {
         struct dax_region *region;
         struct device *dev;
         struct kref kref;
+        bool alive;
         int id;
         int num_resources;
         struct resource res[0];
@@ -150,6 +152,16 @@ static void unregister_dax_dev(void *_dev)
 
         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);
@@ -173,6 +185,7 @@ int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
         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);
 
@@ -217,9 +230,318 @@ int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
 }
 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;
+        unsigned long mask;
+
+        if (!dax_dev->alive)
+                return -ENXIO;
+
+        /* prevent private / writable mappings from being established */
+        if ((vma->vm_flags & (VM_NORESERVE|VM_SHARED|VM_WRITE)) == VM_WRITE) {
+                dev_info(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(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(dev, "%s: %s: fail, dax range requires MADV_DONTFORK\n",
+                                current->comm, func);
+                return -EINVAL;
+        }
+
+        if (!vma_is_dax(vma)) {
+                dev_info(dev, "%s: %s: fail, vma is not DAX capable\n",
+                                current->comm, func);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static phys_addr_t pgoff_to_phys(struct dax_dev *dax_dev, 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];
+                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 (phys + size - 1 <= res->end)
+                        return phys;
+        }
+
+        return -1;
+}
+
+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 dax_region *dax_region;
+        int rc = VM_FAULT_SIGBUS;
+        phys_addr_t phys;
+        pfn_t pfn;
+
+        if (check_vma(dax_dev, vma, __func__))
+                return VM_FAULT_SIGBUS;
+
+        dax_region = dax_dev->region;
+        if (dax_region->align > PAGE_SIZE) {
+                dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+                return VM_FAULT_SIGBUS;
+        }
+
+        phys = pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
+        if (phys == -1) {
+                dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
+                                vmf->pgoff);
+                return VM_FAULT_SIGBUS;
+        }
+
+        pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
+
+        rc = vm_insert_mixed(vma, vaddr, pfn);
+
+        if (rc == -ENOMEM)
+                return VM_FAULT_OOM;
+        if (rc < 0 && rc != -EBUSY)
+                return VM_FAULT_SIGBUS;
+
+        return VM_FAULT_NOPAGE;
+}
+
+static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+        int rc;
+        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__,
+                        current->comm, (vmf->flags & FAULT_FLAG_WRITE)
+                        ? "write" : "read", vma->vm_start, vma->vm_end);
+        rcu_read_lock();
+        rc = __dax_dev_fault(dax_dev, vma, vmf);
+        rcu_read_unlock();
+
+        return rc;
+}
+
+static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
+                struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd,
+                unsigned int flags)
+{
+        unsigned long pmd_addr = addr & PMD_MASK;
+        struct device *dev = dax_dev->dev;
+        struct dax_region *dax_region;
+        phys_addr_t phys;
+        pgoff_t pgoff;
+        pfn_t pfn;
+
+        if (check_vma(dax_dev, vma, __func__))
+                return VM_FAULT_SIGBUS;
+
+        dax_region = dax_dev->region;
+        if (dax_region->align > PMD_SIZE) {
+                dev_dbg(dev, "%s: alignment > fault size\n", __func__);
+                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__);
+                return VM_FAULT_SIGBUS;
+        }
+
+        pgoff = linear_page_index(vma, pmd_addr);
+        phys = pgoff_to_phys(dax_dev, pgoff, PAGE_SIZE);
+        if (phys == -1) {
+                dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
+                                pgoff);
+                return VM_FAULT_SIGBUS;
+        }
+
+        pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
+
+        return vmf_insert_pfn_pmd(vma, addr, pmd, pfn,
+                        flags & FAULT_FLAG_WRITE);
+}
+
+static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
+                pmd_t *pmd, unsigned int flags)
+{
+        int rc;
+        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__,
+                        current->comm, (flags & FAULT_FLAG_WRITE)
+                        ? "write" : "read", vma->vm_start, vma->vm_end);
+
+        rcu_read_lock();
+        rc = __dax_dev_pmd_fault(dax_dev, vma, addr, pmd, flags);
+        rcu_read_unlock();
+
+        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)
+{
+        struct dax_dev *dax_dev = filp->private_data;
+        int rc;
+
+        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;
+
+}
+
 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,
 };
 
 static int __init dax_init(void)