drivers/dax/dax.c

   1 /*
   2  * Copyright(c) 2016 Intel Corporation. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  */
  13 #include <linux/pagemap.h>
  14 #include <linux/module.h>
  15 #include <linux/device.h>
  16 #include <linux/mount.h>
  17 #include <linux/pfn_t.h>
  18 #include <linux/hash.h>
  19 #include <linux/cdev.h>
  20 #include <linux/slab.h>
  21 #include <linux/dax.h>
  22 #include <linux/fs.h>
  23 #include <linux/mm.h>
  24 #include "dax.h"
  25
  26 static dev_t dax_devt;
  27 static struct class *dax_class;
  28 static DEFINE_IDA(dax_minor_ida);
  29 static int nr_dax = CONFIG_NR_DEV_DAX;
  30 module_param(nr_dax, int, S_IRUGO);
  31 static struct vfsmount *dax_mnt;
  32 static struct kmem_cache *dax_cache __read_mostly;
  33 static struct super_block *dax_superblock __read_mostly;
  34 MODULE_PARM_DESC(nr_dax, "max number of device-dax instances");
  35
  36 /**
  37  * struct dax_region - mapping infrastructure for dax devices
  38  * @id: kernel-wide unique region for a memory range
  39  * @base: linear address corresponding to @res
  40  * @kref: to pin while other agents have a need to do lookups
  41  * @dev: parent device backing this region
  42  * @align: allocation and mapping alignment for child dax devices
  43  * @res: physical address range of the region
  44  * @pfn_flags: identify whether the pfns are paged back or not
  45  */
  46 struct dax_region {
  47         int id;
  48         struct ida ida;
  49         void *base;
  50         struct kref kref;
  51         struct device *dev;
  52         unsigned int align;
  53         struct resource res;
  54         unsigned long pfn_flags;
  55 };
  56
  57 /**
  58  * struct dax_dev - subdivision of a dax region
  59  * @region - parent region
  60  * @dev - device backing the character device
  61  * @cdev - core chardev data
  62  * @alive - !alive + rcu grace period == no new mappings can be established
  63  * @id - child id in the region
  64  * @num_resources - number of physical address extents in this device
  65  * @res - array of physical address ranges
  66  */
  67 struct dax_dev {
  68         struct dax_region *region;
  69         struct inode *inode;
  70         struct device dev;
  71         struct cdev cdev;
  72         bool alive;
  73         int id;
  74         int num_resources;
  75         struct resource res[0];
  76 };
  77
  78 static struct inode *dax_alloc_inode(struct super_block *sb)
  79 {
  80         return kmem_cache_alloc(dax_cache, GFP_KERNEL);
  81 }
  82
  83 static void dax_i_callback(struct rcu_head *head)
  84 {
  85         struct inode *inode = container_of(head, struct inode, i_rcu);
  86
  87         kmem_cache_free(dax_cache, inode);
  88 }
  89
  90 static void dax_destroy_inode(struct inode *inode)
  91 {
  92         call_rcu(&inode->i_rcu, dax_i_callback);
  93 }
  94
  95 static const struct super_operations dax_sops = {
  96         .statfs = simple_statfs,
  97         .alloc_inode = dax_alloc_inode,
  98         .destroy_inode = dax_destroy_inode,
  99         .drop_inode = generic_delete_inode,
 100 };
 101
 102 static struct dentry *dax_mount(struct file_system_type *fs_type,
 103                 int flags, const char *dev_name, void *data)
 104 {
 105         return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
 106 }
 107
 108 static struct file_system_type dax_type = {
 109         .name = "dax",
 110         .mount = dax_mount,
 111         .kill_sb = kill_anon_super,
 112 };
 113
 114 static int dax_test(struct inode *inode, void *data)
 115 {
 116         return inode->i_cdev == data;
 117 }
 118
 119 static int dax_set(struct inode *inode, void *data)
 120 {
 121         inode->i_cdev = data;
 122         return 0;
 123 }
 124
 125 static struct inode *dax_inode_get(struct cdev *cdev, dev_t devt)
 126 {
 127         struct inode *inode;
 128
 129         inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
 130                         dax_test, dax_set, cdev);
 131
 132         if (!inode)
 133                 return NULL;
 134
 135         if (inode->i_state & I_NEW) {
 136                 inode->i_mode = S_IFCHR;
 137                 inode->i_flags = S_DAX;
 138                 inode->i_rdev = devt;
 139                 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 140                 unlock_new_inode(inode);
 141         }
 142         return inode;
 143 }
 144
 145 static void init_once(void *inode)
 146 {
 147         inode_init_once(inode);
 148 }
 149
 150 static int dax_inode_init(void)
 151 {
 152         int rc;
 153
 154         dax_cache = kmem_cache_create("dax_cache", sizeof(struct inode), 0,
 155                         (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
 156                          SLAB_MEM_SPREAD|SLAB_ACCOUNT),
 157                         init_once);
 158         if (!dax_cache)
 159                 return -ENOMEM;
 160
 161         rc = register_filesystem(&dax_type);
 162         if (rc)
 163                 goto err_register_fs;
 164
 165         dax_mnt = kern_mount(&dax_type);
 166         if (IS_ERR(dax_mnt)) {
 167                 rc = PTR_ERR(dax_mnt);
 168                 goto err_mount;
 169         }
 170         dax_superblock = dax_mnt->mnt_sb;
 171
 172         return 0;
 173
 174  err_mount:
 175         unregister_filesystem(&dax_type);
 176  err_register_fs:
 177         kmem_cache_destroy(dax_cache);
 178
 179         return rc;
 180 }
 181
 182 static void dax_inode_exit(void)
 183 {
 184         kern_unmount(dax_mnt);
 185         unregister_filesystem(&dax_type);
 186         kmem_cache_destroy(dax_cache);
 187 }
 188
 189 static void dax_region_free(struct kref *kref)
 190 {
 191         struct dax_region *dax_region;
 192
 193         dax_region = container_of(kref, struct dax_region, kref);
 194         kfree(dax_region);
 195 }
 196
 197 void dax_region_put(struct dax_region *dax_region)
 198 {
 199         kref_put(&dax_region->kref, dax_region_free);
 200 }
 201 EXPORT_SYMBOL_GPL(dax_region_put);
 202
 203 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 204                 struct resource *res, unsigned int align, void *addr,
 205                 unsigned long pfn_flags)
 206 {
 207         struct dax_region *dax_region;
 208
 209         if (!IS_ALIGNED(res->start, align)
 210                         || !IS_ALIGNED(resource_size(res), align))
 211                 return NULL;
 212
 213         dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
 214         if (!dax_region)
 215                 return NULL;
 216
 217         memcpy(&dax_region->res, res, sizeof(*res));
 218         dax_region->pfn_flags = pfn_flags;
 219         kref_init(&dax_region->kref);
 220         dax_region->id = region_id;
 221         ida_init(&dax_region->ida);
 222         dax_region->align = align;
 223         dax_region->dev = parent;
 224         dax_region->base = addr;
 225
 226         return dax_region;
 227 }
 228 EXPORT_SYMBOL_GPL(alloc_dax_region);
 229
 230 static struct dax_dev *to_dax_dev(struct device *dev)
 231 {
 232         return container_of(dev, struct dax_dev, dev);
 233 }
 234
 235 static ssize_t size_show(struct device *dev,
 236                 struct device_attribute *attr, char *buf)
 237 {
 238         struct dax_dev *dax_dev = to_dax_dev(dev);
 239         unsigned long long size = 0;
 240         int i;
 241
 242         for (i = 0; i < dax_dev->num_resources; i++)
 243                 size += resource_size(&dax_dev->res[i]);
 244
 245         return sprintf(buf, "%llu\n", size);
 246 }
 247 static DEVICE_ATTR_RO(size);
 248
 249 static struct attribute *dax_device_attributes[] = {
 250         &dev_attr_size.attr,
 251         NULL,
 252 };
 253
 254 static const struct attribute_group dax_device_attribute_group = {
 255         .attrs = dax_device_attributes,
 256 };
 257
 258 static const struct attribute_group *dax_attribute_groups[] = {
 259         &dax_device_attribute_group,
 260         NULL,
 261 };
 262
 263 static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 264                 const char *func)
 265 {
 266         struct dax_region *dax_region = dax_dev->region;
 267         struct device *dev = &dax_dev->dev;
 268         unsigned long mask;
 269
 270         if (!dax_dev->alive)
 271                 return -ENXIO;
 272
 273         /* prevent private mappings from being established */
 274         if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
 275                 dev_info(dev, "%s: %s: fail, attempted private mapping\n",
 276                                 current->comm, func);
 277                 return -EINVAL;
 278         }
 279
 280         mask = dax_region->align - 1;
 281         if (vma->vm_start & mask || vma->vm_end & mask) {
 282                 dev_info(dev, "%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
 283                                 current->comm, func, vma->vm_start, vma->vm_end,
 284                                 mask);
 285                 return -EINVAL;
 286         }
 287
 288         if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) == PFN_DEV
 289                         && (vma->vm_flags & VM_DONTCOPY) == 0) {
 290                 dev_info(dev, "%s: %s: fail, dax range requires MADV_DONTFORK\n",
 291                                 current->comm, func);
 292                 return -EINVAL;
 293         }
 294
 295         if (!vma_is_dax(vma)) {
 296                 dev_info(dev, "%s: %s: fail, vma is not DAX capable\n",
 297                                 current->comm, func);
 298                 return -EINVAL;
 299         }
 300
 301         return 0;
 302 }
 303
 304 static phys_addr_t pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
 305                 unsigned long size)
 306 {
 307         struct resource *res;
 308         phys_addr_t phys;
 309         int i;
 310
 311         for (i = 0; i < dax_dev->num_resources; i++) {
 312                 res = &dax_dev->res[i];
 313                 phys = pgoff * PAGE_SIZE + res->start;
 314                 if (phys >= res->start && phys <= res->end)
 315                         break;
 316                 pgoff -= PHYS_PFN(resource_size(res));
 317         }
 318
 319         if (i < dax_dev->num_resources) {
 320                 res = &dax_dev->res[i];
 321                 if (phys + size - 1 <= res->end)
 322                         return phys;
 323         }
 324
 325         return -1;
 326 }
 327
 328 static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 329                 struct vm_fault *vmf)
 330 {
 331         struct device *dev = &dax_dev->dev;
 332         struct dax_region *dax_region;
 333         int rc = VM_FAULT_SIGBUS;
 334         phys_addr_t phys;
 335         pfn_t pfn;
 336
 337         if (check_vma(dax_dev, vma, __func__))
 338                 return VM_FAULT_SIGBUS;
 339
 340         dax_region = dax_dev->region;
 341         if (dax_region->align > PAGE_SIZE) {
 342                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 343                 return VM_FAULT_SIGBUS;
 344         }
 345
 346         phys = pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
 347         if (phys == -1) {
 348                 dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 349                                 vmf->pgoff);
 350                 return VM_FAULT_SIGBUS;
 351         }
 352
 353         pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
 354
 355         rc = vm_insert_mixed(vma, vmf->address, pfn);
 356
 357         if (rc == -ENOMEM)
 358                 return VM_FAULT_OOM;
 359         if (rc < 0 && rc != -EBUSY)
 360                 return VM_FAULT_SIGBUS;
 361
 362         return VM_FAULT_NOPAGE;
 363 }
 364
 365 static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 366 {
 367         int rc;
 368         struct file *filp = vma->vm_file;
 369         struct dax_dev *dax_dev = filp->private_data;
 370
 371         dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 372                         current->comm, (vmf->flags & FAULT_FLAG_WRITE)
 373                         ? "write" : "read", vma->vm_start, vma->vm_end);
 374         rcu_read_lock();
 375         rc = __dax_dev_fault(dax_dev, vma, vmf);
 376         rcu_read_unlock();
 377
 378         return rc;
 379 }
 380
 381 static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
 382                 struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd,
 383                 unsigned int flags)
 384 {
 385         unsigned long pmd_addr = addr & PMD_MASK;
 386         struct device *dev = &dax_dev->dev;
 387         struct dax_region *dax_region;
 388         phys_addr_t phys;
 389         pgoff_t pgoff;
 390         pfn_t pfn;
 391
 392         if (check_vma(dax_dev, vma, __func__))
 393                 return VM_FAULT_SIGBUS;
 394
 395         dax_region = dax_dev->region;
 396         if (dax_region->align > PMD_SIZE) {
 397                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 398                 return VM_FAULT_SIGBUS;
 399         }
 400
 401         /* dax pmd mappings require pfn_t_devmap() */
 402         if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
 403                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 404                 return VM_FAULT_SIGBUS;
 405         }
 406
 407         pgoff = linear_page_index(vma, pmd_addr);
 408         phys = pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
 409         if (phys == -1) {
 410                 dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 411                                 pgoff);
 412                 return VM_FAULT_SIGBUS;
 413         }
 414
 415         pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
 416
 417         return vmf_insert_pfn_pmd(vma, addr, pmd, pfn,
 418                         flags & FAULT_FLAG_WRITE);
 419 }
 420
 421 static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 422                 pmd_t *pmd, unsigned int flags)
 423 {
 424         int rc;
 425         struct file *filp = vma->vm_file;
 426         struct dax_dev *dax_dev = filp->private_data;
 427
 428         dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 429                         current->comm, (flags & FAULT_FLAG_WRITE)
 430                         ? "write" : "read", vma->vm_start, vma->vm_end);
 431
 432         rcu_read_lock();
 433         rc = __dax_dev_pmd_fault(dax_dev, vma, addr, pmd, flags);
 434         rcu_read_unlock();
 435
 436         return rc;
 437 }
 438
 439 static const struct vm_operations_struct dax_dev_vm_ops = {
 440         .fault = dax_dev_fault,
 441         .pmd_fault = dax_dev_pmd_fault,
 442 };
 443
 444 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
 445 {
 446         struct dax_dev *dax_dev = filp->private_data;
 447         int rc;
 448
 449         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 450
 451         rc = check_vma(dax_dev, vma, __func__);
 452         if (rc)
 453                 return rc;
 454
 455         vma->vm_ops = &dax_dev_vm_ops;
 456         vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
 457         return 0;
 458 }
 459
 460 /* return an unmapped area aligned to the dax region specified alignment */
 461 static unsigned long dax_get_unmapped_area(struct file *filp,
 462                 unsigned long addr, unsigned long len, unsigned long pgoff,
 463                 unsigned long flags)
 464 {
 465         unsigned long off, off_end, off_align, len_align, addr_align, align;
 466         struct dax_dev *dax_dev = filp ? filp->private_data : NULL;
 467         struct dax_region *dax_region;
 468
 469         if (!dax_dev || addr)
 470                 goto out;
 471
 472         dax_region = dax_dev->region;
 473         align = dax_region->align;
 474         off = pgoff << PAGE_SHIFT;
 475         off_end = off + len;
 476         off_align = round_up(off, align);
 477
 478         if ((off_end <= off_align) || ((off_end - off_align) < align))
 479                 goto out;
 480
 481         len_align = len + align;
 482         if ((off + len_align) < off)
 483                 goto out;
 484
 485         addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
 486                         pgoff, flags);
 487         if (!IS_ERR_VALUE(addr_align)) {
 488                 addr_align += (off - addr_align) & (align - 1);
 489                 return addr_align;
 490         }
 491  out:
 492         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 493 }
 494
 495 static int dax_open(struct inode *inode, struct file *filp)
 496 {
 497         struct dax_dev *dax_dev;
 498
 499         dax_dev = container_of(inode->i_cdev, struct dax_dev, cdev);
 500         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 501         inode->i_mapping = dax_dev->inode->i_mapping;
 502         inode->i_mapping->host = dax_dev->inode;
 503         filp->f_mapping = inode->i_mapping;
 504         filp->private_data = dax_dev;
 505         inode->i_flags = S_DAX;
 506
 507         return 0;
 508 }
 509
 510 static int dax_release(struct inode *inode, struct file *filp)
 511 {
 512         struct dax_dev *dax_dev = filp->private_data;
 513
 514         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 515         return 0;
 516 }
 517
 518 static const struct file_operations dax_fops = {
 519         .llseek = noop_llseek,
 520         .owner = THIS_MODULE,
 521         .open = dax_open,
 522         .release = dax_release,
 523         .get_unmapped_area = dax_get_unmapped_area,
 524         .mmap = dax_mmap,
 525 };
 526
 527 static void dax_dev_release(struct device *dev)
 528 {
 529         struct dax_dev *dax_dev = to_dax_dev(dev);
 530         struct dax_region *dax_region = dax_dev->region;
 531
 532         ida_simple_remove(&dax_region->ida, dax_dev->id);
 533         ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
 534         dax_region_put(dax_region);
 535         iput(dax_dev->inode);
 536         kfree(dax_dev);
 537 }
 538
 539 static void unregister_dax_dev(void *dev)
 540 {
 541         struct dax_dev *dax_dev = to_dax_dev(dev);
 542         struct cdev *cdev = &dax_dev->cdev;
 543
 544         dev_dbg(dev, "%s\n", __func__);
 545
 546         /*
 547          * Note, rcu is not protecting the liveness of dax_dev, rcu is
 548          * ensuring that any fault handlers that might have seen
 549          * dax_dev->alive == true, have completed.  Any fault handlers
 550          * that start after synchronize_rcu() has started will abort
 551          * upon seeing dax_dev->alive == false.
 552          */
 553         dax_dev->alive = false;
 554         synchronize_rcu();
 555         unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
 556         cdev_del(cdev);
 557         device_unregister(dev);
 558 }
 559
 560 struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
 561                 struct resource *res, int count)
 562 {
 563         struct device *parent = dax_region->dev;
 564         struct dax_dev *dax_dev;
 565         int rc = 0, minor, i;
 566         struct device *dev;
 567         struct cdev *cdev;
 568         dev_t dev_t;
 569
 570         dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
 571         if (!dax_dev)
 572                 return ERR_PTR(-ENOMEM);
 573
 574         for (i = 0; i < count; i++) {
 575                 if (!IS_ALIGNED(res[i].start, dax_region->align)
 576                                 || !IS_ALIGNED(resource_size(&res[i]),
 577                                         dax_region->align)) {
 578                         rc = -EINVAL;
 579                         break;
 580                 }
 581                 dax_dev->res[i].start = res[i].start;
 582                 dax_dev->res[i].end = res[i].end;
 583         }
 584
 585         if (i < count)
 586                 goto err_id;
 587
 588         dax_dev->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
 589         if (dax_dev->id < 0) {
 590                 rc = dax_dev->id;
 591                 goto err_id;
 592         }
 593
 594         minor = ida_simple_get(&dax_minor_ida, 0, 0, GFP_KERNEL);
 595         if (minor < 0) {
 596                 rc = minor;
 597                 goto err_minor;
 598         }
 599
 600         dev_t = MKDEV(MAJOR(dax_devt), minor);
 601         dev = &dax_dev->dev;
 602         dax_dev->inode = dax_inode_get(&dax_dev->cdev, dev_t);
 603         if (!dax_dev->inode) {
 604                 rc = -ENOMEM;
 605                 goto err_inode;
 606         }
 607
 608         /* device_initialize() so cdev can reference kobj parent */
 609         device_initialize(dev);
 610
 611         cdev = &dax_dev->cdev;
 612         cdev_init(cdev, &dax_fops);
 613         cdev->owner = parent->driver->owner;
 614         cdev->kobj.parent = &dev->kobj;
 615         rc = cdev_add(&dax_dev->cdev, dev_t, 1);
 616         if (rc)
 617                 goto err_cdev;
 618
 619         /* from here on we're committed to teardown via dax_dev_release() */
 620         dax_dev->num_resources = count;
 621         dax_dev->alive = true;
 622         dax_dev->region = dax_region;
 623         kref_get(&dax_region->kref);
 624
 625         dev->devt = dev_t;
 626         dev->class = dax_class;
 627         dev->parent = parent;
 628         dev->groups = dax_attribute_groups;
 629         dev->release = dax_dev_release;
 630         dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
 631         rc = device_add(dev);
 632         if (rc) {
 633                 put_device(dev);
 634                 return ERR_PTR(rc);
 635         }
 636
 637         rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
 638         if (rc)
 639                 return ERR_PTR(rc);
 640
 641         return dax_dev;
 642
 643  err_cdev:
 644         iput(dax_dev->inode);
 645  err_inode:
 646         ida_simple_remove(&dax_minor_ida, minor);
 647  err_minor:
 648         ida_simple_remove(&dax_region->ida, dax_dev->id);
 649  err_id:
 650         kfree(dax_dev);
 651
 652         return ERR_PTR(rc);
 653 }
 654 EXPORT_SYMBOL_GPL(devm_create_dax_dev);
 655
 656 static int __init dax_init(void)
 657 {
 658         int rc;
 659
 660         rc = dax_inode_init();
 661         if (rc)
 662                 return rc;
 663
 664         nr_dax = max(nr_dax, 256);
 665         rc = alloc_chrdev_region(&dax_devt, 0, nr_dax, "dax");
 666         if (rc)
 667                 goto err_chrdev;
 668
 669         dax_class = class_create(THIS_MODULE, "dax");
 670         if (IS_ERR(dax_class)) {
 671                 rc = PTR_ERR(dax_class);
 672                 goto err_class;
 673         }
 674
 675         return 0;
 676
 677  err_class:
 678         unregister_chrdev_region(dax_devt, nr_dax);
 679  err_chrdev:
 680         dax_inode_exit();
 681         return rc;
 682 }
 683
 684 static void __exit dax_exit(void)
 685 {
 686         class_destroy(dax_class);
 687         unregister_chrdev_region(dax_devt, nr_dax);
 688         ida_destroy(&dax_minor_ida);
 689         dax_inode_exit();
 690 }
 691
 692 MODULE_AUTHOR("Intel Corporation");
 693 MODULE_LICENSE("GPL v2");
 694 subsys_initcall(dax_init);
 695 module_exit(dax_exit);