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 DEFINE_STATIC_SRCU(dax_srcu);
  28 static struct class *dax_class;
  29 static DEFINE_IDA(dax_minor_ida);
  30 static int nr_dax = CONFIG_NR_DEV_DAX;
  31 module_param(nr_dax, int, S_IRUGO);
  32 static struct vfsmount *dax_mnt;
  33 static struct kmem_cache *dax_cache __read_mostly;
  34 static struct super_block *dax_superblock __read_mostly;
  35 MODULE_PARM_DESC(nr_dax, "max number of device-dax instances");
  36
  37 /**
  38  * struct dax_region - mapping infrastructure for dax devices
  39  * @id: kernel-wide unique region for a memory range
  40  * @base: linear address corresponding to @res
  41  * @kref: to pin while other agents have a need to do lookups
  42  * @dev: parent device backing this region
  43  * @align: allocation and mapping alignment for child dax devices
  44  * @res: physical address range of the region
  45  * @pfn_flags: identify whether the pfns are paged back or not
  46  */
  47 struct dax_region {
  48         int id;
  49         struct ida ida;
  50         void *base;
  51         struct kref kref;
  52         struct device *dev;
  53         unsigned int align;
  54         struct resource res;
  55         unsigned long pfn_flags;
  56 };
  57
  58 /**
  59  * struct dax_dev - subdivision of a dax region
  60  * @region - parent region
  61  * @dev - device backing the character device
  62  * @cdev - core chardev data
  63  * @alive - !alive + srcu grace period == no new mappings can be established
  64  * @id - child id in the region
  65  * @num_resources - number of physical address extents in this device
  66  * @res - array of physical address ranges
  67  */
  68 struct dax_dev {
  69         struct dax_region *region;
  70         struct inode *inode;
  71         struct device dev;
  72         struct cdev cdev;
  73         bool alive;
  74         int id;
  75         int num_resources;
  76         struct resource res[0];
  77 };
  78
  79 static struct inode *dax_alloc_inode(struct super_block *sb)
  80 {
  81         return kmem_cache_alloc(dax_cache, GFP_KERNEL);
  82 }
  83
  84 static void dax_i_callback(struct rcu_head *head)
  85 {
  86         struct inode *inode = container_of(head, struct inode, i_rcu);
  87
  88         kmem_cache_free(dax_cache, inode);
  89 }
  90
  91 static void dax_destroy_inode(struct inode *inode)
  92 {
  93         call_rcu(&inode->i_rcu, dax_i_callback);
  94 }
  95
  96 static const struct super_operations dax_sops = {
  97         .statfs = simple_statfs,
  98         .alloc_inode = dax_alloc_inode,
  99         .destroy_inode = dax_destroy_inode,
 100         .drop_inode = generic_delete_inode,
 101 };
 102
 103 static struct dentry *dax_mount(struct file_system_type *fs_type,
 104                 int flags, const char *dev_name, void *data)
 105 {
 106         return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
 107 }
 108
 109 static struct file_system_type dax_type = {
 110         .name = "dax",
 111         .mount = dax_mount,
 112         .kill_sb = kill_anon_super,
 113 };
 114
 115 static int dax_test(struct inode *inode, void *data)
 116 {
 117         return inode->i_cdev == data;
 118 }
 119
 120 static int dax_set(struct inode *inode, void *data)
 121 {
 122         inode->i_cdev = data;
 123         return 0;
 124 }
 125
 126 static struct inode *dax_inode_get(struct cdev *cdev, dev_t devt)
 127 {
 128         struct inode *inode;
 129
 130         inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
 131                         dax_test, dax_set, cdev);
 132
 133         if (!inode)
 134                 return NULL;
 135
 136         if (inode->i_state & I_NEW) {
 137                 inode->i_mode = S_IFCHR;
 138                 inode->i_flags = S_DAX;
 139                 inode->i_rdev = devt;
 140                 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 141                 unlock_new_inode(inode);
 142         }
 143         return inode;
 144 }
 145
 146 static void init_once(void *inode)
 147 {
 148         inode_init_once(inode);
 149 }
 150
 151 static int dax_inode_init(void)
 152 {
 153         int rc;
 154
 155         dax_cache = kmem_cache_create("dax_cache", sizeof(struct inode), 0,
 156                         (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
 157                          SLAB_MEM_SPREAD|SLAB_ACCOUNT),
 158                         init_once);
 159         if (!dax_cache)
 160                 return -ENOMEM;
 161
 162         rc = register_filesystem(&dax_type);
 163         if (rc)
 164                 goto err_register_fs;
 165
 166         dax_mnt = kern_mount(&dax_type);
 167         if (IS_ERR(dax_mnt)) {
 168                 rc = PTR_ERR(dax_mnt);
 169                 goto err_mount;
 170         }
 171         dax_superblock = dax_mnt->mnt_sb;
 172
 173         return 0;
 174
 175  err_mount:
 176         unregister_filesystem(&dax_type);
 177  err_register_fs:
 178         kmem_cache_destroy(dax_cache);
 179
 180         return rc;
 181 }
 182
 183 static void dax_inode_exit(void)
 184 {
 185         kern_unmount(dax_mnt);
 186         unregister_filesystem(&dax_type);
 187         kmem_cache_destroy(dax_cache);
 188 }
 189
 190 static void dax_region_free(struct kref *kref)
 191 {
 192         struct dax_region *dax_region;
 193
 194         dax_region = container_of(kref, struct dax_region, kref);
 195         kfree(dax_region);
 196 }
 197
 198 void dax_region_put(struct dax_region *dax_region)
 199 {
 200         kref_put(&dax_region->kref, dax_region_free);
 201 }
 202 EXPORT_SYMBOL_GPL(dax_region_put);
 203
 204 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 205                 struct resource *res, unsigned int align, void *addr,
 206                 unsigned long pfn_flags)
 207 {
 208         struct dax_region *dax_region;
 209
 210         if (!IS_ALIGNED(res->start, align)
 211                         || !IS_ALIGNED(resource_size(res), align))
 212                 return NULL;
 213
 214         dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
 215         if (!dax_region)
 216                 return NULL;
 217
 218         memcpy(&dax_region->res, res, sizeof(*res));
 219         dax_region->pfn_flags = pfn_flags;
 220         kref_init(&dax_region->kref);
 221         dax_region->id = region_id;
 222         ida_init(&dax_region->ida);
 223         dax_region->align = align;
 224         dax_region->dev = parent;
 225         dax_region->base = addr;
 226
 227         return dax_region;
 228 }
 229 EXPORT_SYMBOL_GPL(alloc_dax_region);
 230
 231 static struct dax_dev *to_dax_dev(struct device *dev)
 232 {
 233         return container_of(dev, struct dax_dev, dev);
 234 }
 235
 236 static ssize_t size_show(struct device *dev,
 237                 struct device_attribute *attr, char *buf)
 238 {
 239         struct dax_dev *dax_dev = to_dax_dev(dev);
 240         unsigned long long size = 0;
 241         int i;
 242
 243         for (i = 0; i < dax_dev->num_resources; i++)
 244                 size += resource_size(&dax_dev->res[i]);
 245
 246         return sprintf(buf, "%llu\n", size);
 247 }
 248 static DEVICE_ATTR_RO(size);
 249
 250 static struct attribute *dax_device_attributes[] = {
 251         &dev_attr_size.attr,
 252         NULL,
 253 };
 254
 255 static const struct attribute_group dax_device_attribute_group = {
 256         .attrs = dax_device_attributes,
 257 };
 258
 259 static const struct attribute_group *dax_attribute_groups[] = {
 260         &dax_device_attribute_group,
 261         NULL,
 262 };
 263
 264 static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 265                 const char *func)
 266 {
 267         struct dax_region *dax_region = dax_dev->region;
 268         struct device *dev = &dax_dev->dev;
 269         unsigned long mask;
 270
 271         if (!dax_dev->alive)
 272                 return -ENXIO;
 273
 274         /* prevent private mappings from being established */
 275         if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
 276                 dev_info(dev, "%s: %s: fail, attempted private mapping\n",
 277                                 current->comm, func);
 278                 return -EINVAL;
 279         }
 280
 281         mask = dax_region->align - 1;
 282         if (vma->vm_start & mask || vma->vm_end & mask) {
 283                 dev_info(dev, "%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
 284                                 current->comm, func, vma->vm_start, vma->vm_end,
 285                                 mask);
 286                 return -EINVAL;
 287         }
 288
 289         if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) == PFN_DEV
 290                         && (vma->vm_flags & VM_DONTCOPY) == 0) {
 291                 dev_info(dev, "%s: %s: fail, dax range requires MADV_DONTFORK\n",
 292                                 current->comm, func);
 293                 return -EINVAL;
 294         }
 295
 296         if (!vma_is_dax(vma)) {
 297                 dev_info(dev, "%s: %s: fail, vma is not DAX capable\n",
 298                                 current->comm, func);
 299                 return -EINVAL;
 300         }
 301
 302         return 0;
 303 }
 304
 305 static phys_addr_t pgoff_to_phys(struct dax_dev *dax_dev, pgoff_t pgoff,
 306                 unsigned long size)
 307 {
 308         struct resource *res;
 309         phys_addr_t phys;
 310         int i;
 311
 312         for (i = 0; i < dax_dev->num_resources; i++) {
 313                 res = &dax_dev->res[i];
 314                 phys = pgoff * PAGE_SIZE + res->start;
 315                 if (phys >= res->start && phys <= res->end)
 316                         break;
 317                 pgoff -= PHYS_PFN(resource_size(res));
 318         }
 319
 320         if (i < dax_dev->num_resources) {
 321                 res = &dax_dev->res[i];
 322                 if (phys + size - 1 <= res->end)
 323                         return phys;
 324         }
 325
 326         return -1;
 327 }
 328
 329 static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
 330                 struct vm_fault *vmf)
 331 {
 332         unsigned long vaddr = (unsigned long) vmf->virtual_address;
 333         struct device *dev = &dax_dev->dev;
 334         struct dax_region *dax_region;
 335         int rc = VM_FAULT_SIGBUS;
 336         phys_addr_t phys;
 337         pfn_t pfn;
 338         unsigned int fault_size = PAGE_SIZE;
 339
 340         if (check_vma(dax_dev, vma, __func__))
 341                 return VM_FAULT_SIGBUS;
 342
 343         dax_region = dax_dev->region;
 344         if (dax_region->align > PAGE_SIZE) {
 345                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 346                 return VM_FAULT_SIGBUS;
 347         }
 348
 349         if (fault_size != dax_region->align)
 350                 return VM_FAULT_SIGBUS;
 351
 352         phys = pgoff_to_phys(dax_dev, vmf->pgoff, PAGE_SIZE);
 353         if (phys == -1) {
 354                 dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 355                                 vmf->pgoff);
 356                 return VM_FAULT_SIGBUS;
 357         }
 358
 359         pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
 360
 361         rc = vm_insert_mixed(vma, vaddr, pfn);
 362
 363         if (rc == -ENOMEM)
 364                 return VM_FAULT_OOM;
 365         if (rc < 0 && rc != -EBUSY)
 366                 return VM_FAULT_SIGBUS;
 367
 368         return VM_FAULT_NOPAGE;
 369 }
 370
 371 static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 372 {
 373         int rc;
 374         struct file *filp = vma->vm_file;
 375         struct dax_dev *dax_dev = filp->private_data;
 376
 377         dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 378                         current->comm, (vmf->flags & FAULT_FLAG_WRITE)
 379                         ? "write" : "read", vma->vm_start, vma->vm_end);
 380         rcu_read_lock();
 381         rc = __dax_dev_fault(dax_dev, vma, vmf);
 382         rcu_read_unlock();
 383
 384         return rc;
 385 }
 386
 387 static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
 388                 struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd,
 389                 unsigned int flags)
 390 {
 391         unsigned long pmd_addr = addr & PMD_MASK;
 392         struct device *dev = &dax_dev->dev;
 393         struct dax_region *dax_region;
 394         phys_addr_t phys;
 395         pgoff_t pgoff;
 396         pfn_t pfn;
 397         unsigned int fault_size = PMD_SIZE;
 398
 399         if (check_vma(dax_dev, vma, __func__))
 400                 return VM_FAULT_SIGBUS;
 401
 402         dax_region = dax_dev->region;
 403         if (dax_region->align > PMD_SIZE) {
 404                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 405                 return VM_FAULT_SIGBUS;
 406         }
 407
 408         /* dax pmd mappings require pfn_t_devmap() */
 409         if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
 410                 dev_dbg(dev, "%s: alignment > fault size\n", __func__);
 411                 return VM_FAULT_SIGBUS;
 412         }
 413
 414         if (fault_size < dax_region->align)
 415                 return VM_FAULT_SIGBUS;
 416         else if (fault_size > dax_region->align)
 417                 return VM_FAULT_FALLBACK;
 418
 419         /* if we are outside of the VMA */
 420         if (pmd_addr < vma->vm_start ||
 421                         (pmd_addr + PMD_SIZE) > vma->vm_end)
 422                 return VM_FAULT_SIGBUS;
 423
 424         pgoff = linear_page_index(vma, pmd_addr);
 425         phys = pgoff_to_phys(dax_dev, pgoff, PMD_SIZE);
 426         if (phys == -1) {
 427                 dev_dbg(dev, "%s: phys_to_pgoff(%#lx) failed\n", __func__,
 428                                 pgoff);
 429                 return VM_FAULT_SIGBUS;
 430         }
 431
 432         pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);
 433
 434         return vmf_insert_pfn_pmd(vma, addr, pmd, pfn,
 435                         flags & FAULT_FLAG_WRITE);
 436 }
 437
 438 static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
 439                 pmd_t *pmd, unsigned int flags)
 440 {
 441         int rc, id;
 442         struct file *filp = vma->vm_file;
 443         struct dax_dev *dax_dev = filp->private_data;
 444
 445         dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
 446                         current->comm, (flags & FAULT_FLAG_WRITE)
 447                         ? "write" : "read", vma->vm_start, vma->vm_end);
 448
 449         id = srcu_read_lock(&dax_srcu);
 450         rc = __dax_dev_pmd_fault(dax_dev, vma, addr, pmd, flags);
 451         srcu_read_unlock(&dax_srcu, id);
 452
 453         return rc;
 454 }
 455
 456 static int dax_dev_split(struct vm_area_struct *vma, unsigned long addr)
 457 {
 458         struct file *filp = vma->vm_file;
 459         struct dax_dev *dax_dev = filp->private_data;
 460         struct dax_region *dax_region = dax_dev->region;
 461
 462         if (!IS_ALIGNED(addr, dax_region->align))
 463                 return -EINVAL;
 464         return 0;
 465 }
 466
 467 static const struct vm_operations_struct dax_dev_vm_ops = {
 468         .fault = dax_dev_fault,
 469         .pmd_fault = dax_dev_pmd_fault,
 470         .split = dax_dev_split,
 471 };
 472
 473 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
 474 {
 475         struct dax_dev *dax_dev = filp->private_data;
 476         int rc;
 477
 478         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 479
 480         rc = check_vma(dax_dev, vma, __func__);
 481         if (rc)
 482                 return rc;
 483
 484         vma->vm_ops = &dax_dev_vm_ops;
 485         vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
 486         return 0;
 487 }
 488
 489 /* return an unmapped area aligned to the dax region specified alignment */
 490 static unsigned long dax_get_unmapped_area(struct file *filp,
 491                 unsigned long addr, unsigned long len, unsigned long pgoff,
 492                 unsigned long flags)
 493 {
 494         unsigned long off, off_end, off_align, len_align, addr_align, align;
 495         struct dax_dev *dax_dev = filp ? filp->private_data : NULL;
 496         struct dax_region *dax_region;
 497
 498         if (!dax_dev || addr)
 499                 goto out;
 500
 501         dax_region = dax_dev->region;
 502         align = dax_region->align;
 503         off = pgoff << PAGE_SHIFT;
 504         off_end = off + len;
 505         off_align = round_up(off, align);
 506
 507         if ((off_end <= off_align) || ((off_end - off_align) < align))
 508                 goto out;
 509
 510         len_align = len + align;
 511         if ((off + len_align) < off)
 512                 goto out;
 513
 514         addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
 515                         pgoff, flags);
 516         if (!IS_ERR_VALUE(addr_align)) {
 517                 addr_align += (off - addr_align) & (align - 1);
 518                 return addr_align;
 519         }
 520  out:
 521         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 522 }
 523
 524 static int dax_open(struct inode *inode, struct file *filp)
 525 {
 526         struct dax_dev *dax_dev;
 527
 528         dax_dev = container_of(inode->i_cdev, struct dax_dev, cdev);
 529         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 530         inode->i_mapping = dax_dev->inode->i_mapping;
 531         inode->i_mapping->host = dax_dev->inode;
 532         filp->f_mapping = inode->i_mapping;
 533         filp->private_data = dax_dev;
 534         inode->i_flags = S_DAX;
 535
 536         return 0;
 537 }
 538
 539 static int dax_release(struct inode *inode, struct file *filp)
 540 {
 541         struct dax_dev *dax_dev = filp->private_data;
 542
 543         dev_dbg(&dax_dev->dev, "%s\n", __func__);
 544         return 0;
 545 }
 546
 547 static const struct file_operations dax_fops = {
 548         .llseek = noop_llseek,
 549         .owner = THIS_MODULE,
 550         .open = dax_open,
 551         .release = dax_release,
 552         .get_unmapped_area = dax_get_unmapped_area,
 553         .mmap = dax_mmap,
 554 };
 555
 556 static void dax_dev_release(struct device *dev)
 557 {
 558         struct dax_dev *dax_dev = to_dax_dev(dev);
 559         struct dax_region *dax_region = dax_dev->region;
 560
 561         if (dax_dev->id >= 0)
 562                 ida_simple_remove(&dax_region->ida, dax_dev->id);
 563         ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
 564         dax_region_put(dax_region);
 565         iput(dax_dev->inode);
 566         kfree(dax_dev);
 567 }
 568
 569 static void kill_dax_dev(struct dax_dev *dax_dev)
 570 {
 571         struct cdev *cdev = &dax_dev->cdev;
 572
 573         /*
 574          * Note, rcu is not protecting the liveness of dax_dev, rcu is
 575          * ensuring that any fault handlers that might have seen
 576          * dax_dev->alive == true, have completed.  Any fault handlers
 577          * that start after synchronize_srcu() has started will abort
 578          * upon seeing dax_dev->alive == false.
 579          */
 580         dax_dev->alive = false;
 581         synchronize_srcu(&dax_srcu);
 582         unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
 583         cdev_del(cdev);
 584 }
 585
 586 static void unregister_dax_dev(void *dev)
 587 {
 588         struct dax_dev *dax_dev = to_dax_dev(dev);
 589
 590         dev_dbg(dev, "%s\n", __func__);
 591
 592         kill_dax_dev(dax_dev);
 593         device_unregister(dev);
 594 }
 595
 596 struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
 597                 int id, struct resource *res, int count)
 598 {
 599         struct device *parent = dax_region->dev;
 600         struct dax_dev *dax_dev;
 601         int rc = 0, minor, i;
 602         struct device *dev;
 603         struct cdev *cdev;
 604         dev_t dev_t;
 605
 606         dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
 607         if (!dax_dev)
 608                 return ERR_PTR(-ENOMEM);
 609
 610         for (i = 0; i < count; i++) {
 611                 if (!IS_ALIGNED(res[i].start, dax_region->align)
 612                                 || !IS_ALIGNED(resource_size(&res[i]),
 613                                         dax_region->align)) {
 614                         rc = -EINVAL;
 615                         break;
 616                 }
 617                 dax_dev->res[i].start = res[i].start;
 618                 dax_dev->res[i].end = res[i].end;
 619         }
 620
 621         if (i < count)
 622                 goto err_id;
 623
 624         if (id < 0) {
 625                 id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
 626                 dax_dev->id = id;
 627                 if (id < 0) {
 628                         rc = id;
 629                         goto err_id;
 630                 }
 631         } else {
 632                 /* region provider owns @id lifetime */
 633                 dax_dev->id = -1;
 634         }
 635
 636         minor = ida_simple_get(&dax_minor_ida, 0, 0, GFP_KERNEL);
 637         if (minor < 0) {
 638                 rc = minor;
 639                 goto err_minor;
 640         }
 641
 642         dev_t = MKDEV(MAJOR(dax_devt), minor);
 643         dev = &dax_dev->dev;
 644         dax_dev->inode = dax_inode_get(&dax_dev->cdev, dev_t);
 645         if (!dax_dev->inode) {
 646                 rc = -ENOMEM;
 647                 goto err_inode;
 648         }
 649
 650         /* device_initialize() so cdev can reference kobj parent */
 651         device_initialize(dev);
 652
 653         cdev = &dax_dev->cdev;
 654         cdev_init(cdev, &dax_fops);
 655         cdev->owner = parent->driver->owner;
 656         cdev->kobj.parent = &dev->kobj;
 657         rc = cdev_add(&dax_dev->cdev, dev_t, 1);
 658         if (rc)
 659                 goto err_cdev;
 660
 661         /* from here on we're committed to teardown via dax_dev_release() */
 662         dax_dev->num_resources = count;
 663         dax_dev->alive = true;
 664         dax_dev->region = dax_region;
 665         kref_get(&dax_region->kref);
 666
 667         dev->devt = dev_t;
 668         dev->class = dax_class;
 669         dev->parent = parent;
 670         dev->groups = dax_attribute_groups;
 671         dev->release = dax_dev_release;
 672         dev_set_name(dev, "dax%d.%d", dax_region->id, id);
 673         rc = device_add(dev);
 674         if (rc) {
 675                 kill_dax_dev(dax_dev);
 676                 put_device(dev);
 677                 return ERR_PTR(rc);
 678         }
 679
 680         rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_dev, dev);
 681         if (rc)
 682                 return ERR_PTR(rc);
 683
 684         return dax_dev;
 685
 686  err_cdev:
 687         iput(dax_dev->inode);
 688  err_inode:
 689         ida_simple_remove(&dax_minor_ida, minor);
 690  err_minor:
 691         if (dax_dev->id >= 0)
 692                 ida_simple_remove(&dax_region->ida, dax_dev->id);
 693  err_id:
 694         kfree(dax_dev);
 695
 696         return ERR_PTR(rc);
 697 }
 698 EXPORT_SYMBOL_GPL(devm_create_dax_dev);
 699
 700 static int __init dax_init(void)
 701 {
 702         int rc;
 703
 704         rc = dax_inode_init();
 705         if (rc)
 706                 return rc;
 707
 708         nr_dax = max(nr_dax, 256);
 709         rc = alloc_chrdev_region(&dax_devt, 0, nr_dax, "dax");
 710         if (rc)
 711                 goto err_chrdev;
 712
 713         dax_class = class_create(THIS_MODULE, "dax");
 714         if (IS_ERR(dax_class)) {
 715                 rc = PTR_ERR(dax_class);
 716                 goto err_class;
 717         }
 718
 719         return 0;
 720
 721  err_class:
 722         unregister_chrdev_region(dax_devt, nr_dax);
 723  err_chrdev:
 724         dax_inode_exit();
 725         return rc;
 726 }
 727
 728 static void __exit dax_exit(void)
 729 {
 730         class_destroy(dax_class);
 731         unregister_chrdev_region(dax_devt, nr_dax);
 732         ida_destroy(&dax_minor_ida);
 733         dax_inode_exit();
 734 }
 735
 736 MODULE_AUTHOR("Intel Corporation");
 737 MODULE_LICENSE("GPL v2");
 738 subsys_initcall(dax_init);
 739 module_exit(dax_exit);