drivers/dax/bus.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright(c) 2017-2018 Intel Corporation. All rights reserved. */
   3 #include <linux/memremap.h>
   4 #include <linux/device.h>
   5 #include <linux/mutex.h>
   6 #include <linux/list.h>
   7 #include <linux/slab.h>
   8 #include <linux/dax.h>
   9 #include <linux/io.h>
  10 #include "dax-private.h"
  11 #include "bus.h"
  12
  13 static struct class *dax_class;
  14
  15 static DEFINE_MUTEX(dax_bus_lock);
  16
  17 #define DAX_NAME_LEN 30
  18 struct dax_id {
  19         struct list_head list;
  20         char dev_name[DAX_NAME_LEN];
  21 };
  22
  23 static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
  24 {
  25         /*
  26          * We only ever expect to handle device-dax instances, i.e. the
  27          * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
  28          */
  29         return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
  30 }
  31
  32 static struct dax_device_driver *to_dax_drv(struct device_driver *drv)
  33 {
  34         return container_of(drv, struct dax_device_driver, drv);
  35 }
  36
  37 static struct dax_id *__dax_match_id(struct dax_device_driver *dax_drv,
  38                 const char *dev_name)
  39 {
  40         struct dax_id *dax_id;
  41
  42         lockdep_assert_held(&dax_bus_lock);
  43
  44         list_for_each_entry(dax_id, &dax_drv->ids, list)
  45                 if (sysfs_streq(dax_id->dev_name, dev_name))
  46                         return dax_id;
  47         return NULL;
  48 }
  49
  50 static int dax_match_id(struct dax_device_driver *dax_drv, struct device *dev)
  51 {
  52         int match;
  53
  54         mutex_lock(&dax_bus_lock);
  55         match = !!__dax_match_id(dax_drv, dev_name(dev));
  56         mutex_unlock(&dax_bus_lock);
  57
  58         return match;
  59 }
  60
  61 enum id_action {
  62         ID_REMOVE,
  63         ID_ADD,
  64 };
  65
  66 static ssize_t do_id_store(struct device_driver *drv, const char *buf,
  67                 size_t count, enum id_action action)
  68 {
  69         struct dax_device_driver *dax_drv = to_dax_drv(drv);
  70         unsigned int region_id, id;
  71         char devname[DAX_NAME_LEN];
  72         struct dax_id *dax_id;
  73         ssize_t rc = count;
  74         int fields;
  75
  76         fields = sscanf(buf, "dax%d.%d", &region_id, &id);
  77         if (fields != 2)
  78                 return -EINVAL;
  79         sprintf(devname, "dax%d.%d", region_id, id);
  80         if (!sysfs_streq(buf, devname))
  81                 return -EINVAL;
  82
  83         mutex_lock(&dax_bus_lock);
  84         dax_id = __dax_match_id(dax_drv, buf);
  85         if (!dax_id) {
  86                 if (action == ID_ADD) {
  87                         dax_id = kzalloc(sizeof(*dax_id), GFP_KERNEL);
  88                         if (dax_id) {
  89                                 strncpy(dax_id->dev_name, buf, DAX_NAME_LEN);
  90                                 list_add(&dax_id->list, &dax_drv->ids);
  91                         } else
  92                                 rc = -ENOMEM;
  93                 }
  94         } else if (action == ID_REMOVE) {
  95                 list_del(&dax_id->list);
  96                 kfree(dax_id);
  97         }
  98         mutex_unlock(&dax_bus_lock);
  99
 100         if (rc < 0)
 101                 return rc;
 102         if (action == ID_ADD)
 103                 rc = driver_attach(drv);
 104         if (rc)
 105                 return rc;
 106         return count;
 107 }
 108
 109 static ssize_t new_id_store(struct device_driver *drv, const char *buf,
 110                 size_t count)
 111 {
 112         return do_id_store(drv, buf, count, ID_ADD);
 113 }
 114 static DRIVER_ATTR_WO(new_id);
 115
 116 static ssize_t remove_id_store(struct device_driver *drv, const char *buf,
 117                 size_t count)
 118 {
 119         return do_id_store(drv, buf, count, ID_REMOVE);
 120 }
 121 static DRIVER_ATTR_WO(remove_id);
 122
 123 static struct attribute *dax_drv_attrs[] = {
 124         &driver_attr_new_id.attr,
 125         &driver_attr_remove_id.attr,
 126         NULL,
 127 };
 128 ATTRIBUTE_GROUPS(dax_drv);
 129
 130 static int dax_bus_match(struct device *dev, struct device_driver *drv);
 131
 132 static bool is_static(struct dax_region *dax_region)
 133 {
 134         return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;
 135 }
 136
 137 static u64 dev_dax_size(struct dev_dax *dev_dax)
 138 {
 139         u64 size = 0;
 140         int i;
 141
 142         device_lock_assert(&dev_dax->dev);
 143
 144         for (i = 0; i < dev_dax->nr_range; i++)
 145                 size += range_len(&dev_dax->ranges[i].range);
 146
 147         return size;
 148 }
 149
 150 static int dax_bus_probe(struct device *dev)
 151 {
 152         struct dax_device_driver *dax_drv = to_dax_drv(dev->driver);
 153         struct dev_dax *dev_dax = to_dev_dax(dev);
 154         struct dax_region *dax_region = dev_dax->region;
 155         int rc;
 156
 157         if (dev_dax_size(dev_dax) == 0 || dev_dax->id < 0)
 158                 return -ENXIO;
 159
 160         rc = dax_drv->probe(dev_dax);
 161
 162         if (rc || is_static(dax_region))
 163                 return rc;
 164
 165         /*
 166          * Track new seed creation only after successful probe of the
 167          * previous seed.
 168          */
 169         if (dax_region->seed == dev)
 170                 dax_region->seed = NULL;
 171
 172         return 0;
 173 }
 174
 175 static int dax_bus_remove(struct device *dev)
 176 {
 177         struct dax_device_driver *dax_drv = to_dax_drv(dev->driver);
 178         struct dev_dax *dev_dax = to_dev_dax(dev);
 179
 180         if (dax_drv->remove)
 181                 dax_drv->remove(dev_dax);
 182
 183         return 0;
 184 }
 185
 186 static struct bus_type dax_bus_type = {
 187         .name = "dax",
 188         .uevent = dax_bus_uevent,
 189         .match = dax_bus_match,
 190         .probe = dax_bus_probe,
 191         .remove = dax_bus_remove,
 192         .drv_groups = dax_drv_groups,
 193 };
 194
 195 static int dax_bus_match(struct device *dev, struct device_driver *drv)
 196 {
 197         struct dax_device_driver *dax_drv = to_dax_drv(drv);
 198
 199         /*
 200          * All but the 'device-dax' driver, which has 'match_always'
 201          * set, requires an exact id match.
 202          */
 203         if (dax_drv->match_always)
 204                 return 1;
 205
 206         return dax_match_id(dax_drv, dev);
 207 }
 208
 209 /*
 210  * Rely on the fact that drvdata is set before the attributes are
 211  * registered, and that the attributes are unregistered before drvdata
 212  * is cleared to assume that drvdata is always valid.
 213  */
 214 static ssize_t id_show(struct device *dev,
 215                 struct device_attribute *attr, char *buf)
 216 {
 217         struct dax_region *dax_region = dev_get_drvdata(dev);
 218
 219         return sprintf(buf, "%d\n", dax_region->id);
 220 }
 221 static DEVICE_ATTR_RO(id);
 222
 223 static ssize_t region_size_show(struct device *dev,
 224                 struct device_attribute *attr, char *buf)
 225 {
 226         struct dax_region *dax_region = dev_get_drvdata(dev);
 227
 228         return sprintf(buf, "%llu\n", (unsigned long long)
 229                         resource_size(&dax_region->res));
 230 }
 231 static struct device_attribute dev_attr_region_size = __ATTR(size, 0444,
 232                 region_size_show, NULL);
 233
 234 static ssize_t region_align_show(struct device *dev,
 235                 struct device_attribute *attr, char *buf)
 236 {
 237         struct dax_region *dax_region = dev_get_drvdata(dev);
 238
 239         return sprintf(buf, "%u\n", dax_region->align);
 240 }
 241 static struct device_attribute dev_attr_region_align =
 242                 __ATTR(align, 0400, region_align_show, NULL);
 243
 244 #define for_each_dax_region_resource(dax_region, res) \
 245         for (res = (dax_region)->res.child; res; res = res->sibling)
 246
 247 static unsigned long long dax_region_avail_size(struct dax_region *dax_region)
 248 {
 249         resource_size_t size = resource_size(&dax_region->res);
 250         struct resource *res;
 251
 252         device_lock_assert(dax_region->dev);
 253
 254         for_each_dax_region_resource(dax_region, res)
 255                 size -= resource_size(res);
 256         return size;
 257 }
 258
 259 static ssize_t available_size_show(struct device *dev,
 260                 struct device_attribute *attr, char *buf)
 261 {
 262         struct dax_region *dax_region = dev_get_drvdata(dev);
 263         unsigned long long size;
 264
 265         device_lock(dev);
 266         size = dax_region_avail_size(dax_region);
 267         device_unlock(dev);
 268
 269         return sprintf(buf, "%llu\n", size);
 270 }
 271 static DEVICE_ATTR_RO(available_size);
 272
 273 static ssize_t seed_show(struct device *dev,
 274                 struct device_attribute *attr, char *buf)
 275 {
 276         struct dax_region *dax_region = dev_get_drvdata(dev);
 277         struct device *seed;
 278         ssize_t rc;
 279
 280         if (is_static(dax_region))
 281                 return -EINVAL;
 282
 283         device_lock(dev);
 284         seed = dax_region->seed;
 285         rc = sprintf(buf, "%s\n", seed ? dev_name(seed) : "");
 286         device_unlock(dev);
 287
 288         return rc;
 289 }
 290 static DEVICE_ATTR_RO(seed);
 291
 292 static ssize_t create_show(struct device *dev,
 293                 struct device_attribute *attr, char *buf)
 294 {
 295         struct dax_region *dax_region = dev_get_drvdata(dev);
 296         struct device *youngest;
 297         ssize_t rc;
 298
 299         if (is_static(dax_region))
 300                 return -EINVAL;
 301
 302         device_lock(dev);
 303         youngest = dax_region->youngest;
 304         rc = sprintf(buf, "%s\n", youngest ? dev_name(youngest) : "");
 305         device_unlock(dev);
 306
 307         return rc;
 308 }
 309
 310 static ssize_t create_store(struct device *dev, struct device_attribute *attr,
 311                 const char *buf, size_t len)
 312 {
 313         struct dax_region *dax_region = dev_get_drvdata(dev);
 314         unsigned long long avail;
 315         ssize_t rc;
 316         int val;
 317
 318         if (is_static(dax_region))
 319                 return -EINVAL;
 320
 321         rc = kstrtoint(buf, 0, &val);
 322         if (rc)
 323                 return rc;
 324         if (val != 1)
 325                 return -EINVAL;
 326
 327         device_lock(dev);
 328         avail = dax_region_avail_size(dax_region);
 329         if (avail == 0)
 330                 rc = -ENOSPC;
 331         else {
 332                 struct dev_dax_data data = {
 333                         .dax_region = dax_region,
 334                         .size = 0,
 335                         .id = -1,
 336                 };
 337                 struct dev_dax *dev_dax = devm_create_dev_dax(&data);
 338
 339                 if (IS_ERR(dev_dax))
 340                         rc = PTR_ERR(dev_dax);
 341                 else {
 342                         /*
 343                          * In support of crafting multiple new devices
 344                          * simultaneously multiple seeds can be created,
 345                          * but only the first one that has not been
 346                          * successfully bound is tracked as the region
 347                          * seed.
 348                          */
 349                         if (!dax_region->seed)
 350                                 dax_region->seed = &dev_dax->dev;
 351                         dax_region->youngest = &dev_dax->dev;
 352                         rc = len;
 353                 }
 354         }
 355         device_unlock(dev);
 356
 357         return rc;
 358 }
 359 static DEVICE_ATTR_RW(create);
 360
 361 void kill_dev_dax(struct dev_dax *dev_dax)
 362 {
 363         struct dax_device *dax_dev = dev_dax->dax_dev;
 364         struct inode *inode = dax_inode(dax_dev);
 365
 366         kill_dax(dax_dev);
 367         unmap_mapping_range(inode->i_mapping, 0, 0, 1);
 368 }
 369 EXPORT_SYMBOL_GPL(kill_dev_dax);
 370
 371 static void trim_dev_dax_range(struct dev_dax *dev_dax)
 372 {
 373         int i = dev_dax->nr_range - 1;
 374         struct range *range = &dev_dax->ranges[i].range;
 375         struct dax_region *dax_region = dev_dax->region;
 376
 377         device_lock_assert(dax_region->dev);
 378         dev_dbg(&dev_dax->dev, "delete range[%d]: %#llx:%#llx\n", i,
 379                 (unsigned long long)range->start,
 380                 (unsigned long long)range->end);
 381
 382         __release_region(&dax_region->res, range->start, range_len(range));
 383         if (--dev_dax->nr_range == 0) {
 384                 kfree(dev_dax->ranges);
 385                 dev_dax->ranges = NULL;
 386         }
 387 }
 388
 389 static void free_dev_dax_ranges(struct dev_dax *dev_dax)
 390 {
 391         while (dev_dax->nr_range)
 392                 trim_dev_dax_range(dev_dax);
 393 }
 394
 395 static void unregister_dev_dax(void *dev)
 396 {
 397         struct dev_dax *dev_dax = to_dev_dax(dev);
 398
 399         dev_dbg(dev, "%s\n", __func__);
 400
 401         kill_dev_dax(dev_dax);
 402         free_dev_dax_ranges(dev_dax);
 403         device_del(dev);
 404         put_device(dev);
 405 }
 406
 407 /* a return value >= 0 indicates this invocation invalidated the id */
 408 static int __free_dev_dax_id(struct dev_dax *dev_dax)
 409 {
 410         struct dax_region *dax_region = dev_dax->region;
 411         struct device *dev = &dev_dax->dev;
 412         int rc = dev_dax->id;
 413
 414         device_lock_assert(dev);
 415
 416         if (is_static(dax_region) || dev_dax->id < 0)
 417                 return -1;
 418         ida_free(&dax_region->ida, dev_dax->id);
 419         dev_dax->id = -1;
 420         return rc;
 421 }
 422
 423 static int free_dev_dax_id(struct dev_dax *dev_dax)
 424 {
 425         struct device *dev = &dev_dax->dev;
 426         int rc;
 427
 428         device_lock(dev);
 429         rc = __free_dev_dax_id(dev_dax);
 430         device_unlock(dev);
 431         return rc;
 432 }
 433
 434 static ssize_t delete_store(struct device *dev, struct device_attribute *attr,
 435                 const char *buf, size_t len)
 436 {
 437         struct dax_region *dax_region = dev_get_drvdata(dev);
 438         struct dev_dax *dev_dax;
 439         struct device *victim;
 440         bool do_del = false;
 441         int rc;
 442
 443         if (is_static(dax_region))
 444                 return -EINVAL;
 445
 446         victim = device_find_child_by_name(dax_region->dev, buf);
 447         if (!victim)
 448                 return -ENXIO;
 449
 450         device_lock(dev);
 451         device_lock(victim);
 452         dev_dax = to_dev_dax(victim);
 453         if (victim->driver || dev_dax_size(dev_dax))
 454                 rc = -EBUSY;
 455         else {
 456                 /*
 457                  * Invalidate the device so it does not become active
 458                  * again, but always preserve device-id-0 so that
 459                  * /sys/bus/dax/ is guaranteed to be populated while any
 460                  * dax_region is registered.
 461                  */
 462                 if (dev_dax->id > 0) {
 463                         do_del = __free_dev_dax_id(dev_dax) >= 0;
 464                         rc = len;
 465                         if (dax_region->seed == victim)
 466                                 dax_region->seed = NULL;
 467                         if (dax_region->youngest == victim)
 468                                 dax_region->youngest = NULL;
 469                 } else
 470                         rc = -EBUSY;
 471         }
 472         device_unlock(victim);
 473
 474         /* won the race to invalidate the device, clean it up */
 475         if (do_del)
 476                 devm_release_action(dev, unregister_dev_dax, victim);
 477         device_unlock(dev);
 478         put_device(victim);
 479
 480         return rc;
 481 }
 482 static DEVICE_ATTR_WO(delete);
 483
 484 static umode_t dax_region_visible(struct kobject *kobj, struct attribute *a,
 485                 int n)
 486 {
 487         struct device *dev = container_of(kobj, struct device, kobj);
 488         struct dax_region *dax_region = dev_get_drvdata(dev);
 489
 490         if (is_static(dax_region))
 491                 if (a == &dev_attr_available_size.attr
 492                                 || a == &dev_attr_create.attr
 493                                 || a == &dev_attr_seed.attr
 494                                 || a == &dev_attr_delete.attr)
 495                         return 0;
 496         return a->mode;
 497 }
 498
 499 static struct attribute *dax_region_attributes[] = {
 500         &dev_attr_available_size.attr,
 501         &dev_attr_region_size.attr,
 502         &dev_attr_region_align.attr,
 503         &dev_attr_create.attr,
 504         &dev_attr_seed.attr,
 505         &dev_attr_delete.attr,
 506         &dev_attr_id.attr,
 507         NULL,
 508 };
 509
 510 static const struct attribute_group dax_region_attribute_group = {
 511         .name = "dax_region",
 512         .attrs = dax_region_attributes,
 513         .is_visible = dax_region_visible,
 514 };
 515
 516 static const struct attribute_group *dax_region_attribute_groups[] = {
 517         &dax_region_attribute_group,
 518         NULL,
 519 };
 520
 521 static void dax_region_free(struct kref *kref)
 522 {
 523         struct dax_region *dax_region;
 524
 525         dax_region = container_of(kref, struct dax_region, kref);
 526         kfree(dax_region);
 527 }
 528
 529 void dax_region_put(struct dax_region *dax_region)
 530 {
 531         kref_put(&dax_region->kref, dax_region_free);
 532 }
 533 EXPORT_SYMBOL_GPL(dax_region_put);
 534
 535 static void dax_region_unregister(void *region)
 536 {
 537         struct dax_region *dax_region = region;
 538
 539         sysfs_remove_groups(&dax_region->dev->kobj,
 540                         dax_region_attribute_groups);
 541         dax_region_put(dax_region);
 542 }
 543
 544 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 545                 struct range *range, int target_node, unsigned int align,
 546                 unsigned long flags)
 547 {
 548         struct dax_region *dax_region;
 549
 550         /*
 551          * The DAX core assumes that it can store its private data in
 552          * parent->driver_data. This WARN is a reminder / safeguard for
 553          * developers of device-dax drivers.
 554          */
 555         if (dev_get_drvdata(parent)) {
 556                 dev_WARN(parent, "dax core failed to setup private data\n");
 557                 return NULL;
 558         }
 559
 560         if (!IS_ALIGNED(range->start, align)
 561                         || !IS_ALIGNED(range_len(range), align))
 562                 return NULL;
 563
 564         dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
 565         if (!dax_region)
 566                 return NULL;
 567
 568         dev_set_drvdata(parent, dax_region);
 569         kref_init(&dax_region->kref);
 570         dax_region->id = region_id;
 571         dax_region->align = align;
 572         dax_region->dev = parent;
 573         dax_region->target_node = target_node;
 574         ida_init(&dax_region->ida);
 575         dax_region->res = (struct resource) {
 576                 .start = range->start,
 577                 .end = range->end,
 578                 .flags = IORESOURCE_MEM | flags,
 579         };
 580
 581         if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
 582                 kfree(dax_region);
 583                 return NULL;
 584         }
 585
 586         kref_get(&dax_region->kref);
 587         if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
 588                 return NULL;
 589         return dax_region;
 590 }
 591 EXPORT_SYMBOL_GPL(alloc_dax_region);
 592
 593 static void dax_mapping_release(struct device *dev)
 594 {
 595         struct dax_mapping *mapping = to_dax_mapping(dev);
 596         struct dev_dax *dev_dax = to_dev_dax(dev->parent);
 597
 598         ida_free(&dev_dax->ida, mapping->id);
 599         kfree(mapping);
 600 }
 601
 602 static void unregister_dax_mapping(void *data)
 603 {
 604         struct device *dev = data;
 605         struct dax_mapping *mapping = to_dax_mapping(dev);
 606         struct dev_dax *dev_dax = to_dev_dax(dev->parent);
 607         struct dax_region *dax_region = dev_dax->region;
 608
 609         dev_dbg(dev, "%s\n", __func__);
 610
 611         device_lock_assert(dax_region->dev);
 612
 613         dev_dax->ranges[mapping->range_id].mapping = NULL;
 614         mapping->range_id = -1;
 615
 616         device_del(dev);
 617         put_device(dev);
 618 }
 619
 620 static struct dev_dax_range *get_dax_range(struct device *dev)
 621 {
 622         struct dax_mapping *mapping = to_dax_mapping(dev);
 623         struct dev_dax *dev_dax = to_dev_dax(dev->parent);
 624         struct dax_region *dax_region = dev_dax->region;
 625
 626         device_lock(dax_region->dev);
 627         if (mapping->range_id < 0) {
 628                 device_unlock(dax_region->dev);
 629                 return NULL;
 630         }
 631
 632         return &dev_dax->ranges[mapping->range_id];
 633 }
 634
 635 static void put_dax_range(struct dev_dax_range *dax_range)
 636 {
 637         struct dax_mapping *mapping = dax_range->mapping;
 638         struct dev_dax *dev_dax = to_dev_dax(mapping->dev.parent);
 639         struct dax_region *dax_region = dev_dax->region;
 640
 641         device_unlock(dax_region->dev);
 642 }
 643
 644 static ssize_t start_show(struct device *dev,
 645                 struct device_attribute *attr, char *buf)
 646 {
 647         struct dev_dax_range *dax_range;
 648         ssize_t rc;
 649
 650         dax_range = get_dax_range(dev);
 651         if (!dax_range)
 652                 return -ENXIO;
 653         rc = sprintf(buf, "%#llx\n", dax_range->range.start);
 654         put_dax_range(dax_range);
 655
 656         return rc;
 657 }
 658 static DEVICE_ATTR(start, 0400, start_show, NULL);
 659
 660 static ssize_t end_show(struct device *dev,
 661                 struct device_attribute *attr, char *buf)
 662 {
 663         struct dev_dax_range *dax_range;
 664         ssize_t rc;
 665
 666         dax_range = get_dax_range(dev);
 667         if (!dax_range)
 668                 return -ENXIO;
 669         rc = sprintf(buf, "%#llx\n", dax_range->range.end);
 670         put_dax_range(dax_range);
 671
 672         return rc;
 673 }
 674 static DEVICE_ATTR(end, 0400, end_show, NULL);
 675
 676 static ssize_t pgoff_show(struct device *dev,
 677                 struct device_attribute *attr, char *buf)
 678 {
 679         struct dev_dax_range *dax_range;
 680         ssize_t rc;
 681
 682         dax_range = get_dax_range(dev);
 683         if (!dax_range)
 684                 return -ENXIO;
 685         rc = sprintf(buf, "%#lx\n", dax_range->pgoff);
 686         put_dax_range(dax_range);
 687
 688         return rc;
 689 }
 690 static DEVICE_ATTR(page_offset, 0400, pgoff_show, NULL);
 691
 692 static struct attribute *dax_mapping_attributes[] = {
 693         &dev_attr_start.attr,
 694         &dev_attr_end.attr,
 695         &dev_attr_page_offset.attr,
 696         NULL,
 697 };
 698
 699 static const struct attribute_group dax_mapping_attribute_group = {
 700         .attrs = dax_mapping_attributes,
 701 };
 702
 703 static const struct attribute_group *dax_mapping_attribute_groups[] = {
 704         &dax_mapping_attribute_group,
 705         NULL,
 706 };
 707
 708 static struct device_type dax_mapping_type = {
 709         .release = dax_mapping_release,
 710         .groups = dax_mapping_attribute_groups,
 711 };
 712
 713 static int devm_register_dax_mapping(struct dev_dax *dev_dax, int range_id)
 714 {
 715         struct dax_region *dax_region = dev_dax->region;
 716         struct dax_mapping *mapping;
 717         struct device *dev;
 718         int rc;
 719
 720         device_lock_assert(dax_region->dev);
 721
 722         if (dev_WARN_ONCE(&dev_dax->dev, !dax_region->dev->driver,
 723                                 "region disabled\n"))
 724                 return -ENXIO;
 725
 726         mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
 727         if (!mapping)
 728                 return -ENOMEM;
 729         mapping->range_id = range_id;
 730         mapping->id = ida_alloc(&dev_dax->ida, GFP_KERNEL);
 731         if (mapping->id < 0) {
 732                 kfree(mapping);
 733                 return -ENOMEM;
 734         }
 735         dev_dax->ranges[range_id].mapping = mapping;
 736         dev = &mapping->dev;
 737         device_initialize(dev);
 738         dev->parent = &dev_dax->dev;
 739         dev->type = &dax_mapping_type;
 740         dev_set_name(dev, "mapping%d", mapping->id);
 741         rc = device_add(dev);
 742         if (rc) {
 743                 put_device(dev);
 744                 return rc;
 745         }
 746
 747         rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_mapping,
 748                         dev);
 749         if (rc)
 750                 return rc;
 751         return 0;
 752 }
 753
 754 static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
 755                 resource_size_t size)
 756 {
 757         struct dax_region *dax_region = dev_dax->region;
 758         struct resource *res = &dax_region->res;
 759         struct device *dev = &dev_dax->dev;
 760         struct dev_dax_range *ranges;
 761         unsigned long pgoff = 0;
 762         struct resource *alloc;
 763         int i, rc;
 764
 765         device_lock_assert(dax_region->dev);
 766
 767         /* handle the seed alloc special case */
 768         if (!size) {
 769                 if (dev_WARN_ONCE(dev, dev_dax->nr_range,
 770                                         "0-size allocation must be first\n"))
 771                         return -EBUSY;
 772                 /* nr_range == 0 is elsewhere special cased as 0-size device */
 773                 return 0;
 774         }
 775
 776         alloc = __request_region(res, start, size, dev_name(dev), 0);
 777         if (!alloc)
 778                 return -ENOMEM;
 779
 780         ranges = krealloc(dev_dax->ranges, sizeof(*ranges)
 781                         * (dev_dax->nr_range + 1), GFP_KERNEL);
 782         if (!ranges) {
 783                 __release_region(res, alloc->start, resource_size(alloc));
 784                 return -ENOMEM;
 785         }
 786
 787         for (i = 0; i < dev_dax->nr_range; i++)
 788                 pgoff += PHYS_PFN(range_len(&ranges[i].range));
 789         dev_dax->ranges = ranges;
 790         ranges[dev_dax->nr_range++] = (struct dev_dax_range) {
 791                 .pgoff = pgoff,
 792                 .range = {
 793                         .start = alloc->start,
 794                         .end = alloc->end,
 795                 },
 796         };
 797
 798         dev_dbg(dev, "alloc range[%d]: %pa:%pa\n", dev_dax->nr_range - 1,
 799                         &alloc->start, &alloc->end);
 800         /*
 801          * A dev_dax instance must be registered before mapping device
 802          * children can be added. Defer to devm_create_dev_dax() to add
 803          * the initial mapping device.
 804          */
 805         if (!device_is_registered(&dev_dax->dev))
 806                 return 0;
 807
 808         rc = devm_register_dax_mapping(dev_dax, dev_dax->nr_range - 1);
 809         if (rc)
 810                 trim_dev_dax_range(dev_dax);
 811
 812         return rc;
 813 }
 814
 815 static int adjust_dev_dax_range(struct dev_dax *dev_dax, struct resource *res, resource_size_t size)
 816 {
 817         int last_range = dev_dax->nr_range - 1;
 818         struct dev_dax_range *dax_range = &dev_dax->ranges[last_range];
 819         struct dax_region *dax_region = dev_dax->region;
 820         bool is_shrink = resource_size(res) > size;
 821         struct range *range = &dax_range->range;
 822         struct device *dev = &dev_dax->dev;
 823         int rc;
 824
 825         device_lock_assert(dax_region->dev);
 826
 827         if (dev_WARN_ONCE(dev, !size, "deletion is handled by dev_dax_shrink\n"))
 828                 return -EINVAL;
 829
 830         rc = adjust_resource(res, range->start, size);
 831         if (rc)
 832                 return rc;
 833
 834         *range = (struct range) {
 835                 .start = range->start,
 836                 .end = range->start + size - 1,
 837         };
 838
 839         dev_dbg(dev, "%s range[%d]: %#llx:%#llx\n", is_shrink ? "shrink" : "extend",
 840                         last_range, (unsigned long long) range->start,
 841                         (unsigned long long) range->end);
 842
 843         return 0;
 844 }
 845
 846 static ssize_t size_show(struct device *dev,
 847                 struct device_attribute *attr, char *buf)
 848 {
 849         struct dev_dax *dev_dax = to_dev_dax(dev);
 850         unsigned long long size;
 851
 852         device_lock(dev);
 853         size = dev_dax_size(dev_dax);
 854         device_unlock(dev);
 855
 856         return sprintf(buf, "%llu\n", size);
 857 }
 858
 859 static bool alloc_is_aligned(struct dev_dax *dev_dax, resource_size_t size)
 860 {
 861         /*
 862          * The minimum mapping granularity for a device instance is a
 863          * single subsection, unless the arch says otherwise.
 864          */
 865         return IS_ALIGNED(size, max_t(unsigned long, dev_dax->align, memremap_compat_align()));
 866 }
 867
 868 static int dev_dax_shrink(struct dev_dax *dev_dax, resource_size_t size)
 869 {
 870         resource_size_t to_shrink = dev_dax_size(dev_dax) - size;
 871         struct dax_region *dax_region = dev_dax->region;
 872         struct device *dev = &dev_dax->dev;
 873         int i;
 874
 875         for (i = dev_dax->nr_range - 1; i >= 0; i--) {
 876                 struct range *range = &dev_dax->ranges[i].range;
 877                 struct dax_mapping *mapping = dev_dax->ranges[i].mapping;
 878                 struct resource *adjust = NULL, *res;
 879                 resource_size_t shrink;
 880
 881                 shrink = min_t(u64, to_shrink, range_len(range));
 882                 if (shrink >= range_len(range)) {
 883                         devm_release_action(dax_region->dev,
 884                                         unregister_dax_mapping, &mapping->dev);
 885                         trim_dev_dax_range(dev_dax);
 886                         to_shrink -= shrink;
 887                         if (!to_shrink)
 888                                 break;
 889                         continue;
 890                 }
 891
 892                 for_each_dax_region_resource(dax_region, res)
 893                         if (strcmp(res->name, dev_name(dev)) == 0
 894                                         && res->start == range->start) {
 895                                 adjust = res;
 896                                 break;
 897                         }
 898
 899                 if (dev_WARN_ONCE(dev, !adjust || i != dev_dax->nr_range - 1,
 900                                         "failed to find matching resource\n"))
 901                         return -ENXIO;
 902                 return adjust_dev_dax_range(dev_dax, adjust, range_len(range)
 903                                 - shrink);
 904         }
 905         return 0;
 906 }
 907
 908 /*
 909  * Only allow adjustments that preserve the relative pgoff of existing
 910  * allocations. I.e. the dev_dax->ranges array is ordered by increasing pgoff.
 911  */
 912 static bool adjust_ok(struct dev_dax *dev_dax, struct resource *res)
 913 {
 914         struct dev_dax_range *last;
 915         int i;
 916
 917         if (dev_dax->nr_range == 0)
 918                 return false;
 919         if (strcmp(res->name, dev_name(&dev_dax->dev)) != 0)
 920                 return false;
 921         last = &dev_dax->ranges[dev_dax->nr_range - 1];
 922         if (last->range.start != res->start || last->range.end != res->end)
 923                 return false;
 924         for (i = 0; i < dev_dax->nr_range - 1; i++) {
 925                 struct dev_dax_range *dax_range = &dev_dax->ranges[i];
 926
 927                 if (dax_range->pgoff > last->pgoff)
 928                         return false;
 929         }
 930
 931         return true;
 932 }
 933
 934 static ssize_t dev_dax_resize(struct dax_region *dax_region,
 935                 struct dev_dax *dev_dax, resource_size_t size)
 936 {
 937         resource_size_t avail = dax_region_avail_size(dax_region), to_alloc;
 938         resource_size_t dev_size = dev_dax_size(dev_dax);
 939         struct resource *region_res = &dax_region->res;
 940         struct device *dev = &dev_dax->dev;
 941         struct resource *res, *first;
 942         resource_size_t alloc = 0;
 943         int rc;
 944
 945         if (dev->driver)
 946                 return -EBUSY;
 947         if (size == dev_size)
 948                 return 0;
 949         if (size > dev_size && size - dev_size > avail)
 950                 return -ENOSPC;
 951         if (size < dev_size)
 952                 return dev_dax_shrink(dev_dax, size);
 953
 954         to_alloc = size - dev_size;
 955         if (dev_WARN_ONCE(dev, !alloc_is_aligned(dev_dax, to_alloc),
 956                         "resize of %pa misaligned\n", &to_alloc))
 957                 return -ENXIO;
 958
 959         /*
 960          * Expand the device into the unused portion of the region. This
 961          * may involve adjusting the end of an existing resource, or
 962          * allocating a new resource.
 963          */
 964 retry:
 965         first = region_res->child;
 966         if (!first)
 967                 return alloc_dev_dax_range(dev_dax, dax_region->res.start, to_alloc);
 968
 969         rc = -ENOSPC;
 970         for (res = first; res; res = res->sibling) {
 971                 struct resource *next = res->sibling;
 972
 973                 /* space at the beginning of the region */
 974                 if (res == first && res->start > dax_region->res.start) {
 975                         alloc = min(res->start - dax_region->res.start, to_alloc);
 976                         rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, alloc);
 977                         break;
 978                 }
 979
 980                 alloc = 0;
 981                 /* space between allocations */
 982                 if (next && next->start > res->end + 1)
 983                         alloc = min(next->start - (res->end + 1), to_alloc);
 984
 985                 /* space at the end of the region */
 986                 if (!alloc && !next && res->end < region_res->end)
 987                         alloc = min(region_res->end - res->end, to_alloc);
 988
 989                 if (!alloc)
 990                         continue;
 991
 992                 if (adjust_ok(dev_dax, res)) {
 993                         rc = adjust_dev_dax_range(dev_dax, res, resource_size(res) + alloc);
 994                         break;
 995                 }
 996                 rc = alloc_dev_dax_range(dev_dax, res->end + 1, alloc);
 997                 break;
 998         }
 999         if (rc)
1000                 return rc;
1001         to_alloc -= alloc;
1002         if (to_alloc)
1003                 goto retry;
1004         return 0;
1005 }
1006
1007 static ssize_t size_store(struct device *dev, struct device_attribute *attr,
1008                 const char *buf, size_t len)
1009 {
1010         ssize_t rc;
1011         unsigned long long val;
1012         struct dev_dax *dev_dax = to_dev_dax(dev);
1013         struct dax_region *dax_region = dev_dax->region;
1014
1015         rc = kstrtoull(buf, 0, &val);
1016         if (rc)
1017                 return rc;
1018
1019         if (!alloc_is_aligned(dev_dax, val)) {
1020                 dev_dbg(dev, "%s: size: %lld misaligned\n", __func__, val);
1021                 return -EINVAL;
1022         }
1023
1024         device_lock(dax_region->dev);
1025         if (!dax_region->dev->driver) {
1026                 device_unlock(dax_region->dev);
1027                 return -ENXIO;
1028         }
1029         device_lock(dev);
1030         rc = dev_dax_resize(dax_region, dev_dax, val);
1031         device_unlock(dev);
1032         device_unlock(dax_region->dev);
1033
1034         return rc == 0 ? len : rc;
1035 }
1036 static DEVICE_ATTR_RW(size);
1037
1038 static ssize_t range_parse(const char *opt, size_t len, struct range *range)
1039 {
1040         unsigned long long addr = 0;
1041         char *start, *end, *str;
1042         ssize_t rc = -EINVAL;
1043
1044         str = kstrdup(opt, GFP_KERNEL);
1045         if (!str)
1046                 return rc;
1047
1048         end = str;
1049         start = strsep(&end, "-");
1050         if (!start || !end)
1051                 goto err;
1052
1053         rc = kstrtoull(start, 16, &addr);
1054         if (rc)
1055                 goto err;
1056         range->start = addr;
1057
1058         rc = kstrtoull(end, 16, &addr);
1059         if (rc)
1060                 goto err;
1061         range->end = addr;
1062
1063 err:
1064         kfree(str);
1065         return rc;
1066 }
1067
1068 static ssize_t mapping_store(struct device *dev, struct device_attribute *attr,
1069                 const char *buf, size_t len)
1070 {
1071         struct dev_dax *dev_dax = to_dev_dax(dev);
1072         struct dax_region *dax_region = dev_dax->region;
1073         size_t to_alloc;
1074         struct range r;
1075         ssize_t rc;
1076
1077         rc = range_parse(buf, len, &r);
1078         if (rc)
1079                 return rc;
1080
1081         rc = -ENXIO;
1082         device_lock(dax_region->dev);
1083         if (!dax_region->dev->driver) {
1084                 device_unlock(dax_region->dev);
1085                 return rc;
1086         }
1087         device_lock(dev);
1088
1089         to_alloc = range_len(&r);
1090         if (alloc_is_aligned(dev_dax, to_alloc))
1091                 rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
1092         device_unlock(dev);
1093         device_unlock(dax_region->dev);
1094
1095         return rc == 0 ? len : rc;
1096 }
1097 static DEVICE_ATTR_WO(mapping);
1098
1099 static ssize_t align_show(struct device *dev,
1100                 struct device_attribute *attr, char *buf)
1101 {
1102         struct dev_dax *dev_dax = to_dev_dax(dev);
1103
1104         return sprintf(buf, "%d\n", dev_dax->align);
1105 }
1106
1107 static ssize_t dev_dax_validate_align(struct dev_dax *dev_dax)
1108 {
1109         struct device *dev = &dev_dax->dev;
1110         int i;
1111
1112         for (i = 0; i < dev_dax->nr_range; i++) {
1113                 size_t len = range_len(&dev_dax->ranges[i].range);
1114
1115                 if (!alloc_is_aligned(dev_dax, len)) {
1116                         dev_dbg(dev, "%s: align %u invalid for range %d\n",
1117                                 __func__, dev_dax->align, i);
1118                         return -EINVAL;
1119                 }
1120         }
1121
1122         return 0;
1123 }
1124
1125 static ssize_t align_store(struct device *dev, struct device_attribute *attr,
1126                 const char *buf, size_t len)
1127 {
1128         struct dev_dax *dev_dax = to_dev_dax(dev);
1129         struct dax_region *dax_region = dev_dax->region;
1130         unsigned long val, align_save;
1131         ssize_t rc;
1132
1133         rc = kstrtoul(buf, 0, &val);
1134         if (rc)
1135                 return -ENXIO;
1136
1137         if (!dax_align_valid(val))
1138                 return -EINVAL;
1139
1140         device_lock(dax_region->dev);
1141         if (!dax_region->dev->driver) {
1142                 device_unlock(dax_region->dev);
1143                 return -ENXIO;
1144         }
1145
1146         device_lock(dev);
1147         if (dev->driver) {
1148                 rc = -EBUSY;
1149                 goto out_unlock;
1150         }
1151
1152         align_save = dev_dax->align;
1153         dev_dax->align = val;
1154         rc = dev_dax_validate_align(dev_dax);
1155         if (rc)
1156                 dev_dax->align = align_save;
1157 out_unlock:
1158         device_unlock(dev);
1159         device_unlock(dax_region->dev);
1160         return rc == 0 ? len : rc;
1161 }
1162 static DEVICE_ATTR_RW(align);
1163
1164 static int dev_dax_target_node(struct dev_dax *dev_dax)
1165 {
1166         struct dax_region *dax_region = dev_dax->region;
1167
1168         return dax_region->target_node;
1169 }
1170
1171 static ssize_t target_node_show(struct device *dev,
1172                 struct device_attribute *attr, char *buf)
1173 {
1174         struct dev_dax *dev_dax = to_dev_dax(dev);
1175
1176         return sprintf(buf, "%d\n", dev_dax_target_node(dev_dax));
1177 }
1178 static DEVICE_ATTR_RO(target_node);
1179
1180 static ssize_t resource_show(struct device *dev,
1181                 struct device_attribute *attr, char *buf)
1182 {
1183         struct dev_dax *dev_dax = to_dev_dax(dev);
1184         struct dax_region *dax_region = dev_dax->region;
1185         unsigned long long start;
1186
1187         if (dev_dax->nr_range < 1)
1188                 start = dax_region->res.start;
1189         else
1190                 start = dev_dax->ranges[0].range.start;
1191
1192         return sprintf(buf, "%#llx\n", start);
1193 }
1194 static DEVICE_ATTR(resource, 0400, resource_show, NULL);
1195
1196 static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
1197                 char *buf)
1198 {
1199         /*
1200          * We only ever expect to handle device-dax instances, i.e. the
1201          * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
1202          */
1203         return sprintf(buf, DAX_DEVICE_MODALIAS_FMT "\n", 0);
1204 }
1205 static DEVICE_ATTR_RO(modalias);
1206
1207 static ssize_t numa_node_show(struct device *dev,
1208                 struct device_attribute *attr, char *buf)
1209 {
1210         return sprintf(buf, "%d\n", dev_to_node(dev));
1211 }
1212 static DEVICE_ATTR_RO(numa_node);
1213
1214 static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n)
1215 {
1216         struct device *dev = container_of(kobj, struct device, kobj);
1217         struct dev_dax *dev_dax = to_dev_dax(dev);
1218         struct dax_region *dax_region = dev_dax->region;
1219
1220         if (a == &dev_attr_target_node.attr && dev_dax_target_node(dev_dax) < 0)
1221                 return 0;
1222         if (a == &dev_attr_numa_node.attr && !IS_ENABLED(CONFIG_NUMA))
1223                 return 0;
1224         if (a == &dev_attr_mapping.attr && is_static(dax_region))
1225                 return 0;
1226         if ((a == &dev_attr_align.attr ||
1227              a == &dev_attr_size.attr) && is_static(dax_region))
1228                 return 0444;
1229         return a->mode;
1230 }
1231
1232 static struct attribute *dev_dax_attributes[] = {
1233         &dev_attr_modalias.attr,
1234         &dev_attr_size.attr,
1235         &dev_attr_mapping.attr,
1236         &dev_attr_target_node.attr,
1237         &dev_attr_align.attr,
1238         &dev_attr_resource.attr,
1239         &dev_attr_numa_node.attr,
1240         NULL,
1241 };
1242
1243 static const struct attribute_group dev_dax_attribute_group = {
1244         .attrs = dev_dax_attributes,
1245         .is_visible = dev_dax_visible,
1246 };
1247
1248 static const struct attribute_group *dax_attribute_groups[] = {
1249         &dev_dax_attribute_group,
1250         NULL,
1251 };
1252
1253 static void dev_dax_release(struct device *dev)
1254 {
1255         struct dev_dax *dev_dax = to_dev_dax(dev);
1256         struct dax_region *dax_region = dev_dax->region;
1257         struct dax_device *dax_dev = dev_dax->dax_dev;
1258
1259         put_dax(dax_dev);
1260         free_dev_dax_id(dev_dax);
1261         dax_region_put(dax_region);
1262         kfree(dev_dax->pgmap);
1263         kfree(dev_dax);
1264 }
1265
1266 static const struct device_type dev_dax_type = {
1267         .release = dev_dax_release,
1268         .groups = dax_attribute_groups,
1269 };
1270
1271 struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
1272 {
1273         struct dax_region *dax_region = data->dax_region;
1274         struct device *parent = dax_region->dev;
1275         struct dax_device *dax_dev;
1276         struct dev_dax *dev_dax;
1277         struct inode *inode;
1278         struct device *dev;
1279         int rc;
1280
1281         dev_dax = kzalloc(sizeof(*dev_dax), GFP_KERNEL);
1282         if (!dev_dax)
1283                 return ERR_PTR(-ENOMEM);
1284
1285         if (is_static(dax_region)) {
1286                 if (dev_WARN_ONCE(parent, data->id < 0,
1287                                 "dynamic id specified to static region\n")) {
1288                         rc = -EINVAL;
1289                         goto err_id;
1290                 }
1291
1292                 dev_dax->id = data->id;
1293         } else {
1294                 if (dev_WARN_ONCE(parent, data->id >= 0,
1295                                 "static id specified to dynamic region\n")) {
1296                         rc = -EINVAL;
1297                         goto err_id;
1298                 }
1299
1300                 rc = ida_alloc(&dax_region->ida, GFP_KERNEL);
1301                 if (rc < 0)
1302                         goto err_id;
1303                 dev_dax->id = rc;
1304         }
1305
1306         dev_dax->region = dax_region;
1307         dev = &dev_dax->dev;
1308         device_initialize(dev);
1309         dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id);
1310
1311         rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, data->size);
1312         if (rc)
1313                 goto err_range;
1314
1315         if (data->pgmap) {
1316                 dev_WARN_ONCE(parent, !is_static(dax_region),
1317                         "custom dev_pagemap requires a static dax_region\n");
1318
1319                 dev_dax->pgmap = kmemdup(data->pgmap,
1320                                 sizeof(struct dev_pagemap), GFP_KERNEL);
1321                 if (!dev_dax->pgmap) {
1322                         rc = -ENOMEM;
1323                         goto err_pgmap;
1324                 }
1325         }
1326
1327         /*
1328          * No 'host' or dax_operations since there is no access to this
1329          * device outside of mmap of the resulting character device.
1330          */
1331         dax_dev = alloc_dax(dev_dax, NULL, NULL, DAXDEV_F_SYNC);
1332         if (IS_ERR(dax_dev)) {
1333                 rc = PTR_ERR(dax_dev);
1334                 goto err_alloc_dax;
1335         }
1336
1337         /* a device_dax instance is dead while the driver is not attached */
1338         kill_dax(dax_dev);
1339
1340         dev_dax->dax_dev = dax_dev;
1341         dev_dax->target_node = dax_region->target_node;
1342         dev_dax->align = dax_region->align;
1343         ida_init(&dev_dax->ida);
1344         kref_get(&dax_region->kref);
1345
1346         inode = dax_inode(dax_dev);
1347         dev->devt = inode->i_rdev;
1348         if (data->subsys == DEV_DAX_BUS)
1349                 dev->bus = &dax_bus_type;
1350         else
1351                 dev->class = dax_class;
1352         dev->parent = parent;
1353         dev->type = &dev_dax_type;
1354
1355         rc = device_add(dev);
1356         if (rc) {
1357                 kill_dev_dax(dev_dax);
1358                 put_device(dev);
1359                 return ERR_PTR(rc);
1360         }
1361
1362         rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
1363         if (rc)
1364                 return ERR_PTR(rc);
1365
1366         /* register mapping device for the initial allocation range */
1367         if (dev_dax->nr_range && range_len(&dev_dax->ranges[0].range)) {
1368                 rc = devm_register_dax_mapping(dev_dax, 0);
1369                 if (rc)
1370                         return ERR_PTR(rc);
1371         }
1372
1373         return dev_dax;
1374
1375 err_alloc_dax:
1376         kfree(dev_dax->pgmap);
1377 err_pgmap:
1378         free_dev_dax_ranges(dev_dax);
1379 err_range:
1380         free_dev_dax_id(dev_dax);
1381 err_id:
1382         kfree(dev_dax);
1383
1384         return ERR_PTR(rc);
1385 }
1386 EXPORT_SYMBOL_GPL(devm_create_dev_dax);
1387
1388 static int match_always_count;
1389
1390 int __dax_driver_register(struct dax_device_driver *dax_drv,
1391                 struct module *module, const char *mod_name)
1392 {
1393         struct device_driver *drv = &dax_drv->drv;
1394         int rc = 0;
1395
1396         /*
1397          * dax_bus_probe() calls dax_drv->probe() unconditionally.
1398          * So better be safe than sorry and ensure it is provided.
1399          */
1400         if (!dax_drv->probe)
1401                 return -EINVAL;
1402
1403         INIT_LIST_HEAD(&dax_drv->ids);
1404         drv->owner = module;
1405         drv->name = mod_name;
1406         drv->mod_name = mod_name;
1407         drv->bus = &dax_bus_type;
1408
1409         /* there can only be one default driver */
1410         mutex_lock(&dax_bus_lock);
1411         match_always_count += dax_drv->match_always;
1412         if (match_always_count > 1) {
1413                 match_always_count--;
1414                 WARN_ON(1);
1415                 rc = -EINVAL;
1416         }
1417         mutex_unlock(&dax_bus_lock);
1418         if (rc)
1419                 return rc;
1420
1421         rc = driver_register(drv);
1422         if (rc && dax_drv->match_always) {
1423                 mutex_lock(&dax_bus_lock);
1424                 match_always_count -= dax_drv->match_always;
1425                 mutex_unlock(&dax_bus_lock);
1426         }
1427
1428         return rc;
1429 }
1430 EXPORT_SYMBOL_GPL(__dax_driver_register);
1431
1432 void dax_driver_unregister(struct dax_device_driver *dax_drv)
1433 {
1434         struct device_driver *drv = &dax_drv->drv;
1435         struct dax_id *dax_id, *_id;
1436
1437         mutex_lock(&dax_bus_lock);
1438         match_always_count -= dax_drv->match_always;
1439         list_for_each_entry_safe(dax_id, _id, &dax_drv->ids, list) {
1440                 list_del(&dax_id->list);
1441                 kfree(dax_id);
1442         }
1443         mutex_unlock(&dax_bus_lock);
1444         driver_unregister(drv);
1445 }
1446 EXPORT_SYMBOL_GPL(dax_driver_unregister);
1447
1448 int __init dax_bus_init(void)
1449 {
1450         int rc;
1451
1452         if (IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)) {
1453                 dax_class = class_create(THIS_MODULE, "dax");
1454                 if (IS_ERR(dax_class))
1455                         return PTR_ERR(dax_class);
1456         }
1457
1458         rc = bus_register(&dax_bus_type);
1459         if (rc)
1460                 class_destroy(dax_class);
1461         return rc;
1462 }
1463
1464 void __exit dax_bus_exit(void)
1465 {
1466         bus_unregister(&dax_bus_type);
1467         class_destroy(dax_class);
1468 }