drivers/dax/super.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright(c) 2017 Intel Corporation. All rights reserved.
   4  */
   5 #include <linux/pagemap.h>
   6 #include <linux/module.h>
   7 #include <linux/mount.h>
   8 #include <linux/pseudo_fs.h>
   9 #include <linux/magic.h>
  10 #include <linux/pfn_t.h>
  11 #include <linux/cdev.h>
  12 #include <linux/slab.h>
  13 #include <linux/uio.h>
  14 #include <linux/dax.h>
  15 #include <linux/fs.h>
  16 #include <linux/cacheinfo.h>
  17 #include "dax-private.h"
  18
  19 /**
  20  * struct dax_device - anchor object for dax services
  21  * @inode: core vfs
  22  * @cdev: optional character interface for "device dax"
  23  * @private: dax driver private data
  24  * @flags: state and boolean properties
  25  * @ops: operations for this device
  26  * @holder_data: holder of a dax_device: could be filesystem or mapped device
  27  * @holder_ops: operations for the inner holder
  28  */
  29 struct dax_device {
  30         struct inode inode;
  31         struct cdev cdev;
  32         void *private;
  33         unsigned long flags;
  34         const struct dax_operations *ops;
  35         void *holder_data;
  36         const struct dax_holder_operations *holder_ops;
  37 };
  38
  39 static dev_t dax_devt;
  40 DEFINE_STATIC_SRCU(dax_srcu);
  41 static struct vfsmount *dax_mnt;
  42 static DEFINE_IDA(dax_minor_ida);
  43 static struct kmem_cache *dax_cache __read_mostly;
  44 static struct super_block *dax_superblock __read_mostly;
  45
  46 int dax_read_lock(void)
  47 {
  48         return srcu_read_lock(&dax_srcu);
  49 }
  50 EXPORT_SYMBOL_GPL(dax_read_lock);
  51
  52 void dax_read_unlock(int id)
  53 {
  54         srcu_read_unlock(&dax_srcu, id);
  55 }
  56 EXPORT_SYMBOL_GPL(dax_read_unlock);
  57
  58 #if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
  59 #include <linux/blkdev.h>
  60
  61 static DEFINE_XARRAY(dax_hosts);
  62
  63 int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
  64 {
  65         return xa_insert(&dax_hosts, (unsigned long)disk, dax_dev, GFP_KERNEL);
  66 }
  67 EXPORT_SYMBOL_GPL(dax_add_host);
  68
  69 void dax_remove_host(struct gendisk *disk)
  70 {
  71         xa_erase(&dax_hosts, (unsigned long)disk);
  72 }
  73 EXPORT_SYMBOL_GPL(dax_remove_host);
  74
  75 /**
  76  * fs_dax_get_by_bdev() - temporary lookup mechanism for filesystem-dax
  77  * @bdev: block device to find a dax_device for
  78  * @start_off: returns the byte offset into the dax_device that @bdev starts
  79  * @holder: filesystem or mapped device inside the dax_device
  80  * @ops: operations for the inner holder
  81  */
  82 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,
  83                 void *holder, const struct dax_holder_operations *ops)
  84 {
  85         struct dax_device *dax_dev;
  86         u64 part_size;
  87         int id;
  88
  89         if (!blk_queue_dax(bdev->bd_disk->queue))
  90                 return NULL;
  91
  92         *start_off = get_start_sect(bdev) * SECTOR_SIZE;
  93         part_size = bdev_nr_sectors(bdev) * SECTOR_SIZE;
  94         if (*start_off % PAGE_SIZE || part_size % PAGE_SIZE) {
  95                 pr_info("%pg: error: unaligned partition for dax\n", bdev);
  96                 return NULL;
  97         }
  98
  99         id = dax_read_lock();
 100         dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
 101         if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
 102                 dax_dev = NULL;
 103         else if (holder) {
 104                 if (!cmpxchg(&dax_dev->holder_data, NULL, holder))
 105                         dax_dev->holder_ops = ops;
 106                 else
 107                         dax_dev = NULL;
 108         }
 109         dax_read_unlock(id);
 110
 111         return dax_dev;
 112 }
 113 EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
 114
 115 void fs_put_dax(struct dax_device *dax_dev, void *holder)
 116 {
 117         if (dax_dev && holder &&
 118             cmpxchg(&dax_dev->holder_data, holder, NULL) == holder)
 119                 dax_dev->holder_ops = NULL;
 120         put_dax(dax_dev);
 121 }
 122 EXPORT_SYMBOL_GPL(fs_put_dax);
 123 #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
 124
 125 enum dax_device_flags {
 126         /* !alive + rcu grace period == no new operations / mappings */
 127         DAXDEV_ALIVE,
 128         /* gate whether dax_flush() calls the low level flush routine */
 129         DAXDEV_WRITE_CACHE,
 130         /* flag to check if device supports synchronous flush */
 131         DAXDEV_SYNC,
 132         /* do not leave the caches dirty after writes */
 133         DAXDEV_NOCACHE,
 134         /* handle CPU fetch exceptions during reads */
 135         DAXDEV_NOMC,
 136 };
 137
 138 /**
 139  * dax_direct_access() - translate a device pgoff to an absolute pfn
 140  * @dax_dev: a dax_device instance representing the logical memory range
 141  * @pgoff: offset in pages from the start of the device to translate
 142  * @nr_pages: number of consecutive pages caller can handle relative to @pfn
 143  * @mode: indicator on normal access or recovery write
 144  * @kaddr: output parameter that returns a virtual address mapping of pfn
 145  * @pfn: output parameter that returns an absolute pfn translation of @pgoff
 146  *
 147  * Return: negative errno if an error occurs, otherwise the number of
 148  * pages accessible at the device relative @pgoff.
 149  */
 150 long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
 151                 enum dax_access_mode mode, void **kaddr, pfn_t *pfn)
 152 {
 153         long avail;
 154
 155         if (!dax_dev)
 156                 return -EOPNOTSUPP;
 157
 158         if (!dax_alive(dax_dev))
 159                 return -ENXIO;
 160
 161         if (nr_pages < 0)
 162                 return -EINVAL;
 163
 164         avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
 165                         mode, kaddr, pfn);
 166         if (!avail)
 167                 return -ERANGE;
 168         return min(avail, nr_pages);
 169 }
 170 EXPORT_SYMBOL_GPL(dax_direct_access);
 171
 172 size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
 173                 size_t bytes, struct iov_iter *i)
 174 {
 175         if (!dax_alive(dax_dev))
 176                 return 0;
 177
 178         /*
 179          * The userspace address for the memory copy has already been validated
 180          * via access_ok() in vfs_write, so use the 'no check' version to bypass
 181          * the HARDENED_USERCOPY overhead.
 182          */
 183         if (test_bit(DAXDEV_NOCACHE, &dax_dev->flags))
 184                 return _copy_from_iter_flushcache(addr, bytes, i);
 185         return _copy_from_iter(addr, bytes, i);
 186 }
 187
 188 size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
 189                 size_t bytes, struct iov_iter *i)
 190 {
 191         if (!dax_alive(dax_dev))
 192                 return 0;
 193
 194         /*
 195          * The userspace address for the memory copy has already been validated
 196          * via access_ok() in vfs_red, so use the 'no check' version to bypass
 197          * the HARDENED_USERCOPY overhead.
 198          */
 199         if (test_bit(DAXDEV_NOMC, &dax_dev->flags))
 200                 return _copy_mc_to_iter(addr, bytes, i);
 201         return _copy_to_iter(addr, bytes, i);
 202 }
 203
 204 int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
 205                         size_t nr_pages)
 206 {
 207         int ret;
 208
 209         if (!dax_alive(dax_dev))
 210                 return -ENXIO;
 211         /*
 212          * There are no callers that want to zero more than one page as of now.
 213          * Once users are there, this check can be removed after the
 214          * device mapper code has been updated to split ranges across targets.
 215          */
 216         if (nr_pages != 1)
 217                 return -EIO;
 218
 219         ret = dax_dev->ops->zero_page_range(dax_dev, pgoff, nr_pages);
 220         return dax_mem2blk_err(ret);
 221 }
 222 EXPORT_SYMBOL_GPL(dax_zero_page_range);
 223
 224 size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
 225                 void *addr, size_t bytes, struct iov_iter *iter)
 226 {
 227         if (!dax_dev->ops->recovery_write)
 228                 return 0;
 229         return dax_dev->ops->recovery_write(dax_dev, pgoff, addr, bytes, iter);
 230 }
 231 EXPORT_SYMBOL_GPL(dax_recovery_write);
 232
 233 int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off,
 234                               u64 len, int mf_flags)
 235 {
 236         int rc, id;
 237
 238         id = dax_read_lock();
 239         if (!dax_alive(dax_dev)) {
 240                 rc = -ENXIO;
 241                 goto out;
 242         }
 243
 244         if (!dax_dev->holder_ops) {
 245                 rc = -EOPNOTSUPP;
 246                 goto out;
 247         }
 248
 249         rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags);
 250 out:
 251         dax_read_unlock(id);
 252         return rc;
 253 }
 254 EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
 255
 256 #ifdef CONFIG_ARCH_HAS_PMEM_API
 257 void arch_wb_cache_pmem(void *addr, size_t size);
 258 void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
 259 {
 260         if (unlikely(!dax_write_cache_enabled(dax_dev)))
 261                 return;
 262
 263         arch_wb_cache_pmem(addr, size);
 264 }
 265 #else
 266 void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
 267 {
 268 }
 269 #endif
 270 EXPORT_SYMBOL_GPL(dax_flush);
 271
 272 void dax_write_cache(struct dax_device *dax_dev, bool wc)
 273 {
 274         if (wc)
 275                 set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
 276         else
 277                 clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
 278 }
 279 EXPORT_SYMBOL_GPL(dax_write_cache);
 280
 281 bool dax_write_cache_enabled(struct dax_device *dax_dev)
 282 {
 283         return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
 284 }
 285 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 286
 287 bool dax_synchronous(struct dax_device *dax_dev)
 288 {
 289         return test_bit(DAXDEV_SYNC, &dax_dev->flags);
 290 }
 291 EXPORT_SYMBOL_GPL(dax_synchronous);
 292
 293 void set_dax_synchronous(struct dax_device *dax_dev)
 294 {
 295         set_bit(DAXDEV_SYNC, &dax_dev->flags);
 296 }
 297 EXPORT_SYMBOL_GPL(set_dax_synchronous);
 298
 299 void set_dax_nocache(struct dax_device *dax_dev)
 300 {
 301         set_bit(DAXDEV_NOCACHE, &dax_dev->flags);
 302 }
 303 EXPORT_SYMBOL_GPL(set_dax_nocache);
 304
 305 void set_dax_nomc(struct dax_device *dax_dev)
 306 {
 307         set_bit(DAXDEV_NOMC, &dax_dev->flags);
 308 }
 309 EXPORT_SYMBOL_GPL(set_dax_nomc);
 310
 311 bool dax_alive(struct dax_device *dax_dev)
 312 {
 313         lockdep_assert_held(&dax_srcu);
 314         return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
 315 }
 316 EXPORT_SYMBOL_GPL(dax_alive);
 317
 318 /*
 319  * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
 320  * that any fault handlers or operations that might have seen
 321  * dax_alive(), have completed.  Any operations that start after
 322  * synchronize_srcu() has run will abort upon seeing !dax_alive().
 323  *
 324  * Note, because alloc_dax() returns an ERR_PTR() on error, callers
 325  * typically store its result into a local variable in order to check
 326  * the result. Therefore, care must be taken to populate the struct
 327  * device dax_dev field make sure the dax_dev is not leaked.
 328  */
 329 void kill_dax(struct dax_device *dax_dev)
 330 {
 331         if (!dax_dev)
 332                 return;
 333
 334         if (dax_dev->holder_data != NULL)
 335                 dax_holder_notify_failure(dax_dev, 0, U64_MAX,
 336                                 MF_MEM_PRE_REMOVE);
 337
 338         clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
 339         synchronize_srcu(&dax_srcu);
 340
 341         /* clear holder data */
 342         dax_dev->holder_ops = NULL;
 343         dax_dev->holder_data = NULL;
 344 }
 345 EXPORT_SYMBOL_GPL(kill_dax);
 346
 347 void run_dax(struct dax_device *dax_dev)
 348 {
 349         set_bit(DAXDEV_ALIVE, &dax_dev->flags);
 350 }
 351 EXPORT_SYMBOL_GPL(run_dax);
 352
 353 static struct inode *dax_alloc_inode(struct super_block *sb)
 354 {
 355         struct dax_device *dax_dev;
 356         struct inode *inode;
 357
 358         dax_dev = alloc_inode_sb(sb, dax_cache, GFP_KERNEL);
 359         if (!dax_dev)
 360                 return NULL;
 361
 362         inode = &dax_dev->inode;
 363         inode->i_rdev = 0;
 364         return inode;
 365 }
 366
 367 static struct dax_device *to_dax_dev(struct inode *inode)
 368 {
 369         return container_of(inode, struct dax_device, inode);
 370 }
 371
 372 static void dax_free_inode(struct inode *inode)
 373 {
 374         struct dax_device *dax_dev = to_dax_dev(inode);
 375         if (inode->i_rdev)
 376                 ida_free(&dax_minor_ida, iminor(inode));
 377         kmem_cache_free(dax_cache, dax_dev);
 378 }
 379
 380 static void dax_destroy_inode(struct inode *inode)
 381 {
 382         struct dax_device *dax_dev = to_dax_dev(inode);
 383         WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
 384                         "kill_dax() must be called before final iput()\n");
 385 }
 386
 387 static const struct super_operations dax_sops = {
 388         .statfs = simple_statfs,
 389         .alloc_inode = dax_alloc_inode,
 390         .destroy_inode = dax_destroy_inode,
 391         .free_inode = dax_free_inode,
 392         .drop_inode = generic_delete_inode,
 393 };
 394
 395 static int dax_init_fs_context(struct fs_context *fc)
 396 {
 397         struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
 398         if (!ctx)
 399                 return -ENOMEM;
 400         ctx->ops = &dax_sops;
 401         return 0;
 402 }
 403
 404 static struct file_system_type dax_fs_type = {
 405         .name           = "dax",
 406         .init_fs_context = dax_init_fs_context,
 407         .kill_sb        = kill_anon_super,
 408 };
 409
 410 static int dax_test(struct inode *inode, void *data)
 411 {
 412         dev_t devt = *(dev_t *) data;
 413
 414         return inode->i_rdev == devt;
 415 }
 416
 417 static int dax_set(struct inode *inode, void *data)
 418 {
 419         dev_t devt = *(dev_t *) data;
 420
 421         inode->i_rdev = devt;
 422         return 0;
 423 }
 424
 425 static struct dax_device *dax_dev_get(dev_t devt)
 426 {
 427         struct dax_device *dax_dev;
 428         struct inode *inode;
 429
 430         inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
 431                         dax_test, dax_set, &devt);
 432
 433         if (!inode)
 434                 return NULL;
 435
 436         dax_dev = to_dax_dev(inode);
 437         if (inode->i_state & I_NEW) {
 438                 set_bit(DAXDEV_ALIVE, &dax_dev->flags);
 439                 inode->i_cdev = &dax_dev->cdev;
 440                 inode->i_mode = S_IFCHR;
 441                 inode->i_flags = S_DAX;
 442                 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
 443                 unlock_new_inode(inode);
 444         }
 445
 446         return dax_dev;
 447 }
 448
 449 struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
 450 {
 451         struct dax_device *dax_dev;
 452         dev_t devt;
 453         int minor;
 454
 455         /*
 456          * Unavailable on architectures with virtually aliased data caches,
 457          * except for device-dax (NULL operations pointer), which does
 458          * not use aliased mappings from the kernel.
 459          */
 460         if (ops && cpu_dcache_is_aliasing())
 461                 return ERR_PTR(-EOPNOTSUPP);
 462
 463         if (WARN_ON_ONCE(ops && !ops->zero_page_range))
 464                 return ERR_PTR(-EINVAL);
 465
 466         minor = ida_alloc_max(&dax_minor_ida, MINORMASK, GFP_KERNEL);
 467         if (minor < 0)
 468                 return ERR_PTR(-ENOMEM);
 469
 470         devt = MKDEV(MAJOR(dax_devt), minor);
 471         dax_dev = dax_dev_get(devt);
 472         if (!dax_dev)
 473                 goto err_dev;
 474
 475         dax_dev->ops = ops;
 476         dax_dev->private = private;
 477         return dax_dev;
 478
 479  err_dev:
 480         ida_free(&dax_minor_ida, minor);
 481         return ERR_PTR(-ENOMEM);
 482 }
 483 EXPORT_SYMBOL_GPL(alloc_dax);
 484
 485 void put_dax(struct dax_device *dax_dev)
 486 {
 487         if (!dax_dev)
 488                 return;
 489         iput(&dax_dev->inode);
 490 }
 491 EXPORT_SYMBOL_GPL(put_dax);
 492
 493 /**
 494  * dax_holder() - obtain the holder of a dax device
 495  * @dax_dev: a dax_device instance
 496  *
 497  * Return: the holder's data which represents the holder if registered,
 498  * otherwize NULL.
 499  */
 500 void *dax_holder(struct dax_device *dax_dev)
 501 {
 502         return dax_dev->holder_data;
 503 }
 504 EXPORT_SYMBOL_GPL(dax_holder);
 505
 506 /**
 507  * inode_dax: convert a public inode into its dax_dev
 508  * @inode: An inode with i_cdev pointing to a dax_dev
 509  *
 510  * Note this is not equivalent to to_dax_dev() which is for private
 511  * internal use where we know the inode filesystem type == dax_fs_type.
 512  */
 513 struct dax_device *inode_dax(struct inode *inode)
 514 {
 515         struct cdev *cdev = inode->i_cdev;
 516
 517         return container_of(cdev, struct dax_device, cdev);
 518 }
 519 EXPORT_SYMBOL_GPL(inode_dax);
 520
 521 struct inode *dax_inode(struct dax_device *dax_dev)
 522 {
 523         return &dax_dev->inode;
 524 }
 525 EXPORT_SYMBOL_GPL(dax_inode);
 526
 527 void *dax_get_private(struct dax_device *dax_dev)
 528 {
 529         if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
 530                 return NULL;
 531         return dax_dev->private;
 532 }
 533 EXPORT_SYMBOL_GPL(dax_get_private);
 534
 535 static void init_once(void *_dax_dev)
 536 {
 537         struct dax_device *dax_dev = _dax_dev;
 538         struct inode *inode = &dax_dev->inode;
 539
 540         memset(dax_dev, 0, sizeof(*dax_dev));
 541         inode_init_once(inode);
 542 }
 543
 544 static int dax_fs_init(void)
 545 {
 546         int rc;
 547
 548         dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
 549                         SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
 550                         init_once);
 551         if (!dax_cache)
 552                 return -ENOMEM;
 553
 554         dax_mnt = kern_mount(&dax_fs_type);
 555         if (IS_ERR(dax_mnt)) {
 556                 rc = PTR_ERR(dax_mnt);
 557                 goto err_mount;
 558         }
 559         dax_superblock = dax_mnt->mnt_sb;
 560
 561         return 0;
 562
 563  err_mount:
 564         kmem_cache_destroy(dax_cache);
 565
 566         return rc;
 567 }
 568
 569 static void dax_fs_exit(void)
 570 {
 571         kern_unmount(dax_mnt);
 572         rcu_barrier();
 573         kmem_cache_destroy(dax_cache);
 574 }
 575
 576 static int __init dax_core_init(void)
 577 {
 578         int rc;
 579
 580         rc = dax_fs_init();
 581         if (rc)
 582                 return rc;
 583
 584         rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
 585         if (rc)
 586                 goto err_chrdev;
 587
 588         rc = dax_bus_init();
 589         if (rc)
 590                 goto err_bus;
 591         return 0;
 592
 593 err_bus:
 594         unregister_chrdev_region(dax_devt, MINORMASK+1);
 595 err_chrdev:
 596         dax_fs_exit();
 597         return 0;
 598 }
 599
 600 static void __exit dax_core_exit(void)
 601 {
 602         dax_bus_exit();
 603         unregister_chrdev_region(dax_devt, MINORMASK+1);
 604         ida_destroy(&dax_minor_ida);
 605         dax_fs_exit();
 606 }
 607
 608 MODULE_AUTHOR("Intel Corporation");
 609 MODULE_DESCRIPTION("DAX: direct access to differentiated memory");
 610 MODULE_LICENSE("GPL v2");
 611 subsys_initcall(dax_core_init);
 612 module_exit(dax_core_exit);