1 /* 2 * Copyright(c) 2017 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/mount.h> 16 #include <linux/magic.h> 17 #include <linux/genhd.h> 18 #include <linux/cdev.h> 19 #include <linux/hash.h> 20 #include <linux/slab.h> 21 #include <linux/uio.h> 22 #include <linux/dax.h> 23 #include <linux/fs.h> 24 25 static dev_t dax_devt; 26 DEFINE_STATIC_SRCU(dax_srcu); 27 static struct vfsmount *dax_mnt; 28 static DEFINE_IDA(dax_minor_ida); 29 static struct kmem_cache *dax_cache __read_mostly; 30 static struct super_block *dax_superblock __read_mostly; 31 32 #define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head)) 33 static struct hlist_head dax_host_list[DAX_HASH_SIZE]; 34 static DEFINE_SPINLOCK(dax_host_lock); 35 36 int dax_read_lock(void) 37 { 38 return srcu_read_lock(&dax_srcu); 39 } 40 EXPORT_SYMBOL_GPL(dax_read_lock); 41 42 void dax_read_unlock(int id) 43 { 44 srcu_read_unlock(&dax_srcu, id); 45 } 46 EXPORT_SYMBOL_GPL(dax_read_unlock); 47 48 #ifdef CONFIG_BLOCK 49 int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size, 50 pgoff_t *pgoff) 51 { 52 phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512; 53 54 if (pgoff) 55 *pgoff = PHYS_PFN(phys_off); 56 if (phys_off % PAGE_SIZE || size % PAGE_SIZE) 57 return -EINVAL; 58 return 0; 59 } 60 EXPORT_SYMBOL(bdev_dax_pgoff); 61 62 /** 63 * __bdev_dax_supported() - Check if the device supports dax for filesystem 64 * @sb: The superblock of the device 65 * @blocksize: The block size of the device 66 * 67 * This is a library function for filesystems to check if the block device 68 * can be mounted with dax option. 69 * 70 * Return: negative errno if unsupported, 0 if supported. 71 */ 72 int __bdev_dax_supported(struct super_block *sb, int blocksize) 73 { 74 struct block_device *bdev = sb->s_bdev; 75 struct dax_device *dax_dev; 76 pgoff_t pgoff; 77 int err, id; 78 void *kaddr; 79 pfn_t pfn; 80 long len; 81 82 if (blocksize != PAGE_SIZE) { 83 pr_err("VFS (%s): error: unsupported blocksize for dax\n", 84 sb->s_id); 85 return -EINVAL; 86 } 87 88 err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff); 89 if (err) { 90 pr_err("VFS (%s): error: unaligned partition for dax\n", 91 sb->s_id); 92 return err; 93 } 94 95 dax_dev = dax_get_by_host(bdev->bd_disk->disk_name); 96 if (!dax_dev) { 97 pr_err("VFS (%s): error: device does not support dax\n", 98 sb->s_id); 99 return -EOPNOTSUPP; 100 } 101 102 id = dax_read_lock(); 103 len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn); 104 dax_read_unlock(id); 105 106 put_dax(dax_dev); 107 108 if (len < 1) { 109 pr_err("VFS (%s): error: dax access failed (%ld)", 110 sb->s_id, len); 111 return len < 0 ? len : -EIO; 112 } 113 114 return 0; 115 } 116 EXPORT_SYMBOL_GPL(__bdev_dax_supported); 117 #endif 118 119 enum dax_device_flags { 120 /* !alive + rcu grace period == no new operations / mappings */ 121 DAXDEV_ALIVE, 122 /* gate whether dax_flush() calls the low level flush routine */ 123 DAXDEV_WRITE_CACHE, 124 }; 125 126 /** 127 * struct dax_device - anchor object for dax services 128 * @inode: core vfs 129 * @cdev: optional character interface for "device dax" 130 * @host: optional name for lookups where the device path is not available 131 * @private: dax driver private data 132 * @flags: state and boolean properties 133 */ 134 struct dax_device { 135 struct hlist_node list; 136 struct inode inode; 137 struct cdev cdev; 138 const char *host; 139 void *private; 140 unsigned long flags; 141 const struct dax_operations *ops; 142 }; 143 144 static ssize_t write_cache_show(struct device *dev, 145 struct device_attribute *attr, char *buf) 146 { 147 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev)); 148 ssize_t rc; 149 150 WARN_ON_ONCE(!dax_dev); 151 if (!dax_dev) 152 return -ENXIO; 153 154 rc = sprintf(buf, "%d\n", !!test_bit(DAXDEV_WRITE_CACHE, 155 &dax_dev->flags)); 156 put_dax(dax_dev); 157 return rc; 158 } 159 160 static ssize_t write_cache_store(struct device *dev, 161 struct device_attribute *attr, const char *buf, size_t len) 162 { 163 bool write_cache; 164 int rc = strtobool(buf, &write_cache); 165 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev)); 166 167 WARN_ON_ONCE(!dax_dev); 168 if (!dax_dev) 169 return -ENXIO; 170 171 if (rc) 172 len = rc; 173 else if (write_cache) 174 set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags); 175 else 176 clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags); 177 178 put_dax(dax_dev); 179 return len; 180 } 181 static DEVICE_ATTR_RW(write_cache); 182 183 static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n) 184 { 185 struct device *dev = container_of(kobj, typeof(*dev), kobj); 186 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev)); 187 188 WARN_ON_ONCE(!dax_dev); 189 if (!dax_dev) 190 return 0; 191 192 if (a == &dev_attr_write_cache.attr && !dax_dev->ops->flush) 193 return 0; 194 return a->mode; 195 } 196 197 static struct attribute *dax_attributes[] = { 198 &dev_attr_write_cache.attr, 199 NULL, 200 }; 201 202 struct attribute_group dax_attribute_group = { 203 .name = "dax", 204 .attrs = dax_attributes, 205 .is_visible = dax_visible, 206 }; 207 EXPORT_SYMBOL_GPL(dax_attribute_group); 208 209 /** 210 * dax_direct_access() - translate a device pgoff to an absolute pfn 211 * @dax_dev: a dax_device instance representing the logical memory range 212 * @pgoff: offset in pages from the start of the device to translate 213 * @nr_pages: number of consecutive pages caller can handle relative to @pfn 214 * @kaddr: output parameter that returns a virtual address mapping of pfn 215 * @pfn: output parameter that returns an absolute pfn translation of @pgoff 216 * 217 * Return: negative errno if an error occurs, otherwise the number of 218 * pages accessible at the device relative @pgoff. 219 */ 220 long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages, 221 void **kaddr, pfn_t *pfn) 222 { 223 long avail; 224 225 /* 226 * The device driver is allowed to sleep, in order to make the 227 * memory directly accessible. 228 */ 229 might_sleep(); 230 231 if (!dax_dev) 232 return -EOPNOTSUPP; 233 234 if (!dax_alive(dax_dev)) 235 return -ENXIO; 236 237 if (nr_pages < 0) 238 return nr_pages; 239 240 avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages, 241 kaddr, pfn); 242 if (!avail) 243 return -ERANGE; 244 return min(avail, nr_pages); 245 } 246 EXPORT_SYMBOL_GPL(dax_direct_access); 247 248 size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, 249 size_t bytes, struct iov_iter *i) 250 { 251 if (!dax_alive(dax_dev)) 252 return 0; 253 254 return dax_dev->ops->copy_from_iter(dax_dev, pgoff, addr, bytes, i); 255 } 256 EXPORT_SYMBOL_GPL(dax_copy_from_iter); 257 258 void dax_flush(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, 259 size_t size) 260 { 261 if (!dax_alive(dax_dev)) 262 return; 263 264 if (!test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags)) 265 return; 266 267 if (dax_dev->ops->flush) 268 dax_dev->ops->flush(dax_dev, pgoff, addr, size); 269 } 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_alive(struct dax_device *dax_dev) 282 { 283 lockdep_assert_held(&dax_srcu); 284 return test_bit(DAXDEV_ALIVE, &dax_dev->flags); 285 } 286 EXPORT_SYMBOL_GPL(dax_alive); 287 288 static int dax_host_hash(const char *host) 289 { 290 return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE; 291 } 292 293 /* 294 * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring 295 * that any fault handlers or operations that might have seen 296 * dax_alive(), have completed. Any operations that start after 297 * synchronize_srcu() has run will abort upon seeing !dax_alive(). 298 */ 299 void kill_dax(struct dax_device *dax_dev) 300 { 301 if (!dax_dev) 302 return; 303 304 clear_bit(DAXDEV_ALIVE, &dax_dev->flags); 305 306 synchronize_srcu(&dax_srcu); 307 308 spin_lock(&dax_host_lock); 309 hlist_del_init(&dax_dev->list); 310 spin_unlock(&dax_host_lock); 311 312 dax_dev->private = NULL; 313 } 314 EXPORT_SYMBOL_GPL(kill_dax); 315 316 static struct inode *dax_alloc_inode(struct super_block *sb) 317 { 318 struct dax_device *dax_dev; 319 struct inode *inode; 320 321 dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL); 322 inode = &dax_dev->inode; 323 inode->i_rdev = 0; 324 return inode; 325 } 326 327 static struct dax_device *to_dax_dev(struct inode *inode) 328 { 329 return container_of(inode, struct dax_device, inode); 330 } 331 332 static void dax_i_callback(struct rcu_head *head) 333 { 334 struct inode *inode = container_of(head, struct inode, i_rcu); 335 struct dax_device *dax_dev = to_dax_dev(inode); 336 337 kfree(dax_dev->host); 338 dax_dev->host = NULL; 339 if (inode->i_rdev) 340 ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev)); 341 kmem_cache_free(dax_cache, dax_dev); 342 } 343 344 static void dax_destroy_inode(struct inode *inode) 345 { 346 struct dax_device *dax_dev = to_dax_dev(inode); 347 348 WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags), 349 "kill_dax() must be called before final iput()\n"); 350 call_rcu(&inode->i_rcu, dax_i_callback); 351 } 352 353 static const struct super_operations dax_sops = { 354 .statfs = simple_statfs, 355 .alloc_inode = dax_alloc_inode, 356 .destroy_inode = dax_destroy_inode, 357 .drop_inode = generic_delete_inode, 358 }; 359 360 static struct dentry *dax_mount(struct file_system_type *fs_type, 361 int flags, const char *dev_name, void *data) 362 { 363 return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC); 364 } 365 366 static struct file_system_type dax_fs_type = { 367 .name = "dax", 368 .mount = dax_mount, 369 .kill_sb = kill_anon_super, 370 }; 371 372 static int dax_test(struct inode *inode, void *data) 373 { 374 dev_t devt = *(dev_t *) data; 375 376 return inode->i_rdev == devt; 377 } 378 379 static int dax_set(struct inode *inode, void *data) 380 { 381 dev_t devt = *(dev_t *) data; 382 383 inode->i_rdev = devt; 384 return 0; 385 } 386 387 static struct dax_device *dax_dev_get(dev_t devt) 388 { 389 struct dax_device *dax_dev; 390 struct inode *inode; 391 392 inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31), 393 dax_test, dax_set, &devt); 394 395 if (!inode) 396 return NULL; 397 398 dax_dev = to_dax_dev(inode); 399 if (inode->i_state & I_NEW) { 400 set_bit(DAXDEV_ALIVE, &dax_dev->flags); 401 inode->i_cdev = &dax_dev->cdev; 402 inode->i_mode = S_IFCHR; 403 inode->i_flags = S_DAX; 404 mapping_set_gfp_mask(&inode->i_data, GFP_USER); 405 unlock_new_inode(inode); 406 } 407 408 return dax_dev; 409 } 410 411 static void dax_add_host(struct dax_device *dax_dev, const char *host) 412 { 413 int hash; 414 415 /* 416 * Unconditionally init dax_dev since it's coming from a 417 * non-zeroed slab cache 418 */ 419 INIT_HLIST_NODE(&dax_dev->list); 420 dax_dev->host = host; 421 if (!host) 422 return; 423 424 hash = dax_host_hash(host); 425 spin_lock(&dax_host_lock); 426 hlist_add_head(&dax_dev->list, &dax_host_list[hash]); 427 spin_unlock(&dax_host_lock); 428 } 429 430 struct dax_device *alloc_dax(void *private, const char *__host, 431 const struct dax_operations *ops) 432 { 433 struct dax_device *dax_dev; 434 const char *host; 435 dev_t devt; 436 int minor; 437 438 host = kstrdup(__host, GFP_KERNEL); 439 if (__host && !host) 440 return NULL; 441 442 minor = ida_simple_get(&dax_minor_ida, 0, MINORMASK+1, GFP_KERNEL); 443 if (minor < 0) 444 goto err_minor; 445 446 devt = MKDEV(MAJOR(dax_devt), minor); 447 dax_dev = dax_dev_get(devt); 448 if (!dax_dev) 449 goto err_dev; 450 451 dax_add_host(dax_dev, host); 452 dax_dev->ops = ops; 453 dax_dev->private = private; 454 return dax_dev; 455 456 err_dev: 457 ida_simple_remove(&dax_minor_ida, minor); 458 err_minor: 459 kfree(host); 460 return NULL; 461 } 462 EXPORT_SYMBOL_GPL(alloc_dax); 463 464 void put_dax(struct dax_device *dax_dev) 465 { 466 if (!dax_dev) 467 return; 468 iput(&dax_dev->inode); 469 } 470 EXPORT_SYMBOL_GPL(put_dax); 471 472 /** 473 * dax_get_by_host() - temporary lookup mechanism for filesystem-dax 474 * @host: alternate name for the device registered by a dax driver 475 */ 476 struct dax_device *dax_get_by_host(const char *host) 477 { 478 struct dax_device *dax_dev, *found = NULL; 479 int hash, id; 480 481 if (!host) 482 return NULL; 483 484 hash = dax_host_hash(host); 485 486 id = dax_read_lock(); 487 spin_lock(&dax_host_lock); 488 hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) { 489 if (!dax_alive(dax_dev) 490 || strcmp(host, dax_dev->host) != 0) 491 continue; 492 493 if (igrab(&dax_dev->inode)) 494 found = dax_dev; 495 break; 496 } 497 spin_unlock(&dax_host_lock); 498 dax_read_unlock(id); 499 500 return found; 501 } 502 EXPORT_SYMBOL_GPL(dax_get_by_host); 503 504 /** 505 * inode_dax: convert a public inode into its dax_dev 506 * @inode: An inode with i_cdev pointing to a dax_dev 507 * 508 * Note this is not equivalent to to_dax_dev() which is for private 509 * internal use where we know the inode filesystem type == dax_fs_type. 510 */ 511 struct dax_device *inode_dax(struct inode *inode) 512 { 513 struct cdev *cdev = inode->i_cdev; 514 515 return container_of(cdev, struct dax_device, cdev); 516 } 517 EXPORT_SYMBOL_GPL(inode_dax); 518 519 struct inode *dax_inode(struct dax_device *dax_dev) 520 { 521 return &dax_dev->inode; 522 } 523 EXPORT_SYMBOL_GPL(dax_inode); 524 525 void *dax_get_private(struct dax_device *dax_dev) 526 { 527 return dax_dev->private; 528 } 529 EXPORT_SYMBOL_GPL(dax_get_private); 530 531 static void init_once(void *_dax_dev) 532 { 533 struct dax_device *dax_dev = _dax_dev; 534 struct inode *inode = &dax_dev->inode; 535 536 memset(dax_dev, 0, sizeof(*dax_dev)); 537 inode_init_once(inode); 538 } 539 540 static int __dax_fs_init(void) 541 { 542 int rc; 543 544 dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0, 545 (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT| 546 SLAB_MEM_SPREAD|SLAB_ACCOUNT), 547 init_once); 548 if (!dax_cache) 549 return -ENOMEM; 550 551 rc = register_filesystem(&dax_fs_type); 552 if (rc) 553 goto err_register_fs; 554 555 dax_mnt = kern_mount(&dax_fs_type); 556 if (IS_ERR(dax_mnt)) { 557 rc = PTR_ERR(dax_mnt); 558 goto err_mount; 559 } 560 dax_superblock = dax_mnt->mnt_sb; 561 562 return 0; 563 564 err_mount: 565 unregister_filesystem(&dax_fs_type); 566 err_register_fs: 567 kmem_cache_destroy(dax_cache); 568 569 return rc; 570 } 571 572 static void __dax_fs_exit(void) 573 { 574 kern_unmount(dax_mnt); 575 unregister_filesystem(&dax_fs_type); 576 kmem_cache_destroy(dax_cache); 577 } 578 579 static int __init dax_fs_init(void) 580 { 581 int rc; 582 583 rc = __dax_fs_init(); 584 if (rc) 585 return rc; 586 587 rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax"); 588 if (rc) 589 __dax_fs_exit(); 590 return rc; 591 } 592 593 static void __exit dax_fs_exit(void) 594 { 595 unregister_chrdev_region(dax_devt, MINORMASK+1); 596 ida_destroy(&dax_minor_ida); 597 __dax_fs_exit(); 598 } 599 600 MODULE_AUTHOR("Intel Corporation"); 601 MODULE_LICENSE("GPL v2"); 602 subsys_initcall(dax_fs_init); 603 module_exit(dax_fs_exit); 604