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