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/cdev.h>
11#include <linux/slab.h>
12#include <linux/uio.h>
13#include <linux/dax.h>
14#include <linux/fs.h>
15#include <linux/cacheinfo.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(ssp: &dax_srcu);
48}
49EXPORT_SYMBOL_GPL(dax_read_lock);
50
51void dax_read_unlock(int id)
52{
53 srcu_read_unlock(ssp: &dax_srcu, idx: 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(xa: &dax_hosts, index: (unsigned long)disk, entry: 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, index: (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, index: (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, unsigned long *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 int ret;
207
208 if (!dax_alive(dax_dev))
209 return -ENXIO;
210 /*
211 * There are no callers that want to zero more than one page as of now.
212 * Once users are there, this check can be removed after the
213 * device mapper code has been updated to split ranges across targets.
214 */
215 if (nr_pages != 1)
216 return -EIO;
217
218 ret = dax_dev->ops->zero_page_range(dax_dev, pgoff, nr_pages);
219 return dax_mem2blk_err(err: ret);
220}
221EXPORT_SYMBOL_GPL(dax_zero_page_range);
222
223size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
224 void *addr, size_t bytes, struct iov_iter *iter)
225{
226 if (!dax_dev->ops->recovery_write)
227 return 0;
228 return dax_dev->ops->recovery_write(dax_dev, pgoff, addr, bytes, iter);
229}
230EXPORT_SYMBOL_GPL(dax_recovery_write);
231
232int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off,
233 u64 len, int mf_flags)
234{
235 int rc, id;
236
237 id = dax_read_lock();
238 if (!dax_alive(dax_dev)) {
239 rc = -ENXIO;
240 goto out;
241 }
242
243 if (!dax_dev->holder_ops) {
244 rc = -EOPNOTSUPP;
245 goto out;
246 }
247
248 rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags);
249out:
250 dax_read_unlock(id);
251 return rc;
252}
253EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
254
255#ifdef CONFIG_ARCH_HAS_PMEM_API
256void arch_wb_cache_pmem(void *addr, size_t size);
257void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
258{
259 if (unlikely(!dax_write_cache_enabled(dax_dev)))
260 return;
261
262 arch_wb_cache_pmem(addr, size);
263}
264#else
265void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
266{
267}
268#endif
269EXPORT_SYMBOL_GPL(dax_flush);
270
271void dax_write_cache(struct dax_device *dax_dev, bool wc)
272{
273 if (wc)
274 set_bit(nr: DAXDEV_WRITE_CACHE, addr: &dax_dev->flags);
275 else
276 clear_bit(nr: DAXDEV_WRITE_CACHE, addr: &dax_dev->flags);
277}
278EXPORT_SYMBOL_GPL(dax_write_cache);
279
280bool dax_write_cache_enabled(struct dax_device *dax_dev)
281{
282 return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
283}
284EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
285
286bool dax_synchronous(struct dax_device *dax_dev)
287{
288 return test_bit(DAXDEV_SYNC, &dax_dev->flags);
289}
290EXPORT_SYMBOL_GPL(dax_synchronous);
291
292void set_dax_synchronous(struct dax_device *dax_dev)
293{
294 set_bit(nr: DAXDEV_SYNC, addr: &dax_dev->flags);
295}
296EXPORT_SYMBOL_GPL(set_dax_synchronous);
297
298void set_dax_nocache(struct dax_device *dax_dev)
299{
300 set_bit(nr: DAXDEV_NOCACHE, addr: &dax_dev->flags);
301}
302EXPORT_SYMBOL_GPL(set_dax_nocache);
303
304void set_dax_nomc(struct dax_device *dax_dev)
305{
306 set_bit(nr: DAXDEV_NOMC, addr: &dax_dev->flags);
307}
308EXPORT_SYMBOL_GPL(set_dax_nomc);
309
310bool dax_alive(struct dax_device *dax_dev)
311{
312 lockdep_assert_held(&dax_srcu);
313 return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
314}
315EXPORT_SYMBOL_GPL(dax_alive);
316
317/*
318 * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
319 * that any fault handlers or operations that might have seen
320 * dax_alive(), have completed. Any operations that start after
321 * synchronize_srcu() has run will abort upon seeing !dax_alive().
322 *
323 * Note, because alloc_dax() returns an ERR_PTR() on error, callers
324 * typically store its result into a local variable in order to check
325 * the result. Therefore, care must be taken to populate the struct
326 * device dax_dev field make sure the dax_dev is not leaked.
327 */
328void kill_dax(struct dax_device *dax_dev)
329{
330 if (!dax_dev)
331 return;
332
333 if (dax_dev->holder_data != NULL)
334 dax_holder_notify_failure(dax_dev, 0, U64_MAX,
335 MF_MEM_PRE_REMOVE);
336
337 clear_bit(nr: DAXDEV_ALIVE, addr: &dax_dev->flags);
338 synchronize_srcu(ssp: &dax_srcu);
339
340 /* clear holder data */
341 dax_dev->holder_ops = NULL;
342 dax_dev->holder_data = NULL;
343}
344EXPORT_SYMBOL_GPL(kill_dax);
345
346void run_dax(struct dax_device *dax_dev)
347{
348 set_bit(nr: DAXDEV_ALIVE, addr: &dax_dev->flags);
349}
350EXPORT_SYMBOL_GPL(run_dax);
351
352static struct inode *dax_alloc_inode(struct super_block *sb)
353{
354 struct dax_device *dax_dev;
355 struct inode *inode;
356
357 dax_dev = alloc_inode_sb(sb, dax_cache, GFP_KERNEL);
358 if (!dax_dev)
359 return NULL;
360
361 inode = &dax_dev->inode;
362 inode->i_rdev = 0;
363 return inode;
364}
365
366static struct dax_device *to_dax_dev(struct inode *inode)
367{
368 return container_of(inode, struct dax_device, inode);
369}
370
371static void dax_free_inode(struct inode *inode)
372{
373 struct dax_device *dax_dev = to_dax_dev(inode);
374 if (inode->i_rdev)
375 ida_free(&dax_minor_ida, id: iminor(inode));
376 kmem_cache_free(s: dax_cache, objp: dax_dev);
377}
378
379static void dax_destroy_inode(struct inode *inode)
380{
381 struct dax_device *dax_dev = to_dax_dev(inode);
382 WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
383 "kill_dax() must be called before final iput()\n");
384}
385
386static const struct super_operations dax_sops = {
387 .statfs = simple_statfs,
388 .alloc_inode = dax_alloc_inode,
389 .destroy_inode = dax_destroy_inode,
390 .free_inode = dax_free_inode,
391 .drop_inode = inode_just_drop,
392};
393
394static int dax_init_fs_context(struct fs_context *fc)
395{
396 struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
397 if (!ctx)
398 return -ENOMEM;
399 ctx->ops = &dax_sops;
400 return 0;
401}
402
403static struct file_system_type dax_fs_type = {
404 .name = "dax",
405 .init_fs_context = dax_init_fs_context,
406 .kill_sb = kill_anon_super,
407};
408
409static int dax_test(struct inode *inode, void *data)
410{
411 dev_t devt = *(dev_t *) data;
412
413 return inode->i_rdev == devt;
414}
415
416static int dax_set(struct inode *inode, void *data)
417{
418 dev_t devt = *(dev_t *) data;
419
420 inode->i_rdev = devt;
421 return 0;
422}
423
424static struct dax_device *dax_dev_get(dev_t devt)
425{
426 struct dax_device *dax_dev;
427 struct inode *inode;
428
429 inode = iget5_locked(dax_superblock, hash_32(val: devt + DAXFS_MAGIC, bits: 31),
430 test: dax_test, set: dax_set, &devt);
431
432 if (!inode)
433 return NULL;
434
435 dax_dev = to_dax_dev(inode);
436 if (inode_state_read_once(inode) & I_NEW) {
437 set_bit(nr: DAXDEV_ALIVE, addr: &dax_dev->flags);
438 inode->i_cdev = &dax_dev->cdev;
439 inode->i_mode = S_IFCHR;
440 inode->i_flags = S_DAX;
441 mapping_set_gfp_mask(m: &inode->i_data, GFP_USER);
442 unlock_new_inode(inode);
443 }
444
445 return dax_dev;
446}
447
448struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
449{
450 struct dax_device *dax_dev;
451 dev_t devt;
452 int minor;
453
454 /*
455 * Unavailable on architectures with virtually aliased data caches,
456 * except for device-dax (NULL operations pointer), which does
457 * not use aliased mappings from the kernel.
458 */
459 if (ops && cpu_dcache_is_aliasing())
460 return ERR_PTR(error: -EOPNOTSUPP);
461
462 if (WARN_ON_ONCE(ops && !ops->zero_page_range))
463 return ERR_PTR(error: -EINVAL);
464
465 minor = ida_alloc_max(ida: &dax_minor_ida, MINORMASK, GFP_KERNEL);
466 if (minor < 0)
467 return ERR_PTR(error: -ENOMEM);
468
469 devt = MKDEV(MAJOR(dax_devt), minor);
470 dax_dev = dax_dev_get(devt);
471 if (!dax_dev)
472 goto err_dev;
473
474 dax_dev->ops = ops;
475 dax_dev->private = private;
476 return dax_dev;
477
478 err_dev:
479 ida_free(&dax_minor_ida, id: minor);
480 return ERR_PTR(error: -ENOMEM);
481}
482EXPORT_SYMBOL_GPL(alloc_dax);
483
484void put_dax(struct dax_device *dax_dev)
485{
486 if (!dax_dev)
487 return;
488 iput(&dax_dev->inode);
489}
490EXPORT_SYMBOL_GPL(put_dax);
491
492/**
493 * dax_holder() - obtain the holder of a dax device
494 * @dax_dev: a dax_device instance
495 *
496 * Return: the holder's data which represents the holder if registered,
497 * otherwize NULL.
498 */
499void *dax_holder(struct dax_device *dax_dev)
500{
501 return dax_dev->holder_data;
502}
503EXPORT_SYMBOL_GPL(dax_holder);
504
505/**
506 * inode_dax: convert a public inode into its dax_dev
507 * @inode: An inode with i_cdev pointing to a dax_dev
508 *
509 * Note this is not equivalent to to_dax_dev() which is for private
510 * internal use where we know the inode filesystem type == dax_fs_type.
511 */
512struct dax_device *inode_dax(struct inode *inode)
513{
514 struct cdev *cdev = inode->i_cdev;
515
516 return container_of(cdev, struct dax_device, cdev);
517}
518EXPORT_SYMBOL_GPL(inode_dax);
519
520struct inode *dax_inode(struct dax_device *dax_dev)
521{
522 return &dax_dev->inode;
523}
524EXPORT_SYMBOL_GPL(dax_inode);
525
526void *dax_get_private(struct dax_device *dax_dev)
527{
528 if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
529 return NULL;
530 return dax_dev->private;
531}
532EXPORT_SYMBOL_GPL(dax_get_private);
533
534static void init_once(void *_dax_dev)
535{
536 struct dax_device *dax_dev = _dax_dev;
537 struct inode *inode = &dax_dev->inode;
538
539 memset(dax_dev, 0, sizeof(*dax_dev));
540 inode_init_once(inode);
541}
542
543static int dax_fs_init(void)
544{
545 int rc;
546
547 dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
548 SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
549 init_once);
550 if (!dax_cache)
551 return -ENOMEM;
552
553 dax_mnt = kern_mount(&dax_fs_type);
554 if (IS_ERR(ptr: dax_mnt)) {
555 rc = PTR_ERR(ptr: dax_mnt);
556 goto err_mount;
557 }
558 dax_superblock = dax_mnt->mnt_sb;
559
560 return 0;
561
562 err_mount:
563 kmem_cache_destroy(s: dax_cache);
564
565 return rc;
566}
567
568static void dax_fs_exit(void)
569{
570 kern_unmount(mnt: dax_mnt);
571 rcu_barrier();
572 kmem_cache_destroy(s: dax_cache);
573}
574
575static int __init dax_core_init(void)
576{
577 int rc;
578
579 rc = dax_fs_init();
580 if (rc)
581 return rc;
582
583 rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
584 if (rc)
585 goto err_chrdev;
586
587 rc = dax_bus_init();
588 if (rc)
589 goto err_bus;
590 return 0;
591
592err_bus:
593 unregister_chrdev_region(dax_devt, MINORMASK+1);
594err_chrdev:
595 dax_fs_exit();
596 return 0;
597}
598
599static void __exit dax_core_exit(void)
600{
601 dax_bus_exit();
602 unregister_chrdev_region(dax_devt, MINORMASK+1);
603 ida_destroy(ida: &dax_minor_ida);
604 dax_fs_exit();
605}
606
607MODULE_AUTHOR("Intel Corporation");
608MODULE_DESCRIPTION("DAX: direct access to differentiated memory");
609MODULE_LICENSE("GPL v2");
610subsys_initcall(dax_core_init);
611module_exit(dax_core_exit);
612

source code of linux/drivers/dax/super.c