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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 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(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(DAXDEV_WRITE_CACHE, &dax_dev->flags);
275 else
276 clear_bit(DAXDEV_WRITE_CACHE, &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(DAXDEV_SYNC, &dax_dev->flags);
295}
296EXPORT_SYMBOL_GPL(set_dax_synchronous);
297
298void set_dax_nocache(struct dax_device *dax_dev)
299{
300 set_bit(DAXDEV_NOCACHE, &dax_dev->flags);
301}
302EXPORT_SYMBOL_GPL(set_dax_nocache);
303
304void set_dax_nomc(struct dax_device *dax_dev)
305{
306 set_bit(DAXDEV_NOMC, &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 */
323void kill_dax(struct dax_device *dax_dev)
324{
325 if (!dax_dev)
326 return;
327
328 if (dax_dev->holder_data != NULL)
329 dax_holder_notify_failure(dax_dev, 0, U64_MAX,
330 MF_MEM_PRE_REMOVE);
331
332 clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
333 synchronize_srcu(&dax_srcu);
334
335 /* clear holder data */
336 dax_dev->holder_ops = NULL;
337 dax_dev->holder_data = NULL;
338}
339EXPORT_SYMBOL_GPL(kill_dax);
340
341void run_dax(struct dax_device *dax_dev)
342{
343 set_bit(DAXDEV_ALIVE, &dax_dev->flags);
344}
345EXPORT_SYMBOL_GPL(run_dax);
346
347static struct inode *dax_alloc_inode(struct super_block *sb)
348{
349 struct dax_device *dax_dev;
350 struct inode *inode;
351
352 dax_dev = alloc_inode_sb(sb, dax_cache, GFP_KERNEL);
353 if (!dax_dev)
354 return NULL;
355
356 inode = &dax_dev->inode;
357 inode->i_rdev = 0;
358 return inode;
359}
360
361static struct dax_device *to_dax_dev(struct inode *inode)
362{
363 return container_of(inode, struct dax_device, inode);
364}
365
366static void dax_free_inode(struct inode *inode)
367{
368 struct dax_device *dax_dev = to_dax_dev(inode);
369 if (inode->i_rdev)
370 ida_free(&dax_minor_ida, iminor(inode));
371 kmem_cache_free(dax_cache, dax_dev);
372}
373
374static void dax_destroy_inode(struct inode *inode)
375{
376 struct dax_device *dax_dev = to_dax_dev(inode);
377 WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
378 "kill_dax() must be called before final iput()\n");
379}
380
381static const struct super_operations dax_sops = {
382 .statfs = simple_statfs,
383 .alloc_inode = dax_alloc_inode,
384 .destroy_inode = dax_destroy_inode,
385 .free_inode = dax_free_inode,
386 .drop_inode = generic_delete_inode,
387};
388
389static int dax_init_fs_context(struct fs_context *fc)
390{
391 struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
392 if (!ctx)
393 return -ENOMEM;
394 ctx->ops = &dax_sops;
395 return 0;
396}
397
398static struct file_system_type dax_fs_type = {
399 .name = "dax",
400 .init_fs_context = dax_init_fs_context,
401 .kill_sb = kill_anon_super,
402};
403
404static int dax_test(struct inode *inode, void *data)
405{
406 dev_t devt = *(dev_t *) data;
407
408 return inode->i_rdev == devt;
409}
410
411static int dax_set(struct inode *inode, void *data)
412{
413 dev_t devt = *(dev_t *) data;
414
415 inode->i_rdev = devt;
416 return 0;
417}
418
419static struct dax_device *dax_dev_get(dev_t devt)
420{
421 struct dax_device *dax_dev;
422 struct inode *inode;
423
424 inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
425 dax_test, dax_set, &devt);
426
427 if (!inode)
428 return NULL;
429
430 dax_dev = to_dax_dev(inode);
431 if (inode->i_state & I_NEW) {
432 set_bit(DAXDEV_ALIVE, &dax_dev->flags);
433 inode->i_cdev = &dax_dev->cdev;
434 inode->i_mode = S_IFCHR;
435 inode->i_flags = S_DAX;
436 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
437 unlock_new_inode(inode);
438 }
439
440 return dax_dev;
441}
442
443struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
444{
445 struct dax_device *dax_dev;
446 dev_t devt;
447 int minor;
448
449 if (WARN_ON_ONCE(ops && !ops->zero_page_range))
450 return ERR_PTR(-EINVAL);
451
452 minor = ida_alloc_max(&dax_minor_ida, MINORMASK, GFP_KERNEL);
453 if (minor < 0)
454 return ERR_PTR(-ENOMEM);
455
456 devt = MKDEV(MAJOR(dax_devt), minor);
457 dax_dev = dax_dev_get(devt);
458 if (!dax_dev)
459 goto err_dev;
460
461 dax_dev->ops = ops;
462 dax_dev->private = private;
463 return dax_dev;
464
465 err_dev:
466 ida_free(&dax_minor_ida, minor);
467 return ERR_PTR(-ENOMEM);
468}
469EXPORT_SYMBOL_GPL(alloc_dax);
470
471void put_dax(struct dax_device *dax_dev)
472{
473 if (!dax_dev)
474 return;
475 iput(&dax_dev->inode);
476}
477EXPORT_SYMBOL_GPL(put_dax);
478
479/**
480 * dax_holder() - obtain the holder of a dax device
481 * @dax_dev: a dax_device instance
482 *
483 * Return: the holder's data which represents the holder if registered,
484 * otherwize NULL.
485 */
486void *dax_holder(struct dax_device *dax_dev)
487{
488 return dax_dev->holder_data;
489}
490EXPORT_SYMBOL_GPL(dax_holder);
491
492/**
493 * inode_dax: convert a public inode into its dax_dev
494 * @inode: An inode with i_cdev pointing to a dax_dev
495 *
496 * Note this is not equivalent to to_dax_dev() which is for private
497 * internal use where we know the inode filesystem type == dax_fs_type.
498 */
499struct dax_device *inode_dax(struct inode *inode)
500{
501 struct cdev *cdev = inode->i_cdev;
502
503 return container_of(cdev, struct dax_device, cdev);
504}
505EXPORT_SYMBOL_GPL(inode_dax);
506
507struct inode *dax_inode(struct dax_device *dax_dev)
508{
509 return &dax_dev->inode;
510}
511EXPORT_SYMBOL_GPL(dax_inode);
512
513void *dax_get_private(struct dax_device *dax_dev)
514{
515 if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
516 return NULL;
517 return dax_dev->private;
518}
519EXPORT_SYMBOL_GPL(dax_get_private);
520
521static void init_once(void *_dax_dev)
522{
523 struct dax_device *dax_dev = _dax_dev;
524 struct inode *inode = &dax_dev->inode;
525
526 memset(dax_dev, 0, sizeof(*dax_dev));
527 inode_init_once(inode);
528}
529
530static int dax_fs_init(void)
531{
532 int rc;
533
534 dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
535 (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
536 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
537 init_once);
538 if (!dax_cache)
539 return -ENOMEM;
540
541 dax_mnt = kern_mount(&dax_fs_type);
542 if (IS_ERR(dax_mnt)) {
543 rc = PTR_ERR(dax_mnt);
544 goto err_mount;
545 }
546 dax_superblock = dax_mnt->mnt_sb;
547
548 return 0;
549
550 err_mount:
551 kmem_cache_destroy(dax_cache);
552
553 return rc;
554}
555
556static void dax_fs_exit(void)
557{
558 kern_unmount(dax_mnt);
559 rcu_barrier();
560 kmem_cache_destroy(dax_cache);
561}
562
563static int __init dax_core_init(void)
564{
565 int rc;
566
567 rc = dax_fs_init();
568 if (rc)
569 return rc;
570
571 rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
572 if (rc)
573 goto err_chrdev;
574
575 rc = dax_bus_init();
576 if (rc)
577 goto err_bus;
578 return 0;
579
580err_bus:
581 unregister_chrdev_region(dax_devt, MINORMASK+1);
582err_chrdev:
583 dax_fs_exit();
584 return 0;
585}
586
587static void __exit dax_core_exit(void)
588{
589 dax_bus_exit();
590 unregister_chrdev_region(dax_devt, MINORMASK+1);
591 ida_destroy(&dax_minor_ida);
592 dax_fs_exit();
593}
594
595MODULE_AUTHOR("Intel Corporation");
596MODULE_LICENSE("GPL v2");
597subsys_initcall(dax_core_init);
598module_exit(dax_core_exit);
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/genhd.h>
11#include <linux/pfn_t.h>
12#include <linux/cdev.h>
13#include <linux/hash.h>
14#include <linux/slab.h>
15#include <linux/uio.h>
16#include <linux/dax.h>
17#include <linux/fs.h>
18#include "dax-private.h"
19
20static dev_t dax_devt;
21DEFINE_STATIC_SRCU(dax_srcu);
22static struct vfsmount *dax_mnt;
23static DEFINE_IDA(dax_minor_ida);
24static struct kmem_cache *dax_cache __read_mostly;
25static struct super_block *dax_superblock __read_mostly;
26
27#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
28static struct hlist_head dax_host_list[DAX_HASH_SIZE];
29static DEFINE_SPINLOCK(dax_host_lock);
30
31int dax_read_lock(void)
32{
33 return srcu_read_lock(&dax_srcu);
34}
35EXPORT_SYMBOL_GPL(dax_read_lock);
36
37void dax_read_unlock(int id)
38{
39 srcu_read_unlock(&dax_srcu, id);
40}
41EXPORT_SYMBOL_GPL(dax_read_unlock);
42
43#ifdef CONFIG_BLOCK
44#include <linux/blkdev.h>
45
46int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
47 pgoff_t *pgoff)
48{
49 phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512;
50
51 if (pgoff)
52 *pgoff = PHYS_PFN(phys_off);
53 if (phys_off % PAGE_SIZE || size % PAGE_SIZE)
54 return -EINVAL;
55 return 0;
56}
57EXPORT_SYMBOL(bdev_dax_pgoff);
58
59#if IS_ENABLED(CONFIG_FS_DAX)
60struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
61{
62 if (!blk_queue_dax(bdev->bd_queue))
63 return NULL;
64 return fs_dax_get_by_host(bdev->bd_disk->disk_name);
65}
66EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
67#endif
68
69bool __generic_fsdax_supported(struct dax_device *dax_dev,
70 struct block_device *bdev, int blocksize, sector_t start,
71 sector_t sectors)
72{
73 bool dax_enabled = false;
74 pgoff_t pgoff, pgoff_end;
75 char buf[BDEVNAME_SIZE];
76 void *kaddr, *end_kaddr;
77 pfn_t pfn, end_pfn;
78 sector_t last_page;
79 long len, len2;
80 int err, id;
81
82 if (blocksize != PAGE_SIZE) {
83 pr_debug("%s: error: unsupported blocksize for dax\n",
84 bdevname(bdev, buf));
85 return false;
86 }
87
88 err = bdev_dax_pgoff(bdev, start, PAGE_SIZE, &pgoff);
89 if (err) {
90 pr_debug("%s: error: unaligned partition for dax\n",
91 bdevname(bdev, buf));
92 return false;
93 }
94
95 last_page = PFN_DOWN((start + sectors - 1) * 512) * PAGE_SIZE / 512;
96 err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end);
97 if (err) {
98 pr_debug("%s: error: unaligned partition for dax\n",
99 bdevname(bdev, buf));
100 return false;
101 }
102
103 id = dax_read_lock();
104 len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
105 len2 = dax_direct_access(dax_dev, pgoff_end, 1, &end_kaddr, &end_pfn);
106 dax_read_unlock(id);
107
108 if (len < 1 || len2 < 1) {
109 pr_debug("%s: error: dax access failed (%ld)\n",
110 bdevname(bdev, buf), len < 1 ? len : len2);
111 return false;
112 }
113
114 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
115 /*
116 * An arch that has enabled the pmem api should also
117 * have its drivers support pfn_t_devmap()
118 *
119 * This is a developer warning and should not trigger in
120 * production. dax_flush() will crash since it depends
121 * on being able to do (page_address(pfn_to_page())).
122 */
123 WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
124 dax_enabled = true;
125 } else if (pfn_t_devmap(pfn) && pfn_t_devmap(end_pfn)) {
126 struct dev_pagemap *pgmap, *end_pgmap;
127
128 pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
129 end_pgmap = get_dev_pagemap(pfn_t_to_pfn(end_pfn), NULL);
130 if (pgmap && pgmap == end_pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX
131 && pfn_t_to_page(pfn)->pgmap == pgmap
132 && pfn_t_to_page(end_pfn)->pgmap == pgmap
133 && pfn_t_to_pfn(pfn) == PHYS_PFN(__pa(kaddr))
134 && pfn_t_to_pfn(end_pfn) == PHYS_PFN(__pa(end_kaddr)))
135 dax_enabled = true;
136 put_dev_pagemap(pgmap);
137 put_dev_pagemap(end_pgmap);
138
139 }
140
141 if (!dax_enabled) {
142 pr_debug("%s: error: dax support not enabled\n",
143 bdevname(bdev, buf));
144 return false;
145 }
146 return true;
147}
148EXPORT_SYMBOL_GPL(__generic_fsdax_supported);
149
150/**
151 * __bdev_dax_supported() - Check if the device supports dax for filesystem
152 * @bdev: block device to check
153 * @blocksize: The block size of the device
154 *
155 * This is a library function for filesystems to check if the block device
156 * can be mounted with dax option.
157 *
158 * Return: true if supported, false if unsupported
159 */
160bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
161{
162 struct dax_device *dax_dev;
163 struct request_queue *q;
164 char buf[BDEVNAME_SIZE];
165 bool ret;
166 int id;
167
168 q = bdev_get_queue(bdev);
169 if (!q || !blk_queue_dax(q)) {
170 pr_debug("%s: error: request queue doesn't support dax\n",
171 bdevname(bdev, buf));
172 return false;
173 }
174
175 dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
176 if (!dax_dev) {
177 pr_debug("%s: error: device does not support dax\n",
178 bdevname(bdev, buf));
179 return false;
180 }
181
182 id = dax_read_lock();
183 ret = dax_supported(dax_dev, bdev, blocksize, 0,
184 i_size_read(bdev->bd_inode) / 512);
185 dax_read_unlock(id);
186
187 put_dax(dax_dev);
188
189 return ret;
190}
191EXPORT_SYMBOL_GPL(__bdev_dax_supported);
192#endif
193
194enum dax_device_flags {
195 /* !alive + rcu grace period == no new operations / mappings */
196 DAXDEV_ALIVE,
197 /* gate whether dax_flush() calls the low level flush routine */
198 DAXDEV_WRITE_CACHE,
199 /* flag to check if device supports synchronous flush */
200 DAXDEV_SYNC,
201};
202
203/**
204 * struct dax_device - anchor object for dax services
205 * @inode: core vfs
206 * @cdev: optional character interface for "device dax"
207 * @host: optional name for lookups where the device path is not available
208 * @private: dax driver private data
209 * @flags: state and boolean properties
210 */
211struct dax_device {
212 struct hlist_node list;
213 struct inode inode;
214 struct cdev cdev;
215 const char *host;
216 void *private;
217 unsigned long flags;
218 const struct dax_operations *ops;
219};
220
221static ssize_t write_cache_show(struct device *dev,
222 struct device_attribute *attr, char *buf)
223{
224 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
225 ssize_t rc;
226
227 WARN_ON_ONCE(!dax_dev);
228 if (!dax_dev)
229 return -ENXIO;
230
231 rc = sprintf(buf, "%d\n", !!dax_write_cache_enabled(dax_dev));
232 put_dax(dax_dev);
233 return rc;
234}
235
236static ssize_t write_cache_store(struct device *dev,
237 struct device_attribute *attr, const char *buf, size_t len)
238{
239 bool write_cache;
240 int rc = strtobool(buf, &write_cache);
241 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
242
243 WARN_ON_ONCE(!dax_dev);
244 if (!dax_dev)
245 return -ENXIO;
246
247 if (rc)
248 len = rc;
249 else
250 dax_write_cache(dax_dev, write_cache);
251
252 put_dax(dax_dev);
253 return len;
254}
255static DEVICE_ATTR_RW(write_cache);
256
257static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n)
258{
259 struct device *dev = container_of(kobj, typeof(*dev), kobj);
260 struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
261
262 WARN_ON_ONCE(!dax_dev);
263 if (!dax_dev)
264 return 0;
265
266#ifndef CONFIG_ARCH_HAS_PMEM_API
267 if (a == &dev_attr_write_cache.attr)
268 return 0;
269#endif
270 return a->mode;
271}
272
273static struct attribute *dax_attributes[] = {
274 &dev_attr_write_cache.attr,
275 NULL,
276};
277
278struct attribute_group dax_attribute_group = {
279 .name = "dax",
280 .attrs = dax_attributes,
281 .is_visible = dax_visible,
282};
283EXPORT_SYMBOL_GPL(dax_attribute_group);
284
285/**
286 * dax_direct_access() - translate a device pgoff to an absolute pfn
287 * @dax_dev: a dax_device instance representing the logical memory range
288 * @pgoff: offset in pages from the start of the device to translate
289 * @nr_pages: number of consecutive pages caller can handle relative to @pfn
290 * @kaddr: output parameter that returns a virtual address mapping of pfn
291 * @pfn: output parameter that returns an absolute pfn translation of @pgoff
292 *
293 * Return: negative errno if an error occurs, otherwise the number of
294 * pages accessible at the device relative @pgoff.
295 */
296long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
297 void **kaddr, pfn_t *pfn)
298{
299 long avail;
300
301 if (!dax_dev)
302 return -EOPNOTSUPP;
303
304 if (!dax_alive(dax_dev))
305 return -ENXIO;
306
307 if (nr_pages < 0)
308 return nr_pages;
309
310 avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
311 kaddr, pfn);
312 if (!avail)
313 return -ERANGE;
314 return min(avail, nr_pages);
315}
316EXPORT_SYMBOL_GPL(dax_direct_access);
317
318bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
319 int blocksize, sector_t start, sector_t len)
320{
321 if (!dax_alive(dax_dev))
322 return false;
323
324 return dax_dev->ops->dax_supported(dax_dev, bdev, blocksize, start, len);
325}
326
327size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
328 size_t bytes, struct iov_iter *i)
329{
330 if (!dax_alive(dax_dev))
331 return 0;
332
333 return dax_dev->ops->copy_from_iter(dax_dev, pgoff, addr, bytes, i);
334}
335EXPORT_SYMBOL_GPL(dax_copy_from_iter);
336
337size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
338 size_t bytes, struct iov_iter *i)
339{
340 if (!dax_alive(dax_dev))
341 return 0;
342
343 return dax_dev->ops->copy_to_iter(dax_dev, pgoff, addr, bytes, i);
344}
345EXPORT_SYMBOL_GPL(dax_copy_to_iter);
346
347#ifdef CONFIG_ARCH_HAS_PMEM_API
348void arch_wb_cache_pmem(void *addr, size_t size);
349void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
350{
351 if (unlikely(!dax_write_cache_enabled(dax_dev)))
352 return;
353
354 arch_wb_cache_pmem(addr, size);
355}
356#else
357void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
358{
359}
360#endif
361EXPORT_SYMBOL_GPL(dax_flush);
362
363void dax_write_cache(struct dax_device *dax_dev, bool wc)
364{
365 if (wc)
366 set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
367 else
368 clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
369}
370EXPORT_SYMBOL_GPL(dax_write_cache);
371
372bool dax_write_cache_enabled(struct dax_device *dax_dev)
373{
374 return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
375}
376EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
377
378bool __dax_synchronous(struct dax_device *dax_dev)
379{
380 return test_bit(DAXDEV_SYNC, &dax_dev->flags);
381}
382EXPORT_SYMBOL_GPL(__dax_synchronous);
383
384void __set_dax_synchronous(struct dax_device *dax_dev)
385{
386 set_bit(DAXDEV_SYNC, &dax_dev->flags);
387}
388EXPORT_SYMBOL_GPL(__set_dax_synchronous);
389
390bool dax_alive(struct dax_device *dax_dev)
391{
392 lockdep_assert_held(&dax_srcu);
393 return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
394}
395EXPORT_SYMBOL_GPL(dax_alive);
396
397static int dax_host_hash(const char *host)
398{
399 return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
400}
401
402/*
403 * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
404 * that any fault handlers or operations that might have seen
405 * dax_alive(), have completed. Any operations that start after
406 * synchronize_srcu() has run will abort upon seeing !dax_alive().
407 */
408void kill_dax(struct dax_device *dax_dev)
409{
410 if (!dax_dev)
411 return;
412
413 clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
414
415 synchronize_srcu(&dax_srcu);
416
417 spin_lock(&dax_host_lock);
418 hlist_del_init(&dax_dev->list);
419 spin_unlock(&dax_host_lock);
420}
421EXPORT_SYMBOL_GPL(kill_dax);
422
423void run_dax(struct dax_device *dax_dev)
424{
425 set_bit(DAXDEV_ALIVE, &dax_dev->flags);
426}
427EXPORT_SYMBOL_GPL(run_dax);
428
429static struct inode *dax_alloc_inode(struct super_block *sb)
430{
431 struct dax_device *dax_dev;
432 struct inode *inode;
433
434 dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL);
435 if (!dax_dev)
436 return NULL;
437
438 inode = &dax_dev->inode;
439 inode->i_rdev = 0;
440 return inode;
441}
442
443static struct dax_device *to_dax_dev(struct inode *inode)
444{
445 return container_of(inode, struct dax_device, inode);
446}
447
448static void dax_free_inode(struct inode *inode)
449{
450 struct dax_device *dax_dev = to_dax_dev(inode);
451 kfree(dax_dev->host);
452 dax_dev->host = NULL;
453 if (inode->i_rdev)
454 ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
455 kmem_cache_free(dax_cache, dax_dev);
456}
457
458static void dax_destroy_inode(struct inode *inode)
459{
460 struct dax_device *dax_dev = to_dax_dev(inode);
461 WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
462 "kill_dax() must be called before final iput()\n");
463}
464
465static const struct super_operations dax_sops = {
466 .statfs = simple_statfs,
467 .alloc_inode = dax_alloc_inode,
468 .destroy_inode = dax_destroy_inode,
469 .free_inode = dax_free_inode,
470 .drop_inode = generic_delete_inode,
471};
472
473static int dax_init_fs_context(struct fs_context *fc)
474{
475 struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
476 if (!ctx)
477 return -ENOMEM;
478 ctx->ops = &dax_sops;
479 return 0;
480}
481
482static struct file_system_type dax_fs_type = {
483 .name = "dax",
484 .init_fs_context = dax_init_fs_context,
485 .kill_sb = kill_anon_super,
486};
487
488static int dax_test(struct inode *inode, void *data)
489{
490 dev_t devt = *(dev_t *) data;
491
492 return inode->i_rdev == devt;
493}
494
495static int dax_set(struct inode *inode, void *data)
496{
497 dev_t devt = *(dev_t *) data;
498
499 inode->i_rdev = devt;
500 return 0;
501}
502
503static struct dax_device *dax_dev_get(dev_t devt)
504{
505 struct dax_device *dax_dev;
506 struct inode *inode;
507
508 inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
509 dax_test, dax_set, &devt);
510
511 if (!inode)
512 return NULL;
513
514 dax_dev = to_dax_dev(inode);
515 if (inode->i_state & I_NEW) {
516 set_bit(DAXDEV_ALIVE, &dax_dev->flags);
517 inode->i_cdev = &dax_dev->cdev;
518 inode->i_mode = S_IFCHR;
519 inode->i_flags = S_DAX;
520 mapping_set_gfp_mask(&inode->i_data, GFP_USER);
521 unlock_new_inode(inode);
522 }
523
524 return dax_dev;
525}
526
527static void dax_add_host(struct dax_device *dax_dev, const char *host)
528{
529 int hash;
530
531 /*
532 * Unconditionally init dax_dev since it's coming from a
533 * non-zeroed slab cache
534 */
535 INIT_HLIST_NODE(&dax_dev->list);
536 dax_dev->host = host;
537 if (!host)
538 return;
539
540 hash = dax_host_hash(host);
541 spin_lock(&dax_host_lock);
542 hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
543 spin_unlock(&dax_host_lock);
544}
545
546struct dax_device *alloc_dax(void *private, const char *__host,
547 const struct dax_operations *ops, unsigned long flags)
548{
549 struct dax_device *dax_dev;
550 const char *host;
551 dev_t devt;
552 int minor;
553
554 host = kstrdup(__host, GFP_KERNEL);
555 if (__host && !host)
556 return NULL;
557
558 minor = ida_simple_get(&dax_minor_ida, 0, MINORMASK+1, GFP_KERNEL);
559 if (minor < 0)
560 goto err_minor;
561
562 devt = MKDEV(MAJOR(dax_devt), minor);
563 dax_dev = dax_dev_get(devt);
564 if (!dax_dev)
565 goto err_dev;
566
567 dax_add_host(dax_dev, host);
568 dax_dev->ops = ops;
569 dax_dev->private = private;
570 if (flags & DAXDEV_F_SYNC)
571 set_dax_synchronous(dax_dev);
572
573 return dax_dev;
574
575 err_dev:
576 ida_simple_remove(&dax_minor_ida, minor);
577 err_minor:
578 kfree(host);
579 return NULL;
580}
581EXPORT_SYMBOL_GPL(alloc_dax);
582
583void put_dax(struct dax_device *dax_dev)
584{
585 if (!dax_dev)
586 return;
587 iput(&dax_dev->inode);
588}
589EXPORT_SYMBOL_GPL(put_dax);
590
591/**
592 * dax_get_by_host() - temporary lookup mechanism for filesystem-dax
593 * @host: alternate name for the device registered by a dax driver
594 */
595struct dax_device *dax_get_by_host(const char *host)
596{
597 struct dax_device *dax_dev, *found = NULL;
598 int hash, id;
599
600 if (!host)
601 return NULL;
602
603 hash = dax_host_hash(host);
604
605 id = dax_read_lock();
606 spin_lock(&dax_host_lock);
607 hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
608 if (!dax_alive(dax_dev)
609 || strcmp(host, dax_dev->host) != 0)
610 continue;
611
612 if (igrab(&dax_dev->inode))
613 found = dax_dev;
614 break;
615 }
616 spin_unlock(&dax_host_lock);
617 dax_read_unlock(id);
618
619 return found;
620}
621EXPORT_SYMBOL_GPL(dax_get_by_host);
622
623/**
624 * inode_dax: convert a public inode into its dax_dev
625 * @inode: An inode with i_cdev pointing to a dax_dev
626 *
627 * Note this is not equivalent to to_dax_dev() which is for private
628 * internal use where we know the inode filesystem type == dax_fs_type.
629 */
630struct dax_device *inode_dax(struct inode *inode)
631{
632 struct cdev *cdev = inode->i_cdev;
633
634 return container_of(cdev, struct dax_device, cdev);
635}
636EXPORT_SYMBOL_GPL(inode_dax);
637
638struct inode *dax_inode(struct dax_device *dax_dev)
639{
640 return &dax_dev->inode;
641}
642EXPORT_SYMBOL_GPL(dax_inode);
643
644void *dax_get_private(struct dax_device *dax_dev)
645{
646 if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
647 return NULL;
648 return dax_dev->private;
649}
650EXPORT_SYMBOL_GPL(dax_get_private);
651
652static void init_once(void *_dax_dev)
653{
654 struct dax_device *dax_dev = _dax_dev;
655 struct inode *inode = &dax_dev->inode;
656
657 memset(dax_dev, 0, sizeof(*dax_dev));
658 inode_init_once(inode);
659}
660
661static int dax_fs_init(void)
662{
663 int rc;
664
665 dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
666 (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
667 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
668 init_once);
669 if (!dax_cache)
670 return -ENOMEM;
671
672 dax_mnt = kern_mount(&dax_fs_type);
673 if (IS_ERR(dax_mnt)) {
674 rc = PTR_ERR(dax_mnt);
675 goto err_mount;
676 }
677 dax_superblock = dax_mnt->mnt_sb;
678
679 return 0;
680
681 err_mount:
682 kmem_cache_destroy(dax_cache);
683
684 return rc;
685}
686
687static void dax_fs_exit(void)
688{
689 kern_unmount(dax_mnt);
690 kmem_cache_destroy(dax_cache);
691}
692
693static int __init dax_core_init(void)
694{
695 int rc;
696
697 rc = dax_fs_init();
698 if (rc)
699 return rc;
700
701 rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
702 if (rc)
703 goto err_chrdev;
704
705 rc = dax_bus_init();
706 if (rc)
707 goto err_bus;
708 return 0;
709
710err_bus:
711 unregister_chrdev_region(dax_devt, MINORMASK+1);
712err_chrdev:
713 dax_fs_exit();
714 return 0;
715}
716
717static void __exit dax_core_exit(void)
718{
719 unregister_chrdev_region(dax_devt, MINORMASK+1);
720 ida_destroy(&dax_minor_ida);
721 dax_fs_exit();
722}
723
724MODULE_AUTHOR("Intel Corporation");
725MODULE_LICENSE("GPL v2");
726subsys_initcall(dax_core_init);
727module_exit(dax_core_exit);