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1 /*
2 * fs/dax.c - Direct Access filesystem code
3 * Copyright (c) 2013-2014 Intel Corporation
4 * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
5 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms and conditions of the GNU General Public License,
9 * version 2, as published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 * more details.
15 */
16
17 #include <linux/atomic.h>
18 #include <linux/blkdev.h>
19 #include <linux/buffer_head.h>
20 #include <linux/dax.h>
21 #include <linux/fs.h>
22 #include <linux/genhd.h>
23 #include <linux/highmem.h>
24 #include <linux/memcontrol.h>
25 #include <linux/mm.h>
26 #include <linux/mutex.h>
27 #include <linux/pagevec.h>
28 #include <linux/sched.h>
29 #include <linux/sched/signal.h>
30 #include <linux/uio.h>
31 #include <linux/vmstat.h>
32 #include <linux/pfn_t.h>
33 #include <linux/sizes.h>
34 #include <linux/mmu_notifier.h>
35 #include <linux/iomap.h>
36 #include "internal.h"
37
38 #define CREATE_TRACE_POINTS
39 #include <trace/events/fs_dax.h>
40
41 /* We choose 4096 entries - same as per-zone page wait tables */
42 #define DAX_WAIT_TABLE_BITS 12
43 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
44
45 /* The 'colour' (ie low bits) within a PMD of a page offset. */
46 #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
47 #define PG_PMD_NR (PMD_SIZE >> PAGE_SHIFT)
48
49 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
50
51 static int __init init_dax_wait_table(void)
52 {
53 int i;
54
55 for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
56 init_waitqueue_head(wait_table + i);
57 return 0;
58 }
59 fs_initcall(init_dax_wait_table);
60
61 /*
62 * We use lowest available bit in exceptional entry for locking, one bit for
63 * the entry size (PMD) and two more to tell us if the entry is a zero page or
64 * an empty entry that is just used for locking. In total four special bits.
65 *
66 * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
67 * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
68 * block allocation.
69 */
70 #define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
71 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
72 #define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
73 #define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
74 #define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
75
76 static unsigned long dax_radix_pfn(void *entry)
77 {
78 return (unsigned long)entry >> RADIX_DAX_SHIFT;
79 }
80
81 static void *dax_radix_locked_entry(unsigned long pfn, unsigned long flags)
82 {
83 return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
84 (pfn << RADIX_DAX_SHIFT) | RADIX_DAX_ENTRY_LOCK);
85 }
86
87 static unsigned int dax_radix_order(void *entry)
88 {
89 if ((unsigned long)entry & RADIX_DAX_PMD)
90 return PMD_SHIFT - PAGE_SHIFT;
91 return 0;
92 }
93
94 static int dax_is_pmd_entry(void *entry)
95 {
96 return (unsigned long)entry & RADIX_DAX_PMD;
97 }
98
99 static int dax_is_pte_entry(void *entry)
100 {
101 return !((unsigned long)entry & RADIX_DAX_PMD);
102 }
103
104 static int dax_is_zero_entry(void *entry)
105 {
106 return (unsigned long)entry & RADIX_DAX_ZERO_PAGE;
107 }
108
109 static int dax_is_empty_entry(void *entry)
110 {
111 return (unsigned long)entry & RADIX_DAX_EMPTY;
112 }
113
114 /*
115 * DAX radix tree locking
116 */
117 struct exceptional_entry_key {
118 struct address_space *mapping;
119 pgoff_t entry_start;
120 };
121
122 struct wait_exceptional_entry_queue {
123 wait_queue_entry_t wait;
124 struct exceptional_entry_key key;
125 };
126
127 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
128 pgoff_t index, void *entry, struct exceptional_entry_key *key)
129 {
130 unsigned long hash;
131
132 /*
133 * If 'entry' is a PMD, align the 'index' that we use for the wait
134 * queue to the start of that PMD. This ensures that all offsets in
135 * the range covered by the PMD map to the same bit lock.
136 */
137 if (dax_is_pmd_entry(entry))
138 index &= ~PG_PMD_COLOUR;
139
140 key->mapping = mapping;
141 key->entry_start = index;
142
143 hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
144 return wait_table + hash;
145 }
146
147 static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode,
148 int sync, void *keyp)
149 {
150 struct exceptional_entry_key *key = keyp;
151 struct wait_exceptional_entry_queue *ewait =
152 container_of(wait, struct wait_exceptional_entry_queue, wait);
153
154 if (key->mapping != ewait->key.mapping ||
155 key->entry_start != ewait->key.entry_start)
156 return 0;
157 return autoremove_wake_function(wait, mode, sync, NULL);
158 }
159
160 /*
161 * @entry may no longer be the entry at the index in the mapping.
162 * The important information it's conveying is whether the entry at
163 * this index used to be a PMD entry.
164 */
165 static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
166 pgoff_t index, void *entry, bool wake_all)
167 {
168 struct exceptional_entry_key key;
169 wait_queue_head_t *wq;
170
171 wq = dax_entry_waitqueue(mapping, index, entry, &key);
172
173 /*
174 * Checking for locked entry and prepare_to_wait_exclusive() happens
175 * under the i_pages lock, ditto for entry handling in our callers.
176 * So at this point all tasks that could have seen our entry locked
177 * must be in the waitqueue and the following check will see them.
178 */
179 if (waitqueue_active(wq))
180 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
181 }
182
183 /*
184 * Check whether the given slot is locked. Must be called with the i_pages
185 * lock held.
186 */
187 static inline int slot_locked(struct address_space *mapping, void **slot)
188 {
189 unsigned long entry = (unsigned long)
190 radix_tree_deref_slot_protected(slot, &mapping->i_pages.xa_lock);
191 return entry & RADIX_DAX_ENTRY_LOCK;
192 }
193
194 /*
195 * Mark the given slot as locked. Must be called with the i_pages lock held.
196 */
197 static inline void *lock_slot(struct address_space *mapping, void **slot)
198 {
199 unsigned long entry = (unsigned long)
200 radix_tree_deref_slot_protected(slot, &mapping->i_pages.xa_lock);
201
202 entry |= RADIX_DAX_ENTRY_LOCK;
203 radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry);
204 return (void *)entry;
205 }
206
207 /*
208 * Mark the given slot as unlocked. Must be called with the i_pages lock held.
209 */
210 static inline void *unlock_slot(struct address_space *mapping, void **slot)
211 {
212 unsigned long entry = (unsigned long)
213 radix_tree_deref_slot_protected(slot, &mapping->i_pages.xa_lock);
214
215 entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
216 radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry);
217 return (void *)entry;
218 }
219
220 /*
221 * Lookup entry in radix tree, wait for it to become unlocked if it is
222 * exceptional entry and return it. The caller must call
223 * put_unlocked_mapping_entry() when he decided not to lock the entry or
224 * put_locked_mapping_entry() when he locked the entry and now wants to
225 * unlock it.
226 *
227 * Must be called with the i_pages lock held.
228 */
229 static void *get_unlocked_mapping_entry(struct address_space *mapping,
230 pgoff_t index, void ***slotp)
231 {
232 void *entry, **slot;
233 struct wait_exceptional_entry_queue ewait;
234 wait_queue_head_t *wq;
235
236 init_wait(&ewait.wait);
237 ewait.wait.func = wake_exceptional_entry_func;
238
239 for (;;) {
240 entry = __radix_tree_lookup(&mapping->i_pages, index, NULL,
241 &slot);
242 if (!entry ||
243 WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)) ||
244 !slot_locked(mapping, slot)) {
245 if (slotp)
246 *slotp = slot;
247 return entry;
248 }
249
250 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
251 prepare_to_wait_exclusive(wq, &ewait.wait,
252 TASK_UNINTERRUPTIBLE);
253 xa_unlock_irq(&mapping->i_pages);
254 schedule();
255 finish_wait(wq, &ewait.wait);
256 xa_lock_irq(&mapping->i_pages);
257 }
258 }
259
260 static void dax_unlock_mapping_entry(struct address_space *mapping,
261 pgoff_t index)
262 {
263 void *entry, **slot;
264
265 xa_lock_irq(&mapping->i_pages);
266 entry = __radix_tree_lookup(&mapping->i_pages, index, NULL, &slot);
267 if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
268 !slot_locked(mapping, slot))) {
269 xa_unlock_irq(&mapping->i_pages);
270 return;
271 }
272 unlock_slot(mapping, slot);
273 xa_unlock_irq(&mapping->i_pages);
274 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
275 }
276
277 static void put_locked_mapping_entry(struct address_space *mapping,
278 pgoff_t index)
279 {
280 dax_unlock_mapping_entry(mapping, index);
281 }
282
283 /*
284 * Called when we are done with radix tree entry we looked up via
285 * get_unlocked_mapping_entry() and which we didn't lock in the end.
286 */
287 static void put_unlocked_mapping_entry(struct address_space *mapping,
288 pgoff_t index, void *entry)
289 {
290 if (!entry)
291 return;
292
293 /* We have to wake up next waiter for the radix tree entry lock */
294 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
295 }
296
297 static unsigned long dax_entry_size(void *entry)
298 {
299 if (dax_is_zero_entry(entry))
300 return 0;
301 else if (dax_is_empty_entry(entry))
302 return 0;
303 else if (dax_is_pmd_entry(entry))
304 return PMD_SIZE;
305 else
306 return PAGE_SIZE;
307 }
308
309 static unsigned long dax_radix_end_pfn(void *entry)
310 {
311 return dax_radix_pfn(entry) + dax_entry_size(entry) / PAGE_SIZE;
312 }
313
314 /*
315 * Iterate through all mapped pfns represented by an entry, i.e. skip
316 * 'empty' and 'zero' entries.
317 */
318 #define for_each_mapped_pfn(entry, pfn) \
319 for (pfn = dax_radix_pfn(entry); \
320 pfn < dax_radix_end_pfn(entry); pfn++)
321
322 static void dax_associate_entry(void *entry, struct address_space *mapping)
323 {
324 unsigned long pfn;
325
326 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
327 return;
328
329 for_each_mapped_pfn(entry, pfn) {
330 struct page *page = pfn_to_page(pfn);
331
332 WARN_ON_ONCE(page->mapping);
333 page->mapping = mapping;
334 }
335 }
336
337 static void dax_disassociate_entry(void *entry, struct address_space *mapping,
338 bool trunc)
339 {
340 unsigned long pfn;
341
342 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
343 return;
344
345 for_each_mapped_pfn(entry, pfn) {
346 struct page *page = pfn_to_page(pfn);
347
348 WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
349 WARN_ON_ONCE(page->mapping && page->mapping != mapping);
350 page->mapping = NULL;
351 }
352 }
353
354 static struct page *dax_busy_page(void *entry)
355 {
356 unsigned long pfn;
357
358 for_each_mapped_pfn(entry, pfn) {
359 struct page *page = pfn_to_page(pfn);
360
361 if (page_ref_count(page) > 1)
362 return page;
363 }
364 return NULL;
365 }
366
367 /*
368 * Find radix tree entry at given index. If it points to an exceptional entry,
369 * return it with the radix tree entry locked. If the radix tree doesn't
370 * contain given index, create an empty exceptional entry for the index and
371 * return with it locked.
372 *
373 * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
374 * either return that locked entry or will return an error. This error will
375 * happen if there are any 4k entries within the 2MiB range that we are
376 * requesting.
377 *
378 * We always favor 4k entries over 2MiB entries. There isn't a flow where we
379 * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
380 * insertion will fail if it finds any 4k entries already in the tree, and a
381 * 4k insertion will cause an existing 2MiB entry to be unmapped and
382 * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
383 * well as 2MiB empty entries.
384 *
385 * The exception to this downgrade path is for 2MiB DAX PMD entries that have
386 * real storage backing them. We will leave these real 2MiB DAX entries in
387 * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
388 *
389 * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
390 * persistent memory the benefit is doubtful. We can add that later if we can
391 * show it helps.
392 */
393 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
394 unsigned long size_flag)
395 {
396 bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
397 void *entry, **slot;
398
399 restart:
400 xa_lock_irq(&mapping->i_pages);
401 entry = get_unlocked_mapping_entry(mapping, index, &slot);
402
403 if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
404 entry = ERR_PTR(-EIO);
405 goto out_unlock;
406 }
407
408 if (entry) {
409 if (size_flag & RADIX_DAX_PMD) {
410 if (dax_is_pte_entry(entry)) {
411 put_unlocked_mapping_entry(mapping, index,
412 entry);
413 entry = ERR_PTR(-EEXIST);
414 goto out_unlock;
415 }
416 } else { /* trying to grab a PTE entry */
417 if (dax_is_pmd_entry(entry) &&
418 (dax_is_zero_entry(entry) ||
419 dax_is_empty_entry(entry))) {
420 pmd_downgrade = true;
421 }
422 }
423 }
424
425 /* No entry for given index? Make sure radix tree is big enough. */
426 if (!entry || pmd_downgrade) {
427 int err;
428
429 if (pmd_downgrade) {
430 /*
431 * Make sure 'entry' remains valid while we drop
432 * the i_pages lock.
433 */
434 entry = lock_slot(mapping, slot);
435 }
436
437 xa_unlock_irq(&mapping->i_pages);
438 /*
439 * Besides huge zero pages the only other thing that gets
440 * downgraded are empty entries which don't need to be
441 * unmapped.
442 */
443 if (pmd_downgrade && dax_is_zero_entry(entry))
444 unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
445 PG_PMD_NR, false);
446
447 err = radix_tree_preload(
448 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
449 if (err) {
450 if (pmd_downgrade)
451 put_locked_mapping_entry(mapping, index);
452 return ERR_PTR(err);
453 }
454 xa_lock_irq(&mapping->i_pages);
455
456 if (!entry) {
457 /*
458 * We needed to drop the i_pages lock while calling
459 * radix_tree_preload() and we didn't have an entry to
460 * lock. See if another thread inserted an entry at
461 * our index during this time.
462 */
463 entry = __radix_tree_lookup(&mapping->i_pages, index,
464 NULL, &slot);
465 if (entry) {
466 radix_tree_preload_end();
467 xa_unlock_irq(&mapping->i_pages);
468 goto restart;
469 }
470 }
471
472 if (pmd_downgrade) {
473 dax_disassociate_entry(entry, mapping, false);
474 radix_tree_delete(&mapping->i_pages, index);
475 mapping->nrexceptional--;
476 dax_wake_mapping_entry_waiter(mapping, index, entry,
477 true);
478 }
479
480 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
481
482 err = __radix_tree_insert(&mapping->i_pages, index,
483 dax_radix_order(entry), entry);
484 radix_tree_preload_end();
485 if (err) {
486 xa_unlock_irq(&mapping->i_pages);
487 /*
488 * Our insertion of a DAX entry failed, most likely
489 * because we were inserting a PMD entry and it
490 * collided with a PTE sized entry at a different
491 * index in the PMD range. We haven't inserted
492 * anything into the radix tree and have no waiters to
493 * wake.
494 */
495 return ERR_PTR(err);
496 }
497 /* Good, we have inserted empty locked entry into the tree. */
498 mapping->nrexceptional++;
499 xa_unlock_irq(&mapping->i_pages);
500 return entry;
501 }
502 entry = lock_slot(mapping, slot);
503 out_unlock:
504 xa_unlock_irq(&mapping->i_pages);
505 return entry;
506 }
507
508 /**
509 * dax_layout_busy_page - find first pinned page in @mapping
510 * @mapping: address space to scan for a page with ref count > 1
511 *
512 * DAX requires ZONE_DEVICE mapped pages. These pages are never
513 * 'onlined' to the page allocator so they are considered idle when
514 * page->count == 1. A filesystem uses this interface to determine if
515 * any page in the mapping is busy, i.e. for DMA, or other
516 * get_user_pages() usages.
517 *
518 * It is expected that the filesystem is holding locks to block the
519 * establishment of new mappings in this address_space. I.e. it expects
520 * to be able to run unmap_mapping_range() and subsequently not race
521 * mapping_mapped() becoming true.
522 */
523 struct page *dax_layout_busy_page(struct address_space *mapping)
524 {
525 pgoff_t indices[PAGEVEC_SIZE];
526 struct page *page = NULL;
527 struct pagevec pvec;
528 pgoff_t index, end;
529 unsigned i;
530
531 /*
532 * In the 'limited' case get_user_pages() for dax is disabled.
533 */
534 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
535 return NULL;
536
537 if (!dax_mapping(mapping) || !mapping_mapped(mapping))
538 return NULL;
539
540 pagevec_init(&pvec);
541 index = 0;
542 end = -1;
543
544 /*
545 * If we race get_user_pages_fast() here either we'll see the
546 * elevated page count in the pagevec_lookup and wait, or
547 * get_user_pages_fast() will see that the page it took a reference
548 * against is no longer mapped in the page tables and bail to the
549 * get_user_pages() slow path. The slow path is protected by
550 * pte_lock() and pmd_lock(). New references are not taken without
551 * holding those locks, and unmap_mapping_range() will not zero the
552 * pte or pmd without holding the respective lock, so we are
553 * guaranteed to either see new references or prevent new
554 * references from being established.
555 */
556 unmap_mapping_range(mapping, 0, 0, 1);
557
558 while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
559 min(end - index, (pgoff_t)PAGEVEC_SIZE),
560 indices)) {
561 for (i = 0; i < pagevec_count(&pvec); i++) {
562 struct page *pvec_ent = pvec.pages[i];
563 void *entry;
564
565 index = indices[i];
566 if (index >= end)
567 break;
568
569 if (WARN_ON_ONCE(
570 !radix_tree_exceptional_entry(pvec_ent)))
571 continue;
572
573 xa_lock_irq(&mapping->i_pages);
574 entry = get_unlocked_mapping_entry(mapping, index, NULL);
575 if (entry)
576 page = dax_busy_page(entry);
577 put_unlocked_mapping_entry(mapping, index, entry);
578 xa_unlock_irq(&mapping->i_pages);
579 if (page)
580 break;
581 }
582
583 /*
584 * We don't expect normal struct page entries to exist in our
585 * tree, but we keep these pagevec calls so that this code is
586 * consistent with the common pattern for handling pagevecs
587 * throughout the kernel.
588 */
589 pagevec_remove_exceptionals(&pvec);
590 pagevec_release(&pvec);
591 index++;
592
593 if (page)
594 break;
595 }
596 return page;
597 }
598 EXPORT_SYMBOL_GPL(dax_layout_busy_page);
599
600 static int __dax_invalidate_mapping_entry(struct address_space *mapping,
601 pgoff_t index, bool trunc)
602 {
603 int ret = 0;
604 void *entry;
605 struct radix_tree_root *pages = &mapping->i_pages;
606
607 xa_lock_irq(pages);
608 entry = get_unlocked_mapping_entry(mapping, index, NULL);
609 if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)))
610 goto out;
611 if (!trunc &&
612 (radix_tree_tag_get(pages, index, PAGECACHE_TAG_DIRTY) ||
613 radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE)))
614 goto out;
615 dax_disassociate_entry(entry, mapping, trunc);
616 radix_tree_delete(pages, index);
617 mapping->nrexceptional--;
618 ret = 1;
619 out:
620 put_unlocked_mapping_entry(mapping, index, entry);
621 xa_unlock_irq(pages);
622 return ret;
623 }
624 /*
625 * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
626 * entry to get unlocked before deleting it.
627 */
628 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
629 {
630 int ret = __dax_invalidate_mapping_entry(mapping, index, true);
631
632 /*
633 * This gets called from truncate / punch_hole path. As such, the caller
634 * must hold locks protecting against concurrent modifications of the
635 * radix tree (usually fs-private i_mmap_sem for writing). Since the
636 * caller has seen exceptional entry for this index, we better find it
637 * at that index as well...
638 */
639 WARN_ON_ONCE(!ret);
640 return ret;
641 }
642
643 /*
644 * Invalidate exceptional DAX entry if it is clean.
645 */
646 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
647 pgoff_t index)
648 {
649 return __dax_invalidate_mapping_entry(mapping, index, false);
650 }
651
652 static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
653 sector_t sector, size_t size, struct page *to,
654 unsigned long vaddr)
655 {
656 void *vto, *kaddr;
657 pgoff_t pgoff;
658 pfn_t pfn;
659 long rc;
660 int id;
661
662 rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
663 if (rc)
664 return rc;
665
666 id = dax_read_lock();
667 rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
668 if (rc < 0) {
669 dax_read_unlock(id);
670 return rc;
671 }
672 vto = kmap_atomic(to);
673 copy_user_page(vto, (void __force *)kaddr, vaddr, to);
674 kunmap_atomic(vto);
675 dax_read_unlock(id);
676 return 0;
677 }
678
679 /*
680 * By this point grab_mapping_entry() has ensured that we have a locked entry
681 * of the appropriate size so we don't have to worry about downgrading PMDs to
682 * PTEs. If we happen to be trying to insert a PTE and there is a PMD
683 * already in the tree, we will skip the insertion and just dirty the PMD as
684 * appropriate.
685 */
686 static void *dax_insert_mapping_entry(struct address_space *mapping,
687 struct vm_fault *vmf,
688 void *entry, pfn_t pfn_t,
689 unsigned long flags, bool dirty)
690 {
691 struct radix_tree_root *pages = &mapping->i_pages;
692 unsigned long pfn = pfn_t_to_pfn(pfn_t);
693 pgoff_t index = vmf->pgoff;
694 void *new_entry;
695
696 if (dirty)
697 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
698
699 if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
700 /* we are replacing a zero page with block mapping */
701 if (dax_is_pmd_entry(entry))
702 unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
703 PG_PMD_NR, false);
704 else /* pte entry */
705 unmap_mapping_pages(mapping, vmf->pgoff, 1, false);
706 }
707
708 xa_lock_irq(pages);
709 new_entry = dax_radix_locked_entry(pfn, flags);
710 if (dax_entry_size(entry) != dax_entry_size(new_entry)) {
711 dax_disassociate_entry(entry, mapping, false);
712 dax_associate_entry(new_entry, mapping);
713 }
714
715 if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
716 /*
717 * Only swap our new entry into the radix tree if the current
718 * entry is a zero page or an empty entry. If a normal PTE or
719 * PMD entry is already in the tree, we leave it alone. This
720 * means that if we are trying to insert a PTE and the
721 * existing entry is a PMD, we will just leave the PMD in the
722 * tree and dirty it if necessary.
723 */
724 struct radix_tree_node *node;
725 void **slot;
726 void *ret;
727
728 ret = __radix_tree_lookup(pages, index, &node, &slot);
729 WARN_ON_ONCE(ret != entry);
730 __radix_tree_replace(pages, node, slot,
731 new_entry, NULL);
732 entry = new_entry;
733 }
734
735 if (dirty)
736 radix_tree_tag_set(pages, index, PAGECACHE_TAG_DIRTY);
737
738 xa_unlock_irq(pages);
739 return entry;
740 }
741
742 static inline unsigned long
743 pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
744 {
745 unsigned long address;
746
747 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
748 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
749 return address;
750 }
751
752 /* Walk all mappings of a given index of a file and writeprotect them */
753 static void dax_mapping_entry_mkclean(struct address_space *mapping,
754 pgoff_t index, unsigned long pfn)
755 {
756 struct vm_area_struct *vma;
757 pte_t pte, *ptep = NULL;
758 pmd_t *pmdp = NULL;
759 spinlock_t *ptl;
760
761 i_mmap_lock_read(mapping);
762 vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
763 unsigned long address, start, end;
764
765 cond_resched();
766
767 if (!(vma->vm_flags & VM_SHARED))
768 continue;
769
770 address = pgoff_address(index, vma);
771
772 /*
773 * Note because we provide start/end to follow_pte_pmd it will
774 * call mmu_notifier_invalidate_range_start() on our behalf
775 * before taking any lock.
776 */
777 if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
778 continue;
779
780 /*
781 * No need to call mmu_notifier_invalidate_range() as we are
782 * downgrading page table protection not changing it to point
783 * to a new page.
784 *
785 * See Documentation/vm/mmu_notifier.rst
786 */
787 if (pmdp) {
788 #ifdef CONFIG_FS_DAX_PMD
789 pmd_t pmd;
790
791 if (pfn != pmd_pfn(*pmdp))
792 goto unlock_pmd;
793 if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
794 goto unlock_pmd;
795
796 flush_cache_page(vma, address, pfn);
797 pmd = pmdp_huge_clear_flush(vma, address, pmdp);
798 pmd = pmd_wrprotect(pmd);
799 pmd = pmd_mkclean(pmd);
800 set_pmd_at(vma->vm_mm, address, pmdp, pmd);
801 unlock_pmd:
802 #endif
803 spin_unlock(ptl);
804 } else {
805 if (pfn != pte_pfn(*ptep))
806 goto unlock_pte;
807 if (!pte_dirty(*ptep) && !pte_write(*ptep))
808 goto unlock_pte;
809
810 flush_cache_page(vma, address, pfn);
811 pte = ptep_clear_flush(vma, address, ptep);
812 pte = pte_wrprotect(pte);
813 pte = pte_mkclean(pte);
814 set_pte_at(vma->vm_mm, address, ptep, pte);
815 unlock_pte:
816 pte_unmap_unlock(ptep, ptl);
817 }
818
819 mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
820 }
821 i_mmap_unlock_read(mapping);
822 }
823
824 static int dax_writeback_one(struct dax_device *dax_dev,
825 struct address_space *mapping, pgoff_t index, void *entry)
826 {
827 struct radix_tree_root *pages = &mapping->i_pages;
828 void *entry2, **slot;
829 unsigned long pfn;
830 long ret = 0;
831 size_t size;
832
833 /*
834 * A page got tagged dirty in DAX mapping? Something is seriously
835 * wrong.
836 */
837 if (WARN_ON(!radix_tree_exceptional_entry(entry)))
838 return -EIO;
839
840 xa_lock_irq(pages);
841 entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
842 /* Entry got punched out / reallocated? */
843 if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2)))
844 goto put_unlocked;
845 /*
846 * Entry got reallocated elsewhere? No need to writeback. We have to
847 * compare pfns as we must not bail out due to difference in lockbit
848 * or entry type.
849 */
850 if (dax_radix_pfn(entry2) != dax_radix_pfn(entry))
851 goto put_unlocked;
852 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
853 dax_is_zero_entry(entry))) {
854 ret = -EIO;
855 goto put_unlocked;
856 }
857
858 /* Another fsync thread may have already written back this entry */
859 if (!radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))
860 goto put_unlocked;
861 /* Lock the entry to serialize with page faults */
862 entry = lock_slot(mapping, slot);
863 /*
864 * We can clear the tag now but we have to be careful so that concurrent
865 * dax_writeback_one() calls for the same index cannot finish before we
866 * actually flush the caches. This is achieved as the calls will look
867 * at the entry only under the i_pages lock and once they do that
868 * they will see the entry locked and wait for it to unlock.
869 */
870 radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE);
871 xa_unlock_irq(pages);
872
873 /*
874 * Even if dax_writeback_mapping_range() was given a wbc->range_start
875 * in the middle of a PMD, the 'index' we are given will be aligned to
876 * the start index of the PMD, as will the pfn we pull from 'entry'.
877 * This allows us to flush for PMD_SIZE and not have to worry about
878 * partial PMD writebacks.
879 */
880 pfn = dax_radix_pfn(entry);
881 size = PAGE_SIZE << dax_radix_order(entry);
882
883 dax_mapping_entry_mkclean(mapping, index, pfn);
884 dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
885 /*
886 * After we have flushed the cache, we can clear the dirty tag. There
887 * cannot be new dirty data in the pfn after the flush has completed as
888 * the pfn mappings are writeprotected and fault waits for mapping
889 * entry lock.
890 */
891 xa_lock_irq(pages);
892 radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY);
893 xa_unlock_irq(pages);
894 trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
895 put_locked_mapping_entry(mapping, index);
896 return ret;
897
898 put_unlocked:
899 put_unlocked_mapping_entry(mapping, index, entry2);
900 xa_unlock_irq(pages);
901 return ret;
902 }
903
904 /*
905 * Flush the mapping to the persistent domain within the byte range of [start,
906 * end]. This is required by data integrity operations to ensure file data is
907 * on persistent storage prior to completion of the operation.
908 */
909 int dax_writeback_mapping_range(struct address_space *mapping,
910 struct block_device *bdev, struct writeback_control *wbc)
911 {
912 struct inode *inode = mapping->host;
913 pgoff_t start_index, end_index;
914 pgoff_t indices[PAGEVEC_SIZE];
915 struct dax_device *dax_dev;
916 struct pagevec pvec;
917 bool done = false;
918 int i, ret = 0;
919
920 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
921 return -EIO;
922
923 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
924 return 0;
925
926 dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
927 if (!dax_dev)
928 return -EIO;
929
930 start_index = wbc->range_start >> PAGE_SHIFT;
931 end_index = wbc->range_end >> PAGE_SHIFT;
932
933 trace_dax_writeback_range(inode, start_index, end_index);
934
935 tag_pages_for_writeback(mapping, start_index, end_index);
936
937 pagevec_init(&pvec);
938 while (!done) {
939 pvec.nr = find_get_entries_tag(mapping, start_index,
940 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
941 pvec.pages, indices);
942
943 if (pvec.nr == 0)
944 break;
945
946 for (i = 0; i < pvec.nr; i++) {
947 if (indices[i] > end_index) {
948 done = true;
949 break;
950 }
951
952 ret = dax_writeback_one(dax_dev, mapping, indices[i],
953 pvec.pages[i]);
954 if (ret < 0) {
955 mapping_set_error(mapping, ret);
956 goto out;
957 }
958 }
959 start_index = indices[pvec.nr - 1] + 1;
960 }
961 out:
962 put_dax(dax_dev);
963 trace_dax_writeback_range_done(inode, start_index, end_index);
964 return (ret < 0 ? ret : 0);
965 }
966 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
967
968 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
969 {
970 return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
971 }
972
973 static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
974 pfn_t *pfnp)
975 {
976 const sector_t sector = dax_iomap_sector(iomap, pos);
977 pgoff_t pgoff;
978 void *kaddr;
979 int id, rc;
980 long length;
981
982 rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
983 if (rc)
984 return rc;
985 id = dax_read_lock();
986 length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
987 &kaddr, pfnp);
988 if (length < 0) {
989 rc = length;
990 goto out;
991 }
992 rc = -EINVAL;
993 if (PFN_PHYS(length) < size)
994 goto out;
995 if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
996 goto out;
997 /* For larger pages we need devmap */
998 if (length > 1 && !pfn_t_devmap(*pfnp))
999 goto out;
1000 rc = 0;
1001 out:
1002 dax_read_unlock(id);
1003 return rc;
1004 }
1005
1006 /*
1007 * The user has performed a load from a hole in the file. Allocating a new
1008 * page in the file would cause excessive storage usage for workloads with
1009 * sparse files. Instead we insert a read-only mapping of the 4k zero page.
1010 * If this page is ever written to we will re-fault and change the mapping to
1011 * point to real DAX storage instead.
1012 */
1013 static vm_fault_t dax_load_hole(struct address_space *mapping, void *entry,
1014 struct vm_fault *vmf)
1015 {
1016 struct inode *inode = mapping->host;
1017 unsigned long vaddr = vmf->address;
1018 vm_fault_t ret = VM_FAULT_NOPAGE;
1019 struct page *zero_page;
1020 pfn_t pfn;
1021
1022 zero_page = ZERO_PAGE(0);
1023 if (unlikely(!zero_page)) {
1024 ret = VM_FAULT_OOM;
1025 goto out;
1026 }
1027
1028 pfn = page_to_pfn_t(zero_page);
1029 dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE,
1030 false);
1031 ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
1032 out:
1033 trace_dax_load_hole(inode, vmf, ret);
1034 return ret;
1035 }
1036
1037 static bool dax_range_is_aligned(struct block_device *bdev,
1038 unsigned int offset, unsigned int length)
1039 {
1040 unsigned short sector_size = bdev_logical_block_size(bdev);
1041
1042 if (!IS_ALIGNED(offset, sector_size))
1043 return false;
1044 if (!IS_ALIGNED(length, sector_size))
1045 return false;
1046
1047 return true;
1048 }
1049
1050 int __dax_zero_page_range(struct block_device *bdev,
1051 struct dax_device *dax_dev, sector_t sector,
1052 unsigned int offset, unsigned int size)
1053 {
1054 if (dax_range_is_aligned(bdev, offset, size)) {
1055 sector_t start_sector = sector + (offset >> 9);
1056
1057 return blkdev_issue_zeroout(bdev, start_sector,
1058 size >> 9, GFP_NOFS, 0);
1059 } else {
1060 pgoff_t pgoff;
1061 long rc, id;
1062 void *kaddr;
1063 pfn_t pfn;
1064
1065 rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
1066 if (rc)
1067 return rc;
1068
1069 id = dax_read_lock();
1070 rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
1071 &pfn);
1072 if (rc < 0) {
1073 dax_read_unlock(id);
1074 return rc;
1075 }
1076 memset(kaddr + offset, 0, size);
1077 dax_flush(dax_dev, kaddr + offset, size);
1078 dax_read_unlock(id);
1079 }
1080 return 0;
1081 }
1082 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
1083
1084 static loff_t
1085 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
1086 struct iomap *iomap)
1087 {
1088 struct block_device *bdev = iomap->bdev;
1089 struct dax_device *dax_dev = iomap->dax_dev;
1090 struct iov_iter *iter = data;
1091 loff_t end = pos + length, done = 0;
1092 ssize_t ret = 0;
1093 size_t xfer;
1094 int id;
1095
1096 if (iov_iter_rw(iter) == READ) {
1097 end = min(end, i_size_read(inode));
1098 if (pos >= end)
1099 return 0;
1100
1101 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1102 return iov_iter_zero(min(length, end - pos), iter);
1103 }
1104
1105 if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
1106 return -EIO;
1107
1108 /*
1109 * Write can allocate block for an area which has a hole page mapped
1110 * into page tables. We have to tear down these mappings so that data
1111 * written by write(2) is visible in mmap.
1112 */
1113 if (iomap->flags & IOMAP_F_NEW) {
1114 invalidate_inode_pages2_range(inode->i_mapping,
1115 pos >> PAGE_SHIFT,
1116 (end - 1) >> PAGE_SHIFT);
1117 }
1118
1119 id = dax_read_lock();
1120 while (pos < end) {
1121 unsigned offset = pos & (PAGE_SIZE - 1);
1122 const size_t size = ALIGN(length + offset, PAGE_SIZE);
1123 const sector_t sector = dax_iomap_sector(iomap, pos);
1124 ssize_t map_len;
1125 pgoff_t pgoff;
1126 void *kaddr;
1127 pfn_t pfn;
1128
1129 if (fatal_signal_pending(current)) {
1130 ret = -EINTR;
1131 break;
1132 }
1133
1134 ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
1135 if (ret)
1136 break;
1137
1138 map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
1139 &kaddr, &pfn);
1140 if (map_len < 0) {
1141 ret = map_len;
1142 break;
1143 }
1144
1145 map_len = PFN_PHYS(map_len);
1146 kaddr += offset;
1147 map_len -= offset;
1148 if (map_len > end - pos)
1149 map_len = end - pos;
1150
1151 /*
1152 * The userspace address for the memory copy has already been
1153 * validated via access_ok() in either vfs_read() or
1154 * vfs_write(), depending on which operation we are doing.
1155 */
1156 if (iov_iter_rw(iter) == WRITE)
1157 xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr,
1158 map_len, iter);
1159 else
1160 xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr,
1161 map_len, iter);
1162
1163 pos += xfer;
1164 length -= xfer;
1165 done += xfer;
1166
1167 if (xfer == 0)
1168 ret = -EFAULT;
1169 if (xfer < map_len)
1170 break;
1171 }
1172 dax_read_unlock(id);
1173
1174 return done ? done : ret;
1175 }
1176
1177 /**
1178 * dax_iomap_rw - Perform I/O to a DAX file
1179 * @iocb: The control block for this I/O
1180 * @iter: The addresses to do I/O from or to
1181 * @ops: iomap ops passed from the file system
1182 *
1183 * This function performs read and write operations to directly mapped
1184 * persistent memory. The callers needs to take care of read/write exclusion
1185 * and evicting any page cache pages in the region under I/O.
1186 */
1187 ssize_t
1188 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1189 const struct iomap_ops *ops)
1190 {
1191 struct address_space *mapping = iocb->ki_filp->f_mapping;
1192 struct inode *inode = mapping->host;
1193 loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1194 unsigned flags = 0;
1195
1196 if (iov_iter_rw(iter) == WRITE) {
1197 lockdep_assert_held_exclusive(&inode->i_rwsem);
1198 flags |= IOMAP_WRITE;
1199 } else {
1200 lockdep_assert_held(&inode->i_rwsem);
1201 }
1202
1203 while (iov_iter_count(iter)) {
1204 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1205 iter, dax_iomap_actor);
1206 if (ret <= 0)
1207 break;
1208 pos += ret;
1209 done += ret;
1210 }
1211
1212 iocb->ki_pos += done;
1213 return done ? done : ret;
1214 }
1215 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1216
1217 static vm_fault_t dax_fault_return(int error)
1218 {
1219 if (error == 0)
1220 return VM_FAULT_NOPAGE;
1221 if (error == -ENOMEM)
1222 return VM_FAULT_OOM;
1223 return VM_FAULT_SIGBUS;
1224 }
1225
1226 /*
1227 * MAP_SYNC on a dax mapping guarantees dirty metadata is
1228 * flushed on write-faults (non-cow), but not read-faults.
1229 */
1230 static bool dax_fault_is_synchronous(unsigned long flags,
1231 struct vm_area_struct *vma, struct iomap *iomap)
1232 {
1233 return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
1234 && (iomap->flags & IOMAP_F_DIRTY);
1235 }
1236
1237 static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
1238 int *iomap_errp, const struct iomap_ops *ops)
1239 {
1240 struct vm_area_struct *vma = vmf->vma;
1241 struct address_space *mapping = vma->vm_file->f_mapping;
1242 struct inode *inode = mapping->host;
1243 unsigned long vaddr = vmf->address;
1244 loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1245 struct iomap iomap = { 0 };
1246 unsigned flags = IOMAP_FAULT;
1247 int error, major = 0;
1248 bool write = vmf->flags & FAULT_FLAG_WRITE;
1249 bool sync;
1250 vm_fault_t ret = 0;
1251 void *entry;
1252 pfn_t pfn;
1253
1254 trace_dax_pte_fault(inode, vmf, ret);
1255 /*
1256 * Check whether offset isn't beyond end of file now. Caller is supposed
1257 * to hold locks serializing us with truncate / punch hole so this is
1258 * a reliable test.
1259 */
1260 if (pos >= i_size_read(inode)) {
1261 ret = VM_FAULT_SIGBUS;
1262 goto out;
1263 }
1264
1265 if (write && !vmf->cow_page)
1266 flags |= IOMAP_WRITE;
1267
1268 entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
1269 if (IS_ERR(entry)) {
1270 ret = dax_fault_return(PTR_ERR(entry));
1271 goto out;
1272 }
1273
1274 /*
1275 * It is possible, particularly with mixed reads & writes to private
1276 * mappings, that we have raced with a PMD fault that overlaps with
1277 * the PTE we need to set up. If so just return and the fault will be
1278 * retried.
1279 */
1280 if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
1281 ret = VM_FAULT_NOPAGE;
1282 goto unlock_entry;
1283 }
1284
1285 /*
1286 * Note that we don't bother to use iomap_apply here: DAX required
1287 * the file system block size to be equal the page size, which means
1288 * that we never have to deal with more than a single extent here.
1289 */
1290 error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1291 if (iomap_errp)
1292 *iomap_errp = error;
1293 if (error) {
1294 ret = dax_fault_return(error);
1295 goto unlock_entry;
1296 }
1297 if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1298 error = -EIO; /* fs corruption? */
1299 goto error_finish_iomap;
1300 }
1301
1302 if (vmf->cow_page) {
1303 sector_t sector = dax_iomap_sector(&iomap, pos);
1304
1305 switch (iomap.type) {
1306 case IOMAP_HOLE:
1307 case IOMAP_UNWRITTEN:
1308 clear_user_highpage(vmf->cow_page, vaddr);
1309 break;
1310 case IOMAP_MAPPED:
1311 error = copy_user_dax(iomap.bdev, iomap.dax_dev,
1312 sector, PAGE_SIZE, vmf->cow_page, vaddr);
1313 break;
1314 default:
1315 WARN_ON_ONCE(1);
1316 error = -EIO;
1317 break;
1318 }
1319
1320 if (error)
1321 goto error_finish_iomap;
1322
1323 __SetPageUptodate(vmf->cow_page);
1324 ret = finish_fault(vmf);
1325 if (!ret)
1326 ret = VM_FAULT_DONE_COW;
1327 goto finish_iomap;
1328 }
1329
1330 sync = dax_fault_is_synchronous(flags, vma, &iomap);
1331
1332 switch (iomap.type) {
1333 case IOMAP_MAPPED:
1334 if (iomap.flags & IOMAP_F_NEW) {
1335 count_vm_event(PGMAJFAULT);
1336 count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
1337 major = VM_FAULT_MAJOR;
1338 }
1339 error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
1340 if (error < 0)
1341 goto error_finish_iomap;
1342
1343 entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1344 0, write && !sync);
1345
1346 /*
1347 * If we are doing synchronous page fault and inode needs fsync,
1348 * we can insert PTE into page tables only after that happens.
1349 * Skip insertion for now and return the pfn so that caller can
1350 * insert it after fsync is done.
1351 */
1352 if (sync) {
1353 if (WARN_ON_ONCE(!pfnp)) {
1354 error = -EIO;
1355 goto error_finish_iomap;
1356 }
1357 *pfnp = pfn;
1358 ret = VM_FAULT_NEEDDSYNC | major;
1359 goto finish_iomap;
1360 }
1361 trace_dax_insert_mapping(inode, vmf, entry);
1362 if (write)
1363 ret = vmf_insert_mixed_mkwrite(vma, vaddr, pfn);
1364 else
1365 ret = vmf_insert_mixed(vma, vaddr, pfn);
1366
1367 goto finish_iomap;
1368 case IOMAP_UNWRITTEN:
1369 case IOMAP_HOLE:
1370 if (!write) {
1371 ret = dax_load_hole(mapping, entry, vmf);
1372 goto finish_iomap;
1373 }
1374 /*FALLTHRU*/
1375 default:
1376 WARN_ON_ONCE(1);
1377 error = -EIO;
1378 break;
1379 }
1380
1381 error_finish_iomap:
1382 ret = dax_fault_return(error);
1383 finish_iomap:
1384 if (ops->iomap_end) {
1385 int copied = PAGE_SIZE;
1386
1387 if (ret & VM_FAULT_ERROR)
1388 copied = 0;
1389 /*
1390 * The fault is done by now and there's no way back (other
1391 * thread may be already happily using PTE we have installed).
1392 * Just ignore error from ->iomap_end since we cannot do much
1393 * with it.
1394 */
1395 ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
1396 }
1397 unlock_entry:
1398 put_locked_mapping_entry(mapping, vmf->pgoff);
1399 out:
1400 trace_dax_pte_fault_done(inode, vmf, ret);
1401 return ret | major;
1402 }
1403
1404 #ifdef CONFIG_FS_DAX_PMD
1405 static vm_fault_t dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
1406 void *entry)
1407 {
1408 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1409 unsigned long pmd_addr = vmf->address & PMD_MASK;
1410 struct inode *inode = mapping->host;
1411 struct page *zero_page;
1412 void *ret = NULL;
1413 spinlock_t *ptl;
1414 pmd_t pmd_entry;
1415 pfn_t pfn;
1416
1417 zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
1418
1419 if (unlikely(!zero_page))
1420 goto fallback;
1421
1422 pfn = page_to_pfn_t(zero_page);
1423 ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1424 RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
1425
1426 ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1427 if (!pmd_none(*(vmf->pmd))) {
1428 spin_unlock(ptl);
1429 goto fallback;
1430 }
1431
1432 pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1433 pmd_entry = pmd_mkhuge(pmd_entry);
1434 set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
1435 spin_unlock(ptl);
1436 trace_dax_pmd_load_hole(inode, vmf, zero_page, ret);
1437 return VM_FAULT_NOPAGE;
1438
1439 fallback:
1440 trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret);
1441 return VM_FAULT_FALLBACK;
1442 }
1443
1444 static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1445 const struct iomap_ops *ops)
1446 {
1447 struct vm_area_struct *vma = vmf->vma;
1448 struct address_space *mapping = vma->vm_file->f_mapping;
1449 unsigned long pmd_addr = vmf->address & PMD_MASK;
1450 bool write = vmf->flags & FAULT_FLAG_WRITE;
1451 bool sync;
1452 unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1453 struct inode *inode = mapping->host;
1454 vm_fault_t result = VM_FAULT_FALLBACK;
1455 struct iomap iomap = { 0 };
1456 pgoff_t max_pgoff, pgoff;
1457 void *entry;
1458 loff_t pos;
1459 int error;
1460 pfn_t pfn;
1461
1462 /*
1463 * Check whether offset isn't beyond end of file now. Caller is
1464 * supposed to hold locks serializing us with truncate / punch hole so
1465 * this is a reliable test.
1466 */
1467 pgoff = linear_page_index(vma, pmd_addr);
1468 max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
1469
1470 trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
1471
1472 /*
1473 * Make sure that the faulting address's PMD offset (color) matches
1474 * the PMD offset from the start of the file. This is necessary so
1475 * that a PMD range in the page table overlaps exactly with a PMD
1476 * range in the radix tree.
1477 */
1478 if ((vmf->pgoff & PG_PMD_COLOUR) !=
1479 ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
1480 goto fallback;
1481
1482 /* Fall back to PTEs if we're going to COW */
1483 if (write && !(vma->vm_flags & VM_SHARED))
1484 goto fallback;
1485
1486 /* If the PMD would extend outside the VMA */
1487 if (pmd_addr < vma->vm_start)
1488 goto fallback;
1489 if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1490 goto fallback;
1491
1492 if (pgoff >= max_pgoff) {
1493 result = VM_FAULT_SIGBUS;
1494 goto out;
1495 }
1496
1497 /* If the PMD would extend beyond the file size */
1498 if ((pgoff | PG_PMD_COLOUR) >= max_pgoff)
1499 goto fallback;
1500
1501 /*
1502 * grab_mapping_entry() will make sure we get a 2MiB empty entry, a
1503 * 2MiB zero page entry or a DAX PMD. If it can't (because a 4k page
1504 * is already in the tree, for instance), it will return -EEXIST and
1505 * we just fall back to 4k entries.
1506 */
1507 entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1508 if (IS_ERR(entry))
1509 goto fallback;
1510
1511 /*
1512 * It is possible, particularly with mixed reads & writes to private
1513 * mappings, that we have raced with a PTE fault that overlaps with
1514 * the PMD we need to set up. If so just return and the fault will be
1515 * retried.
1516 */
1517 if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
1518 !pmd_devmap(*vmf->pmd)) {
1519 result = 0;
1520 goto unlock_entry;
1521 }
1522
1523 /*
1524 * Note that we don't use iomap_apply here. We aren't doing I/O, only
1525 * setting up a mapping, so really we're using iomap_begin() as a way
1526 * to look up our filesystem block.
1527 */
1528 pos = (loff_t)pgoff << PAGE_SHIFT;
1529 error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1530 if (error)
1531 goto unlock_entry;
1532
1533 if (iomap.offset + iomap.length < pos + PMD_SIZE)
1534 goto finish_iomap;
1535
1536 sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
1537
1538 switch (iomap.type) {
1539 case IOMAP_MAPPED:
1540 error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
1541 if (error < 0)
1542 goto finish_iomap;
1543
1544 entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1545 RADIX_DAX_PMD, write && !sync);
1546
1547 /*
1548 * If we are doing synchronous page fault and inode needs fsync,
1549 * we can insert PMD into page tables only after that happens.
1550 * Skip insertion for now and return the pfn so that caller can
1551 * insert it after fsync is done.
1552 */
1553 if (sync) {
1554 if (WARN_ON_ONCE(!pfnp))
1555 goto finish_iomap;
1556 *pfnp = pfn;
1557 result = VM_FAULT_NEEDDSYNC;
1558 goto finish_iomap;
1559 }
1560
1561 trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
1562 result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
1563 write);
1564 break;
1565 case IOMAP_UNWRITTEN:
1566 case IOMAP_HOLE:
1567 if (WARN_ON_ONCE(write))
1568 break;
1569 result = dax_pmd_load_hole(vmf, &iomap, entry);
1570 break;
1571 default:
1572 WARN_ON_ONCE(1);
1573 break;
1574 }
1575
1576 finish_iomap:
1577 if (ops->iomap_end) {
1578 int copied = PMD_SIZE;
1579
1580 if (result == VM_FAULT_FALLBACK)
1581 copied = 0;
1582 /*
1583 * The fault is done by now and there's no way back (other
1584 * thread may be already happily using PMD we have installed).
1585 * Just ignore error from ->iomap_end since we cannot do much
1586 * with it.
1587 */
1588 ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
1589 &iomap);
1590 }
1591 unlock_entry:
1592 put_locked_mapping_entry(mapping, pgoff);
1593 fallback:
1594 if (result == VM_FAULT_FALLBACK) {
1595 split_huge_pmd(vma, vmf->pmd, vmf->address);
1596 count_vm_event(THP_FAULT_FALLBACK);
1597 }
1598 out:
1599 trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
1600 return result;
1601 }
1602 #else
1603 static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1604 const struct iomap_ops *ops)
1605 {
1606 return VM_FAULT_FALLBACK;
1607 }
1608 #endif /* CONFIG_FS_DAX_PMD */
1609
1610 /**
1611 * dax_iomap_fault - handle a page fault on a DAX file
1612 * @vmf: The description of the fault
1613 * @pe_size: Size of the page to fault in
1614 * @pfnp: PFN to insert for synchronous faults if fsync is required
1615 * @iomap_errp: Storage for detailed error code in case of error
1616 * @ops: Iomap ops passed from the file system
1617 *
1618 * When a page fault occurs, filesystems may call this helper in
1619 * their fault handler for DAX files. dax_iomap_fault() assumes the caller
1620 * has done all the necessary locking for page fault to proceed
1621 * successfully.
1622 */
1623 vm_fault_t dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
1624 pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
1625 {
1626 switch (pe_size) {
1627 case PE_SIZE_PTE:
1628 return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
1629 case PE_SIZE_PMD:
1630 return dax_iomap_pmd_fault(vmf, pfnp, ops);
1631 default:
1632 return VM_FAULT_FALLBACK;
1633 }
1634 }
1635 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1636
1637 /**
1638 * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
1639 * @vmf: The description of the fault
1640 * @pe_size: Size of entry to be inserted
1641 * @pfn: PFN to insert
1642 *
1643 * This function inserts writeable PTE or PMD entry into page tables for mmaped
1644 * DAX file. It takes care of marking corresponding radix tree entry as dirty
1645 * as well.
1646 */
1647 static vm_fault_t dax_insert_pfn_mkwrite(struct vm_fault *vmf,
1648 enum page_entry_size pe_size,
1649 pfn_t pfn)
1650 {
1651 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1652 void *entry, **slot;
1653 pgoff_t index = vmf->pgoff;
1654 vm_fault_t ret;
1655
1656 xa_lock_irq(&mapping->i_pages);
1657 entry = get_unlocked_mapping_entry(mapping, index, &slot);
1658 /* Did we race with someone splitting entry or so? */
1659 if (!entry ||
1660 (pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
1661 (pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
1662 put_unlocked_mapping_entry(mapping, index, entry);
1663 xa_unlock_irq(&mapping->i_pages);
1664 trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
1665 VM_FAULT_NOPAGE);
1666 return VM_FAULT_NOPAGE;
1667 }
1668 radix_tree_tag_set(&mapping->i_pages, index, PAGECACHE_TAG_DIRTY);
1669 entry = lock_slot(mapping, slot);
1670 xa_unlock_irq(&mapping->i_pages);
1671 switch (pe_size) {
1672 case PE_SIZE_PTE:
1673 ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
1674 break;
1675 #ifdef CONFIG_FS_DAX_PMD
1676 case PE_SIZE_PMD:
1677 ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
1678 pfn, true);
1679 break;
1680 #endif
1681 default:
1682 ret = VM_FAULT_FALLBACK;
1683 }
1684 put_locked_mapping_entry(mapping, index);
1685 trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret);
1686 return ret;
1687 }
1688
1689 /**
1690 * dax_finish_sync_fault - finish synchronous page fault
1691 * @vmf: The description of the fault
1692 * @pe_size: Size of entry to be inserted
1693 * @pfn: PFN to insert
1694 *
1695 * This function ensures that the file range touched by the page fault is
1696 * stored persistently on the media and handles inserting of appropriate page
1697 * table entry.
1698 */
1699 vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
1700 enum page_entry_size pe_size, pfn_t pfn)
1701 {
1702 int err;
1703 loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
1704 size_t len = 0;
1705
1706 if (pe_size == PE_SIZE_PTE)
1707 len = PAGE_SIZE;
1708 else if (pe_size == PE_SIZE_PMD)
1709 len = PMD_SIZE;
1710 else
1711 WARN_ON_ONCE(1);
1712 err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
1713 if (err)
1714 return VM_FAULT_SIGBUS;
1715 return dax_insert_pfn_mkwrite(vmf, pe_size, pfn);
1716 }
1717 EXPORT_SYMBOL_GPL(dax_finish_sync_fault);