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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
48 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
49
50 static int __init init_dax_wait_table(void)
51 {
52 int i;
53
54 for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
55 init_waitqueue_head(wait_table + i);
56 return 0;
57 }
58 fs_initcall(init_dax_wait_table);
59
60 /*
61 * We use lowest available bit in exceptional entry for locking, one bit for
62 * the entry size (PMD) and two more to tell us if the entry is a zero page or
63 * an empty entry that is just used for locking. In total four special bits.
64 *
65 * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
66 * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
67 * block allocation.
68 */
69 #define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4)
70 #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
71 #define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
72 #define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
73 #define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))
74
75 static unsigned long dax_radix_sector(void *entry)
76 {
77 return (unsigned long)entry >> RADIX_DAX_SHIFT;
78 }
79
80 static void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
81 {
82 return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
83 ((unsigned long)sector << RADIX_DAX_SHIFT) |
84 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 * We do not necessarily hold the mapping->tree_lock when we call this
162 * function so it is possible that 'entry' is no longer a valid item in the
163 * radix tree. This is okay because all we really need to do is to find the
164 * correct waitqueue where tasks might be waiting for that old 'entry' and
165 * wake them.
166 */
167 static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
168 pgoff_t index, void *entry, bool wake_all)
169 {
170 struct exceptional_entry_key key;
171 wait_queue_head_t *wq;
172
173 wq = dax_entry_waitqueue(mapping, index, entry, &key);
174
175 /*
176 * Checking for locked entry and prepare_to_wait_exclusive() happens
177 * under mapping->tree_lock, ditto for entry handling in our callers.
178 * So at this point all tasks that could have seen our entry locked
179 * must be in the waitqueue and the following check will see them.
180 */
181 if (waitqueue_active(wq))
182 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
183 }
184
185 /*
186 * Check whether the given slot is locked. The function must be called with
187 * mapping->tree_lock held
188 */
189 static inline int slot_locked(struct address_space *mapping, void **slot)
190 {
191 unsigned long entry = (unsigned long)
192 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
193 return entry & RADIX_DAX_ENTRY_LOCK;
194 }
195
196 /*
197 * Mark the given slot is locked. The function must be called with
198 * mapping->tree_lock held
199 */
200 static inline void *lock_slot(struct address_space *mapping, void **slot)
201 {
202 unsigned long entry = (unsigned long)
203 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
204
205 entry |= RADIX_DAX_ENTRY_LOCK;
206 radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
207 return (void *)entry;
208 }
209
210 /*
211 * Mark the given slot is unlocked. The function must be called with
212 * mapping->tree_lock held
213 */
214 static inline void *unlock_slot(struct address_space *mapping, void **slot)
215 {
216 unsigned long entry = (unsigned long)
217 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
218
219 entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
220 radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
221 return (void *)entry;
222 }
223
224 /*
225 * Lookup entry in radix tree, wait for it to become unlocked if it is
226 * exceptional entry and return it. The caller must call
227 * put_unlocked_mapping_entry() when he decided not to lock the entry or
228 * put_locked_mapping_entry() when he locked the entry and now wants to
229 * unlock it.
230 *
231 * The function must be called with mapping->tree_lock held.
232 */
233 static void *get_unlocked_mapping_entry(struct address_space *mapping,
234 pgoff_t index, void ***slotp)
235 {
236 void *entry, **slot;
237 struct wait_exceptional_entry_queue ewait;
238 wait_queue_head_t *wq;
239
240 init_wait(&ewait.wait);
241 ewait.wait.func = wake_exceptional_entry_func;
242
243 for (;;) {
244 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
245 &slot);
246 if (!entry ||
247 WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)) ||
248 !slot_locked(mapping, slot)) {
249 if (slotp)
250 *slotp = slot;
251 return entry;
252 }
253
254 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
255 prepare_to_wait_exclusive(wq, &ewait.wait,
256 TASK_UNINTERRUPTIBLE);
257 spin_unlock_irq(&mapping->tree_lock);
258 schedule();
259 finish_wait(wq, &ewait.wait);
260 spin_lock_irq(&mapping->tree_lock);
261 }
262 }
263
264 static void dax_unlock_mapping_entry(struct address_space *mapping,
265 pgoff_t index)
266 {
267 void *entry, **slot;
268
269 spin_lock_irq(&mapping->tree_lock);
270 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
271 if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
272 !slot_locked(mapping, slot))) {
273 spin_unlock_irq(&mapping->tree_lock);
274 return;
275 }
276 unlock_slot(mapping, slot);
277 spin_unlock_irq(&mapping->tree_lock);
278 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
279 }
280
281 static void put_locked_mapping_entry(struct address_space *mapping,
282 pgoff_t index)
283 {
284 dax_unlock_mapping_entry(mapping, index);
285 }
286
287 /*
288 * Called when we are done with radix tree entry we looked up via
289 * get_unlocked_mapping_entry() and which we didn't lock in the end.
290 */
291 static void put_unlocked_mapping_entry(struct address_space *mapping,
292 pgoff_t index, void *entry)
293 {
294 if (!entry)
295 return;
296
297 /* We have to wake up next waiter for the radix tree entry lock */
298 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
299 }
300
301 /*
302 * Find radix tree entry at given index. If it points to an exceptional entry,
303 * return it with the radix tree entry locked. If the radix tree doesn't
304 * contain given index, create an empty exceptional entry for the index and
305 * return with it locked.
306 *
307 * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
308 * either return that locked entry or will return an error. This error will
309 * happen if there are any 4k entries within the 2MiB range that we are
310 * requesting.
311 *
312 * We always favor 4k entries over 2MiB entries. There isn't a flow where we
313 * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
314 * insertion will fail if it finds any 4k entries already in the tree, and a
315 * 4k insertion will cause an existing 2MiB entry to be unmapped and
316 * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
317 * well as 2MiB empty entries.
318 *
319 * The exception to this downgrade path is for 2MiB DAX PMD entries that have
320 * real storage backing them. We will leave these real 2MiB DAX entries in
321 * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
322 *
323 * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
324 * persistent memory the benefit is doubtful. We can add that later if we can
325 * show it helps.
326 */
327 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
328 unsigned long size_flag)
329 {
330 bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
331 void *entry, **slot;
332
333 restart:
334 spin_lock_irq(&mapping->tree_lock);
335 entry = get_unlocked_mapping_entry(mapping, index, &slot);
336
337 if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
338 entry = ERR_PTR(-EIO);
339 goto out_unlock;
340 }
341
342 if (entry) {
343 if (size_flag & RADIX_DAX_PMD) {
344 if (dax_is_pte_entry(entry)) {
345 put_unlocked_mapping_entry(mapping, index,
346 entry);
347 entry = ERR_PTR(-EEXIST);
348 goto out_unlock;
349 }
350 } else { /* trying to grab a PTE entry */
351 if (dax_is_pmd_entry(entry) &&
352 (dax_is_zero_entry(entry) ||
353 dax_is_empty_entry(entry))) {
354 pmd_downgrade = true;
355 }
356 }
357 }
358
359 /* No entry for given index? Make sure radix tree is big enough. */
360 if (!entry || pmd_downgrade) {
361 int err;
362
363 if (pmd_downgrade) {
364 /*
365 * Make sure 'entry' remains valid while we drop
366 * mapping->tree_lock.
367 */
368 entry = lock_slot(mapping, slot);
369 }
370
371 spin_unlock_irq(&mapping->tree_lock);
372 /*
373 * Besides huge zero pages the only other thing that gets
374 * downgraded are empty entries which don't need to be
375 * unmapped.
376 */
377 if (pmd_downgrade && dax_is_zero_entry(entry))
378 unmap_mapping_range(mapping,
379 (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
380
381 err = radix_tree_preload(
382 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
383 if (err) {
384 if (pmd_downgrade)
385 put_locked_mapping_entry(mapping, index);
386 return ERR_PTR(err);
387 }
388 spin_lock_irq(&mapping->tree_lock);
389
390 if (!entry) {
391 /*
392 * We needed to drop the page_tree lock while calling
393 * radix_tree_preload() and we didn't have an entry to
394 * lock. See if another thread inserted an entry at
395 * our index during this time.
396 */
397 entry = __radix_tree_lookup(&mapping->page_tree, index,
398 NULL, &slot);
399 if (entry) {
400 radix_tree_preload_end();
401 spin_unlock_irq(&mapping->tree_lock);
402 goto restart;
403 }
404 }
405
406 if (pmd_downgrade) {
407 radix_tree_delete(&mapping->page_tree, index);
408 mapping->nrexceptional--;
409 dax_wake_mapping_entry_waiter(mapping, index, entry,
410 true);
411 }
412
413 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
414
415 err = __radix_tree_insert(&mapping->page_tree, index,
416 dax_radix_order(entry), entry);
417 radix_tree_preload_end();
418 if (err) {
419 spin_unlock_irq(&mapping->tree_lock);
420 /*
421 * Our insertion of a DAX entry failed, most likely
422 * because we were inserting a PMD entry and it
423 * collided with a PTE sized entry at a different
424 * index in the PMD range. We haven't inserted
425 * anything into the radix tree and have no waiters to
426 * wake.
427 */
428 return ERR_PTR(err);
429 }
430 /* Good, we have inserted empty locked entry into the tree. */
431 mapping->nrexceptional++;
432 spin_unlock_irq(&mapping->tree_lock);
433 return entry;
434 }
435 entry = lock_slot(mapping, slot);
436 out_unlock:
437 spin_unlock_irq(&mapping->tree_lock);
438 return entry;
439 }
440
441 static int __dax_invalidate_mapping_entry(struct address_space *mapping,
442 pgoff_t index, bool trunc)
443 {
444 int ret = 0;
445 void *entry;
446 struct radix_tree_root *page_tree = &mapping->page_tree;
447
448 spin_lock_irq(&mapping->tree_lock);
449 entry = get_unlocked_mapping_entry(mapping, index, NULL);
450 if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)))
451 goto out;
452 if (!trunc &&
453 (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) ||
454 radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)))
455 goto out;
456 radix_tree_delete(page_tree, index);
457 mapping->nrexceptional--;
458 ret = 1;
459 out:
460 put_unlocked_mapping_entry(mapping, index, entry);
461 spin_unlock_irq(&mapping->tree_lock);
462 return ret;
463 }
464 /*
465 * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
466 * entry to get unlocked before deleting it.
467 */
468 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
469 {
470 int ret = __dax_invalidate_mapping_entry(mapping, index, true);
471
472 /*
473 * This gets called from truncate / punch_hole path. As such, the caller
474 * must hold locks protecting against concurrent modifications of the
475 * radix tree (usually fs-private i_mmap_sem for writing). Since the
476 * caller has seen exceptional entry for this index, we better find it
477 * at that index as well...
478 */
479 WARN_ON_ONCE(!ret);
480 return ret;
481 }
482
483 /*
484 * Invalidate exceptional DAX entry if it is clean.
485 */
486 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
487 pgoff_t index)
488 {
489 return __dax_invalidate_mapping_entry(mapping, index, false);
490 }
491
492 static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
493 sector_t sector, size_t size, struct page *to,
494 unsigned long vaddr)
495 {
496 void *vto, *kaddr;
497 pgoff_t pgoff;
498 pfn_t pfn;
499 long rc;
500 int id;
501
502 rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
503 if (rc)
504 return rc;
505
506 id = dax_read_lock();
507 rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
508 if (rc < 0) {
509 dax_read_unlock(id);
510 return rc;
511 }
512 vto = kmap_atomic(to);
513 copy_user_page(vto, (void __force *)kaddr, vaddr, to);
514 kunmap_atomic(vto);
515 dax_read_unlock(id);
516 return 0;
517 }
518
519 /*
520 * By this point grab_mapping_entry() has ensured that we have a locked entry
521 * of the appropriate size so we don't have to worry about downgrading PMDs to
522 * PTEs. If we happen to be trying to insert a PTE and there is a PMD
523 * already in the tree, we will skip the insertion and just dirty the PMD as
524 * appropriate.
525 */
526 static void *dax_insert_mapping_entry(struct address_space *mapping,
527 struct vm_fault *vmf,
528 void *entry, sector_t sector,
529 unsigned long flags)
530 {
531 struct radix_tree_root *page_tree = &mapping->page_tree;
532 void *new_entry;
533 pgoff_t index = vmf->pgoff;
534
535 if (vmf->flags & FAULT_FLAG_WRITE)
536 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
537
538 if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
539 /* we are replacing a zero page with block mapping */
540 if (dax_is_pmd_entry(entry))
541 unmap_mapping_range(mapping,
542 (vmf->pgoff << PAGE_SHIFT) & PMD_MASK,
543 PMD_SIZE, 0);
544 else /* pte entry */
545 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
546 PAGE_SIZE, 0);
547 }
548
549 spin_lock_irq(&mapping->tree_lock);
550 new_entry = dax_radix_locked_entry(sector, flags);
551
552 if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
553 /*
554 * Only swap our new entry into the radix tree if the current
555 * entry is a zero page or an empty entry. If a normal PTE or
556 * PMD entry is already in the tree, we leave it alone. This
557 * means that if we are trying to insert a PTE and the
558 * existing entry is a PMD, we will just leave the PMD in the
559 * tree and dirty it if necessary.
560 */
561 struct radix_tree_node *node;
562 void **slot;
563 void *ret;
564
565 ret = __radix_tree_lookup(page_tree, index, &node, &slot);
566 WARN_ON_ONCE(ret != entry);
567 __radix_tree_replace(page_tree, node, slot,
568 new_entry, NULL, NULL);
569 entry = new_entry;
570 }
571
572 if (vmf->flags & FAULT_FLAG_WRITE)
573 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
574
575 spin_unlock_irq(&mapping->tree_lock);
576 return entry;
577 }
578
579 static inline unsigned long
580 pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
581 {
582 unsigned long address;
583
584 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
585 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
586 return address;
587 }
588
589 /* Walk all mappings of a given index of a file and writeprotect them */
590 static void dax_mapping_entry_mkclean(struct address_space *mapping,
591 pgoff_t index, unsigned long pfn)
592 {
593 struct vm_area_struct *vma;
594 pte_t pte, *ptep = NULL;
595 pmd_t *pmdp = NULL;
596 spinlock_t *ptl;
597
598 i_mmap_lock_read(mapping);
599 vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
600 unsigned long address, start, end;
601
602 cond_resched();
603
604 if (!(vma->vm_flags & VM_SHARED))
605 continue;
606
607 address = pgoff_address(index, vma);
608
609 /*
610 * Note because we provide start/end to follow_pte_pmd it will
611 * call mmu_notifier_invalidate_range_start() on our behalf
612 * before taking any lock.
613 */
614 if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
615 continue;
616
617 if (pmdp) {
618 #ifdef CONFIG_FS_DAX_PMD
619 pmd_t pmd;
620
621 if (pfn != pmd_pfn(*pmdp))
622 goto unlock_pmd;
623 if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
624 goto unlock_pmd;
625
626 flush_cache_page(vma, address, pfn);
627 pmd = pmdp_huge_clear_flush(vma, address, pmdp);
628 pmd = pmd_wrprotect(pmd);
629 pmd = pmd_mkclean(pmd);
630 set_pmd_at(vma->vm_mm, address, pmdp, pmd);
631 mmu_notifier_invalidate_range(vma->vm_mm, start, end);
632 unlock_pmd:
633 spin_unlock(ptl);
634 #endif
635 } else {
636 if (pfn != pte_pfn(*ptep))
637 goto unlock_pte;
638 if (!pte_dirty(*ptep) && !pte_write(*ptep))
639 goto unlock_pte;
640
641 flush_cache_page(vma, address, pfn);
642 pte = ptep_clear_flush(vma, address, ptep);
643 pte = pte_wrprotect(pte);
644 pte = pte_mkclean(pte);
645 set_pte_at(vma->vm_mm, address, ptep, pte);
646 mmu_notifier_invalidate_range(vma->vm_mm, start, end);
647 unlock_pte:
648 pte_unmap_unlock(ptep, ptl);
649 }
650
651 mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
652 }
653 i_mmap_unlock_read(mapping);
654 }
655
656 static int dax_writeback_one(struct block_device *bdev,
657 struct dax_device *dax_dev, struct address_space *mapping,
658 pgoff_t index, void *entry)
659 {
660 struct radix_tree_root *page_tree = &mapping->page_tree;
661 void *entry2, **slot, *kaddr;
662 long ret = 0, id;
663 sector_t sector;
664 pgoff_t pgoff;
665 size_t size;
666 pfn_t pfn;
667
668 /*
669 * A page got tagged dirty in DAX mapping? Something is seriously
670 * wrong.
671 */
672 if (WARN_ON(!radix_tree_exceptional_entry(entry)))
673 return -EIO;
674
675 spin_lock_irq(&mapping->tree_lock);
676 entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
677 /* Entry got punched out / reallocated? */
678 if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2)))
679 goto put_unlocked;
680 /*
681 * Entry got reallocated elsewhere? No need to writeback. We have to
682 * compare sectors as we must not bail out due to difference in lockbit
683 * or entry type.
684 */
685 if (dax_radix_sector(entry2) != dax_radix_sector(entry))
686 goto put_unlocked;
687 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
688 dax_is_zero_entry(entry))) {
689 ret = -EIO;
690 goto put_unlocked;
691 }
692
693 /* Another fsync thread may have already written back this entry */
694 if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
695 goto put_unlocked;
696 /* Lock the entry to serialize with page faults */
697 entry = lock_slot(mapping, slot);
698 /*
699 * We can clear the tag now but we have to be careful so that concurrent
700 * dax_writeback_one() calls for the same index cannot finish before we
701 * actually flush the caches. This is achieved as the calls will look
702 * at the entry only under tree_lock and once they do that they will
703 * see the entry locked and wait for it to unlock.
704 */
705 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
706 spin_unlock_irq(&mapping->tree_lock);
707
708 /*
709 * Even if dax_writeback_mapping_range() was given a wbc->range_start
710 * in the middle of a PMD, the 'index' we are given will be aligned to
711 * the start index of the PMD, as will the sector we pull from
712 * 'entry'. This allows us to flush for PMD_SIZE and not have to
713 * worry about partial PMD writebacks.
714 */
715 sector = dax_radix_sector(entry);
716 size = PAGE_SIZE << dax_radix_order(entry);
717
718 id = dax_read_lock();
719 ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
720 if (ret)
721 goto dax_unlock;
722
723 /*
724 * dax_direct_access() may sleep, so cannot hold tree_lock over
725 * its invocation.
726 */
727 ret = dax_direct_access(dax_dev, pgoff, size / PAGE_SIZE, &kaddr, &pfn);
728 if (ret < 0)
729 goto dax_unlock;
730
731 if (WARN_ON_ONCE(ret < size / PAGE_SIZE)) {
732 ret = -EIO;
733 goto dax_unlock;
734 }
735
736 dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(pfn));
737 dax_flush(dax_dev, kaddr, size);
738 /*
739 * After we have flushed the cache, we can clear the dirty tag. There
740 * cannot be new dirty data in the pfn after the flush has completed as
741 * the pfn mappings are writeprotected and fault waits for mapping
742 * entry lock.
743 */
744 spin_lock_irq(&mapping->tree_lock);
745 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY);
746 spin_unlock_irq(&mapping->tree_lock);
747 trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
748 dax_unlock:
749 dax_read_unlock(id);
750 put_locked_mapping_entry(mapping, index);
751 return ret;
752
753 put_unlocked:
754 put_unlocked_mapping_entry(mapping, index, entry2);
755 spin_unlock_irq(&mapping->tree_lock);
756 return ret;
757 }
758
759 /*
760 * Flush the mapping to the persistent domain within the byte range of [start,
761 * end]. This is required by data integrity operations to ensure file data is
762 * on persistent storage prior to completion of the operation.
763 */
764 int dax_writeback_mapping_range(struct address_space *mapping,
765 struct block_device *bdev, struct writeback_control *wbc)
766 {
767 struct inode *inode = mapping->host;
768 pgoff_t start_index, end_index;
769 pgoff_t indices[PAGEVEC_SIZE];
770 struct dax_device *dax_dev;
771 struct pagevec pvec;
772 bool done = false;
773 int i, ret = 0;
774
775 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
776 return -EIO;
777
778 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
779 return 0;
780
781 dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
782 if (!dax_dev)
783 return -EIO;
784
785 start_index = wbc->range_start >> PAGE_SHIFT;
786 end_index = wbc->range_end >> PAGE_SHIFT;
787
788 trace_dax_writeback_range(inode, start_index, end_index);
789
790 tag_pages_for_writeback(mapping, start_index, end_index);
791
792 pagevec_init(&pvec, 0);
793 while (!done) {
794 pvec.nr = find_get_entries_tag(mapping, start_index,
795 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
796 pvec.pages, indices);
797
798 if (pvec.nr == 0)
799 break;
800
801 for (i = 0; i < pvec.nr; i++) {
802 if (indices[i] > end_index) {
803 done = true;
804 break;
805 }
806
807 ret = dax_writeback_one(bdev, dax_dev, mapping,
808 indices[i], pvec.pages[i]);
809 if (ret < 0) {
810 mapping_set_error(mapping, ret);
811 goto out;
812 }
813 }
814 start_index = indices[pvec.nr - 1] + 1;
815 }
816 out:
817 put_dax(dax_dev);
818 trace_dax_writeback_range_done(inode, start_index, end_index);
819 return (ret < 0 ? ret : 0);
820 }
821 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
822
823 static int dax_insert_mapping(struct address_space *mapping,
824 struct block_device *bdev, struct dax_device *dax_dev,
825 sector_t sector, size_t size, void *entry,
826 struct vm_area_struct *vma, struct vm_fault *vmf)
827 {
828 unsigned long vaddr = vmf->address;
829 void *ret, *kaddr;
830 pgoff_t pgoff;
831 int id, rc;
832 pfn_t pfn;
833
834 rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
835 if (rc)
836 return rc;
837
838 id = dax_read_lock();
839 rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
840 if (rc < 0) {
841 dax_read_unlock(id);
842 return rc;
843 }
844 dax_read_unlock(id);
845
846 ret = dax_insert_mapping_entry(mapping, vmf, entry, sector, 0);
847 if (IS_ERR(ret))
848 return PTR_ERR(ret);
849
850 trace_dax_insert_mapping(mapping->host, vmf, ret);
851 if (vmf->flags & FAULT_FLAG_WRITE)
852 return vm_insert_mixed_mkwrite(vma, vaddr, pfn);
853 else
854 return vm_insert_mixed(vma, vaddr, pfn);
855 }
856
857 /*
858 * The user has performed a load from a hole in the file. Allocating a new
859 * page in the file would cause excessive storage usage for workloads with
860 * sparse files. Instead we insert a read-only mapping of the 4k zero page.
861 * If this page is ever written to we will re-fault and change the mapping to
862 * point to real DAX storage instead.
863 */
864 static int dax_load_hole(struct address_space *mapping, void *entry,
865 struct vm_fault *vmf)
866 {
867 struct inode *inode = mapping->host;
868 unsigned long vaddr = vmf->address;
869 int ret = VM_FAULT_NOPAGE;
870 struct page *zero_page;
871 void *entry2;
872
873 zero_page = ZERO_PAGE(0);
874 if (unlikely(!zero_page)) {
875 ret = VM_FAULT_OOM;
876 goto out;
877 }
878
879 entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0,
880 RADIX_DAX_ZERO_PAGE);
881 if (IS_ERR(entry2)) {
882 ret = VM_FAULT_SIGBUS;
883 goto out;
884 }
885
886 vm_insert_mixed(vmf->vma, vaddr, page_to_pfn_t(zero_page));
887 out:
888 trace_dax_load_hole(inode, vmf, ret);
889 return ret;
890 }
891
892 static bool dax_range_is_aligned(struct block_device *bdev,
893 unsigned int offset, unsigned int length)
894 {
895 unsigned short sector_size = bdev_logical_block_size(bdev);
896
897 if (!IS_ALIGNED(offset, sector_size))
898 return false;
899 if (!IS_ALIGNED(length, sector_size))
900 return false;
901
902 return true;
903 }
904
905 int __dax_zero_page_range(struct block_device *bdev,
906 struct dax_device *dax_dev, sector_t sector,
907 unsigned int offset, unsigned int size)
908 {
909 if (dax_range_is_aligned(bdev, offset, size)) {
910 sector_t start_sector = sector + (offset >> 9);
911
912 return blkdev_issue_zeroout(bdev, start_sector,
913 size >> 9, GFP_NOFS, 0);
914 } else {
915 pgoff_t pgoff;
916 long rc, id;
917 void *kaddr;
918 pfn_t pfn;
919
920 rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
921 if (rc)
922 return rc;
923
924 id = dax_read_lock();
925 rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
926 &pfn);
927 if (rc < 0) {
928 dax_read_unlock(id);
929 return rc;
930 }
931 memset(kaddr + offset, 0, size);
932 dax_flush(dax_dev, kaddr + offset, size);
933 dax_read_unlock(id);
934 }
935 return 0;
936 }
937 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
938
939 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
940 {
941 return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
942 }
943
944 static loff_t
945 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
946 struct iomap *iomap)
947 {
948 struct block_device *bdev = iomap->bdev;
949 struct dax_device *dax_dev = iomap->dax_dev;
950 struct iov_iter *iter = data;
951 loff_t end = pos + length, done = 0;
952 ssize_t ret = 0;
953 int id;
954
955 if (iov_iter_rw(iter) == READ) {
956 end = min(end, i_size_read(inode));
957 if (pos >= end)
958 return 0;
959
960 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
961 return iov_iter_zero(min(length, end - pos), iter);
962 }
963
964 if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
965 return -EIO;
966
967 /*
968 * Write can allocate block for an area which has a hole page mapped
969 * into page tables. We have to tear down these mappings so that data
970 * written by write(2) is visible in mmap.
971 */
972 if (iomap->flags & IOMAP_F_NEW) {
973 invalidate_inode_pages2_range(inode->i_mapping,
974 pos >> PAGE_SHIFT,
975 (end - 1) >> PAGE_SHIFT);
976 }
977
978 id = dax_read_lock();
979 while (pos < end) {
980 unsigned offset = pos & (PAGE_SIZE - 1);
981 const size_t size = ALIGN(length + offset, PAGE_SIZE);
982 const sector_t sector = dax_iomap_sector(iomap, pos);
983 ssize_t map_len;
984 pgoff_t pgoff;
985 void *kaddr;
986 pfn_t pfn;
987
988 if (fatal_signal_pending(current)) {
989 ret = -EINTR;
990 break;
991 }
992
993 ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
994 if (ret)
995 break;
996
997 map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
998 &kaddr, &pfn);
999 if (map_len < 0) {
1000 ret = map_len;
1001 break;
1002 }
1003
1004 map_len = PFN_PHYS(map_len);
1005 kaddr += offset;
1006 map_len -= offset;
1007 if (map_len > end - pos)
1008 map_len = end - pos;
1009
1010 /*
1011 * The userspace address for the memory copy has already been
1012 * validated via access_ok() in either vfs_read() or
1013 * vfs_write(), depending on which operation we are doing.
1014 */
1015 if (iov_iter_rw(iter) == WRITE)
1016 map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr,
1017 map_len, iter);
1018 else
1019 map_len = copy_to_iter(kaddr, map_len, iter);
1020 if (map_len <= 0) {
1021 ret = map_len ? map_len : -EFAULT;
1022 break;
1023 }
1024
1025 pos += map_len;
1026 length -= map_len;
1027 done += map_len;
1028 }
1029 dax_read_unlock(id);
1030
1031 return done ? done : ret;
1032 }
1033
1034 /**
1035 * dax_iomap_rw - Perform I/O to a DAX file
1036 * @iocb: The control block for this I/O
1037 * @iter: The addresses to do I/O from or to
1038 * @ops: iomap ops passed from the file system
1039 *
1040 * This function performs read and write operations to directly mapped
1041 * persistent memory. The callers needs to take care of read/write exclusion
1042 * and evicting any page cache pages in the region under I/O.
1043 */
1044 ssize_t
1045 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1046 const struct iomap_ops *ops)
1047 {
1048 struct address_space *mapping = iocb->ki_filp->f_mapping;
1049 struct inode *inode = mapping->host;
1050 loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1051 unsigned flags = 0;
1052
1053 if (iov_iter_rw(iter) == WRITE) {
1054 lockdep_assert_held_exclusive(&inode->i_rwsem);
1055 flags |= IOMAP_WRITE;
1056 } else {
1057 lockdep_assert_held(&inode->i_rwsem);
1058 }
1059
1060 while (iov_iter_count(iter)) {
1061 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1062 iter, dax_iomap_actor);
1063 if (ret <= 0)
1064 break;
1065 pos += ret;
1066 done += ret;
1067 }
1068
1069 iocb->ki_pos += done;
1070 return done ? done : ret;
1071 }
1072 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1073
1074 static int dax_fault_return(int error)
1075 {
1076 if (error == 0)
1077 return VM_FAULT_NOPAGE;
1078 if (error == -ENOMEM)
1079 return VM_FAULT_OOM;
1080 return VM_FAULT_SIGBUS;
1081 }
1082
1083 static int dax_iomap_pte_fault(struct vm_fault *vmf,
1084 const struct iomap_ops *ops)
1085 {
1086 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1087 struct inode *inode = mapping->host;
1088 unsigned long vaddr = vmf->address;
1089 loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1090 sector_t sector;
1091 struct iomap iomap = { 0 };
1092 unsigned flags = IOMAP_FAULT;
1093 int error, major = 0;
1094 int vmf_ret = 0;
1095 void *entry;
1096
1097 trace_dax_pte_fault(inode, vmf, vmf_ret);
1098 /*
1099 * Check whether offset isn't beyond end of file now. Caller is supposed
1100 * to hold locks serializing us with truncate / punch hole so this is
1101 * a reliable test.
1102 */
1103 if (pos >= i_size_read(inode)) {
1104 vmf_ret = VM_FAULT_SIGBUS;
1105 goto out;
1106 }
1107
1108 if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
1109 flags |= IOMAP_WRITE;
1110
1111 entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
1112 if (IS_ERR(entry)) {
1113 vmf_ret = dax_fault_return(PTR_ERR(entry));
1114 goto out;
1115 }
1116
1117 /*
1118 * It is possible, particularly with mixed reads & writes to private
1119 * mappings, that we have raced with a PMD fault that overlaps with
1120 * the PTE we need to set up. If so just return and the fault will be
1121 * retried.
1122 */
1123 if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
1124 vmf_ret = VM_FAULT_NOPAGE;
1125 goto unlock_entry;
1126 }
1127
1128 /*
1129 * Note that we don't bother to use iomap_apply here: DAX required
1130 * the file system block size to be equal the page size, which means
1131 * that we never have to deal with more than a single extent here.
1132 */
1133 error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1134 if (error) {
1135 vmf_ret = dax_fault_return(error);
1136 goto unlock_entry;
1137 }
1138 if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1139 error = -EIO; /* fs corruption? */
1140 goto error_finish_iomap;
1141 }
1142
1143 sector = dax_iomap_sector(&iomap, pos);
1144
1145 if (vmf->cow_page) {
1146 switch (iomap.type) {
1147 case IOMAP_HOLE:
1148 case IOMAP_UNWRITTEN:
1149 clear_user_highpage(vmf->cow_page, vaddr);
1150 break;
1151 case IOMAP_MAPPED:
1152 error = copy_user_dax(iomap.bdev, iomap.dax_dev,
1153 sector, PAGE_SIZE, vmf->cow_page, vaddr);
1154 break;
1155 default:
1156 WARN_ON_ONCE(1);
1157 error = -EIO;
1158 break;
1159 }
1160
1161 if (error)
1162 goto error_finish_iomap;
1163
1164 __SetPageUptodate(vmf->cow_page);
1165 vmf_ret = finish_fault(vmf);
1166 if (!vmf_ret)
1167 vmf_ret = VM_FAULT_DONE_COW;
1168 goto finish_iomap;
1169 }
1170
1171 switch (iomap.type) {
1172 case IOMAP_MAPPED:
1173 if (iomap.flags & IOMAP_F_NEW) {
1174 count_vm_event(PGMAJFAULT);
1175 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
1176 major = VM_FAULT_MAJOR;
1177 }
1178 error = dax_insert_mapping(mapping, iomap.bdev, iomap.dax_dev,
1179 sector, PAGE_SIZE, entry, vmf->vma, vmf);
1180 /* -EBUSY is fine, somebody else faulted on the same PTE */
1181 if (error == -EBUSY)
1182 error = 0;
1183 break;
1184 case IOMAP_UNWRITTEN:
1185 case IOMAP_HOLE:
1186 if (!(vmf->flags & FAULT_FLAG_WRITE)) {
1187 vmf_ret = dax_load_hole(mapping, entry, vmf);
1188 goto finish_iomap;
1189 }
1190 /*FALLTHRU*/
1191 default:
1192 WARN_ON_ONCE(1);
1193 error = -EIO;
1194 break;
1195 }
1196
1197 error_finish_iomap:
1198 vmf_ret = dax_fault_return(error) | major;
1199 finish_iomap:
1200 if (ops->iomap_end) {
1201 int copied = PAGE_SIZE;
1202
1203 if (vmf_ret & VM_FAULT_ERROR)
1204 copied = 0;
1205 /*
1206 * The fault is done by now and there's no way back (other
1207 * thread may be already happily using PTE we have installed).
1208 * Just ignore error from ->iomap_end since we cannot do much
1209 * with it.
1210 */
1211 ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
1212 }
1213 unlock_entry:
1214 put_locked_mapping_entry(mapping, vmf->pgoff);
1215 out:
1216 trace_dax_pte_fault_done(inode, vmf, vmf_ret);
1217 return vmf_ret;
1218 }
1219
1220 #ifdef CONFIG_FS_DAX_PMD
1221 static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
1222 loff_t pos, void *entry)
1223 {
1224 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1225 const sector_t sector = dax_iomap_sector(iomap, pos);
1226 struct dax_device *dax_dev = iomap->dax_dev;
1227 struct block_device *bdev = iomap->bdev;
1228 struct inode *inode = mapping->host;
1229 const size_t size = PMD_SIZE;
1230 void *ret = NULL, *kaddr;
1231 long length = 0;
1232 pgoff_t pgoff;
1233 pfn_t pfn = {};
1234 int id;
1235
1236 if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
1237 goto fallback;
1238
1239 id = dax_read_lock();
1240 length = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
1241 if (length < 0)
1242 goto unlock_fallback;
1243 length = PFN_PHYS(length);
1244
1245 if (length < size)
1246 goto unlock_fallback;
1247 if (pfn_t_to_pfn(pfn) & PG_PMD_COLOUR)
1248 goto unlock_fallback;
1249 if (!pfn_t_devmap(pfn))
1250 goto unlock_fallback;
1251 dax_read_unlock(id);
1252
1253 ret = dax_insert_mapping_entry(mapping, vmf, entry, sector,
1254 RADIX_DAX_PMD);
1255 if (IS_ERR(ret))
1256 goto fallback;
1257
1258 trace_dax_pmd_insert_mapping(inode, vmf, length, pfn, ret);
1259 return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
1260 pfn, vmf->flags & FAULT_FLAG_WRITE);
1261
1262 unlock_fallback:
1263 dax_read_unlock(id);
1264 fallback:
1265 trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret);
1266 return VM_FAULT_FALLBACK;
1267 }
1268
1269 static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
1270 void *entry)
1271 {
1272 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1273 unsigned long pmd_addr = vmf->address & PMD_MASK;
1274 struct inode *inode = mapping->host;
1275 struct page *zero_page;
1276 void *ret = NULL;
1277 spinlock_t *ptl;
1278 pmd_t pmd_entry;
1279
1280 zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
1281
1282 if (unlikely(!zero_page))
1283 goto fallback;
1284
1285 ret = dax_insert_mapping_entry(mapping, vmf, entry, 0,
1286 RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE);
1287 if (IS_ERR(ret))
1288 goto fallback;
1289
1290 ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1291 if (!pmd_none(*(vmf->pmd))) {
1292 spin_unlock(ptl);
1293 goto fallback;
1294 }
1295
1296 pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1297 pmd_entry = pmd_mkhuge(pmd_entry);
1298 set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
1299 spin_unlock(ptl);
1300 trace_dax_pmd_load_hole(inode, vmf, zero_page, ret);
1301 return VM_FAULT_NOPAGE;
1302
1303 fallback:
1304 trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret);
1305 return VM_FAULT_FALLBACK;
1306 }
1307
1308 static int dax_iomap_pmd_fault(struct vm_fault *vmf,
1309 const struct iomap_ops *ops)
1310 {
1311 struct vm_area_struct *vma = vmf->vma;
1312 struct address_space *mapping = vma->vm_file->f_mapping;
1313 unsigned long pmd_addr = vmf->address & PMD_MASK;
1314 bool write = vmf->flags & FAULT_FLAG_WRITE;
1315 unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1316 struct inode *inode = mapping->host;
1317 int result = VM_FAULT_FALLBACK;
1318 struct iomap iomap = { 0 };
1319 pgoff_t max_pgoff, pgoff;
1320 void *entry;
1321 loff_t pos;
1322 int error;
1323
1324 /*
1325 * Check whether offset isn't beyond end of file now. Caller is
1326 * supposed to hold locks serializing us with truncate / punch hole so
1327 * this is a reliable test.
1328 */
1329 pgoff = linear_page_index(vma, pmd_addr);
1330 max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
1331
1332 trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
1333
1334 /*
1335 * Make sure that the faulting address's PMD offset (color) matches
1336 * the PMD offset from the start of the file. This is necessary so
1337 * that a PMD range in the page table overlaps exactly with a PMD
1338 * range in the radix tree.
1339 */
1340 if ((vmf->pgoff & PG_PMD_COLOUR) !=
1341 ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
1342 goto fallback;
1343
1344 /* Fall back to PTEs if we're going to COW */
1345 if (write && !(vma->vm_flags & VM_SHARED))
1346 goto fallback;
1347
1348 /* If the PMD would extend outside the VMA */
1349 if (pmd_addr < vma->vm_start)
1350 goto fallback;
1351 if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1352 goto fallback;
1353
1354 if (pgoff > max_pgoff) {
1355 result = VM_FAULT_SIGBUS;
1356 goto out;
1357 }
1358
1359 /* If the PMD would extend beyond the file size */
1360 if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
1361 goto fallback;
1362
1363 /*
1364 * grab_mapping_entry() will make sure we get a 2MiB empty entry, a
1365 * 2MiB zero page entry or a DAX PMD. If it can't (because a 4k page
1366 * is already in the tree, for instance), it will return -EEXIST and
1367 * we just fall back to 4k entries.
1368 */
1369 entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1370 if (IS_ERR(entry))
1371 goto fallback;
1372
1373 /*
1374 * It is possible, particularly with mixed reads & writes to private
1375 * mappings, that we have raced with a PTE fault that overlaps with
1376 * the PMD we need to set up. If so just return and the fault will be
1377 * retried.
1378 */
1379 if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
1380 !pmd_devmap(*vmf->pmd)) {
1381 result = 0;
1382 goto unlock_entry;
1383 }
1384
1385 /*
1386 * Note that we don't use iomap_apply here. We aren't doing I/O, only
1387 * setting up a mapping, so really we're using iomap_begin() as a way
1388 * to look up our filesystem block.
1389 */
1390 pos = (loff_t)pgoff << PAGE_SHIFT;
1391 error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1392 if (error)
1393 goto unlock_entry;
1394
1395 if (iomap.offset + iomap.length < pos + PMD_SIZE)
1396 goto finish_iomap;
1397
1398 switch (iomap.type) {
1399 case IOMAP_MAPPED:
1400 result = dax_pmd_insert_mapping(vmf, &iomap, pos, entry);
1401 break;
1402 case IOMAP_UNWRITTEN:
1403 case IOMAP_HOLE:
1404 if (WARN_ON_ONCE(write))
1405 break;
1406 result = dax_pmd_load_hole(vmf, &iomap, entry);
1407 break;
1408 default:
1409 WARN_ON_ONCE(1);
1410 break;
1411 }
1412
1413 finish_iomap:
1414 if (ops->iomap_end) {
1415 int copied = PMD_SIZE;
1416
1417 if (result == VM_FAULT_FALLBACK)
1418 copied = 0;
1419 /*
1420 * The fault is done by now and there's no way back (other
1421 * thread may be already happily using PMD we have installed).
1422 * Just ignore error from ->iomap_end since we cannot do much
1423 * with it.
1424 */
1425 ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
1426 &iomap);
1427 }
1428 unlock_entry:
1429 put_locked_mapping_entry(mapping, pgoff);
1430 fallback:
1431 if (result == VM_FAULT_FALLBACK) {
1432 split_huge_pmd(vma, vmf->pmd, vmf->address);
1433 count_vm_event(THP_FAULT_FALLBACK);
1434 }
1435 out:
1436 trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
1437 return result;
1438 }
1439 #else
1440 static int dax_iomap_pmd_fault(struct vm_fault *vmf,
1441 const struct iomap_ops *ops)
1442 {
1443 return VM_FAULT_FALLBACK;
1444 }
1445 #endif /* CONFIG_FS_DAX_PMD */
1446
1447 /**
1448 * dax_iomap_fault - handle a page fault on a DAX file
1449 * @vmf: The description of the fault
1450 * @ops: iomap ops passed from the file system
1451 *
1452 * When a page fault occurs, filesystems may call this helper in
1453 * their fault handler for DAX files. dax_iomap_fault() assumes the caller
1454 * has done all the necessary locking for page fault to proceed
1455 * successfully.
1456 */
1457 int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
1458 const struct iomap_ops *ops)
1459 {
1460 switch (pe_size) {
1461 case PE_SIZE_PTE:
1462 return dax_iomap_pte_fault(vmf, ops);
1463 case PE_SIZE_PMD:
1464 return dax_iomap_pmd_fault(vmf, ops);
1465 default:
1466 return VM_FAULT_FALLBACK;
1467 }
1468 }
1469 EXPORT_SYMBOL_GPL(dax_iomap_fault);