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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
49static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
50
51static 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}
59fs_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
76static unsigned long dax_radix_pfn(void *entry)
77{
78 return (unsigned long)entry >> RADIX_DAX_SHIFT;
79}
80
81static 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
87static 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
94static int dax_is_pmd_entry(void *entry)
95{
96 return (unsigned long)entry & RADIX_DAX_PMD;
97}
98
99static int dax_is_pte_entry(void *entry)
100{
101 return !((unsigned long)entry & RADIX_DAX_PMD);
102}
103
104static int dax_is_zero_entry(void *entry)
105{
106 return (unsigned long)entry & RADIX_DAX_ZERO_PAGE;
107}
108
109static 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 */
117struct exceptional_entry_key {
118 struct address_space *mapping;
119 pgoff_t entry_start;
120};
121
122struct wait_exceptional_entry_queue {
123 wait_queue_entry_t wait;
124 struct exceptional_entry_key key;
125};
126
127static 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
147static 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 */
165static 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 */
187static 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 */
197static 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 */
210static 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 */
229static 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
260static 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
277static 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 */
287static 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
297static 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
309static 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
322static 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
337static 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/*
355 * Find radix tree entry at given index. If it points to an exceptional entry,
356 * return it with the radix tree entry locked. If the radix tree doesn't
357 * contain given index, create an empty exceptional entry for the index and
358 * return with it locked.
359 *
360 * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
361 * either return that locked entry or will return an error. This error will
362 * happen if there are any 4k entries within the 2MiB range that we are
363 * requesting.
364 *
365 * We always favor 4k entries over 2MiB entries. There isn't a flow where we
366 * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
367 * insertion will fail if it finds any 4k entries already in the tree, and a
368 * 4k insertion will cause an existing 2MiB entry to be unmapped and
369 * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
370 * well as 2MiB empty entries.
371 *
372 * The exception to this downgrade path is for 2MiB DAX PMD entries that have
373 * real storage backing them. We will leave these real 2MiB DAX entries in
374 * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
375 *
376 * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
377 * persistent memory the benefit is doubtful. We can add that later if we can
378 * show it helps.
379 */
380static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
381 unsigned long size_flag)
382{
383 bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
384 void *entry, **slot;
385
386restart:
387 xa_lock_irq(&mapping->i_pages);
388 entry = get_unlocked_mapping_entry(mapping, index, &slot);
389
390 if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) {
391 entry = ERR_PTR(-EIO);
392 goto out_unlock;
393 }
394
395 if (entry) {
396 if (size_flag & RADIX_DAX_PMD) {
397 if (dax_is_pte_entry(entry)) {
398 put_unlocked_mapping_entry(mapping, index,
399 entry);
400 entry = ERR_PTR(-EEXIST);
401 goto out_unlock;
402 }
403 } else { /* trying to grab a PTE entry */
404 if (dax_is_pmd_entry(entry) &&
405 (dax_is_zero_entry(entry) ||
406 dax_is_empty_entry(entry))) {
407 pmd_downgrade = true;
408 }
409 }
410 }
411
412 /* No entry for given index? Make sure radix tree is big enough. */
413 if (!entry || pmd_downgrade) {
414 int err;
415
416 if (pmd_downgrade) {
417 /*
418 * Make sure 'entry' remains valid while we drop
419 * the i_pages lock.
420 */
421 entry = lock_slot(mapping, slot);
422 }
423
424 xa_unlock_irq(&mapping->i_pages);
425 /*
426 * Besides huge zero pages the only other thing that gets
427 * downgraded are empty entries which don't need to be
428 * unmapped.
429 */
430 if (pmd_downgrade && dax_is_zero_entry(entry))
431 unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
432 PG_PMD_NR, false);
433
434 err = radix_tree_preload(
435 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
436 if (err) {
437 if (pmd_downgrade)
438 put_locked_mapping_entry(mapping, index);
439 return ERR_PTR(err);
440 }
441 xa_lock_irq(&mapping->i_pages);
442
443 if (!entry) {
444 /*
445 * We needed to drop the i_pages lock while calling
446 * radix_tree_preload() and we didn't have an entry to
447 * lock. See if another thread inserted an entry at
448 * our index during this time.
449 */
450 entry = __radix_tree_lookup(&mapping->i_pages, index,
451 NULL, &slot);
452 if (entry) {
453 radix_tree_preload_end();
454 xa_unlock_irq(&mapping->i_pages);
455 goto restart;
456 }
457 }
458
459 if (pmd_downgrade) {
460 dax_disassociate_entry(entry, mapping, false);
461 radix_tree_delete(&mapping->i_pages, index);
462 mapping->nrexceptional--;
463 dax_wake_mapping_entry_waiter(mapping, index, entry,
464 true);
465 }
466
467 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
468
469 err = __radix_tree_insert(&mapping->i_pages, index,
470 dax_radix_order(entry), entry);
471 radix_tree_preload_end();
472 if (err) {
473 xa_unlock_irq(&mapping->i_pages);
474 /*
475 * Our insertion of a DAX entry failed, most likely
476 * because we were inserting a PMD entry and it
477 * collided with a PTE sized entry at a different
478 * index in the PMD range. We haven't inserted
479 * anything into the radix tree and have no waiters to
480 * wake.
481 */
482 return ERR_PTR(err);
483 }
484 /* Good, we have inserted empty locked entry into the tree. */
485 mapping->nrexceptional++;
486 xa_unlock_irq(&mapping->i_pages);
487 return entry;
488 }
489 entry = lock_slot(mapping, slot);
490 out_unlock:
491 xa_unlock_irq(&mapping->i_pages);
492 return entry;
493}
494
495static int __dax_invalidate_mapping_entry(struct address_space *mapping,
496 pgoff_t index, bool trunc)
497{
498 int ret = 0;
499 void *entry;
500 struct radix_tree_root *pages = &mapping->i_pages;
501
502 xa_lock_irq(pages);
503 entry = get_unlocked_mapping_entry(mapping, index, NULL);
504 if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)))
505 goto out;
506 if (!trunc &&
507 (radix_tree_tag_get(pages, index, PAGECACHE_TAG_DIRTY) ||
508 radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE)))
509 goto out;
510 dax_disassociate_entry(entry, mapping, trunc);
511 radix_tree_delete(pages, index);
512 mapping->nrexceptional--;
513 ret = 1;
514out:
515 put_unlocked_mapping_entry(mapping, index, entry);
516 xa_unlock_irq(pages);
517 return ret;
518}
519/*
520 * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
521 * entry to get unlocked before deleting it.
522 */
523int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
524{
525 int ret = __dax_invalidate_mapping_entry(mapping, index, true);
526
527 /*
528 * This gets called from truncate / punch_hole path. As such, the caller
529 * must hold locks protecting against concurrent modifications of the
530 * radix tree (usually fs-private i_mmap_sem for writing). Since the
531 * caller has seen exceptional entry for this index, we better find it
532 * at that index as well...
533 */
534 WARN_ON_ONCE(!ret);
535 return ret;
536}
537
538/*
539 * Invalidate exceptional DAX entry if it is clean.
540 */
541int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
542 pgoff_t index)
543{
544 return __dax_invalidate_mapping_entry(mapping, index, false);
545}
546
547static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
548 sector_t sector, size_t size, struct page *to,
549 unsigned long vaddr)
550{
551 void *vto, *kaddr;
552 pgoff_t pgoff;
553 pfn_t pfn;
554 long rc;
555 int id;
556
557 rc = bdev_dax_pgoff(bdev, sector, size, &pgoff);
558 if (rc)
559 return rc;
560
561 id = dax_read_lock();
562 rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
563 if (rc < 0) {
564 dax_read_unlock(id);
565 return rc;
566 }
567 vto = kmap_atomic(to);
568 copy_user_page(vto, (void __force *)kaddr, vaddr, to);
569 kunmap_atomic(vto);
570 dax_read_unlock(id);
571 return 0;
572}
573
574/*
575 * By this point grab_mapping_entry() has ensured that we have a locked entry
576 * of the appropriate size so we don't have to worry about downgrading PMDs to
577 * PTEs. If we happen to be trying to insert a PTE and there is a PMD
578 * already in the tree, we will skip the insertion and just dirty the PMD as
579 * appropriate.
580 */
581static void *dax_insert_mapping_entry(struct address_space *mapping,
582 struct vm_fault *vmf,
583 void *entry, pfn_t pfn_t,
584 unsigned long flags, bool dirty)
585{
586 struct radix_tree_root *pages = &mapping->i_pages;
587 unsigned long pfn = pfn_t_to_pfn(pfn_t);
588 pgoff_t index = vmf->pgoff;
589 void *new_entry;
590
591 if (dirty)
592 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
593
594 if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
595 /* we are replacing a zero page with block mapping */
596 if (dax_is_pmd_entry(entry))
597 unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
598 PG_PMD_NR, false);
599 else /* pte entry */
600 unmap_mapping_pages(mapping, vmf->pgoff, 1, false);
601 }
602
603 xa_lock_irq(pages);
604 new_entry = dax_radix_locked_entry(pfn, flags);
605 if (dax_entry_size(entry) != dax_entry_size(new_entry)) {
606 dax_disassociate_entry(entry, mapping, false);
607 dax_associate_entry(new_entry, mapping);
608 }
609
610 if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
611 /*
612 * Only swap our new entry into the radix tree if the current
613 * entry is a zero page or an empty entry. If a normal PTE or
614 * PMD entry is already in the tree, we leave it alone. This
615 * means that if we are trying to insert a PTE and the
616 * existing entry is a PMD, we will just leave the PMD in the
617 * tree and dirty it if necessary.
618 */
619 struct radix_tree_node *node;
620 void **slot;
621 void *ret;
622
623 ret = __radix_tree_lookup(pages, index, &node, &slot);
624 WARN_ON_ONCE(ret != entry);
625 __radix_tree_replace(pages, node, slot,
626 new_entry, NULL);
627 entry = new_entry;
628 }
629
630 if (dirty)
631 radix_tree_tag_set(pages, index, PAGECACHE_TAG_DIRTY);
632
633 xa_unlock_irq(pages);
634 return entry;
635}
636
637static inline unsigned long
638pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
639{
640 unsigned long address;
641
642 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
643 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
644 return address;
645}
646
647/* Walk all mappings of a given index of a file and writeprotect them */
648static void dax_mapping_entry_mkclean(struct address_space *mapping,
649 pgoff_t index, unsigned long pfn)
650{
651 struct vm_area_struct *vma;
652 pte_t pte, *ptep = NULL;
653 pmd_t *pmdp = NULL;
654 spinlock_t *ptl;
655
656 i_mmap_lock_read(mapping);
657 vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
658 unsigned long address, start, end;
659
660 cond_resched();
661
662 if (!(vma->vm_flags & VM_SHARED))
663 continue;
664
665 address = pgoff_address(index, vma);
666
667 /*
668 * Note because we provide start/end to follow_pte_pmd it will
669 * call mmu_notifier_invalidate_range_start() on our behalf
670 * before taking any lock.
671 */
672 if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
673 continue;
674
675 /*
676 * No need to call mmu_notifier_invalidate_range() as we are
677 * downgrading page table protection not changing it to point
678 * to a new page.
679 *
680 * See Documentation/vm/mmu_notifier.txt
681 */
682 if (pmdp) {
683#ifdef CONFIG_FS_DAX_PMD
684 pmd_t pmd;
685
686 if (pfn != pmd_pfn(*pmdp))
687 goto unlock_pmd;
688 if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
689 goto unlock_pmd;
690
691 flush_cache_page(vma, address, pfn);
692 pmd = pmdp_huge_clear_flush(vma, address, pmdp);
693 pmd = pmd_wrprotect(pmd);
694 pmd = pmd_mkclean(pmd);
695 set_pmd_at(vma->vm_mm, address, pmdp, pmd);
696unlock_pmd:
697#endif
698 spin_unlock(ptl);
699 } else {
700 if (pfn != pte_pfn(*ptep))
701 goto unlock_pte;
702 if (!pte_dirty(*ptep) && !pte_write(*ptep))
703 goto unlock_pte;
704
705 flush_cache_page(vma, address, pfn);
706 pte = ptep_clear_flush(vma, address, ptep);
707 pte = pte_wrprotect(pte);
708 pte = pte_mkclean(pte);
709 set_pte_at(vma->vm_mm, address, ptep, pte);
710unlock_pte:
711 pte_unmap_unlock(ptep, ptl);
712 }
713
714 mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
715 }
716 i_mmap_unlock_read(mapping);
717}
718
719static int dax_writeback_one(struct dax_device *dax_dev,
720 struct address_space *mapping, pgoff_t index, void *entry)
721{
722 struct radix_tree_root *pages = &mapping->i_pages;
723 void *entry2, **slot;
724 unsigned long pfn;
725 long ret = 0;
726 size_t size;
727
728 /*
729 * A page got tagged dirty in DAX mapping? Something is seriously
730 * wrong.
731 */
732 if (WARN_ON(!radix_tree_exceptional_entry(entry)))
733 return -EIO;
734
735 xa_lock_irq(pages);
736 entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
737 /* Entry got punched out / reallocated? */
738 if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2)))
739 goto put_unlocked;
740 /*
741 * Entry got reallocated elsewhere? No need to writeback. We have to
742 * compare pfns as we must not bail out due to difference in lockbit
743 * or entry type.
744 */
745 if (dax_radix_pfn(entry2) != dax_radix_pfn(entry))
746 goto put_unlocked;
747 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
748 dax_is_zero_entry(entry))) {
749 ret = -EIO;
750 goto put_unlocked;
751 }
752
753 /* Another fsync thread may have already written back this entry */
754 if (!radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))
755 goto put_unlocked;
756 /* Lock the entry to serialize with page faults */
757 entry = lock_slot(mapping, slot);
758 /*
759 * We can clear the tag now but we have to be careful so that concurrent
760 * dax_writeback_one() calls for the same index cannot finish before we
761 * actually flush the caches. This is achieved as the calls will look
762 * at the entry only under the i_pages lock and once they do that
763 * they will see the entry locked and wait for it to unlock.
764 */
765 radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE);
766 xa_unlock_irq(pages);
767
768 /*
769 * Even if dax_writeback_mapping_range() was given a wbc->range_start
770 * in the middle of a PMD, the 'index' we are given will be aligned to
771 * the start index of the PMD, as will the pfn we pull from 'entry'.
772 * This allows us to flush for PMD_SIZE and not have to worry about
773 * partial PMD writebacks.
774 */
775 pfn = dax_radix_pfn(entry);
776 size = PAGE_SIZE << dax_radix_order(entry);
777
778 dax_mapping_entry_mkclean(mapping, index, pfn);
779 dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
780 /*
781 * After we have flushed the cache, we can clear the dirty tag. There
782 * cannot be new dirty data in the pfn after the flush has completed as
783 * the pfn mappings are writeprotected and fault waits for mapping
784 * entry lock.
785 */
786 xa_lock_irq(pages);
787 radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY);
788 xa_unlock_irq(pages);
789 trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
790 put_locked_mapping_entry(mapping, index);
791 return ret;
792
793 put_unlocked:
794 put_unlocked_mapping_entry(mapping, index, entry2);
795 xa_unlock_irq(pages);
796 return ret;
797}
798
799/*
800 * Flush the mapping to the persistent domain within the byte range of [start,
801 * end]. This is required by data integrity operations to ensure file data is
802 * on persistent storage prior to completion of the operation.
803 */
804int dax_writeback_mapping_range(struct address_space *mapping,
805 struct block_device *bdev, struct writeback_control *wbc)
806{
807 struct inode *inode = mapping->host;
808 pgoff_t start_index, end_index;
809 pgoff_t indices[PAGEVEC_SIZE];
810 struct dax_device *dax_dev;
811 struct pagevec pvec;
812 bool done = false;
813 int i, ret = 0;
814
815 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
816 return -EIO;
817
818 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
819 return 0;
820
821 dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
822 if (!dax_dev)
823 return -EIO;
824
825 start_index = wbc->range_start >> PAGE_SHIFT;
826 end_index = wbc->range_end >> PAGE_SHIFT;
827
828 trace_dax_writeback_range(inode, start_index, end_index);
829
830 tag_pages_for_writeback(mapping, start_index, end_index);
831
832 pagevec_init(&pvec);
833 while (!done) {
834 pvec.nr = find_get_entries_tag(mapping, start_index,
835 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
836 pvec.pages, indices);
837
838 if (pvec.nr == 0)
839 break;
840
841 for (i = 0; i < pvec.nr; i++) {
842 if (indices[i] > end_index) {
843 done = true;
844 break;
845 }
846
847 ret = dax_writeback_one(dax_dev, mapping, indices[i],
848 pvec.pages[i]);
849 if (ret < 0) {
850 mapping_set_error(mapping, ret);
851 goto out;
852 }
853 }
854 start_index = indices[pvec.nr - 1] + 1;
855 }
856out:
857 put_dax(dax_dev);
858 trace_dax_writeback_range_done(inode, start_index, end_index);
859 return (ret < 0 ? ret : 0);
860}
861EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
862
863static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
864{
865 return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
866}
867
868static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
869 pfn_t *pfnp)
870{
871 const sector_t sector = dax_iomap_sector(iomap, pos);
872 pgoff_t pgoff;
873 void *kaddr;
874 int id, rc;
875 long length;
876
877 rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
878 if (rc)
879 return rc;
880 id = dax_read_lock();
881 length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
882 &kaddr, pfnp);
883 if (length < 0) {
884 rc = length;
885 goto out;
886 }
887 rc = -EINVAL;
888 if (PFN_PHYS(length) < size)
889 goto out;
890 if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
891 goto out;
892 /* For larger pages we need devmap */
893 if (length > 1 && !pfn_t_devmap(*pfnp))
894 goto out;
895 rc = 0;
896out:
897 dax_read_unlock(id);
898 return rc;
899}
900
901/*
902 * The user has performed a load from a hole in the file. Allocating a new
903 * page in the file would cause excessive storage usage for workloads with
904 * sparse files. Instead we insert a read-only mapping of the 4k zero page.
905 * If this page is ever written to we will re-fault and change the mapping to
906 * point to real DAX storage instead.
907 */
908static int dax_load_hole(struct address_space *mapping, void *entry,
909 struct vm_fault *vmf)
910{
911 struct inode *inode = mapping->host;
912 unsigned long vaddr = vmf->address;
913 int ret = VM_FAULT_NOPAGE;
914 struct page *zero_page;
915 void *entry2;
916 pfn_t pfn;
917
918 zero_page = ZERO_PAGE(0);
919 if (unlikely(!zero_page)) {
920 ret = VM_FAULT_OOM;
921 goto out;
922 }
923
924 pfn = page_to_pfn_t(zero_page);
925 entry2 = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
926 RADIX_DAX_ZERO_PAGE, false);
927 if (IS_ERR(entry2)) {
928 ret = VM_FAULT_SIGBUS;
929 goto out;
930 }
931
932 vm_insert_mixed(vmf->vma, vaddr, pfn);
933out:
934 trace_dax_load_hole(inode, vmf, ret);
935 return ret;
936}
937
938static bool dax_range_is_aligned(struct block_device *bdev,
939 unsigned int offset, unsigned int length)
940{
941 unsigned short sector_size = bdev_logical_block_size(bdev);
942
943 if (!IS_ALIGNED(offset, sector_size))
944 return false;
945 if (!IS_ALIGNED(length, sector_size))
946 return false;
947
948 return true;
949}
950
951int __dax_zero_page_range(struct block_device *bdev,
952 struct dax_device *dax_dev, sector_t sector,
953 unsigned int offset, unsigned int size)
954{
955 if (dax_range_is_aligned(bdev, offset, size)) {
956 sector_t start_sector = sector + (offset >> 9);
957
958 return blkdev_issue_zeroout(bdev, start_sector,
959 size >> 9, GFP_NOFS, 0);
960 } else {
961 pgoff_t pgoff;
962 long rc, id;
963 void *kaddr;
964 pfn_t pfn;
965
966 rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
967 if (rc)
968 return rc;
969
970 id = dax_read_lock();
971 rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
972 &pfn);
973 if (rc < 0) {
974 dax_read_unlock(id);
975 return rc;
976 }
977 memset(kaddr + offset, 0, size);
978 dax_flush(dax_dev, kaddr + offset, size);
979 dax_read_unlock(id);
980 }
981 return 0;
982}
983EXPORT_SYMBOL_GPL(__dax_zero_page_range);
984
985static loff_t
986dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
987 struct iomap *iomap)
988{
989 struct block_device *bdev = iomap->bdev;
990 struct dax_device *dax_dev = iomap->dax_dev;
991 struct iov_iter *iter = data;
992 loff_t end = pos + length, done = 0;
993 ssize_t ret = 0;
994 int id;
995
996 if (iov_iter_rw(iter) == READ) {
997 end = min(end, i_size_read(inode));
998 if (pos >= end)
999 return 0;
1000
1001 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1002 return iov_iter_zero(min(length, end - pos), iter);
1003 }
1004
1005 if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
1006 return -EIO;
1007
1008 /*
1009 * Write can allocate block for an area which has a hole page mapped
1010 * into page tables. We have to tear down these mappings so that data
1011 * written by write(2) is visible in mmap.
1012 */
1013 if (iomap->flags & IOMAP_F_NEW) {
1014 invalidate_inode_pages2_range(inode->i_mapping,
1015 pos >> PAGE_SHIFT,
1016 (end - 1) >> PAGE_SHIFT);
1017 }
1018
1019 id = dax_read_lock();
1020 while (pos < end) {
1021 unsigned offset = pos & (PAGE_SIZE - 1);
1022 const size_t size = ALIGN(length + offset, PAGE_SIZE);
1023 const sector_t sector = dax_iomap_sector(iomap, pos);
1024 ssize_t map_len;
1025 pgoff_t pgoff;
1026 void *kaddr;
1027 pfn_t pfn;
1028
1029 if (fatal_signal_pending(current)) {
1030 ret = -EINTR;
1031 break;
1032 }
1033
1034 ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
1035 if (ret)
1036 break;
1037
1038 map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
1039 &kaddr, &pfn);
1040 if (map_len < 0) {
1041 ret = map_len;
1042 break;
1043 }
1044
1045 map_len = PFN_PHYS(map_len);
1046 kaddr += offset;
1047 map_len -= offset;
1048 if (map_len > end - pos)
1049 map_len = end - pos;
1050
1051 /*
1052 * The userspace address for the memory copy has already been
1053 * validated via access_ok() in either vfs_read() or
1054 * vfs_write(), depending on which operation we are doing.
1055 */
1056 if (iov_iter_rw(iter) == WRITE)
1057 map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr,
1058 map_len, iter);
1059 else
1060 map_len = copy_to_iter(kaddr, map_len, iter);
1061 if (map_len <= 0) {
1062 ret = map_len ? map_len : -EFAULT;
1063 break;
1064 }
1065
1066 pos += map_len;
1067 length -= map_len;
1068 done += map_len;
1069 }
1070 dax_read_unlock(id);
1071
1072 return done ? done : ret;
1073}
1074
1075/**
1076 * dax_iomap_rw - Perform I/O to a DAX file
1077 * @iocb: The control block for this I/O
1078 * @iter: The addresses to do I/O from or to
1079 * @ops: iomap ops passed from the file system
1080 *
1081 * This function performs read and write operations to directly mapped
1082 * persistent memory. The callers needs to take care of read/write exclusion
1083 * and evicting any page cache pages in the region under I/O.
1084 */
1085ssize_t
1086dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1087 const struct iomap_ops *ops)
1088{
1089 struct address_space *mapping = iocb->ki_filp->f_mapping;
1090 struct inode *inode = mapping->host;
1091 loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1092 unsigned flags = 0;
1093
1094 if (iov_iter_rw(iter) == WRITE) {
1095 lockdep_assert_held_exclusive(&inode->i_rwsem);
1096 flags |= IOMAP_WRITE;
1097 } else {
1098 lockdep_assert_held(&inode->i_rwsem);
1099 }
1100
1101 while (iov_iter_count(iter)) {
1102 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1103 iter, dax_iomap_actor);
1104 if (ret <= 0)
1105 break;
1106 pos += ret;
1107 done += ret;
1108 }
1109
1110 iocb->ki_pos += done;
1111 return done ? done : ret;
1112}
1113EXPORT_SYMBOL_GPL(dax_iomap_rw);
1114
1115static int dax_fault_return(int error)
1116{
1117 if (error == 0)
1118 return VM_FAULT_NOPAGE;
1119 if (error == -ENOMEM)
1120 return VM_FAULT_OOM;
1121 return VM_FAULT_SIGBUS;
1122}
1123
1124/*
1125 * MAP_SYNC on a dax mapping guarantees dirty metadata is
1126 * flushed on write-faults (non-cow), but not read-faults.
1127 */
1128static bool dax_fault_is_synchronous(unsigned long flags,
1129 struct vm_area_struct *vma, struct iomap *iomap)
1130{
1131 return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
1132 && (iomap->flags & IOMAP_F_DIRTY);
1133}
1134
1135static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
1136 int *iomap_errp, const struct iomap_ops *ops)
1137{
1138 struct vm_area_struct *vma = vmf->vma;
1139 struct address_space *mapping = vma->vm_file->f_mapping;
1140 struct inode *inode = mapping->host;
1141 unsigned long vaddr = vmf->address;
1142 loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1143 struct iomap iomap = { 0 };
1144 unsigned flags = IOMAP_FAULT;
1145 int error, major = 0;
1146 bool write = vmf->flags & FAULT_FLAG_WRITE;
1147 bool sync;
1148 int vmf_ret = 0;
1149 void *entry;
1150 pfn_t pfn;
1151
1152 trace_dax_pte_fault(inode, vmf, vmf_ret);
1153 /*
1154 * Check whether offset isn't beyond end of file now. Caller is supposed
1155 * to hold locks serializing us with truncate / punch hole so this is
1156 * a reliable test.
1157 */
1158 if (pos >= i_size_read(inode)) {
1159 vmf_ret = VM_FAULT_SIGBUS;
1160 goto out;
1161 }
1162
1163 if (write && !vmf->cow_page)
1164 flags |= IOMAP_WRITE;
1165
1166 entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
1167 if (IS_ERR(entry)) {
1168 vmf_ret = dax_fault_return(PTR_ERR(entry));
1169 goto out;
1170 }
1171
1172 /*
1173 * It is possible, particularly with mixed reads & writes to private
1174 * mappings, that we have raced with a PMD fault that overlaps with
1175 * the PTE we need to set up. If so just return and the fault will be
1176 * retried.
1177 */
1178 if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
1179 vmf_ret = VM_FAULT_NOPAGE;
1180 goto unlock_entry;
1181 }
1182
1183 /*
1184 * Note that we don't bother to use iomap_apply here: DAX required
1185 * the file system block size to be equal the page size, which means
1186 * that we never have to deal with more than a single extent here.
1187 */
1188 error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1189 if (iomap_errp)
1190 *iomap_errp = error;
1191 if (error) {
1192 vmf_ret = dax_fault_return(error);
1193 goto unlock_entry;
1194 }
1195 if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1196 error = -EIO; /* fs corruption? */
1197 goto error_finish_iomap;
1198 }
1199
1200 if (vmf->cow_page) {
1201 sector_t sector = dax_iomap_sector(&iomap, pos);
1202
1203 switch (iomap.type) {
1204 case IOMAP_HOLE:
1205 case IOMAP_UNWRITTEN:
1206 clear_user_highpage(vmf->cow_page, vaddr);
1207 break;
1208 case IOMAP_MAPPED:
1209 error = copy_user_dax(iomap.bdev, iomap.dax_dev,
1210 sector, PAGE_SIZE, vmf->cow_page, vaddr);
1211 break;
1212 default:
1213 WARN_ON_ONCE(1);
1214 error = -EIO;
1215 break;
1216 }
1217
1218 if (error)
1219 goto error_finish_iomap;
1220
1221 __SetPageUptodate(vmf->cow_page);
1222 vmf_ret = finish_fault(vmf);
1223 if (!vmf_ret)
1224 vmf_ret = VM_FAULT_DONE_COW;
1225 goto finish_iomap;
1226 }
1227
1228 sync = dax_fault_is_synchronous(flags, vma, &iomap);
1229
1230 switch (iomap.type) {
1231 case IOMAP_MAPPED:
1232 if (iomap.flags & IOMAP_F_NEW) {
1233 count_vm_event(PGMAJFAULT);
1234 count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
1235 major = VM_FAULT_MAJOR;
1236 }
1237 error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
1238 if (error < 0)
1239 goto error_finish_iomap;
1240
1241 entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1242 0, write && !sync);
1243 if (IS_ERR(entry)) {
1244 error = PTR_ERR(entry);
1245 goto error_finish_iomap;
1246 }
1247
1248 /*
1249 * If we are doing synchronous page fault and inode needs fsync,
1250 * we can insert PTE into page tables only after that happens.
1251 * Skip insertion for now and return the pfn so that caller can
1252 * insert it after fsync is done.
1253 */
1254 if (sync) {
1255 if (WARN_ON_ONCE(!pfnp)) {
1256 error = -EIO;
1257 goto error_finish_iomap;
1258 }
1259 *pfnp = pfn;
1260 vmf_ret = VM_FAULT_NEEDDSYNC | major;
1261 goto finish_iomap;
1262 }
1263 trace_dax_insert_mapping(inode, vmf, entry);
1264 if (write)
1265 error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
1266 else
1267 error = vm_insert_mixed(vma, vaddr, pfn);
1268
1269 /* -EBUSY is fine, somebody else faulted on the same PTE */
1270 if (error == -EBUSY)
1271 error = 0;
1272 break;
1273 case IOMAP_UNWRITTEN:
1274 case IOMAP_HOLE:
1275 if (!write) {
1276 vmf_ret = dax_load_hole(mapping, entry, vmf);
1277 goto finish_iomap;
1278 }
1279 /*FALLTHRU*/
1280 default:
1281 WARN_ON_ONCE(1);
1282 error = -EIO;
1283 break;
1284 }
1285
1286 error_finish_iomap:
1287 vmf_ret = dax_fault_return(error) | major;
1288 finish_iomap:
1289 if (ops->iomap_end) {
1290 int copied = PAGE_SIZE;
1291
1292 if (vmf_ret & VM_FAULT_ERROR)
1293 copied = 0;
1294 /*
1295 * The fault is done by now and there's no way back (other
1296 * thread may be already happily using PTE we have installed).
1297 * Just ignore error from ->iomap_end since we cannot do much
1298 * with it.
1299 */
1300 ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
1301 }
1302 unlock_entry:
1303 put_locked_mapping_entry(mapping, vmf->pgoff);
1304 out:
1305 trace_dax_pte_fault_done(inode, vmf, vmf_ret);
1306 return vmf_ret;
1307}
1308
1309#ifdef CONFIG_FS_DAX_PMD
1310static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
1311 void *entry)
1312{
1313 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1314 unsigned long pmd_addr = vmf->address & PMD_MASK;
1315 struct inode *inode = mapping->host;
1316 struct page *zero_page;
1317 void *ret = NULL;
1318 spinlock_t *ptl;
1319 pmd_t pmd_entry;
1320 pfn_t pfn;
1321
1322 zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
1323
1324 if (unlikely(!zero_page))
1325 goto fallback;
1326
1327 pfn = page_to_pfn_t(zero_page);
1328 ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1329 RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
1330 if (IS_ERR(ret))
1331 goto fallback;
1332
1333 ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1334 if (!pmd_none(*(vmf->pmd))) {
1335 spin_unlock(ptl);
1336 goto fallback;
1337 }
1338
1339 pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1340 pmd_entry = pmd_mkhuge(pmd_entry);
1341 set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
1342 spin_unlock(ptl);
1343 trace_dax_pmd_load_hole(inode, vmf, zero_page, ret);
1344 return VM_FAULT_NOPAGE;
1345
1346fallback:
1347 trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret);
1348 return VM_FAULT_FALLBACK;
1349}
1350
1351static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1352 const struct iomap_ops *ops)
1353{
1354 struct vm_area_struct *vma = vmf->vma;
1355 struct address_space *mapping = vma->vm_file->f_mapping;
1356 unsigned long pmd_addr = vmf->address & PMD_MASK;
1357 bool write = vmf->flags & FAULT_FLAG_WRITE;
1358 bool sync;
1359 unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1360 struct inode *inode = mapping->host;
1361 int result = VM_FAULT_FALLBACK;
1362 struct iomap iomap = { 0 };
1363 pgoff_t max_pgoff, pgoff;
1364 void *entry;
1365 loff_t pos;
1366 int error;
1367 pfn_t pfn;
1368
1369 /*
1370 * Check whether offset isn't beyond end of file now. Caller is
1371 * supposed to hold locks serializing us with truncate / punch hole so
1372 * this is a reliable test.
1373 */
1374 pgoff = linear_page_index(vma, pmd_addr);
1375 max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
1376
1377 trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
1378
1379 /*
1380 * Make sure that the faulting address's PMD offset (color) matches
1381 * the PMD offset from the start of the file. This is necessary so
1382 * that a PMD range in the page table overlaps exactly with a PMD
1383 * range in the radix tree.
1384 */
1385 if ((vmf->pgoff & PG_PMD_COLOUR) !=
1386 ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
1387 goto fallback;
1388
1389 /* Fall back to PTEs if we're going to COW */
1390 if (write && !(vma->vm_flags & VM_SHARED))
1391 goto fallback;
1392
1393 /* If the PMD would extend outside the VMA */
1394 if (pmd_addr < vma->vm_start)
1395 goto fallback;
1396 if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1397 goto fallback;
1398
1399 if (pgoff >= max_pgoff) {
1400 result = VM_FAULT_SIGBUS;
1401 goto out;
1402 }
1403
1404 /* If the PMD would extend beyond the file size */
1405 if ((pgoff | PG_PMD_COLOUR) >= max_pgoff)
1406 goto fallback;
1407
1408 /*
1409 * grab_mapping_entry() will make sure we get a 2MiB empty entry, a
1410 * 2MiB zero page entry or a DAX PMD. If it can't (because a 4k page
1411 * is already in the tree, for instance), it will return -EEXIST and
1412 * we just fall back to 4k entries.
1413 */
1414 entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1415 if (IS_ERR(entry))
1416 goto fallback;
1417
1418 /*
1419 * It is possible, particularly with mixed reads & writes to private
1420 * mappings, that we have raced with a PTE fault that overlaps with
1421 * the PMD we need to set up. If so just return and the fault will be
1422 * retried.
1423 */
1424 if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
1425 !pmd_devmap(*vmf->pmd)) {
1426 result = 0;
1427 goto unlock_entry;
1428 }
1429
1430 /*
1431 * Note that we don't use iomap_apply here. We aren't doing I/O, only
1432 * setting up a mapping, so really we're using iomap_begin() as a way
1433 * to look up our filesystem block.
1434 */
1435 pos = (loff_t)pgoff << PAGE_SHIFT;
1436 error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1437 if (error)
1438 goto unlock_entry;
1439
1440 if (iomap.offset + iomap.length < pos + PMD_SIZE)
1441 goto finish_iomap;
1442
1443 sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
1444
1445 switch (iomap.type) {
1446 case IOMAP_MAPPED:
1447 error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
1448 if (error < 0)
1449 goto finish_iomap;
1450
1451 entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
1452 RADIX_DAX_PMD, write && !sync);
1453 if (IS_ERR(entry))
1454 goto finish_iomap;
1455
1456 /*
1457 * If we are doing synchronous page fault and inode needs fsync,
1458 * we can insert PMD into page tables only after that happens.
1459 * Skip insertion for now and return the pfn so that caller can
1460 * insert it after fsync is done.
1461 */
1462 if (sync) {
1463 if (WARN_ON_ONCE(!pfnp))
1464 goto finish_iomap;
1465 *pfnp = pfn;
1466 result = VM_FAULT_NEEDDSYNC;
1467 goto finish_iomap;
1468 }
1469
1470 trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
1471 result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
1472 write);
1473 break;
1474 case IOMAP_UNWRITTEN:
1475 case IOMAP_HOLE:
1476 if (WARN_ON_ONCE(write))
1477 break;
1478 result = dax_pmd_load_hole(vmf, &iomap, entry);
1479 break;
1480 default:
1481 WARN_ON_ONCE(1);
1482 break;
1483 }
1484
1485 finish_iomap:
1486 if (ops->iomap_end) {
1487 int copied = PMD_SIZE;
1488
1489 if (result == VM_FAULT_FALLBACK)
1490 copied = 0;
1491 /*
1492 * The fault is done by now and there's no way back (other
1493 * thread may be already happily using PMD we have installed).
1494 * Just ignore error from ->iomap_end since we cannot do much
1495 * with it.
1496 */
1497 ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
1498 &iomap);
1499 }
1500 unlock_entry:
1501 put_locked_mapping_entry(mapping, pgoff);
1502 fallback:
1503 if (result == VM_FAULT_FALLBACK) {
1504 split_huge_pmd(vma, vmf->pmd, vmf->address);
1505 count_vm_event(THP_FAULT_FALLBACK);
1506 }
1507out:
1508 trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
1509 return result;
1510}
1511#else
1512static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1513 const struct iomap_ops *ops)
1514{
1515 return VM_FAULT_FALLBACK;
1516}
1517#endif /* CONFIG_FS_DAX_PMD */
1518
1519/**
1520 * dax_iomap_fault - handle a page fault on a DAX file
1521 * @vmf: The description of the fault
1522 * @pe_size: Size of the page to fault in
1523 * @pfnp: PFN to insert for synchronous faults if fsync is required
1524 * @iomap_errp: Storage for detailed error code in case of error
1525 * @ops: Iomap ops passed from the file system
1526 *
1527 * When a page fault occurs, filesystems may call this helper in
1528 * their fault handler for DAX files. dax_iomap_fault() assumes the caller
1529 * has done all the necessary locking for page fault to proceed
1530 * successfully.
1531 */
1532int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
1533 pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
1534{
1535 switch (pe_size) {
1536 case PE_SIZE_PTE:
1537 return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
1538 case PE_SIZE_PMD:
1539 return dax_iomap_pmd_fault(vmf, pfnp, ops);
1540 default:
1541 return VM_FAULT_FALLBACK;
1542 }
1543}
1544EXPORT_SYMBOL_GPL(dax_iomap_fault);
1545
1546/**
1547 * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
1548 * @vmf: The description of the fault
1549 * @pe_size: Size of entry to be inserted
1550 * @pfn: PFN to insert
1551 *
1552 * This function inserts writeable PTE or PMD entry into page tables for mmaped
1553 * DAX file. It takes care of marking corresponding radix tree entry as dirty
1554 * as well.
1555 */
1556static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
1557 enum page_entry_size pe_size,
1558 pfn_t pfn)
1559{
1560 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1561 void *entry, **slot;
1562 pgoff_t index = vmf->pgoff;
1563 int vmf_ret, error;
1564
1565 xa_lock_irq(&mapping->i_pages);
1566 entry = get_unlocked_mapping_entry(mapping, index, &slot);
1567 /* Did we race with someone splitting entry or so? */
1568 if (!entry ||
1569 (pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
1570 (pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
1571 put_unlocked_mapping_entry(mapping, index, entry);
1572 xa_unlock_irq(&mapping->i_pages);
1573 trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
1574 VM_FAULT_NOPAGE);
1575 return VM_FAULT_NOPAGE;
1576 }
1577 radix_tree_tag_set(&mapping->i_pages, index, PAGECACHE_TAG_DIRTY);
1578 entry = lock_slot(mapping, slot);
1579 xa_unlock_irq(&mapping->i_pages);
1580 switch (pe_size) {
1581 case PE_SIZE_PTE:
1582 error = vm_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
1583 vmf_ret = dax_fault_return(error);
1584 break;
1585#ifdef CONFIG_FS_DAX_PMD
1586 case PE_SIZE_PMD:
1587 vmf_ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
1588 pfn, true);
1589 break;
1590#endif
1591 default:
1592 vmf_ret = VM_FAULT_FALLBACK;
1593 }
1594 put_locked_mapping_entry(mapping, index);
1595 trace_dax_insert_pfn_mkwrite(mapping->host, vmf, vmf_ret);
1596 return vmf_ret;
1597}
1598
1599/**
1600 * dax_finish_sync_fault - finish synchronous page fault
1601 * @vmf: The description of the fault
1602 * @pe_size: Size of entry to be inserted
1603 * @pfn: PFN to insert
1604 *
1605 * This function ensures that the file range touched by the page fault is
1606 * stored persistently on the media and handles inserting of appropriate page
1607 * table entry.
1608 */
1609int dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
1610 pfn_t pfn)
1611{
1612 int err;
1613 loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
1614 size_t len = 0;
1615
1616 if (pe_size == PE_SIZE_PTE)
1617 len = PAGE_SIZE;
1618 else if (pe_size == PE_SIZE_PMD)
1619 len = PMD_SIZE;
1620 else
1621 WARN_ON_ONCE(1);
1622 err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
1623 if (err)
1624 return VM_FAULT_SIGBUS;
1625 return dax_insert_pfn_mkwrite(vmf, pe_size, pfn);
1626}
1627EXPORT_SYMBOL_GPL(dax_finish_sync_fault);