Merge tag 'x86-urgent-2023-09-01' of git://git.kernel.org/pub/scm/linux/kernel/git...
[platform/kernel/linux-starfive.git] / fs / dax.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * fs/dax.c - Direct Access filesystem code
4  * Copyright (c) 2013-2014 Intel Corporation
5  * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
6  * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
7  */
8
9 #include <linux/atomic.h>
10 #include <linux/blkdev.h>
11 #include <linux/buffer_head.h>
12 #include <linux/dax.h>
13 #include <linux/fs.h>
14 #include <linux/highmem.h>
15 #include <linux/memcontrol.h>
16 #include <linux/mm.h>
17 #include <linux/mutex.h>
18 #include <linux/pagevec.h>
19 #include <linux/sched.h>
20 #include <linux/sched/signal.h>
21 #include <linux/uio.h>
22 #include <linux/vmstat.h>
23 #include <linux/pfn_t.h>
24 #include <linux/sizes.h>
25 #include <linux/mmu_notifier.h>
26 #include <linux/iomap.h>
27 #include <linux/rmap.h>
28 #include <asm/pgalloc.h>
29
30 #define CREATE_TRACE_POINTS
31 #include <trace/events/fs_dax.h>
32
33 /* We choose 4096 entries - same as per-zone page wait tables */
34 #define DAX_WAIT_TABLE_BITS 12
35 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
36
37 /* The 'colour' (ie low bits) within a PMD of a page offset.  */
38 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
39 #define PG_PMD_NR       (PMD_SIZE >> PAGE_SHIFT)
40
41 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
42
43 static int __init init_dax_wait_table(void)
44 {
45         int i;
46
47         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
48                 init_waitqueue_head(wait_table + i);
49         return 0;
50 }
51 fs_initcall(init_dax_wait_table);
52
53 /*
54  * DAX pagecache entries use XArray value entries so they can't be mistaken
55  * for pages.  We use one bit for locking, one bit for the entry size (PMD)
56  * and two more to tell us if the entry is a zero page or an empty entry that
57  * is just used for locking.  In total four special bits.
58  *
59  * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
60  * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
61  * block allocation.
62  */
63 #define DAX_SHIFT       (4)
64 #define DAX_LOCKED      (1UL << 0)
65 #define DAX_PMD         (1UL << 1)
66 #define DAX_ZERO_PAGE   (1UL << 2)
67 #define DAX_EMPTY       (1UL << 3)
68
69 static unsigned long dax_to_pfn(void *entry)
70 {
71         return xa_to_value(entry) >> DAX_SHIFT;
72 }
73
74 static void *dax_make_entry(pfn_t pfn, unsigned long flags)
75 {
76         return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT));
77 }
78
79 static bool dax_is_locked(void *entry)
80 {
81         return xa_to_value(entry) & DAX_LOCKED;
82 }
83
84 static unsigned int dax_entry_order(void *entry)
85 {
86         if (xa_to_value(entry) & DAX_PMD)
87                 return PMD_ORDER;
88         return 0;
89 }
90
91 static unsigned long dax_is_pmd_entry(void *entry)
92 {
93         return xa_to_value(entry) & DAX_PMD;
94 }
95
96 static bool dax_is_pte_entry(void *entry)
97 {
98         return !(xa_to_value(entry) & DAX_PMD);
99 }
100
101 static int dax_is_zero_entry(void *entry)
102 {
103         return xa_to_value(entry) & DAX_ZERO_PAGE;
104 }
105
106 static int dax_is_empty_entry(void *entry)
107 {
108         return xa_to_value(entry) & DAX_EMPTY;
109 }
110
111 /*
112  * true if the entry that was found is of a smaller order than the entry
113  * we were looking for
114  */
115 static bool dax_is_conflict(void *entry)
116 {
117         return entry == XA_RETRY_ENTRY;
118 }
119
120 /*
121  * DAX page cache entry locking
122  */
123 struct exceptional_entry_key {
124         struct xarray *xa;
125         pgoff_t entry_start;
126 };
127
128 struct wait_exceptional_entry_queue {
129         wait_queue_entry_t wait;
130         struct exceptional_entry_key key;
131 };
132
133 /**
134  * enum dax_wake_mode: waitqueue wakeup behaviour
135  * @WAKE_ALL: wake all waiters in the waitqueue
136  * @WAKE_NEXT: wake only the first waiter in the waitqueue
137  */
138 enum dax_wake_mode {
139         WAKE_ALL,
140         WAKE_NEXT,
141 };
142
143 static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
144                 void *entry, struct exceptional_entry_key *key)
145 {
146         unsigned long hash;
147         unsigned long index = xas->xa_index;
148
149         /*
150          * If 'entry' is a PMD, align the 'index' that we use for the wait
151          * queue to the start of that PMD.  This ensures that all offsets in
152          * the range covered by the PMD map to the same bit lock.
153          */
154         if (dax_is_pmd_entry(entry))
155                 index &= ~PG_PMD_COLOUR;
156         key->xa = xas->xa;
157         key->entry_start = index;
158
159         hash = hash_long((unsigned long)xas->xa ^ index, DAX_WAIT_TABLE_BITS);
160         return wait_table + hash;
161 }
162
163 static int wake_exceptional_entry_func(wait_queue_entry_t *wait,
164                 unsigned int mode, int sync, void *keyp)
165 {
166         struct exceptional_entry_key *key = keyp;
167         struct wait_exceptional_entry_queue *ewait =
168                 container_of(wait, struct wait_exceptional_entry_queue, wait);
169
170         if (key->xa != ewait->key.xa ||
171             key->entry_start != ewait->key.entry_start)
172                 return 0;
173         return autoremove_wake_function(wait, mode, sync, NULL);
174 }
175
176 /*
177  * @entry may no longer be the entry at the index in the mapping.
178  * The important information it's conveying is whether the entry at
179  * this index used to be a PMD entry.
180  */
181 static void dax_wake_entry(struct xa_state *xas, void *entry,
182                            enum dax_wake_mode mode)
183 {
184         struct exceptional_entry_key key;
185         wait_queue_head_t *wq;
186
187         wq = dax_entry_waitqueue(xas, entry, &key);
188
189         /*
190          * Checking for locked entry and prepare_to_wait_exclusive() happens
191          * under the i_pages lock, ditto for entry handling in our callers.
192          * So at this point all tasks that could have seen our entry locked
193          * must be in the waitqueue and the following check will see them.
194          */
195         if (waitqueue_active(wq))
196                 __wake_up(wq, TASK_NORMAL, mode == WAKE_ALL ? 0 : 1, &key);
197 }
198
199 /*
200  * Look up entry in page cache, wait for it to become unlocked if it
201  * is a DAX entry and return it.  The caller must subsequently call
202  * put_unlocked_entry() if it did not lock the entry or dax_unlock_entry()
203  * if it did.  The entry returned may have a larger order than @order.
204  * If @order is larger than the order of the entry found in i_pages, this
205  * function returns a dax_is_conflict entry.
206  *
207  * Must be called with the i_pages lock held.
208  */
209 static void *get_unlocked_entry(struct xa_state *xas, unsigned int order)
210 {
211         void *entry;
212         struct wait_exceptional_entry_queue ewait;
213         wait_queue_head_t *wq;
214
215         init_wait(&ewait.wait);
216         ewait.wait.func = wake_exceptional_entry_func;
217
218         for (;;) {
219                 entry = xas_find_conflict(xas);
220                 if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
221                         return entry;
222                 if (dax_entry_order(entry) < order)
223                         return XA_RETRY_ENTRY;
224                 if (!dax_is_locked(entry))
225                         return entry;
226
227                 wq = dax_entry_waitqueue(xas, entry, &ewait.key);
228                 prepare_to_wait_exclusive(wq, &ewait.wait,
229                                           TASK_UNINTERRUPTIBLE);
230                 xas_unlock_irq(xas);
231                 xas_reset(xas);
232                 schedule();
233                 finish_wait(wq, &ewait.wait);
234                 xas_lock_irq(xas);
235         }
236 }
237
238 /*
239  * The only thing keeping the address space around is the i_pages lock
240  * (it's cycled in clear_inode() after removing the entries from i_pages)
241  * After we call xas_unlock_irq(), we cannot touch xas->xa.
242  */
243 static void wait_entry_unlocked(struct xa_state *xas, void *entry)
244 {
245         struct wait_exceptional_entry_queue ewait;
246         wait_queue_head_t *wq;
247
248         init_wait(&ewait.wait);
249         ewait.wait.func = wake_exceptional_entry_func;
250
251         wq = dax_entry_waitqueue(xas, entry, &ewait.key);
252         /*
253          * Unlike get_unlocked_entry() there is no guarantee that this
254          * path ever successfully retrieves an unlocked entry before an
255          * inode dies. Perform a non-exclusive wait in case this path
256          * never successfully performs its own wake up.
257          */
258         prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
259         xas_unlock_irq(xas);
260         schedule();
261         finish_wait(wq, &ewait.wait);
262 }
263
264 static void put_unlocked_entry(struct xa_state *xas, void *entry,
265                                enum dax_wake_mode mode)
266 {
267         if (entry && !dax_is_conflict(entry))
268                 dax_wake_entry(xas, entry, mode);
269 }
270
271 /*
272  * We used the xa_state to get the entry, but then we locked the entry and
273  * dropped the xa_lock, so we know the xa_state is stale and must be reset
274  * before use.
275  */
276 static void dax_unlock_entry(struct xa_state *xas, void *entry)
277 {
278         void *old;
279
280         BUG_ON(dax_is_locked(entry));
281         xas_reset(xas);
282         xas_lock_irq(xas);
283         old = xas_store(xas, entry);
284         xas_unlock_irq(xas);
285         BUG_ON(!dax_is_locked(old));
286         dax_wake_entry(xas, entry, WAKE_NEXT);
287 }
288
289 /*
290  * Return: The entry stored at this location before it was locked.
291  */
292 static void *dax_lock_entry(struct xa_state *xas, void *entry)
293 {
294         unsigned long v = xa_to_value(entry);
295         return xas_store(xas, xa_mk_value(v | DAX_LOCKED));
296 }
297
298 static unsigned long dax_entry_size(void *entry)
299 {
300         if (dax_is_zero_entry(entry))
301                 return 0;
302         else if (dax_is_empty_entry(entry))
303                 return 0;
304         else if (dax_is_pmd_entry(entry))
305                 return PMD_SIZE;
306         else
307                 return PAGE_SIZE;
308 }
309
310 static unsigned long dax_end_pfn(void *entry)
311 {
312         return dax_to_pfn(entry) + dax_entry_size(entry) / PAGE_SIZE;
313 }
314
315 /*
316  * Iterate through all mapped pfns represented by an entry, i.e. skip
317  * 'empty' and 'zero' entries.
318  */
319 #define for_each_mapped_pfn(entry, pfn) \
320         for (pfn = dax_to_pfn(entry); \
321                         pfn < dax_end_pfn(entry); pfn++)
322
323 static inline bool dax_page_is_shared(struct page *page)
324 {
325         return page->mapping == PAGE_MAPPING_DAX_SHARED;
326 }
327
328 /*
329  * Set the page->mapping with PAGE_MAPPING_DAX_SHARED flag, increase the
330  * refcount.
331  */
332 static inline void dax_page_share_get(struct page *page)
333 {
334         if (page->mapping != PAGE_MAPPING_DAX_SHARED) {
335                 /*
336                  * Reset the index if the page was already mapped
337                  * regularly before.
338                  */
339                 if (page->mapping)
340                         page->share = 1;
341                 page->mapping = PAGE_MAPPING_DAX_SHARED;
342         }
343         page->share++;
344 }
345
346 static inline unsigned long dax_page_share_put(struct page *page)
347 {
348         return --page->share;
349 }
350
351 /*
352  * When it is called in dax_insert_entry(), the shared flag will indicate that
353  * whether this entry is shared by multiple files.  If so, set the page->mapping
354  * PAGE_MAPPING_DAX_SHARED, and use page->share as refcount.
355  */
356 static void dax_associate_entry(void *entry, struct address_space *mapping,
357                 struct vm_area_struct *vma, unsigned long address, bool shared)
358 {
359         unsigned long size = dax_entry_size(entry), pfn, index;
360         int i = 0;
361
362         if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
363                 return;
364
365         index = linear_page_index(vma, address & ~(size - 1));
366         for_each_mapped_pfn(entry, pfn) {
367                 struct page *page = pfn_to_page(pfn);
368
369                 if (shared) {
370                         dax_page_share_get(page);
371                 } else {
372                         WARN_ON_ONCE(page->mapping);
373                         page->mapping = mapping;
374                         page->index = index + i++;
375                 }
376         }
377 }
378
379 static void dax_disassociate_entry(void *entry, struct address_space *mapping,
380                 bool trunc)
381 {
382         unsigned long pfn;
383
384         if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
385                 return;
386
387         for_each_mapped_pfn(entry, pfn) {
388                 struct page *page = pfn_to_page(pfn);
389
390                 WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
391                 if (dax_page_is_shared(page)) {
392                         /* keep the shared flag if this page is still shared */
393                         if (dax_page_share_put(page) > 0)
394                                 continue;
395                 } else
396                         WARN_ON_ONCE(page->mapping && page->mapping != mapping);
397                 page->mapping = NULL;
398                 page->index = 0;
399         }
400 }
401
402 static struct page *dax_busy_page(void *entry)
403 {
404         unsigned long pfn;
405
406         for_each_mapped_pfn(entry, pfn) {
407                 struct page *page = pfn_to_page(pfn);
408
409                 if (page_ref_count(page) > 1)
410                         return page;
411         }
412         return NULL;
413 }
414
415 /*
416  * dax_lock_page - Lock the DAX entry corresponding to a page
417  * @page: The page whose entry we want to lock
418  *
419  * Context: Process context.
420  * Return: A cookie to pass to dax_unlock_page() or 0 if the entry could
421  * not be locked.
422  */
423 dax_entry_t dax_lock_page(struct page *page)
424 {
425         XA_STATE(xas, NULL, 0);
426         void *entry;
427
428         /* Ensure page->mapping isn't freed while we look at it */
429         rcu_read_lock();
430         for (;;) {
431                 struct address_space *mapping = READ_ONCE(page->mapping);
432
433                 entry = NULL;
434                 if (!mapping || !dax_mapping(mapping))
435                         break;
436
437                 /*
438                  * In the device-dax case there's no need to lock, a
439                  * struct dev_pagemap pin is sufficient to keep the
440                  * inode alive, and we assume we have dev_pagemap pin
441                  * otherwise we would not have a valid pfn_to_page()
442                  * translation.
443                  */
444                 entry = (void *)~0UL;
445                 if (S_ISCHR(mapping->host->i_mode))
446                         break;
447
448                 xas.xa = &mapping->i_pages;
449                 xas_lock_irq(&xas);
450                 if (mapping != page->mapping) {
451                         xas_unlock_irq(&xas);
452                         continue;
453                 }
454                 xas_set(&xas, page->index);
455                 entry = xas_load(&xas);
456                 if (dax_is_locked(entry)) {
457                         rcu_read_unlock();
458                         wait_entry_unlocked(&xas, entry);
459                         rcu_read_lock();
460                         continue;
461                 }
462                 dax_lock_entry(&xas, entry);
463                 xas_unlock_irq(&xas);
464                 break;
465         }
466         rcu_read_unlock();
467         return (dax_entry_t)entry;
468 }
469
470 void dax_unlock_page(struct page *page, dax_entry_t cookie)
471 {
472         struct address_space *mapping = page->mapping;
473         XA_STATE(xas, &mapping->i_pages, page->index);
474
475         if (S_ISCHR(mapping->host->i_mode))
476                 return;
477
478         dax_unlock_entry(&xas, (void *)cookie);
479 }
480
481 /*
482  * dax_lock_mapping_entry - Lock the DAX entry corresponding to a mapping
483  * @mapping: the file's mapping whose entry we want to lock
484  * @index: the offset within this file
485  * @page: output the dax page corresponding to this dax entry
486  *
487  * Return: A cookie to pass to dax_unlock_mapping_entry() or 0 if the entry
488  * could not be locked.
489  */
490 dax_entry_t dax_lock_mapping_entry(struct address_space *mapping, pgoff_t index,
491                 struct page **page)
492 {
493         XA_STATE(xas, NULL, 0);
494         void *entry;
495
496         rcu_read_lock();
497         for (;;) {
498                 entry = NULL;
499                 if (!dax_mapping(mapping))
500                         break;
501
502                 xas.xa = &mapping->i_pages;
503                 xas_lock_irq(&xas);
504                 xas_set(&xas, index);
505                 entry = xas_load(&xas);
506                 if (dax_is_locked(entry)) {
507                         rcu_read_unlock();
508                         wait_entry_unlocked(&xas, entry);
509                         rcu_read_lock();
510                         continue;
511                 }
512                 if (!entry ||
513                     dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
514                         /*
515                          * Because we are looking for entry from file's mapping
516                          * and index, so the entry may not be inserted for now,
517                          * or even a zero/empty entry.  We don't think this is
518                          * an error case.  So, return a special value and do
519                          * not output @page.
520                          */
521                         entry = (void *)~0UL;
522                 } else {
523                         *page = pfn_to_page(dax_to_pfn(entry));
524                         dax_lock_entry(&xas, entry);
525                 }
526                 xas_unlock_irq(&xas);
527                 break;
528         }
529         rcu_read_unlock();
530         return (dax_entry_t)entry;
531 }
532
533 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index,
534                 dax_entry_t cookie)
535 {
536         XA_STATE(xas, &mapping->i_pages, index);
537
538         if (cookie == ~0UL)
539                 return;
540
541         dax_unlock_entry(&xas, (void *)cookie);
542 }
543
544 /*
545  * Find page cache entry at given index. If it is a DAX entry, return it
546  * with the entry locked. If the page cache doesn't contain an entry at
547  * that index, add a locked empty entry.
548  *
549  * When requesting an entry with size DAX_PMD, grab_mapping_entry() will
550  * either return that locked entry or will return VM_FAULT_FALLBACK.
551  * This will happen if there are any PTE entries within the PMD range
552  * that we are requesting.
553  *
554  * We always favor PTE entries over PMD entries. There isn't a flow where we
555  * evict PTE entries in order to 'upgrade' them to a PMD entry.  A PMD
556  * insertion will fail if it finds any PTE entries already in the tree, and a
557  * PTE insertion will cause an existing PMD entry to be unmapped and
558  * downgraded to PTE entries.  This happens for both PMD zero pages as
559  * well as PMD empty entries.
560  *
561  * The exception to this downgrade path is for PMD entries that have
562  * real storage backing them.  We will leave these real PMD entries in
563  * the tree, and PTE writes will simply dirty the entire PMD entry.
564  *
565  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
566  * persistent memory the benefit is doubtful. We can add that later if we can
567  * show it helps.
568  *
569  * On error, this function does not return an ERR_PTR.  Instead it returns
570  * a VM_FAULT code, encoded as an xarray internal entry.  The ERR_PTR values
571  * overlap with xarray value entries.
572  */
573 static void *grab_mapping_entry(struct xa_state *xas,
574                 struct address_space *mapping, unsigned int order)
575 {
576         unsigned long index = xas->xa_index;
577         bool pmd_downgrade;     /* splitting PMD entry into PTE entries? */
578         void *entry;
579
580 retry:
581         pmd_downgrade = false;
582         xas_lock_irq(xas);
583         entry = get_unlocked_entry(xas, order);
584
585         if (entry) {
586                 if (dax_is_conflict(entry))
587                         goto fallback;
588                 if (!xa_is_value(entry)) {
589                         xas_set_err(xas, -EIO);
590                         goto out_unlock;
591                 }
592
593                 if (order == 0) {
594                         if (dax_is_pmd_entry(entry) &&
595                             (dax_is_zero_entry(entry) ||
596                              dax_is_empty_entry(entry))) {
597                                 pmd_downgrade = true;
598                         }
599                 }
600         }
601
602         if (pmd_downgrade) {
603                 /*
604                  * Make sure 'entry' remains valid while we drop
605                  * the i_pages lock.
606                  */
607                 dax_lock_entry(xas, entry);
608
609                 /*
610                  * Besides huge zero pages the only other thing that gets
611                  * downgraded are empty entries which don't need to be
612                  * unmapped.
613                  */
614                 if (dax_is_zero_entry(entry)) {
615                         xas_unlock_irq(xas);
616                         unmap_mapping_pages(mapping,
617                                         xas->xa_index & ~PG_PMD_COLOUR,
618                                         PG_PMD_NR, false);
619                         xas_reset(xas);
620                         xas_lock_irq(xas);
621                 }
622
623                 dax_disassociate_entry(entry, mapping, false);
624                 xas_store(xas, NULL);   /* undo the PMD join */
625                 dax_wake_entry(xas, entry, WAKE_ALL);
626                 mapping->nrpages -= PG_PMD_NR;
627                 entry = NULL;
628                 xas_set(xas, index);
629         }
630
631         if (entry) {
632                 dax_lock_entry(xas, entry);
633         } else {
634                 unsigned long flags = DAX_EMPTY;
635
636                 if (order > 0)
637                         flags |= DAX_PMD;
638                 entry = dax_make_entry(pfn_to_pfn_t(0), flags);
639                 dax_lock_entry(xas, entry);
640                 if (xas_error(xas))
641                         goto out_unlock;
642                 mapping->nrpages += 1UL << order;
643         }
644
645 out_unlock:
646         xas_unlock_irq(xas);
647         if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
648                 goto retry;
649         if (xas->xa_node == XA_ERROR(-ENOMEM))
650                 return xa_mk_internal(VM_FAULT_OOM);
651         if (xas_error(xas))
652                 return xa_mk_internal(VM_FAULT_SIGBUS);
653         return entry;
654 fallback:
655         xas_unlock_irq(xas);
656         return xa_mk_internal(VM_FAULT_FALLBACK);
657 }
658
659 /**
660  * dax_layout_busy_page_range - find first pinned page in @mapping
661  * @mapping: address space to scan for a page with ref count > 1
662  * @start: Starting offset. Page containing 'start' is included.
663  * @end: End offset. Page containing 'end' is included. If 'end' is LLONG_MAX,
664  *       pages from 'start' till the end of file are included.
665  *
666  * DAX requires ZONE_DEVICE mapped pages. These pages are never
667  * 'onlined' to the page allocator so they are considered idle when
668  * page->count == 1. A filesystem uses this interface to determine if
669  * any page in the mapping is busy, i.e. for DMA, or other
670  * get_user_pages() usages.
671  *
672  * It is expected that the filesystem is holding locks to block the
673  * establishment of new mappings in this address_space. I.e. it expects
674  * to be able to run unmap_mapping_range() and subsequently not race
675  * mapping_mapped() becoming true.
676  */
677 struct page *dax_layout_busy_page_range(struct address_space *mapping,
678                                         loff_t start, loff_t end)
679 {
680         void *entry;
681         unsigned int scanned = 0;
682         struct page *page = NULL;
683         pgoff_t start_idx = start >> PAGE_SHIFT;
684         pgoff_t end_idx;
685         XA_STATE(xas, &mapping->i_pages, start_idx);
686
687         /*
688          * In the 'limited' case get_user_pages() for dax is disabled.
689          */
690         if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
691                 return NULL;
692
693         if (!dax_mapping(mapping) || !mapping_mapped(mapping))
694                 return NULL;
695
696         /* If end == LLONG_MAX, all pages from start to till end of file */
697         if (end == LLONG_MAX)
698                 end_idx = ULONG_MAX;
699         else
700                 end_idx = end >> PAGE_SHIFT;
701         /*
702          * If we race get_user_pages_fast() here either we'll see the
703          * elevated page count in the iteration and wait, or
704          * get_user_pages_fast() will see that the page it took a reference
705          * against is no longer mapped in the page tables and bail to the
706          * get_user_pages() slow path.  The slow path is protected by
707          * pte_lock() and pmd_lock(). New references are not taken without
708          * holding those locks, and unmap_mapping_pages() will not zero the
709          * pte or pmd without holding the respective lock, so we are
710          * guaranteed to either see new references or prevent new
711          * references from being established.
712          */
713         unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1, 0);
714
715         xas_lock_irq(&xas);
716         xas_for_each(&xas, entry, end_idx) {
717                 if (WARN_ON_ONCE(!xa_is_value(entry)))
718                         continue;
719                 if (unlikely(dax_is_locked(entry)))
720                         entry = get_unlocked_entry(&xas, 0);
721                 if (entry)
722                         page = dax_busy_page(entry);
723                 put_unlocked_entry(&xas, entry, WAKE_NEXT);
724                 if (page)
725                         break;
726                 if (++scanned % XA_CHECK_SCHED)
727                         continue;
728
729                 xas_pause(&xas);
730                 xas_unlock_irq(&xas);
731                 cond_resched();
732                 xas_lock_irq(&xas);
733         }
734         xas_unlock_irq(&xas);
735         return page;
736 }
737 EXPORT_SYMBOL_GPL(dax_layout_busy_page_range);
738
739 struct page *dax_layout_busy_page(struct address_space *mapping)
740 {
741         return dax_layout_busy_page_range(mapping, 0, LLONG_MAX);
742 }
743 EXPORT_SYMBOL_GPL(dax_layout_busy_page);
744
745 static int __dax_invalidate_entry(struct address_space *mapping,
746                                           pgoff_t index, bool trunc)
747 {
748         XA_STATE(xas, &mapping->i_pages, index);
749         int ret = 0;
750         void *entry;
751
752         xas_lock_irq(&xas);
753         entry = get_unlocked_entry(&xas, 0);
754         if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
755                 goto out;
756         if (!trunc &&
757             (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY) ||
758              xas_get_mark(&xas, PAGECACHE_TAG_TOWRITE)))
759                 goto out;
760         dax_disassociate_entry(entry, mapping, trunc);
761         xas_store(&xas, NULL);
762         mapping->nrpages -= 1UL << dax_entry_order(entry);
763         ret = 1;
764 out:
765         put_unlocked_entry(&xas, entry, WAKE_ALL);
766         xas_unlock_irq(&xas);
767         return ret;
768 }
769
770 static int __dax_clear_dirty_range(struct address_space *mapping,
771                 pgoff_t start, pgoff_t end)
772 {
773         XA_STATE(xas, &mapping->i_pages, start);
774         unsigned int scanned = 0;
775         void *entry;
776
777         xas_lock_irq(&xas);
778         xas_for_each(&xas, entry, end) {
779                 entry = get_unlocked_entry(&xas, 0);
780                 xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
781                 xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
782                 put_unlocked_entry(&xas, entry, WAKE_NEXT);
783
784                 if (++scanned % XA_CHECK_SCHED)
785                         continue;
786
787                 xas_pause(&xas);
788                 xas_unlock_irq(&xas);
789                 cond_resched();
790                 xas_lock_irq(&xas);
791         }
792         xas_unlock_irq(&xas);
793
794         return 0;
795 }
796
797 /*
798  * Delete DAX entry at @index from @mapping.  Wait for it
799  * to be unlocked before deleting it.
800  */
801 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
802 {
803         int ret = __dax_invalidate_entry(mapping, index, true);
804
805         /*
806          * This gets called from truncate / punch_hole path. As such, the caller
807          * must hold locks protecting against concurrent modifications of the
808          * page cache (usually fs-private i_mmap_sem for writing). Since the
809          * caller has seen a DAX entry for this index, we better find it
810          * at that index as well...
811          */
812         WARN_ON_ONCE(!ret);
813         return ret;
814 }
815
816 /*
817  * Invalidate DAX entry if it is clean.
818  */
819 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
820                                       pgoff_t index)
821 {
822         return __dax_invalidate_entry(mapping, index, false);
823 }
824
825 static pgoff_t dax_iomap_pgoff(const struct iomap *iomap, loff_t pos)
826 {
827         return PHYS_PFN(iomap->addr + (pos & PAGE_MASK) - iomap->offset);
828 }
829
830 static int copy_cow_page_dax(struct vm_fault *vmf, const struct iomap_iter *iter)
831 {
832         pgoff_t pgoff = dax_iomap_pgoff(&iter->iomap, iter->pos);
833         void *vto, *kaddr;
834         long rc;
835         int id;
836
837         id = dax_read_lock();
838         rc = dax_direct_access(iter->iomap.dax_dev, pgoff, 1, DAX_ACCESS,
839                                 &kaddr, NULL);
840         if (rc < 0) {
841                 dax_read_unlock(id);
842                 return rc;
843         }
844         vto = kmap_atomic(vmf->cow_page);
845         copy_user_page(vto, kaddr, vmf->address, vmf->cow_page);
846         kunmap_atomic(vto);
847         dax_read_unlock(id);
848         return 0;
849 }
850
851 /*
852  * MAP_SYNC on a dax mapping guarantees dirty metadata is
853  * flushed on write-faults (non-cow), but not read-faults.
854  */
855 static bool dax_fault_is_synchronous(const struct iomap_iter *iter,
856                 struct vm_area_struct *vma)
857 {
858         return (iter->flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC) &&
859                 (iter->iomap.flags & IOMAP_F_DIRTY);
860 }
861
862 /*
863  * By this point grab_mapping_entry() has ensured that we have a locked entry
864  * of the appropriate size so we don't have to worry about downgrading PMDs to
865  * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
866  * already in the tree, we will skip the insertion and just dirty the PMD as
867  * appropriate.
868  */
869 static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
870                 const struct iomap_iter *iter, void *entry, pfn_t pfn,
871                 unsigned long flags)
872 {
873         struct address_space *mapping = vmf->vma->vm_file->f_mapping;
874         void *new_entry = dax_make_entry(pfn, flags);
875         bool write = iter->flags & IOMAP_WRITE;
876         bool dirty = write && !dax_fault_is_synchronous(iter, vmf->vma);
877         bool shared = iter->iomap.flags & IOMAP_F_SHARED;
878
879         if (dirty)
880                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
881
882         if (shared || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
883                 unsigned long index = xas->xa_index;
884                 /* we are replacing a zero page with block mapping */
885                 if (dax_is_pmd_entry(entry))
886                         unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
887                                         PG_PMD_NR, false);
888                 else /* pte entry */
889                         unmap_mapping_pages(mapping, index, 1, false);
890         }
891
892         xas_reset(xas);
893         xas_lock_irq(xas);
894         if (shared || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
895                 void *old;
896
897                 dax_disassociate_entry(entry, mapping, false);
898                 dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address,
899                                 shared);
900                 /*
901                  * Only swap our new entry into the page cache if the current
902                  * entry is a zero page or an empty entry.  If a normal PTE or
903                  * PMD entry is already in the cache, we leave it alone.  This
904                  * means that if we are trying to insert a PTE and the
905                  * existing entry is a PMD, we will just leave the PMD in the
906                  * tree and dirty it if necessary.
907                  */
908                 old = dax_lock_entry(xas, new_entry);
909                 WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) |
910                                         DAX_LOCKED));
911                 entry = new_entry;
912         } else {
913                 xas_load(xas);  /* Walk the xa_state */
914         }
915
916         if (dirty)
917                 xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
918
919         if (write && shared)
920                 xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);
921
922         xas_unlock_irq(xas);
923         return entry;
924 }
925
926 static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
927                 struct address_space *mapping, void *entry)
928 {
929         unsigned long pfn, index, count, end;
930         long ret = 0;
931         struct vm_area_struct *vma;
932
933         /*
934          * A page got tagged dirty in DAX mapping? Something is seriously
935          * wrong.
936          */
937         if (WARN_ON(!xa_is_value(entry)))
938                 return -EIO;
939
940         if (unlikely(dax_is_locked(entry))) {
941                 void *old_entry = entry;
942
943                 entry = get_unlocked_entry(xas, 0);
944
945                 /* Entry got punched out / reallocated? */
946                 if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
947                         goto put_unlocked;
948                 /*
949                  * Entry got reallocated elsewhere? No need to writeback.
950                  * We have to compare pfns as we must not bail out due to
951                  * difference in lockbit or entry type.
952                  */
953                 if (dax_to_pfn(old_entry) != dax_to_pfn(entry))
954                         goto put_unlocked;
955                 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
956                                         dax_is_zero_entry(entry))) {
957                         ret = -EIO;
958                         goto put_unlocked;
959                 }
960
961                 /* Another fsync thread may have already done this entry */
962                 if (!xas_get_mark(xas, PAGECACHE_TAG_TOWRITE))
963                         goto put_unlocked;
964         }
965
966         /* Lock the entry to serialize with page faults */
967         dax_lock_entry(xas, entry);
968
969         /*
970          * We can clear the tag now but we have to be careful so that concurrent
971          * dax_writeback_one() calls for the same index cannot finish before we
972          * actually flush the caches. This is achieved as the calls will look
973          * at the entry only under the i_pages lock and once they do that
974          * they will see the entry locked and wait for it to unlock.
975          */
976         xas_clear_mark(xas, PAGECACHE_TAG_TOWRITE);
977         xas_unlock_irq(xas);
978
979         /*
980          * If dax_writeback_mapping_range() was given a wbc->range_start
981          * in the middle of a PMD, the 'index' we use needs to be
982          * aligned to the start of the PMD.
983          * This allows us to flush for PMD_SIZE and not have to worry about
984          * partial PMD writebacks.
985          */
986         pfn = dax_to_pfn(entry);
987         count = 1UL << dax_entry_order(entry);
988         index = xas->xa_index & ~(count - 1);
989         end = index + count - 1;
990
991         /* Walk all mappings of a given index of a file and writeprotect them */
992         i_mmap_lock_read(mapping);
993         vma_interval_tree_foreach(vma, &mapping->i_mmap, index, end) {
994                 pfn_mkclean_range(pfn, count, index, vma);
995                 cond_resched();
996         }
997         i_mmap_unlock_read(mapping);
998
999         dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_SIZE);
1000         /*
1001          * After we have flushed the cache, we can clear the dirty tag. There
1002          * cannot be new dirty data in the pfn after the flush has completed as
1003          * the pfn mappings are writeprotected and fault waits for mapping
1004          * entry lock.
1005          */
1006         xas_reset(xas);
1007         xas_lock_irq(xas);
1008         xas_store(xas, entry);
1009         xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
1010         dax_wake_entry(xas, entry, WAKE_NEXT);
1011
1012         trace_dax_writeback_one(mapping->host, index, count);
1013         return ret;
1014
1015  put_unlocked:
1016         put_unlocked_entry(xas, entry, WAKE_NEXT);
1017         return ret;
1018 }
1019
1020 /*
1021  * Flush the mapping to the persistent domain within the byte range of [start,
1022  * end]. This is required by data integrity operations to ensure file data is
1023  * on persistent storage prior to completion of the operation.
1024  */
1025 int dax_writeback_mapping_range(struct address_space *mapping,
1026                 struct dax_device *dax_dev, struct writeback_control *wbc)
1027 {
1028         XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
1029         struct inode *inode = mapping->host;
1030         pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
1031         void *entry;
1032         int ret = 0;
1033         unsigned int scanned = 0;
1034
1035         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
1036                 return -EIO;
1037
1038         if (mapping_empty(mapping) || wbc->sync_mode != WB_SYNC_ALL)
1039                 return 0;
1040
1041         trace_dax_writeback_range(inode, xas.xa_index, end_index);
1042
1043         tag_pages_for_writeback(mapping, xas.xa_index, end_index);
1044
1045         xas_lock_irq(&xas);
1046         xas_for_each_marked(&xas, entry, end_index, PAGECACHE_TAG_TOWRITE) {
1047                 ret = dax_writeback_one(&xas, dax_dev, mapping, entry);
1048                 if (ret < 0) {
1049                         mapping_set_error(mapping, ret);
1050                         break;
1051                 }
1052                 if (++scanned % XA_CHECK_SCHED)
1053                         continue;
1054
1055                 xas_pause(&xas);
1056                 xas_unlock_irq(&xas);
1057                 cond_resched();
1058                 xas_lock_irq(&xas);
1059         }
1060         xas_unlock_irq(&xas);
1061         trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
1062         return ret;
1063 }
1064 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
1065
1066 static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
1067                 size_t size, void **kaddr, pfn_t *pfnp)
1068 {
1069         pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
1070         int id, rc = 0;
1071         long length;
1072
1073         id = dax_read_lock();
1074         length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
1075                                    DAX_ACCESS, kaddr, pfnp);
1076         if (length < 0) {
1077                 rc = length;
1078                 goto out;
1079         }
1080         if (!pfnp)
1081                 goto out_check_addr;
1082         rc = -EINVAL;
1083         if (PFN_PHYS(length) < size)
1084                 goto out;
1085         if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
1086                 goto out;
1087         /* For larger pages we need devmap */
1088         if (length > 1 && !pfn_t_devmap(*pfnp))
1089                 goto out;
1090         rc = 0;
1091
1092 out_check_addr:
1093         if (!kaddr)
1094                 goto out;
1095         if (!*kaddr)
1096                 rc = -EFAULT;
1097 out:
1098         dax_read_unlock(id);
1099         return rc;
1100 }
1101
1102 /**
1103  * dax_iomap_copy_around - Prepare for an unaligned write to a shared/cow page
1104  * by copying the data before and after the range to be written.
1105  * @pos:        address to do copy from.
1106  * @length:     size of copy operation.
1107  * @align_size: aligned w.r.t align_size (either PMD_SIZE or PAGE_SIZE)
1108  * @srcmap:     iomap srcmap
1109  * @daddr:      destination address to copy to.
1110  *
1111  * This can be called from two places. Either during DAX write fault (page
1112  * aligned), to copy the length size data to daddr. Or, while doing normal DAX
1113  * write operation, dax_iomap_iter() might call this to do the copy of either
1114  * start or end unaligned address. In the latter case the rest of the copy of
1115  * aligned ranges is taken care by dax_iomap_iter() itself.
1116  * If the srcmap contains invalid data, such as HOLE and UNWRITTEN, zero the
1117  * area to make sure no old data remains.
1118  */
1119 static int dax_iomap_copy_around(loff_t pos, uint64_t length, size_t align_size,
1120                 const struct iomap *srcmap, void *daddr)
1121 {
1122         loff_t head_off = pos & (align_size - 1);
1123         size_t size = ALIGN(head_off + length, align_size);
1124         loff_t end = pos + length;
1125         loff_t pg_end = round_up(end, align_size);
1126         /* copy_all is usually in page fault case */
1127         bool copy_all = head_off == 0 && end == pg_end;
1128         /* zero the edges if srcmap is a HOLE or IOMAP_UNWRITTEN */
1129         bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||
1130                          srcmap->type == IOMAP_UNWRITTEN;
1131         void *saddr = 0;
1132         int ret = 0;
1133
1134         if (!zero_edge) {
1135                 ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
1136                 if (ret)
1137                         return dax_mem2blk_err(ret);
1138         }
1139
1140         if (copy_all) {
1141                 if (zero_edge)
1142                         memset(daddr, 0, size);
1143                 else
1144                         ret = copy_mc_to_kernel(daddr, saddr, length);
1145                 goto out;
1146         }
1147
1148         /* Copy the head part of the range */
1149         if (head_off) {
1150                 if (zero_edge)
1151                         memset(daddr, 0, head_off);
1152                 else {
1153                         ret = copy_mc_to_kernel(daddr, saddr, head_off);
1154                         if (ret)
1155                                 return -EIO;
1156                 }
1157         }
1158
1159         /* Copy the tail part of the range */
1160         if (end < pg_end) {
1161                 loff_t tail_off = head_off + length;
1162                 loff_t tail_len = pg_end - end;
1163
1164                 if (zero_edge)
1165                         memset(daddr + tail_off, 0, tail_len);
1166                 else {
1167                         ret = copy_mc_to_kernel(daddr + tail_off,
1168                                                 saddr + tail_off, tail_len);
1169                         if (ret)
1170                                 return -EIO;
1171                 }
1172         }
1173 out:
1174         if (zero_edge)
1175                 dax_flush(srcmap->dax_dev, daddr, size);
1176         return ret ? -EIO : 0;
1177 }
1178
1179 /*
1180  * The user has performed a load from a hole in the file.  Allocating a new
1181  * page in the file would cause excessive storage usage for workloads with
1182  * sparse files.  Instead we insert a read-only mapping of the 4k zero page.
1183  * If this page is ever written to we will re-fault and change the mapping to
1184  * point to real DAX storage instead.
1185  */
1186 static vm_fault_t dax_load_hole(struct xa_state *xas, struct vm_fault *vmf,
1187                 const struct iomap_iter *iter, void **entry)
1188 {
1189         struct inode *inode = iter->inode;
1190         unsigned long vaddr = vmf->address;
1191         pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
1192         vm_fault_t ret;
1193
1194         *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, DAX_ZERO_PAGE);
1195
1196         ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
1197         trace_dax_load_hole(inode, vmf, ret);
1198         return ret;
1199 }
1200
1201 #ifdef CONFIG_FS_DAX_PMD
1202 static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
1203                 const struct iomap_iter *iter, void **entry)
1204 {
1205         struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1206         unsigned long pmd_addr = vmf->address & PMD_MASK;
1207         struct vm_area_struct *vma = vmf->vma;
1208         struct inode *inode = mapping->host;
1209         pgtable_t pgtable = NULL;
1210         struct page *zero_page;
1211         spinlock_t *ptl;
1212         pmd_t pmd_entry;
1213         pfn_t pfn;
1214
1215         zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
1216
1217         if (unlikely(!zero_page))
1218                 goto fallback;
1219
1220         pfn = page_to_pfn_t(zero_page);
1221         *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn,
1222                                   DAX_PMD | DAX_ZERO_PAGE);
1223
1224         if (arch_needs_pgtable_deposit()) {
1225                 pgtable = pte_alloc_one(vma->vm_mm);
1226                 if (!pgtable)
1227                         return VM_FAULT_OOM;
1228         }
1229
1230         ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1231         if (!pmd_none(*(vmf->pmd))) {
1232                 spin_unlock(ptl);
1233                 goto fallback;
1234         }
1235
1236         if (pgtable) {
1237                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
1238                 mm_inc_nr_ptes(vma->vm_mm);
1239         }
1240         pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1241         pmd_entry = pmd_mkhuge(pmd_entry);
1242         set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
1243         spin_unlock(ptl);
1244         trace_dax_pmd_load_hole(inode, vmf, zero_page, *entry);
1245         return VM_FAULT_NOPAGE;
1246
1247 fallback:
1248         if (pgtable)
1249                 pte_free(vma->vm_mm, pgtable);
1250         trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, *entry);
1251         return VM_FAULT_FALLBACK;
1252 }
1253 #else
1254 static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
1255                 const struct iomap_iter *iter, void **entry)
1256 {
1257         return VM_FAULT_FALLBACK;
1258 }
1259 #endif /* CONFIG_FS_DAX_PMD */
1260
1261 static s64 dax_unshare_iter(struct iomap_iter *iter)
1262 {
1263         struct iomap *iomap = &iter->iomap;
1264         const struct iomap *srcmap = iomap_iter_srcmap(iter);
1265         loff_t pos = iter->pos;
1266         loff_t length = iomap_length(iter);
1267         int id = 0;
1268         s64 ret = 0;
1269         void *daddr = NULL, *saddr = NULL;
1270
1271         /* don't bother with blocks that are not shared to start with */
1272         if (!(iomap->flags & IOMAP_F_SHARED))
1273                 return length;
1274
1275         id = dax_read_lock();
1276         ret = dax_iomap_direct_access(iomap, pos, length, &daddr, NULL);
1277         if (ret < 0)
1278                 goto out_unlock;
1279
1280         /* zero the distance if srcmap is HOLE or UNWRITTEN */
1281         if (srcmap->flags & IOMAP_F_SHARED || srcmap->type == IOMAP_UNWRITTEN) {
1282                 memset(daddr, 0, length);
1283                 dax_flush(iomap->dax_dev, daddr, length);
1284                 ret = length;
1285                 goto out_unlock;
1286         }
1287
1288         ret = dax_iomap_direct_access(srcmap, pos, length, &saddr, NULL);
1289         if (ret < 0)
1290                 goto out_unlock;
1291
1292         if (copy_mc_to_kernel(daddr, saddr, length) == 0)
1293                 ret = length;
1294         else
1295                 ret = -EIO;
1296
1297 out_unlock:
1298         dax_read_unlock(id);
1299         return dax_mem2blk_err(ret);
1300 }
1301
1302 int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,
1303                 const struct iomap_ops *ops)
1304 {
1305         struct iomap_iter iter = {
1306                 .inode          = inode,
1307                 .pos            = pos,
1308                 .len            = len,
1309                 .flags          = IOMAP_WRITE | IOMAP_UNSHARE | IOMAP_DAX,
1310         };
1311         int ret;
1312
1313         while ((ret = iomap_iter(&iter, ops)) > 0)
1314                 iter.processed = dax_unshare_iter(&iter);
1315         return ret;
1316 }
1317 EXPORT_SYMBOL_GPL(dax_file_unshare);
1318
1319 static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
1320 {
1321         const struct iomap *iomap = &iter->iomap;
1322         const struct iomap *srcmap = iomap_iter_srcmap(iter);
1323         unsigned offset = offset_in_page(pos);
1324         pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
1325         void *kaddr;
1326         long ret;
1327
1328         ret = dax_direct_access(iomap->dax_dev, pgoff, 1, DAX_ACCESS, &kaddr,
1329                                 NULL);
1330         if (ret < 0)
1331                 return dax_mem2blk_err(ret);
1332
1333         memset(kaddr + offset, 0, size);
1334         if (iomap->flags & IOMAP_F_SHARED)
1335                 ret = dax_iomap_copy_around(pos, size, PAGE_SIZE, srcmap,
1336                                             kaddr);
1337         else
1338                 dax_flush(iomap->dax_dev, kaddr + offset, size);
1339         return ret;
1340 }
1341
1342 static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
1343 {
1344         const struct iomap *iomap = &iter->iomap;
1345         const struct iomap *srcmap = iomap_iter_srcmap(iter);
1346         loff_t pos = iter->pos;
1347         u64 length = iomap_length(iter);
1348         s64 written = 0;
1349
1350         /* already zeroed?  we're done. */
1351         if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
1352                 return length;
1353
1354         /*
1355          * invalidate the pages whose sharing state is to be changed
1356          * because of CoW.
1357          */
1358         if (iomap->flags & IOMAP_F_SHARED)
1359                 invalidate_inode_pages2_range(iter->inode->i_mapping,
1360                                               pos >> PAGE_SHIFT,
1361                                               (pos + length - 1) >> PAGE_SHIFT);
1362
1363         do {
1364                 unsigned offset = offset_in_page(pos);
1365                 unsigned size = min_t(u64, PAGE_SIZE - offset, length);
1366                 pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
1367                 long rc;
1368                 int id;
1369
1370                 id = dax_read_lock();
1371                 if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
1372                         rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
1373                 else
1374                         rc = dax_memzero(iter, pos, size);
1375                 dax_read_unlock(id);
1376
1377                 if (rc < 0)
1378                         return rc;
1379                 pos += size;
1380                 length -= size;
1381                 written += size;
1382         } while (length > 0);
1383
1384         if (did_zero)
1385                 *did_zero = true;
1386         return written;
1387 }
1388
1389 int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
1390                 const struct iomap_ops *ops)
1391 {
1392         struct iomap_iter iter = {
1393                 .inode          = inode,
1394                 .pos            = pos,
1395                 .len            = len,
1396                 .flags          = IOMAP_DAX | IOMAP_ZERO,
1397         };
1398         int ret;
1399
1400         while ((ret = iomap_iter(&iter, ops)) > 0)
1401                 iter.processed = dax_zero_iter(&iter, did_zero);
1402         return ret;
1403 }
1404 EXPORT_SYMBOL_GPL(dax_zero_range);
1405
1406 int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
1407                 const struct iomap_ops *ops)
1408 {
1409         unsigned int blocksize = i_blocksize(inode);
1410         unsigned int off = pos & (blocksize - 1);
1411
1412         /* Block boundary? Nothing to do */
1413         if (!off)
1414                 return 0;
1415         return dax_zero_range(inode, pos, blocksize - off, did_zero, ops);
1416 }
1417 EXPORT_SYMBOL_GPL(dax_truncate_page);
1418
1419 static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
1420                 struct iov_iter *iter)
1421 {
1422         const struct iomap *iomap = &iomi->iomap;
1423         const struct iomap *srcmap = iomap_iter_srcmap(iomi);
1424         loff_t length = iomap_length(iomi);
1425         loff_t pos = iomi->pos;
1426         struct dax_device *dax_dev = iomap->dax_dev;
1427         loff_t end = pos + length, done = 0;
1428         bool write = iov_iter_rw(iter) == WRITE;
1429         bool cow = write && iomap->flags & IOMAP_F_SHARED;
1430         ssize_t ret = 0;
1431         size_t xfer;
1432         int id;
1433
1434         if (!write) {
1435                 end = min(end, i_size_read(iomi->inode));
1436                 if (pos >= end)
1437                         return 0;
1438
1439                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1440                         return iov_iter_zero(min(length, end - pos), iter);
1441         }
1442
1443         /*
1444          * In DAX mode, enforce either pure overwrites of written extents, or
1445          * writes to unwritten extents as part of a copy-on-write operation.
1446          */
1447         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED &&
1448                         !(iomap->flags & IOMAP_F_SHARED)))
1449                 return -EIO;
1450
1451         /*
1452          * Write can allocate block for an area which has a hole page mapped
1453          * into page tables. We have to tear down these mappings so that data
1454          * written by write(2) is visible in mmap.
1455          */
1456         if (iomap->flags & IOMAP_F_NEW || cow) {
1457                 /*
1458                  * Filesystem allows CoW on non-shared extents. The src extents
1459                  * may have been mmapped with dirty mark before. To be able to
1460                  * invalidate its dax entries, we need to clear the dirty mark
1461                  * in advance.
1462                  */
1463                 if (cow)
1464                         __dax_clear_dirty_range(iomi->inode->i_mapping,
1465                                                 pos >> PAGE_SHIFT,
1466                                                 (end - 1) >> PAGE_SHIFT);
1467                 invalidate_inode_pages2_range(iomi->inode->i_mapping,
1468                                               pos >> PAGE_SHIFT,
1469                                               (end - 1) >> PAGE_SHIFT);
1470         }
1471
1472         id = dax_read_lock();
1473         while (pos < end) {
1474                 unsigned offset = pos & (PAGE_SIZE - 1);
1475                 const size_t size = ALIGN(length + offset, PAGE_SIZE);
1476                 pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
1477                 ssize_t map_len;
1478                 bool recovery = false;
1479                 void *kaddr;
1480
1481                 if (fatal_signal_pending(current)) {
1482                         ret = -EINTR;
1483                         break;
1484                 }
1485
1486                 map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
1487                                 DAX_ACCESS, &kaddr, NULL);
1488                 if (map_len == -EHWPOISON && iov_iter_rw(iter) == WRITE) {
1489                         map_len = dax_direct_access(dax_dev, pgoff,
1490                                         PHYS_PFN(size), DAX_RECOVERY_WRITE,
1491                                         &kaddr, NULL);
1492                         if (map_len > 0)
1493                                 recovery = true;
1494                 }
1495                 if (map_len < 0) {
1496                         ret = dax_mem2blk_err(map_len);
1497                         break;
1498                 }
1499
1500                 if (cow) {
1501                         ret = dax_iomap_copy_around(pos, length, PAGE_SIZE,
1502                                                     srcmap, kaddr);
1503                         if (ret)
1504                                 break;
1505                 }
1506
1507                 map_len = PFN_PHYS(map_len);
1508                 kaddr += offset;
1509                 map_len -= offset;
1510                 if (map_len > end - pos)
1511                         map_len = end - pos;
1512
1513                 if (recovery)
1514                         xfer = dax_recovery_write(dax_dev, pgoff, kaddr,
1515                                         map_len, iter);
1516                 else if (write)
1517                         xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr,
1518                                         map_len, iter);
1519                 else
1520                         xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr,
1521                                         map_len, iter);
1522
1523                 pos += xfer;
1524                 length -= xfer;
1525                 done += xfer;
1526
1527                 if (xfer == 0)
1528                         ret = -EFAULT;
1529                 if (xfer < map_len)
1530                         break;
1531         }
1532         dax_read_unlock(id);
1533
1534         return done ? done : ret;
1535 }
1536
1537 /**
1538  * dax_iomap_rw - Perform I/O to a DAX file
1539  * @iocb:       The control block for this I/O
1540  * @iter:       The addresses to do I/O from or to
1541  * @ops:        iomap ops passed from the file system
1542  *
1543  * This function performs read and write operations to directly mapped
1544  * persistent memory.  The callers needs to take care of read/write exclusion
1545  * and evicting any page cache pages in the region under I/O.
1546  */
1547 ssize_t
1548 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1549                 const struct iomap_ops *ops)
1550 {
1551         struct iomap_iter iomi = {
1552                 .inode          = iocb->ki_filp->f_mapping->host,
1553                 .pos            = iocb->ki_pos,
1554                 .len            = iov_iter_count(iter),
1555                 .flags          = IOMAP_DAX,
1556         };
1557         loff_t done = 0;
1558         int ret;
1559
1560         if (!iomi.len)
1561                 return 0;
1562
1563         if (iov_iter_rw(iter) == WRITE) {
1564                 lockdep_assert_held_write(&iomi.inode->i_rwsem);
1565                 iomi.flags |= IOMAP_WRITE;
1566         } else {
1567                 lockdep_assert_held(&iomi.inode->i_rwsem);
1568         }
1569
1570         if (iocb->ki_flags & IOCB_NOWAIT)
1571                 iomi.flags |= IOMAP_NOWAIT;
1572
1573         while ((ret = iomap_iter(&iomi, ops)) > 0)
1574                 iomi.processed = dax_iomap_iter(&iomi, iter);
1575
1576         done = iomi.pos - iocb->ki_pos;
1577         iocb->ki_pos = iomi.pos;
1578         return done ? done : ret;
1579 }
1580 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1581
1582 static vm_fault_t dax_fault_return(int error)
1583 {
1584         if (error == 0)
1585                 return VM_FAULT_NOPAGE;
1586         return vmf_error(error);
1587 }
1588
1589 /*
1590  * When handling a synchronous page fault and the inode need a fsync, we can
1591  * insert the PTE/PMD into page tables only after that fsync happened. Skip
1592  * insertion for now and return the pfn so that caller can insert it after the
1593  * fsync is done.
1594  */
1595 static vm_fault_t dax_fault_synchronous_pfnp(pfn_t *pfnp, pfn_t pfn)
1596 {
1597         if (WARN_ON_ONCE(!pfnp))
1598                 return VM_FAULT_SIGBUS;
1599         *pfnp = pfn;
1600         return VM_FAULT_NEEDDSYNC;
1601 }
1602
1603 static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf,
1604                 const struct iomap_iter *iter)
1605 {
1606         vm_fault_t ret;
1607         int error = 0;
1608
1609         switch (iter->iomap.type) {
1610         case IOMAP_HOLE:
1611         case IOMAP_UNWRITTEN:
1612                 clear_user_highpage(vmf->cow_page, vmf->address);
1613                 break;
1614         case IOMAP_MAPPED:
1615                 error = copy_cow_page_dax(vmf, iter);
1616                 break;
1617         default:
1618                 WARN_ON_ONCE(1);
1619                 error = -EIO;
1620                 break;
1621         }
1622
1623         if (error)
1624                 return dax_fault_return(error);
1625
1626         __SetPageUptodate(vmf->cow_page);
1627         ret = finish_fault(vmf);
1628         if (!ret)
1629                 return VM_FAULT_DONE_COW;
1630         return ret;
1631 }
1632
1633 /**
1634  * dax_fault_iter - Common actor to handle pfn insertion in PTE/PMD fault.
1635  * @vmf:        vm fault instance
1636  * @iter:       iomap iter
1637  * @pfnp:       pfn to be returned
1638  * @xas:        the dax mapping tree of a file
1639  * @entry:      an unlocked dax entry to be inserted
1640  * @pmd:        distinguish whether it is a pmd fault
1641  */
1642 static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
1643                 const struct iomap_iter *iter, pfn_t *pfnp,
1644                 struct xa_state *xas, void **entry, bool pmd)
1645 {
1646         const struct iomap *iomap = &iter->iomap;
1647         const struct iomap *srcmap = iomap_iter_srcmap(iter);
1648         size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
1649         loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
1650         bool write = iter->flags & IOMAP_WRITE;
1651         unsigned long entry_flags = pmd ? DAX_PMD : 0;
1652         int err = 0;
1653         pfn_t pfn;
1654         void *kaddr;
1655
1656         if (!pmd && vmf->cow_page)
1657                 return dax_fault_cow_page(vmf, iter);
1658
1659         /* if we are reading UNWRITTEN and HOLE, return a hole. */
1660         if (!write &&
1661             (iomap->type == IOMAP_UNWRITTEN || iomap->type == IOMAP_HOLE)) {
1662                 if (!pmd)
1663                         return dax_load_hole(xas, vmf, iter, entry);
1664                 return dax_pmd_load_hole(xas, vmf, iter, entry);
1665         }
1666
1667         if (iomap->type != IOMAP_MAPPED && !(iomap->flags & IOMAP_F_SHARED)) {
1668                 WARN_ON_ONCE(1);
1669                 return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
1670         }
1671
1672         err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn);
1673         if (err)
1674                 return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
1675
1676         *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
1677
1678         if (write && iomap->flags & IOMAP_F_SHARED) {
1679                 err = dax_iomap_copy_around(pos, size, size, srcmap, kaddr);
1680                 if (err)
1681                         return dax_fault_return(err);
1682         }
1683
1684         if (dax_fault_is_synchronous(iter, vmf->vma))
1685                 return dax_fault_synchronous_pfnp(pfnp, pfn);
1686
1687         /* insert PMD pfn */
1688         if (pmd)
1689                 return vmf_insert_pfn_pmd(vmf, pfn, write);
1690
1691         /* insert PTE pfn */
1692         if (write)
1693                 return vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
1694         return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
1695 }
1696
1697 static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
1698                                int *iomap_errp, const struct iomap_ops *ops)
1699 {
1700         struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1701         XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
1702         struct iomap_iter iter = {
1703                 .inode          = mapping->host,
1704                 .pos            = (loff_t)vmf->pgoff << PAGE_SHIFT,
1705                 .len            = PAGE_SIZE,
1706                 .flags          = IOMAP_DAX | IOMAP_FAULT,
1707         };
1708         vm_fault_t ret = 0;
1709         void *entry;
1710         int error;
1711
1712         trace_dax_pte_fault(iter.inode, vmf, ret);
1713         /*
1714          * Check whether offset isn't beyond end of file now. Caller is supposed
1715          * to hold locks serializing us with truncate / punch hole so this is
1716          * a reliable test.
1717          */
1718         if (iter.pos >= i_size_read(iter.inode)) {
1719                 ret = VM_FAULT_SIGBUS;
1720                 goto out;
1721         }
1722
1723         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
1724                 iter.flags |= IOMAP_WRITE;
1725
1726         entry = grab_mapping_entry(&xas, mapping, 0);
1727         if (xa_is_internal(entry)) {
1728                 ret = xa_to_internal(entry);
1729                 goto out;
1730         }
1731
1732         /*
1733          * It is possible, particularly with mixed reads & writes to private
1734          * mappings, that we have raced with a PMD fault that overlaps with
1735          * the PTE we need to set up.  If so just return and the fault will be
1736          * retried.
1737          */
1738         if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
1739                 ret = VM_FAULT_NOPAGE;
1740                 goto unlock_entry;
1741         }
1742
1743         while ((error = iomap_iter(&iter, ops)) > 0) {
1744                 if (WARN_ON_ONCE(iomap_length(&iter) < PAGE_SIZE)) {
1745                         iter.processed = -EIO;  /* fs corruption? */
1746                         continue;
1747                 }
1748
1749                 ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, false);
1750                 if (ret != VM_FAULT_SIGBUS &&
1751                     (iter.iomap.flags & IOMAP_F_NEW)) {
1752                         count_vm_event(PGMAJFAULT);
1753                         count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
1754                         ret |= VM_FAULT_MAJOR;
1755                 }
1756
1757                 if (!(ret & VM_FAULT_ERROR))
1758                         iter.processed = PAGE_SIZE;
1759         }
1760
1761         if (iomap_errp)
1762                 *iomap_errp = error;
1763         if (!ret && error)
1764                 ret = dax_fault_return(error);
1765
1766 unlock_entry:
1767         dax_unlock_entry(&xas, entry);
1768 out:
1769         trace_dax_pte_fault_done(iter.inode, vmf, ret);
1770         return ret;
1771 }
1772
1773 #ifdef CONFIG_FS_DAX_PMD
1774 static bool dax_fault_check_fallback(struct vm_fault *vmf, struct xa_state *xas,
1775                 pgoff_t max_pgoff)
1776 {
1777         unsigned long pmd_addr = vmf->address & PMD_MASK;
1778         bool write = vmf->flags & FAULT_FLAG_WRITE;
1779
1780         /*
1781          * Make sure that the faulting address's PMD offset (color) matches
1782          * the PMD offset from the start of the file.  This is necessary so
1783          * that a PMD range in the page table overlaps exactly with a PMD
1784          * range in the page cache.
1785          */
1786         if ((vmf->pgoff & PG_PMD_COLOUR) !=
1787             ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
1788                 return true;
1789
1790         /* Fall back to PTEs if we're going to COW */
1791         if (write && !(vmf->vma->vm_flags & VM_SHARED))
1792                 return true;
1793
1794         /* If the PMD would extend outside the VMA */
1795         if (pmd_addr < vmf->vma->vm_start)
1796                 return true;
1797         if ((pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
1798                 return true;
1799
1800         /* If the PMD would extend beyond the file size */
1801         if ((xas->xa_index | PG_PMD_COLOUR) >= max_pgoff)
1802                 return true;
1803
1804         return false;
1805 }
1806
1807 static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1808                                const struct iomap_ops *ops)
1809 {
1810         struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1811         XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER);
1812         struct iomap_iter iter = {
1813                 .inode          = mapping->host,
1814                 .len            = PMD_SIZE,
1815                 .flags          = IOMAP_DAX | IOMAP_FAULT,
1816         };
1817         vm_fault_t ret = VM_FAULT_FALLBACK;
1818         pgoff_t max_pgoff;
1819         void *entry;
1820
1821         if (vmf->flags & FAULT_FLAG_WRITE)
1822                 iter.flags |= IOMAP_WRITE;
1823
1824         /*
1825          * Check whether offset isn't beyond end of file now. Caller is
1826          * supposed to hold locks serializing us with truncate / punch hole so
1827          * this is a reliable test.
1828          */
1829         max_pgoff = DIV_ROUND_UP(i_size_read(iter.inode), PAGE_SIZE);
1830
1831         trace_dax_pmd_fault(iter.inode, vmf, max_pgoff, 0);
1832
1833         if (xas.xa_index >= max_pgoff) {
1834                 ret = VM_FAULT_SIGBUS;
1835                 goto out;
1836         }
1837
1838         if (dax_fault_check_fallback(vmf, &xas, max_pgoff))
1839                 goto fallback;
1840
1841         /*
1842          * grab_mapping_entry() will make sure we get an empty PMD entry,
1843          * a zero PMD entry or a DAX PMD.  If it can't (because a PTE
1844          * entry is already in the array, for instance), it will return
1845          * VM_FAULT_FALLBACK.
1846          */
1847         entry = grab_mapping_entry(&xas, mapping, PMD_ORDER);
1848         if (xa_is_internal(entry)) {
1849                 ret = xa_to_internal(entry);
1850                 goto fallback;
1851         }
1852
1853         /*
1854          * It is possible, particularly with mixed reads & writes to private
1855          * mappings, that we have raced with a PTE fault that overlaps with
1856          * the PMD we need to set up.  If so just return and the fault will be
1857          * retried.
1858          */
1859         if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
1860                         !pmd_devmap(*vmf->pmd)) {
1861                 ret = 0;
1862                 goto unlock_entry;
1863         }
1864
1865         iter.pos = (loff_t)xas.xa_index << PAGE_SHIFT;
1866         while (iomap_iter(&iter, ops) > 0) {
1867                 if (iomap_length(&iter) < PMD_SIZE)
1868                         continue; /* actually breaks out of the loop */
1869
1870                 ret = dax_fault_iter(vmf, &iter, pfnp, &xas, &entry, true);
1871                 if (ret != VM_FAULT_FALLBACK)
1872                         iter.processed = PMD_SIZE;
1873         }
1874
1875 unlock_entry:
1876         dax_unlock_entry(&xas, entry);
1877 fallback:
1878         if (ret == VM_FAULT_FALLBACK) {
1879                 split_huge_pmd(vmf->vma, vmf->pmd, vmf->address);
1880                 count_vm_event(THP_FAULT_FALLBACK);
1881         }
1882 out:
1883         trace_dax_pmd_fault_done(iter.inode, vmf, max_pgoff, ret);
1884         return ret;
1885 }
1886 #else
1887 static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1888                                const struct iomap_ops *ops)
1889 {
1890         return VM_FAULT_FALLBACK;
1891 }
1892 #endif /* CONFIG_FS_DAX_PMD */
1893
1894 /**
1895  * dax_iomap_fault - handle a page fault on a DAX file
1896  * @vmf: The description of the fault
1897  * @order: Order of the page to fault in
1898  * @pfnp: PFN to insert for synchronous faults if fsync is required
1899  * @iomap_errp: Storage for detailed error code in case of error
1900  * @ops: Iomap ops passed from the file system
1901  *
1902  * When a page fault occurs, filesystems may call this helper in
1903  * their fault handler for DAX files. dax_iomap_fault() assumes the caller
1904  * has done all the necessary locking for page fault to proceed
1905  * successfully.
1906  */
1907 vm_fault_t dax_iomap_fault(struct vm_fault *vmf, unsigned int order,
1908                     pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
1909 {
1910         if (order == 0)
1911                 return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
1912         else if (order == PMD_ORDER)
1913                 return dax_iomap_pmd_fault(vmf, pfnp, ops);
1914         else
1915                 return VM_FAULT_FALLBACK;
1916 }
1917 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1918
1919 /*
1920  * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
1921  * @vmf: The description of the fault
1922  * @pfn: PFN to insert
1923  * @order: Order of entry to insert.
1924  *
1925  * This function inserts a writeable PTE or PMD entry into the page tables
1926  * for an mmaped DAX file.  It also marks the page cache entry as dirty.
1927  */
1928 static vm_fault_t
1929 dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order)
1930 {
1931         struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1932         XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, order);
1933         void *entry;
1934         vm_fault_t ret;
1935
1936         xas_lock_irq(&xas);
1937         entry = get_unlocked_entry(&xas, order);
1938         /* Did we race with someone splitting entry or so? */
1939         if (!entry || dax_is_conflict(entry) ||
1940             (order == 0 && !dax_is_pte_entry(entry))) {
1941                 put_unlocked_entry(&xas, entry, WAKE_NEXT);
1942                 xas_unlock_irq(&xas);
1943                 trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
1944                                                       VM_FAULT_NOPAGE);
1945                 return VM_FAULT_NOPAGE;
1946         }
1947         xas_set_mark(&xas, PAGECACHE_TAG_DIRTY);
1948         dax_lock_entry(&xas, entry);
1949         xas_unlock_irq(&xas);
1950         if (order == 0)
1951                 ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
1952 #ifdef CONFIG_FS_DAX_PMD
1953         else if (order == PMD_ORDER)
1954                 ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE);
1955 #endif
1956         else
1957                 ret = VM_FAULT_FALLBACK;
1958         dax_unlock_entry(&xas, entry);
1959         trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret);
1960         return ret;
1961 }
1962
1963 /**
1964  * dax_finish_sync_fault - finish synchronous page fault
1965  * @vmf: The description of the fault
1966  * @order: Order of entry to be inserted
1967  * @pfn: PFN to insert
1968  *
1969  * This function ensures that the file range touched by the page fault is
1970  * stored persistently on the media and handles inserting of appropriate page
1971  * table entry.
1972  */
1973 vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, unsigned int order,
1974                 pfn_t pfn)
1975 {
1976         int err;
1977         loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
1978         size_t len = PAGE_SIZE << order;
1979
1980         err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
1981         if (err)
1982                 return VM_FAULT_SIGBUS;
1983         return dax_insert_pfn_mkwrite(vmf, pfn, order);
1984 }
1985 EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
1986
1987 static loff_t dax_range_compare_iter(struct iomap_iter *it_src,
1988                 struct iomap_iter *it_dest, u64 len, bool *same)
1989 {
1990         const struct iomap *smap = &it_src->iomap;
1991         const struct iomap *dmap = &it_dest->iomap;
1992         loff_t pos1 = it_src->pos, pos2 = it_dest->pos;
1993         void *saddr, *daddr;
1994         int id, ret;
1995
1996         len = min(len, min(smap->length, dmap->length));
1997
1998         if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE) {
1999                 *same = true;
2000                 return len;
2001         }
2002
2003         if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
2004                 *same = false;
2005                 return 0;
2006         }
2007
2008         id = dax_read_lock();
2009         ret = dax_iomap_direct_access(smap, pos1, ALIGN(pos1 + len, PAGE_SIZE),
2010                                       &saddr, NULL);
2011         if (ret < 0)
2012                 goto out_unlock;
2013
2014         ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE),
2015                                       &daddr, NULL);
2016         if (ret < 0)
2017                 goto out_unlock;
2018
2019         *same = !memcmp(saddr, daddr, len);
2020         if (!*same)
2021                 len = 0;
2022         dax_read_unlock(id);
2023         return len;
2024
2025 out_unlock:
2026         dax_read_unlock(id);
2027         return -EIO;
2028 }
2029
2030 int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
2031                 struct inode *dst, loff_t dstoff, loff_t len, bool *same,
2032                 const struct iomap_ops *ops)
2033 {
2034         struct iomap_iter src_iter = {
2035                 .inode          = src,
2036                 .pos            = srcoff,
2037                 .len            = len,
2038                 .flags          = IOMAP_DAX,
2039         };
2040         struct iomap_iter dst_iter = {
2041                 .inode          = dst,
2042                 .pos            = dstoff,
2043                 .len            = len,
2044                 .flags          = IOMAP_DAX,
2045         };
2046         int ret, compared = 0;
2047
2048         while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
2049                (ret = iomap_iter(&dst_iter, ops)) > 0) {
2050                 compared = dax_range_compare_iter(&src_iter, &dst_iter,
2051                                 min(src_iter.len, dst_iter.len), same);
2052                 if (compared < 0)
2053                         return ret;
2054                 src_iter.processed = dst_iter.processed = compared;
2055         }
2056         return ret;
2057 }
2058
2059 int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in,
2060                               struct file *file_out, loff_t pos_out,
2061                               loff_t *len, unsigned int remap_flags,
2062                               const struct iomap_ops *ops)
2063 {
2064         return __generic_remap_file_range_prep(file_in, pos_in, file_out,
2065                                                pos_out, len, remap_flags, ops);
2066 }
2067 EXPORT_SYMBOL_GPL(dax_remap_file_range_prep);