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
41static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
42
43static 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}
51fs_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
69static unsigned long dax_to_pfn(void *entry)
70{
71 return xa_to_value(entry) >> DAX_SHIFT;
72}
73
74static void *dax_make_entry(pfn_t pfn, unsigned long flags)
75{
76 return xa_mk_value(v: flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT));
77}
78
79static bool dax_is_locked(void *entry)
80{
81 return xa_to_value(entry) & DAX_LOCKED;
82}
83
84static 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
91static unsigned long dax_is_pmd_entry(void *entry)
92{
93 return xa_to_value(entry) & DAX_PMD;
94}
95
96static bool dax_is_pte_entry(void *entry)
97{
98 return !(xa_to_value(entry) & DAX_PMD);
99}
100
101static int dax_is_zero_entry(void *entry)
102{
103 return xa_to_value(entry) & DAX_ZERO_PAGE;
104}
105
106static 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 */
115static bool dax_is_conflict(void *entry)
116{
117 return entry == XA_RETRY_ENTRY;
118}
119
120/*
121 * DAX page cache entry locking
122 */
123struct exceptional_entry_key {
124 struct xarray *xa;
125 pgoff_t entry_start;
126};
127
128struct 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 */
138enum dax_wake_mode {
139 WAKE_ALL,
140 WAKE_NEXT,
141};
142
143static 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
163static 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(wq_entry: 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 */
181static 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: &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_head: wq))
196 __wake_up(wq_head: wq, TASK_NORMAL, nr: mode == WAKE_ALL ? 0 : 1, key: &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 */
209static 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, key: &ewait.key);
228 prepare_to_wait_exclusive(wq_head: wq, wq_entry: &ewait.wait,
229 TASK_UNINTERRUPTIBLE);
230 xas_unlock_irq(xas);
231 xas_reset(xas);
232 schedule();
233 finish_wait(wq_head: wq, wq_entry: &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 */
243static 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, key: &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_head: wq, wq_entry: &ewait.wait, TASK_UNINTERRUPTIBLE);
259 xas_unlock_irq(xas);
260 schedule();
261 finish_wait(wq_head: wq, wq_entry: &ewait.wait);
262}
263
264static 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 */
276static 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, mode: WAKE_NEXT);
287}
288
289/*
290 * Return: The entry stored at this location before it was locked.
291 */
292static void *dax_lock_entry(struct xa_state *xas, void *entry)
293{
294 unsigned long v = xa_to_value(entry);
295 return xas_store(xas, entry: xa_mk_value(v: v | DAX_LOCKED));
296}
297
298static 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
310static 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
323static 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 */
332static 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
346static 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 */
356static 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: 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
379static 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
402static 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_folio - Lock the DAX entry corresponding to a folio
417 * @folio: The folio whose entry we want to lock
418 *
419 * Context: Process context.
420 * Return: A cookie to pass to dax_unlock_folio() or 0 if the entry could
421 * not be locked.
422 */
423dax_entry_t dax_lock_folio(struct folio *folio)
424{
425 XA_STATE(xas, NULL, 0);
426 void *entry;
427
428 /* Ensure folio->mapping isn't freed while we look at it */
429 rcu_read_lock();
430 for (;;) {
431 struct address_space *mapping = READ_ONCE(folio->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 != folio->mapping) {
451 xas_unlock_irq(&xas);
452 continue;
453 }
454 xas_set(xas: &xas, index: folio->index);
455 entry = xas_load(&xas);
456 if (dax_is_locked(entry)) {
457 rcu_read_unlock();
458 wait_entry_unlocked(xas: &xas, entry);
459 rcu_read_lock();
460 continue;
461 }
462 dax_lock_entry(xas: &xas, entry);
463 xas_unlock_irq(&xas);
464 break;
465 }
466 rcu_read_unlock();
467 return (dax_entry_t)entry;
468}
469
470void dax_unlock_folio(struct folio *folio, dax_entry_t cookie)
471{
472 struct address_space *mapping = folio->mapping;
473 XA_STATE(xas, &mapping->i_pages, folio->index);
474
475 if (S_ISCHR(mapping->host->i_mode))
476 return;
477
478 dax_unlock_entry(xas: &xas, entry: (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 */
490dax_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: &xas, index);
505 entry = xas_load(&xas);
506 if (dax_is_locked(entry)) {
507 rcu_read_unlock();
508 wait_entry_unlocked(xas: &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: &xas, entry);
525 }
526 xas_unlock_irq(&xas);
527 break;
528 }
529 rcu_read_unlock();
530 return (dax_entry_t)entry;
531}
532
533void 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: &xas, entry: (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 */
573static 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
580retry:
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, err: -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 start: xas->xa_index & ~PG_PMD_COLOUR,
618 PG_PMD_NR, even_cows: false);
619 xas_reset(xas);
620 xas_lock_irq(xas);
621 }
622
623 dax_disassociate_entry(entry, mapping, trunc: false);
624 xas_store(xas, NULL); /* undo the PMD join */
625 dax_wake_entry(xas, entry, mode: 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: pfn_to_pfn_t(pfn: 0), flags);
639 dax_lock_entry(xas, entry);
640 if (xas_error(xas))
641 goto out_unlock;
642 mapping->nrpages += 1UL << order;
643 }
644
645out_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(v: VM_FAULT_OOM);
651 if (xas_error(xas))
652 return xa_mk_internal(v: VM_FAULT_SIGBUS);
653 return entry;
654fallback:
655 xas_unlock_irq(xas);
656 return xa_mk_internal(v: 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 */
677struct 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: start_idx, nr: end_idx - start_idx + 1, even_cows: 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: &xas, order: 0);
721 if (entry)
722 page = dax_busy_page(entry);
723 put_unlocked_entry(xas: &xas, entry, mode: 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}
737EXPORT_SYMBOL_GPL(dax_layout_busy_page_range);
738
739struct page *dax_layout_busy_page(struct address_space *mapping)
740{
741 return dax_layout_busy_page_range(mapping, 0, LLONG_MAX);
742}
743EXPORT_SYMBOL_GPL(dax_layout_busy_page);
744
745static 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: &xas, order: 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;
764out:
765 put_unlocked_entry(xas: &xas, entry, mode: WAKE_ALL);
766 xas_unlock_irq(&xas);
767 return ret;
768}
769
770static 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: &xas, order: 0);
780 xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
781 xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
782 put_unlocked_entry(xas: &xas, entry, mode: 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 */
801int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
802{
803 int ret = __dax_invalidate_entry(mapping, index, trunc: 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 */
819int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
820 pgoff_t index)
821{
822 return __dax_invalidate_entry(mapping, index, trunc: false);
823}
824
825static 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
830static int copy_cow_page_dax(struct vm_fault *vmf, const struct iomap_iter *iter)
831{
832 pgoff_t pgoff = dax_iomap_pgoff(iomap: &iter->iomap, pos: iter->pos);
833 void *vto, *kaddr;
834 long rc;
835 int id;
836
837 id = dax_read_lock();
838 rc = dax_direct_access(dax_dev: iter->iomap.dax_dev, pgoff, nr_pages: 1, mode: DAX_ACCESS,
839 kaddr: &kaddr, NULL);
840 if (rc < 0) {
841 dax_read_unlock(id);
842 return rc;
843 }
844 vto = kmap_atomic(page: vmf->cow_page);
845 copy_user_page(to: vto, from: kaddr, vaddr: vmf->address, topage: 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 */
855static 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 */
869static 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, vma: 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, start: index & ~PG_PMD_COLOUR,
887 PG_PMD_NR, even_cows: false);
888 else /* pte entry */
889 unmap_mapping_pages(mapping, start: index, nr: 1, even_cows: 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, trunc: false);
898 dax_associate_entry(entry: new_entry, mapping, vma: vmf->vma, address: 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, entry: 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
926static 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, order: 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(entry: 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, nr_pages: count, pgoff: index, vma);
995 cond_resched();
996 }
997 i_mmap_unlock_read(mapping);
998
999 dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size: 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, mode: WAKE_NEXT);
1011
1012 trace_dax_writeback_one(inode: mapping->host, pgoff: index, pglen: count);
1013 return ret;
1014
1015 put_unlocked:
1016 put_unlocked_entry(xas, entry, mode: 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 */
1025int 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, start_index: xas.xa_index, end_index);
1042
1043 tag_pages_for_writeback(mapping, start: xas.xa_index, end: 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: &xas, dax_dev, mapping, entry);
1048 if (ret < 0) {
1049 mapping_set_error(mapping, error: 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, start_index: xas.xa_index, end_index);
1062 return ret;
1063}
1064EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
1065
1066static 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(dax_dev: iomap->dax_dev, pgoff, PHYS_PFN(size),
1075 mode: DAX_ACCESS, kaddr, pfn: 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(pfn: *pfnp) & (PHYS_PFN(size)-1))
1086 goto out;
1087 /* For larger pages we need devmap */
1088 if (length > 1 && !pfn_t_devmap(pfn: *pfnp))
1089 goto out;
1090 rc = 0;
1091
1092out_check_addr:
1093 if (!kaddr)
1094 goto out;
1095 if (!*kaddr)
1096 rc = -EFAULT;
1097out:
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 */
1119static 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(iomap: srcmap, pos, size, kaddr: &saddr, NULL);
1136 if (ret)
1137 return dax_mem2blk_err(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(to: daddr, from: saddr, len: 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(to: daddr, from: saddr, len: 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(to: daddr + tail_off,
1168 from: saddr + tail_off, len: tail_len);
1169 if (ret)
1170 return -EIO;
1171 }
1172 }
1173out:
1174 if (zero_edge)
1175 dax_flush(dax_dev: srcmap->dax_dev, addr: 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 */
1186static 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(pfn: my_zero_pfn(addr: vaddr));
1192 vm_fault_t ret;
1193
1194 *entry = dax_insert_entry(xas, vmf, iter, entry: *entry, pfn, DAX_ZERO_PAGE);
1195
1196 ret = vmf_insert_mixed(vma: vmf->vma, addr: vaddr, pfn);
1197 trace_dax_load_hole(inode, vmf, result: ret);
1198 return ret;
1199}
1200
1201#ifdef CONFIG_FS_DAX_PMD
1202static 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(mm: vmf->vma->vm_mm);
1216
1217 if (unlikely(!zero_page))
1218 goto fallback;
1219
1220 pfn = page_to_pfn_t(page: zero_page);
1221 *entry = dax_insert_entry(xas, vmf, iter, entry: *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(mm: vmf->vma->vm_mm, pmd: vmf->pmd);
1231 if (!pmd_none(pmd: *(vmf->pmd))) {
1232 spin_unlock(lock: ptl);
1233 goto fallback;
1234 }
1235
1236 if (pgtable) {
1237 pgtable_trans_huge_deposit(mm: vma->vm_mm, pmdp: vmf->pmd, pgtable);
1238 mm_inc_nr_ptes(mm: vma->vm_mm);
1239 }
1240 pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1241 pmd_entry = pmd_mkhuge(pmd: pmd_entry);
1242 set_pmd_at(mm: vmf->vma->vm_mm, addr: pmd_addr, pmdp: vmf->pmd, pmd: pmd_entry);
1243 spin_unlock(lock: ptl);
1244 trace_dax_pmd_load_hole(inode, vmf, zero_page, radix_entry: *entry);
1245 return VM_FAULT_NOPAGE;
1246
1247fallback:
1248 if (pgtable)
1249 pte_free(mm: vma->vm_mm, pte_page: pgtable);
1250 trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, radix_entry: *entry);
1251 return VM_FAULT_FALLBACK;
1252}
1253#else
1254static 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
1261static s64 dax_unshare_iter(struct iomap_iter *iter)
1262{
1263 struct iomap *iomap = &iter->iomap;
1264 const struct iomap *srcmap = iomap_iter_srcmap(i: 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, size: length, kaddr: &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(dax_dev: iomap->dax_dev, addr: daddr, size: length);
1284 ret = length;
1285 goto out_unlock;
1286 }
1287
1288 ret = dax_iomap_direct_access(iomap: srcmap, pos, size: length, kaddr: &saddr, NULL);
1289 if (ret < 0)
1290 goto out_unlock;
1291
1292 if (copy_mc_to_kernel(to: daddr, from: saddr, len: length) == 0)
1293 ret = length;
1294 else
1295 ret = -EIO;
1296
1297out_unlock:
1298 dax_read_unlock(id);
1299 return dax_mem2blk_err(err: ret);
1300}
1301
1302int 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: &iter, ops)) > 0)
1314 iter.processed = dax_unshare_iter(iter: &iter);
1315 return ret;
1316}
1317EXPORT_SYMBOL_GPL(dax_file_unshare);
1318
1319static 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(i: 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(dax_dev: iomap->dax_dev, pgoff, nr_pages: 1, mode: DAX_ACCESS, kaddr: &kaddr,
1329 NULL);
1330 if (ret < 0)
1331 return dax_mem2blk_err(err: ret);
1332
1333 memset(kaddr + offset, 0, size);
1334 if (iomap->flags & IOMAP_F_SHARED)
1335 ret = dax_iomap_copy_around(pos, length: size, PAGE_SIZE, srcmap,
1336 daddr: kaddr);
1337 else
1338 dax_flush(dax_dev: iomap->dax_dev, addr: kaddr + offset, size);
1339 return ret;
1340}
1341
1342static 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(i: 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(mapping: iter->inode->i_mapping,
1360 start: pos >> PAGE_SHIFT,
1361 end: (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(dax_dev: iomap->dax_dev, pgoff, nr_pages: 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
1389int 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: &iter, ops)) > 0)
1401 iter.processed = dax_zero_iter(iter: &iter, did_zero);
1402 return ret;
1403}
1404EXPORT_SYMBOL_GPL(dax_zero_range);
1405
1406int 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(node: 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}
1417EXPORT_SYMBOL_GPL(dax_truncate_page);
1418
1419static 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(i: iomi);
1424 loff_t length = iomap_length(iter: 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(i: 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(mapping: iomi->inode->i_mapping,
1465 start: pos >> PAGE_SHIFT,
1466 end: (end - 1) >> PAGE_SHIFT);
1467 invalidate_inode_pages2_range(mapping: iomi->inode->i_mapping,
1468 start: pos >> PAGE_SHIFT,
1469 end: (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 mode: DAX_ACCESS, kaddr: &kaddr, NULL);
1488 if (map_len == -EHWPOISON && iov_iter_rw(i: iter) == WRITE) {
1489 map_len = dax_direct_access(dax_dev, pgoff,
1490 PHYS_PFN(size), mode: DAX_RECOVERY_WRITE,
1491 kaddr: &kaddr, NULL);
1492 if (map_len > 0)
1493 recovery = true;
1494 }
1495 if (map_len < 0) {
1496 ret = dax_mem2blk_err(err: map_len);
1497 break;
1498 }
1499
1500 if (cow) {
1501 ret = dax_iomap_copy_around(pos, length, PAGE_SIZE,
1502 srcmap, daddr: 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, addr: kaddr,
1515 bytes: map_len, i: iter);
1516 else if (write)
1517 xfer = dax_copy_from_iter(dax_dev, pgoff, addr: kaddr,
1518 bytes: map_len, i: iter);
1519 else
1520 xfer = dax_copy_to_iter(dax_dev, pgoff, addr: kaddr,
1521 bytes: map_len, i: 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 */
1547ssize_t
1548dax_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(i: 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(i: 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(iter: &iomi, ops)) > 0)
1574 iomi.processed = dax_iomap_iter(iomi: &iomi, iter);
1575
1576 done = iomi.pos - iocb->ki_pos;
1577 iocb->ki_pos = iomi.pos;
1578 return done ? done : ret;
1579}
1580EXPORT_SYMBOL_GPL(dax_iomap_rw);
1581
1582static vm_fault_t dax_fault_return(int error)
1583{
1584 if (error == 0)
1585 return VM_FAULT_NOPAGE;
1586 return vmf_error(err: 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 */
1595static 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
1603static 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(page: vmf->cow_page, vaddr: 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(page: 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 */
1642static 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(i: 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: &kaddr, pfnp: &pfn);
1673 if (err)
1674 return pmd ? VM_FAULT_FALLBACK : dax_fault_return(error: err);
1675
1676 *entry = dax_insert_entry(xas, vmf, iter, entry: *entry, pfn, flags: entry_flags);
1677
1678 if (write && iomap->flags & IOMAP_F_SHARED) {
1679 err = dax_iomap_copy_around(pos, length: size, align_size: size, srcmap, daddr: kaddr);
1680 if (err)
1681 return dax_fault_return(error: err);
1682 }
1683
1684 if (dax_fault_is_synchronous(iter, vma: 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(vma: vmf->vma, addr: vmf->address, pfn);
1694 return vmf_insert_mixed(vma: vmf->vma, addr: vmf->address, pfn);
1695}
1696
1697static 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(inode: iter.inode, vmf, result: 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(inode: 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: &xas, mapping, order: 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(pmd: *vmf->pmd) || pmd_devmap(pmd: *vmf->pmd)) {
1739 ret = VM_FAULT_NOPAGE;
1740 goto unlock_entry;
1741 }
1742
1743 while ((error = iomap_iter(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: &iter, pfnp, xas: &xas, entry: &entry, pmd: false);
1750 if (ret != VM_FAULT_SIGBUS &&
1751 (iter.iomap.flags & IOMAP_F_NEW)) {
1752 count_vm_event(item: PGMAJFAULT);
1753 count_memcg_event_mm(mm: vmf->vma->vm_mm, idx: 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
1766unlock_entry:
1767 dax_unlock_entry(xas: &xas, entry);
1768out:
1769 trace_dax_pte_fault_done(inode: iter.inode, vmf, result: ret);
1770 return ret;
1771}
1772
1773#ifdef CONFIG_FS_DAX_PMD
1774static 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
1807static 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(inode: iter.inode, vmf, max_pgoff, result: 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: &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: &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(pmd: *vmf->pmd) && !pmd_trans_huge(pmd: *vmf->pmd) &&
1860 !pmd_devmap(pmd: *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: &iter, ops) > 0) {
1867 if (iomap_length(iter: &iter) < PMD_SIZE)
1868 continue; /* actually breaks out of the loop */
1869
1870 ret = dax_fault_iter(vmf, iter: &iter, pfnp, xas: &xas, entry: &entry, pmd: true);
1871 if (ret != VM_FAULT_FALLBACK)
1872 iter.processed = PMD_SIZE;
1873 }
1874
1875unlock_entry:
1876 dax_unlock_entry(xas: &xas, entry);
1877fallback:
1878 if (ret == VM_FAULT_FALLBACK) {
1879 split_huge_pmd(vmf->vma, vmf->pmd, vmf->address);
1880 count_vm_event(item: THP_FAULT_FALLBACK);
1881 }
1882out:
1883 trace_dax_pmd_fault_done(inode: iter.inode, vmf, max_pgoff, result: ret);
1884 return ret;
1885}
1886#else
1887static 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 */
1907vm_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}
1917EXPORT_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 */
1928static vm_fault_t
1929dax_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: &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: &xas, entry, mode: WAKE_NEXT);
1942 xas_unlock_irq(&xas);
1943 trace_dax_insert_pfn_mkwrite_no_entry(inode: mapping->host, vmf,
1944 result: VM_FAULT_NOPAGE);
1945 return VM_FAULT_NOPAGE;
1946 }
1947 xas_set_mark(&xas, PAGECACHE_TAG_DIRTY);
1948 dax_lock_entry(xas: &xas, entry);
1949 xas_unlock_irq(&xas);
1950 if (order == 0)
1951 ret = vmf_insert_mixed_mkwrite(vma: vmf->vma, addr: vmf->address, pfn);
1952#ifdef CONFIG_FS_DAX_PMD
1953 else if (order == PMD_ORDER)
1954 ret = vmf_insert_pfn_pmd(vmf, pfn, write: FAULT_FLAG_WRITE);
1955#endif
1956 else
1957 ret = VM_FAULT_FALLBACK;
1958 dax_unlock_entry(xas: &xas, entry);
1959 trace_dax_insert_pfn_mkwrite(inode: mapping->host, vmf, result: 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 */
1973vm_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(file: vmf->vma->vm_file, start, end: start + len - 1, datasync: 1);
1981 if (err)
1982 return VM_FAULT_SIGBUS;
1983 return dax_insert_pfn_mkwrite(vmf, pfn, order);
1984}
1985EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
1986
1987static 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(iomap: smap, pos: pos1, ALIGN(pos1 + len, PAGE_SIZE),
2010 kaddr: &saddr, NULL);
2011 if (ret < 0)
2012 goto out_unlock;
2013
2014 ret = dax_iomap_direct_access(iomap: dmap, pos: pos2, ALIGN(pos2 + len, PAGE_SIZE),
2015 kaddr: &daddr, NULL);
2016 if (ret < 0)
2017 goto out_unlock;
2018
2019 *same = !memcmp(p: saddr, q: daddr, size: len);
2020 if (!*same)
2021 len = 0;
2022 dax_read_unlock(id);
2023 return len;
2024
2025out_unlock:
2026 dax_read_unlock(id);
2027 return -EIO;
2028}
2029
2030int 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(iter: &src_iter, ops)) > 0 &&
2049 (ret = iomap_iter(iter: &dst_iter, ops)) > 0) {
2050 compared = dax_range_compare_iter(it_src: &src_iter, it_dest: &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
2059int 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, dax_read_ops: ops);
2066}
2067EXPORT_SYMBOL_GPL(dax_remap_file_range_prep);
2068

source code of linux/fs/dax.c