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