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