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Linux/fs/dax.c

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  1 /*
  2  * fs/dax.c - Direct Access filesystem code
  3  * Copyright (c) 2013-2014 Intel Corporation
  4  * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
  5  * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
  6  *
  7  * This program is free software; you can redistribute it and/or modify it
  8  * under the terms and conditions of the GNU General Public License,
  9  * version 2, as published by the Free Software Foundation.
 10  *
 11  * This program is distributed in the hope it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 14  * more details.
 15  */
 16 
 17 #include <linux/atomic.h>
 18 #include <linux/blkdev.h>
 19 #include <linux/buffer_head.h>
 20 #include <linux/dax.h>
 21 #include <linux/fs.h>
 22 #include <linux/genhd.h>
 23 #include <linux/highmem.h>
 24 #include <linux/memcontrol.h>
 25 #include <linux/mm.h>
 26 #include <linux/mutex.h>
 27 #include <linux/pagevec.h>
 28 #include <linux/sched.h>
 29 #include <linux/sched/signal.h>
 30 #include <linux/uio.h>
 31 #include <linux/vmstat.h>
 32 #include <linux/pfn_t.h>
 33 #include <linux/sizes.h>
 34 #include <linux/mmu_notifier.h>
 35 #include <linux/iomap.h>
 36 #include "internal.h"
 37 
 38 #define CREATE_TRACE_POINTS
 39 #include <trace/events/fs_dax.h>
 40 
 41 /* We choose 4096 entries - same as per-zone page wait tables */
 42 #define DAX_WAIT_TABLE_BITS 12
 43 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
 44 
 45 /* The 'colour' (ie low bits) within a PMD of a page offset.  */
 46 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
 47 #define PG_PMD_NR       (PMD_SIZE >> PAGE_SHIFT)
 48 
 49 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 50 
 51 static 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 }
 59 fs_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 
 76 static unsigned long dax_radix_pfn(void *entry)
 77 {
 78         return (unsigned long)entry >> RADIX_DAX_SHIFT;
 79 }
 80 
 81 static 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 
 87 static 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 
 94 static int dax_is_pmd_entry(void *entry)
 95 {
 96         return (unsigned long)entry & RADIX_DAX_PMD;
 97 }
 98 
 99 static int dax_is_pte_entry(void *entry)
100 {
101         return !((unsigned long)entry & RADIX_DAX_PMD);
102 }
103 
104 static int dax_is_zero_entry(void *entry)
105 {
106         return (unsigned long)entry & RADIX_DAX_ZERO_PAGE;
107 }
108 
109 static 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  */
117 struct exceptional_entry_key {
118         struct address_space *mapping;
119         pgoff_t entry_start;
120 };
121 
122 struct wait_exceptional_entry_queue {
123         wait_queue_entry_t wait;
124         struct exceptional_entry_key key;
125 };
126 
127 static 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 
147 static 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  */
165 static 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  */
187 static 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  */
197 static 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  */
210 static 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  */
229 static 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 
260 static 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 
277 static 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  */
287 static 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 
297 static 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 
309 static 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 
322 static 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 
337 static 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  */
380 static 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 
386 restart:
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 
495 static 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;
514 out:
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  */
523 int 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  */
541 int 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 
547 static 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  */
581 static 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 
637 static inline unsigned long
638 pgoff_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 */
648 static 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);
696 unlock_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);
710 unlock_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 
719 static 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  */
804 int 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         }
856 out:
857         put_dax(dax_dev);
858         trace_dax_writeback_range_done(inode, start_index, end_index);
859         return (ret < 0 ? ret : 0);
860 }
861 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
862 
863 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
864 {
865         return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
866 }
867 
868 static 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;
896 out:
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  */
908 static 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);
933 out:
934         trace_dax_load_hole(inode, vmf, ret);
935         return ret;
936 }
937 
938 static 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 
951 int __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 }
983 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
984 
985 static loff_t
986 dax_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  */
1085 ssize_t
1086 dax_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 }
1113 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1114 
1115 static 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  */
1128 static 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 
1135 static 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
1310 static 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 
1346 fallback:
1347         trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret);
1348         return VM_FAULT_FALLBACK;
1349 }
1350 
1351 static 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         }
1507 out:
1508         trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
1509         return result;
1510 }
1511 #else
1512 static 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  */
1532 int 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 }
1544 EXPORT_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  */
1556 static 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  */
1609 int 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 }
1627 EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
1628 

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