GNU Linux-libre 4.9.308-gnu1
[releases.git] / fs / dax.c
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/iomap.h>
35 #include "internal.h"
36
37 /*
38  * We use lowest available bit in exceptional entry for locking, other two
39  * bits to determine entry type. In total 3 special bits.
40  */
41 #define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
42 #define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
43 #define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
44 #define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
45 #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
46 #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
47 #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
48                 RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
49                 RADIX_TREE_EXCEPTIONAL_ENTRY))
50
51 /* We choose 4096 entries - same as per-zone page wait tables */
52 #define DAX_WAIT_TABLE_BITS 12
53 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
54
55 wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
56
57 static int __init init_dax_wait_table(void)
58 {
59         int i;
60
61         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
62                 init_waitqueue_head(wait_table + i);
63         return 0;
64 }
65 fs_initcall(init_dax_wait_table);
66
67 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
68                                               pgoff_t index)
69 {
70         unsigned long hash = hash_long((unsigned long)mapping ^ index,
71                                        DAX_WAIT_TABLE_BITS);
72         return wait_table + hash;
73 }
74
75 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
76 {
77         struct request_queue *q = bdev->bd_queue;
78         long rc = -EIO;
79
80         dax->addr = ERR_PTR(-EIO);
81         if (blk_queue_enter(q, true) != 0)
82                 return rc;
83
84         rc = bdev_direct_access(bdev, dax);
85         if (rc < 0) {
86                 dax->addr = ERR_PTR(rc);
87                 blk_queue_exit(q);
88                 return rc;
89         }
90         return rc;
91 }
92
93 static void dax_unmap_atomic(struct block_device *bdev,
94                 const struct blk_dax_ctl *dax)
95 {
96         if (IS_ERR(dax->addr))
97                 return;
98         blk_queue_exit(bdev->bd_queue);
99 }
100
101 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
102 {
103         struct page *page = alloc_pages(GFP_KERNEL, 0);
104         struct blk_dax_ctl dax = {
105                 .size = PAGE_SIZE,
106                 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
107         };
108         long rc;
109
110         if (!page)
111                 return ERR_PTR(-ENOMEM);
112
113         rc = dax_map_atomic(bdev, &dax);
114         if (rc < 0)
115                 return ERR_PTR(rc);
116         memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
117         dax_unmap_atomic(bdev, &dax);
118         return page;
119 }
120
121 static bool buffer_written(struct buffer_head *bh)
122 {
123         return buffer_mapped(bh) && !buffer_unwritten(bh);
124 }
125
126 /*
127  * When ext4 encounters a hole, it returns without modifying the buffer_head
128  * which means that we can't trust b_size.  To cope with this, we set b_state
129  * to 0 before calling get_block and, if any bit is set, we know we can trust
130  * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
131  * and would save us time calling get_block repeatedly.
132  */
133 static bool buffer_size_valid(struct buffer_head *bh)
134 {
135         return bh->b_state != 0;
136 }
137
138
139 static sector_t to_sector(const struct buffer_head *bh,
140                 const struct inode *inode)
141 {
142         sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
143
144         return sector;
145 }
146
147 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
148                       loff_t start, loff_t end, get_block_t get_block,
149                       struct buffer_head *bh)
150 {
151         loff_t pos = start, max = start, bh_max = start;
152         bool hole = false;
153         struct block_device *bdev = NULL;
154         int rw = iov_iter_rw(iter), rc;
155         long map_len = 0;
156         struct blk_dax_ctl dax = {
157                 .addr = ERR_PTR(-EIO),
158         };
159         unsigned blkbits = inode->i_blkbits;
160         sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1)
161                                                                 >> blkbits;
162
163         if (rw == READ)
164                 end = min(end, i_size_read(inode));
165
166         while (pos < end) {
167                 size_t len;
168                 if (pos == max) {
169                         long page = pos >> PAGE_SHIFT;
170                         sector_t block = page << (PAGE_SHIFT - blkbits);
171                         unsigned first = pos - (block << blkbits);
172                         long size;
173
174                         if (pos == bh_max) {
175                                 bh->b_size = PAGE_ALIGN(end - pos);
176                                 bh->b_state = 0;
177                                 rc = get_block(inode, block, bh, rw == WRITE);
178                                 if (rc)
179                                         break;
180                                 if (!buffer_size_valid(bh))
181                                         bh->b_size = 1 << blkbits;
182                                 bh_max = pos - first + bh->b_size;
183                                 bdev = bh->b_bdev;
184                                 /*
185                                  * We allow uninitialized buffers for writes
186                                  * beyond EOF as those cannot race with faults
187                                  */
188                                 WARN_ON_ONCE(
189                                         (buffer_new(bh) && block < file_blks) ||
190                                         (rw == WRITE && buffer_unwritten(bh)));
191                         } else {
192                                 unsigned done = bh->b_size -
193                                                 (bh_max - (pos - first));
194                                 bh->b_blocknr += done >> blkbits;
195                                 bh->b_size -= done;
196                         }
197
198                         hole = rw == READ && !buffer_written(bh);
199                         if (hole) {
200                                 size = bh->b_size - first;
201                         } else {
202                                 dax_unmap_atomic(bdev, &dax);
203                                 dax.sector = to_sector(bh, inode);
204                                 dax.size = bh->b_size;
205                                 map_len = dax_map_atomic(bdev, &dax);
206                                 if (map_len < 0) {
207                                         rc = map_len;
208                                         break;
209                                 }
210                                 dax.addr += first;
211                                 size = map_len - first;
212                         }
213                         /*
214                          * pos + size is one past the last offset for IO,
215                          * so pos + size can overflow loff_t at extreme offsets.
216                          * Cast to u64 to catch this and get the true minimum.
217                          */
218                         max = min_t(u64, pos + size, end);
219                 }
220
221                 if (iov_iter_rw(iter) == WRITE) {
222                         len = copy_from_iter_pmem(dax.addr, max - pos, iter);
223                 } else if (!hole)
224                         len = copy_to_iter((void __force *) dax.addr, max - pos,
225                                         iter);
226                 else
227                         len = iov_iter_zero(max - pos, iter);
228
229                 if (!len) {
230                         rc = -EFAULT;
231                         break;
232                 }
233
234                 pos += len;
235                 if (!IS_ERR(dax.addr))
236                         dax.addr += len;
237         }
238
239         dax_unmap_atomic(bdev, &dax);
240
241         return (pos == start) ? rc : pos - start;
242 }
243
244 /**
245  * dax_do_io - Perform I/O to a DAX file
246  * @iocb: The control block for this I/O
247  * @inode: The file which the I/O is directed at
248  * @iter: The addresses to do I/O from or to
249  * @get_block: The filesystem method used to translate file offsets to blocks
250  * @end_io: A filesystem callback for I/O completion
251  * @flags: See below
252  *
253  * This function uses the same locking scheme as do_blockdev_direct_IO:
254  * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
255  * caller for writes.  For reads, we take and release the i_mutex ourselves.
256  * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
257  * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
258  * is in progress.
259  */
260 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
261                   struct iov_iter *iter, get_block_t get_block,
262                   dio_iodone_t end_io, int flags)
263 {
264         struct buffer_head bh;
265         ssize_t retval = -EINVAL;
266         loff_t pos = iocb->ki_pos;
267         loff_t end = pos + iov_iter_count(iter);
268
269         memset(&bh, 0, sizeof(bh));
270         bh.b_bdev = inode->i_sb->s_bdev;
271
272         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
273                 inode_lock(inode);
274
275         /* Protects against truncate */
276         if (!(flags & DIO_SKIP_DIO_COUNT))
277                 inode_dio_begin(inode);
278
279         retval = dax_io(inode, iter, pos, end, get_block, &bh);
280
281         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
282                 inode_unlock(inode);
283
284         if (end_io) {
285                 int err;
286
287                 err = end_io(iocb, pos, retval, bh.b_private);
288                 if (err)
289                         retval = err;
290         }
291
292         if (!(flags & DIO_SKIP_DIO_COUNT))
293                 inode_dio_end(inode);
294         return retval;
295 }
296 EXPORT_SYMBOL_GPL(dax_do_io);
297
298 /*
299  * DAX radix tree locking
300  */
301 struct exceptional_entry_key {
302         struct address_space *mapping;
303         unsigned long index;
304 };
305
306 struct wait_exceptional_entry_queue {
307         wait_queue_t wait;
308         struct exceptional_entry_key key;
309 };
310
311 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
312                                        int sync, void *keyp)
313 {
314         struct exceptional_entry_key *key = keyp;
315         struct wait_exceptional_entry_queue *ewait =
316                 container_of(wait, struct wait_exceptional_entry_queue, wait);
317
318         if (key->mapping != ewait->key.mapping ||
319             key->index != ewait->key.index)
320                 return 0;
321         return autoremove_wake_function(wait, mode, sync, NULL);
322 }
323
324 /*
325  * Check whether the given slot is locked. The function must be called with
326  * mapping->tree_lock held
327  */
328 static inline int slot_locked(struct address_space *mapping, void **slot)
329 {
330         unsigned long entry = (unsigned long)
331                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
332         return entry & RADIX_DAX_ENTRY_LOCK;
333 }
334
335 /*
336  * Mark the given slot is locked. The function must be called with
337  * mapping->tree_lock held
338  */
339 static inline void *lock_slot(struct address_space *mapping, void **slot)
340 {
341         unsigned long entry = (unsigned long)
342                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
343
344         entry |= RADIX_DAX_ENTRY_LOCK;
345         radix_tree_replace_slot(slot, (void *)entry);
346         return (void *)entry;
347 }
348
349 /*
350  * Mark the given slot is unlocked. The function must be called with
351  * mapping->tree_lock held
352  */
353 static inline void *unlock_slot(struct address_space *mapping, void **slot)
354 {
355         unsigned long entry = (unsigned long)
356                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
357
358         entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
359         radix_tree_replace_slot(slot, (void *)entry);
360         return (void *)entry;
361 }
362
363 /*
364  * Lookup entry in radix tree, wait for it to become unlocked if it is
365  * exceptional entry and return it. The caller must call
366  * put_unlocked_mapping_entry() when he decided not to lock the entry or
367  * put_locked_mapping_entry() when he locked the entry and now wants to
368  * unlock it.
369  *
370  * The function must be called with mapping->tree_lock held.
371  */
372 static void *get_unlocked_mapping_entry(struct address_space *mapping,
373                                         pgoff_t index, void ***slotp)
374 {
375         void *ret, **slot;
376         struct wait_exceptional_entry_queue ewait;
377         wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
378
379         init_wait(&ewait.wait);
380         ewait.wait.func = wake_exceptional_entry_func;
381         ewait.key.mapping = mapping;
382         ewait.key.index = index;
383
384         for (;;) {
385                 ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
386                                           &slot);
387                 if (!ret || !radix_tree_exceptional_entry(ret) ||
388                     !slot_locked(mapping, slot)) {
389                         if (slotp)
390                                 *slotp = slot;
391                         return ret;
392                 }
393                 prepare_to_wait_exclusive(wq, &ewait.wait,
394                                           TASK_UNINTERRUPTIBLE);
395                 spin_unlock_irq(&mapping->tree_lock);
396                 schedule();
397                 finish_wait(wq, &ewait.wait);
398                 spin_lock_irq(&mapping->tree_lock);
399         }
400 }
401
402 /*
403  * Find radix tree entry at given index. If it points to a page, return with
404  * the page locked. If it points to the exceptional entry, return with the
405  * radix tree entry locked. If the radix tree doesn't contain given index,
406  * create empty exceptional entry for the index and return with it locked.
407  *
408  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
409  * persistent memory the benefit is doubtful. We can add that later if we can
410  * show it helps.
411  */
412 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
413 {
414         void *ret, **slot;
415
416 restart:
417         spin_lock_irq(&mapping->tree_lock);
418         ret = get_unlocked_mapping_entry(mapping, index, &slot);
419         /* No entry for given index? Make sure radix tree is big enough. */
420         if (!ret) {
421                 int err;
422
423                 spin_unlock_irq(&mapping->tree_lock);
424                 err = radix_tree_preload(
425                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
426                 if (err)
427                         return ERR_PTR(err);
428                 ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
429                                RADIX_DAX_ENTRY_LOCK);
430                 spin_lock_irq(&mapping->tree_lock);
431                 err = radix_tree_insert(&mapping->page_tree, index, ret);
432                 radix_tree_preload_end();
433                 if (err) {
434                         spin_unlock_irq(&mapping->tree_lock);
435                         /* Someone already created the entry? */
436                         if (err == -EEXIST)
437                                 goto restart;
438                         return ERR_PTR(err);
439                 }
440                 /* Good, we have inserted empty locked entry into the tree. */
441                 mapping->nrexceptional++;
442                 spin_unlock_irq(&mapping->tree_lock);
443                 return ret;
444         }
445         /* Normal page in radix tree? */
446         if (!radix_tree_exceptional_entry(ret)) {
447                 struct page *page = ret;
448
449                 get_page(page);
450                 spin_unlock_irq(&mapping->tree_lock);
451                 lock_page(page);
452                 /* Page got truncated? Retry... */
453                 if (unlikely(page->mapping != mapping)) {
454                         unlock_page(page);
455                         put_page(page);
456                         goto restart;
457                 }
458                 return page;
459         }
460         ret = lock_slot(mapping, slot);
461         spin_unlock_irq(&mapping->tree_lock);
462         return ret;
463 }
464
465 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
466                                    pgoff_t index, bool wake_all)
467 {
468         wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
469
470         /*
471          * Checking for locked entry and prepare_to_wait_exclusive() happens
472          * under mapping->tree_lock, ditto for entry handling in our callers.
473          * So at this point all tasks that could have seen our entry locked
474          * must be in the waitqueue and the following check will see them.
475          */
476         if (waitqueue_active(wq)) {
477                 struct exceptional_entry_key key;
478
479                 key.mapping = mapping;
480                 key.index = index;
481                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
482         }
483 }
484
485 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
486 {
487         void *ret, **slot;
488
489         spin_lock_irq(&mapping->tree_lock);
490         ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
491         if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
492                          !slot_locked(mapping, slot))) {
493                 spin_unlock_irq(&mapping->tree_lock);
494                 return;
495         }
496         unlock_slot(mapping, slot);
497         spin_unlock_irq(&mapping->tree_lock);
498         dax_wake_mapping_entry_waiter(mapping, index, false);
499 }
500
501 static void put_locked_mapping_entry(struct address_space *mapping,
502                                      pgoff_t index, void *entry)
503 {
504         if (!radix_tree_exceptional_entry(entry)) {
505                 unlock_page(entry);
506                 put_page(entry);
507         } else {
508                 dax_unlock_mapping_entry(mapping, index);
509         }
510 }
511
512 /*
513  * Called when we are done with radix tree entry we looked up via
514  * get_unlocked_mapping_entry() and which we didn't lock in the end.
515  */
516 static void put_unlocked_mapping_entry(struct address_space *mapping,
517                                        pgoff_t index, void *entry)
518 {
519         if (!radix_tree_exceptional_entry(entry))
520                 return;
521
522         /* We have to wake up next waiter for the radix tree entry lock */
523         dax_wake_mapping_entry_waiter(mapping, index, false);
524 }
525
526 /*
527  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
528  * entry to get unlocked before deleting it.
529  */
530 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
531 {
532         void *entry;
533
534         spin_lock_irq(&mapping->tree_lock);
535         entry = get_unlocked_mapping_entry(mapping, index, NULL);
536         /*
537          * This gets called from truncate / punch_hole path. As such, the caller
538          * must hold locks protecting against concurrent modifications of the
539          * radix tree (usually fs-private i_mmap_sem for writing). Since the
540          * caller has seen exceptional entry for this index, we better find it
541          * at that index as well...
542          */
543         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
544                 spin_unlock_irq(&mapping->tree_lock);
545                 return 0;
546         }
547         radix_tree_delete(&mapping->page_tree, index);
548         mapping->nrexceptional--;
549         spin_unlock_irq(&mapping->tree_lock);
550         dax_wake_mapping_entry_waiter(mapping, index, true);
551
552         return 1;
553 }
554
555 /*
556  * The user has performed a load from a hole in the file.  Allocating
557  * a new page in the file would cause excessive storage usage for
558  * workloads with sparse files.  We allocate a page cache page instead.
559  * We'll kick it out of the page cache if it's ever written to,
560  * otherwise it will simply fall out of the page cache under memory
561  * pressure without ever having been dirtied.
562  */
563 static int dax_load_hole(struct address_space *mapping, void *entry,
564                          struct vm_fault *vmf)
565 {
566         struct page *page;
567
568         /* Hole page already exists? Return it...  */
569         if (!radix_tree_exceptional_entry(entry)) {
570                 vmf->page = entry;
571                 return VM_FAULT_LOCKED;
572         }
573
574         /* This will replace locked radix tree entry with a hole page */
575         page = find_or_create_page(mapping, vmf->pgoff,
576                                    vmf->gfp_mask | __GFP_ZERO);
577         if (!page) {
578                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
579                 return VM_FAULT_OOM;
580         }
581         vmf->page = page;
582         return VM_FAULT_LOCKED;
583 }
584
585 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
586                 struct page *to, unsigned long vaddr)
587 {
588         struct blk_dax_ctl dax = {
589                 .sector = sector,
590                 .size = size,
591         };
592         void *vto;
593
594         if (dax_map_atomic(bdev, &dax) < 0)
595                 return PTR_ERR(dax.addr);
596         vto = kmap_atomic(to);
597         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
598         kunmap_atomic(vto);
599         dax_unmap_atomic(bdev, &dax);
600         return 0;
601 }
602
603 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
604
605 static void *dax_insert_mapping_entry(struct address_space *mapping,
606                                       struct vm_fault *vmf,
607                                       void *entry, sector_t sector)
608 {
609         struct radix_tree_root *page_tree = &mapping->page_tree;
610         int error = 0;
611         bool hole_fill = false;
612         void *new_entry;
613         pgoff_t index = vmf->pgoff;
614
615         if (vmf->flags & FAULT_FLAG_WRITE)
616                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
617
618         /* Replacing hole page with block mapping? */
619         if (!radix_tree_exceptional_entry(entry)) {
620                 hole_fill = true;
621                 /*
622                  * Unmap the page now before we remove it from page cache below.
623                  * The page is locked so it cannot be faulted in again.
624                  */
625                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
626                                     PAGE_SIZE, 0);
627                 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
628                 if (error)
629                         return ERR_PTR(error);
630         }
631
632         spin_lock_irq(&mapping->tree_lock);
633         new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
634                        RADIX_DAX_ENTRY_LOCK);
635         if (hole_fill) {
636                 __delete_from_page_cache(entry, NULL);
637                 /* Drop pagecache reference */
638                 put_page(entry);
639                 error = radix_tree_insert(page_tree, index, new_entry);
640                 if (error) {
641                         new_entry = ERR_PTR(error);
642                         goto unlock;
643                 }
644                 mapping->nrexceptional++;
645         } else {
646                 void **slot;
647                 void *ret;
648
649                 ret = __radix_tree_lookup(page_tree, index, NULL, &slot);
650                 WARN_ON_ONCE(ret != entry);
651                 radix_tree_replace_slot(slot, new_entry);
652         }
653         if (vmf->flags & FAULT_FLAG_WRITE)
654                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
655  unlock:
656         spin_unlock_irq(&mapping->tree_lock);
657         if (hole_fill) {
658                 radix_tree_preload_end();
659                 /*
660                  * We don't need hole page anymore, it has been replaced with
661                  * locked radix tree entry now.
662                  */
663                 if (mapping->a_ops->freepage)
664                         mapping->a_ops->freepage(entry);
665                 unlock_page(entry);
666                 put_page(entry);
667         }
668         return new_entry;
669 }
670
671 static int dax_writeback_one(struct block_device *bdev,
672                 struct address_space *mapping, pgoff_t index, void *entry)
673 {
674         struct radix_tree_root *page_tree = &mapping->page_tree;
675         int type = RADIX_DAX_TYPE(entry);
676         struct radix_tree_node *node;
677         struct blk_dax_ctl dax;
678         void **slot;
679         int ret = 0;
680
681         spin_lock_irq(&mapping->tree_lock);
682         /*
683          * Regular page slots are stabilized by the page lock even
684          * without the tree itself locked.  These unlocked entries
685          * need verification under the tree lock.
686          */
687         if (!__radix_tree_lookup(page_tree, index, &node, &slot))
688                 goto unlock;
689         if (*slot != entry)
690                 goto unlock;
691
692         /* another fsync thread may have already written back this entry */
693         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
694                 goto unlock;
695
696         if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
697                 ret = -EIO;
698                 goto unlock;
699         }
700
701         dax.sector = RADIX_DAX_SECTOR(entry);
702         dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
703         spin_unlock_irq(&mapping->tree_lock);
704
705         /*
706          * We cannot hold tree_lock while calling dax_map_atomic() because it
707          * eventually calls cond_resched().
708          */
709         ret = dax_map_atomic(bdev, &dax);
710         if (ret < 0)
711                 return ret;
712
713         if (WARN_ON_ONCE(ret < dax.size)) {
714                 ret = -EIO;
715                 goto unmap;
716         }
717
718         wb_cache_pmem(dax.addr, dax.size);
719
720         spin_lock_irq(&mapping->tree_lock);
721         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
722         spin_unlock_irq(&mapping->tree_lock);
723  unmap:
724         dax_unmap_atomic(bdev, &dax);
725         return ret;
726
727  unlock:
728         spin_unlock_irq(&mapping->tree_lock);
729         return ret;
730 }
731
732 /*
733  * Flush the mapping to the persistent domain within the byte range of [start,
734  * end]. This is required by data integrity operations to ensure file data is
735  * on persistent storage prior to completion of the operation.
736  */
737 int dax_writeback_mapping_range(struct address_space *mapping,
738                 struct block_device *bdev, struct writeback_control *wbc)
739 {
740         struct inode *inode = mapping->host;
741         pgoff_t start_index, end_index, pmd_index;
742         pgoff_t indices[PAGEVEC_SIZE];
743         struct pagevec pvec;
744         bool done = false;
745         int i, ret = 0;
746         void *entry;
747
748         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
749                 return -EIO;
750
751         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
752                 return 0;
753
754         start_index = wbc->range_start >> PAGE_SHIFT;
755         end_index = wbc->range_end >> PAGE_SHIFT;
756         pmd_index = DAX_PMD_INDEX(start_index);
757
758         rcu_read_lock();
759         entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
760         rcu_read_unlock();
761
762         /* see if the start of our range is covered by a PMD entry */
763         if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
764                 start_index = pmd_index;
765
766         tag_pages_for_writeback(mapping, start_index, end_index);
767
768         pagevec_init(&pvec, 0);
769         while (!done) {
770                 pvec.nr = find_get_entries_tag(mapping, start_index,
771                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
772                                 pvec.pages, indices);
773
774                 if (pvec.nr == 0)
775                         break;
776
777                 for (i = 0; i < pvec.nr; i++) {
778                         if (indices[i] > end_index) {
779                                 done = true;
780                                 break;
781                         }
782
783                         ret = dax_writeback_one(bdev, mapping, indices[i],
784                                         pvec.pages[i]);
785                         if (ret < 0)
786                                 return ret;
787                 }
788                 start_index = indices[pvec.nr - 1] + 1;
789         }
790         return 0;
791 }
792 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
793
794 static int dax_insert_mapping(struct address_space *mapping,
795                 struct block_device *bdev, sector_t sector, size_t size,
796                 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
797 {
798         unsigned long vaddr = (unsigned long)vmf->virtual_address;
799         struct blk_dax_ctl dax = {
800                 .sector = sector,
801                 .size = size,
802         };
803         void *ret;
804         void *entry = *entryp;
805
806         if (dax_map_atomic(bdev, &dax) < 0)
807                 return PTR_ERR(dax.addr);
808         dax_unmap_atomic(bdev, &dax);
809
810         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
811         if (IS_ERR(ret))
812                 return PTR_ERR(ret);
813         *entryp = ret;
814
815         return vm_insert_mixed(vma, vaddr, dax.pfn);
816 }
817
818 /**
819  * dax_fault - handle a page fault on a DAX file
820  * @vma: The virtual memory area where the fault occurred
821  * @vmf: The description of the fault
822  * @get_block: The filesystem method used to translate file offsets to blocks
823  *
824  * When a page fault occurs, filesystems may call this helper in their
825  * fault handler for DAX files. dax_fault() assumes the caller has done all
826  * the necessary locking for the page fault to proceed successfully.
827  */
828 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
829                         get_block_t get_block)
830 {
831         struct file *file = vma->vm_file;
832         struct address_space *mapping = file->f_mapping;
833         struct inode *inode = mapping->host;
834         void *entry;
835         struct buffer_head bh;
836         unsigned long vaddr = (unsigned long)vmf->virtual_address;
837         unsigned blkbits = inode->i_blkbits;
838         sector_t block;
839         pgoff_t size;
840         int error;
841         int major = 0;
842
843         /*
844          * Check whether offset isn't beyond end of file now. Caller is supposed
845          * to hold locks serializing us with truncate / punch hole so this is
846          * a reliable test.
847          */
848         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
849         if (vmf->pgoff >= size)
850                 return VM_FAULT_SIGBUS;
851
852         memset(&bh, 0, sizeof(bh));
853         block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
854         bh.b_bdev = inode->i_sb->s_bdev;
855         bh.b_size = PAGE_SIZE;
856
857         entry = grab_mapping_entry(mapping, vmf->pgoff);
858         if (IS_ERR(entry)) {
859                 error = PTR_ERR(entry);
860                 goto out;
861         }
862
863         error = get_block(inode, block, &bh, 0);
864         if (!error && (bh.b_size < PAGE_SIZE))
865                 error = -EIO;           /* fs corruption? */
866         if (error)
867                 goto unlock_entry;
868
869         if (vmf->cow_page) {
870                 struct page *new_page = vmf->cow_page;
871                 if (buffer_written(&bh))
872                         error = copy_user_dax(bh.b_bdev, to_sector(&bh, inode),
873                                         bh.b_size, new_page, vaddr);
874                 else
875                         clear_user_highpage(new_page, vaddr);
876                 if (error)
877                         goto unlock_entry;
878                 if (!radix_tree_exceptional_entry(entry)) {
879                         vmf->page = entry;
880                         return VM_FAULT_LOCKED;
881                 }
882                 vmf->entry = entry;
883                 return VM_FAULT_DAX_LOCKED;
884         }
885
886         if (!buffer_mapped(&bh)) {
887                 if (vmf->flags & FAULT_FLAG_WRITE) {
888                         error = get_block(inode, block, &bh, 1);
889                         count_vm_event(PGMAJFAULT);
890                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
891                         major = VM_FAULT_MAJOR;
892                         if (!error && (bh.b_size < PAGE_SIZE))
893                                 error = -EIO;
894                         if (error)
895                                 goto unlock_entry;
896                 } else {
897                         return dax_load_hole(mapping, entry, vmf);
898                 }
899         }
900
901         /* Filesystem should not return unwritten buffers to us! */
902         WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
903         error = dax_insert_mapping(mapping, bh.b_bdev, to_sector(&bh, inode),
904                         bh.b_size, &entry, vma, vmf);
905  unlock_entry:
906         put_locked_mapping_entry(mapping, vmf->pgoff, entry);
907  out:
908         if (error == -ENOMEM)
909                 return VM_FAULT_OOM | major;
910         /* -EBUSY is fine, somebody else faulted on the same PTE */
911         if ((error < 0) && (error != -EBUSY))
912                 return VM_FAULT_SIGBUS | major;
913         return VM_FAULT_NOPAGE | major;
914 }
915 EXPORT_SYMBOL_GPL(dax_fault);
916
917 #if defined(CONFIG_TRANSPARENT_HUGEPAGE)
918 /*
919  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
920  * more often than one might expect in the below function.
921  */
922 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
923
924 static void __dax_dbg(struct buffer_head *bh, unsigned long address,
925                 const char *reason, const char *fn)
926 {
927         if (bh) {
928                 char bname[BDEVNAME_SIZE];
929                 bdevname(bh->b_bdev, bname);
930                 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
931                         "length %zd fallback: %s\n", fn, current->comm,
932                         address, bname, bh->b_state, (u64)bh->b_blocknr,
933                         bh->b_size, reason);
934         } else {
935                 pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
936                         current->comm, address, reason);
937         }
938 }
939
940 #define dax_pmd_dbg(bh, address, reason)        __dax_dbg(bh, address, reason, "dax_pmd")
941
942 /**
943  * dax_pmd_fault - handle a PMD fault on a DAX file
944  * @vma: The virtual memory area where the fault occurred
945  * @vmf: The description of the fault
946  * @get_block: The filesystem method used to translate file offsets to blocks
947  *
948  * When a page fault occurs, filesystems may call this helper in their
949  * pmd_fault handler for DAX files.
950  */
951 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
952                 pmd_t *pmd, unsigned int flags, get_block_t get_block)
953 {
954         struct file *file = vma->vm_file;
955         struct address_space *mapping = file->f_mapping;
956         struct inode *inode = mapping->host;
957         struct buffer_head bh;
958         unsigned blkbits = inode->i_blkbits;
959         unsigned long pmd_addr = address & PMD_MASK;
960         bool write = flags & FAULT_FLAG_WRITE;
961         struct block_device *bdev;
962         pgoff_t size, pgoff;
963         sector_t block;
964         int result = 0;
965         bool alloc = false;
966
967         /* dax pmd mappings require pfn_t_devmap() */
968         if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
969                 return VM_FAULT_FALLBACK;
970
971         /* Fall back to PTEs if we're going to COW */
972         if (write && !(vma->vm_flags & VM_SHARED)) {
973                 split_huge_pmd(vma, pmd, address);
974                 dax_pmd_dbg(NULL, address, "cow write");
975                 return VM_FAULT_FALLBACK;
976         }
977         /* If the PMD would extend outside the VMA */
978         if (pmd_addr < vma->vm_start) {
979                 dax_pmd_dbg(NULL, address, "vma start unaligned");
980                 return VM_FAULT_FALLBACK;
981         }
982         if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
983                 dax_pmd_dbg(NULL, address, "vma end unaligned");
984                 return VM_FAULT_FALLBACK;
985         }
986
987         pgoff = linear_page_index(vma, pmd_addr);
988         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
989         if (pgoff >= size)
990                 return VM_FAULT_SIGBUS;
991         /* If the PMD would cover blocks out of the file */
992         if ((pgoff | PG_PMD_COLOUR) >= size) {
993                 dax_pmd_dbg(NULL, address,
994                                 "offset + huge page size > file size");
995                 return VM_FAULT_FALLBACK;
996         }
997
998         memset(&bh, 0, sizeof(bh));
999         bh.b_bdev = inode->i_sb->s_bdev;
1000         block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
1001
1002         bh.b_size = PMD_SIZE;
1003
1004         if (get_block(inode, block, &bh, 0) != 0)
1005                 return VM_FAULT_SIGBUS;
1006
1007         if (!buffer_mapped(&bh) && write) {
1008                 if (get_block(inode, block, &bh, 1) != 0)
1009                         return VM_FAULT_SIGBUS;
1010                 alloc = true;
1011                 WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
1012         }
1013
1014         bdev = bh.b_bdev;
1015
1016         /*
1017          * If the filesystem isn't willing to tell us the length of a hole,
1018          * just fall back to PTEs.  Calling get_block 512 times in a loop
1019          * would be silly.
1020          */
1021         if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
1022                 dax_pmd_dbg(&bh, address, "allocated block too small");
1023                 return VM_FAULT_FALLBACK;
1024         }
1025
1026         /*
1027          * If we allocated new storage, make sure no process has any
1028          * zero pages covering this hole
1029          */
1030         if (alloc) {
1031                 loff_t lstart = pgoff << PAGE_SHIFT;
1032                 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
1033
1034                 truncate_pagecache_range(inode, lstart, lend);
1035         }
1036
1037         if (!write && !buffer_mapped(&bh)) {
1038                 spinlock_t *ptl;
1039                 pmd_t entry;
1040                 struct page *zero_page = mm_get_huge_zero_page(vma->vm_mm);
1041
1042                 if (unlikely(!zero_page)) {
1043                         dax_pmd_dbg(&bh, address, "no zero page");
1044                         goto fallback;
1045                 }
1046
1047                 ptl = pmd_lock(vma->vm_mm, pmd);
1048                 if (!pmd_none(*pmd)) {
1049                         spin_unlock(ptl);
1050                         dax_pmd_dbg(&bh, address, "pmd already present");
1051                         goto fallback;
1052                 }
1053
1054                 dev_dbg(part_to_dev(bdev->bd_part),
1055                                 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
1056                                 __func__, current->comm, address,
1057                                 (unsigned long long) to_sector(&bh, inode));
1058
1059                 entry = mk_pmd(zero_page, vma->vm_page_prot);
1060                 entry = pmd_mkhuge(entry);
1061                 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
1062                 result = VM_FAULT_NOPAGE;
1063                 spin_unlock(ptl);
1064         } else {
1065                 struct blk_dax_ctl dax = {
1066                         .sector = to_sector(&bh, inode),
1067                         .size = PMD_SIZE,
1068                 };
1069                 long length = dax_map_atomic(bdev, &dax);
1070
1071                 if (length < 0) {
1072                         dax_pmd_dbg(&bh, address, "dax-error fallback");
1073                         goto fallback;
1074                 }
1075                 if (length < PMD_SIZE) {
1076                         dax_pmd_dbg(&bh, address, "dax-length too small");
1077                         dax_unmap_atomic(bdev, &dax);
1078                         goto fallback;
1079                 }
1080                 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
1081                         dax_pmd_dbg(&bh, address, "pfn unaligned");
1082                         dax_unmap_atomic(bdev, &dax);
1083                         goto fallback;
1084                 }
1085
1086                 if (!pfn_t_devmap(dax.pfn)) {
1087                         dax_unmap_atomic(bdev, &dax);
1088                         dax_pmd_dbg(&bh, address, "pfn not in memmap");
1089                         goto fallback;
1090                 }
1091                 dax_unmap_atomic(bdev, &dax);
1092
1093                 /*
1094                  * For PTE faults we insert a radix tree entry for reads, and
1095                  * leave it clean.  Then on the first write we dirty the radix
1096                  * tree entry via the dax_pfn_mkwrite() path.  This sequence
1097                  * allows the dax_pfn_mkwrite() call to be simpler and avoid a
1098                  * call into get_block() to translate the pgoff to a sector in
1099                  * order to be able to create a new radix tree entry.
1100                  *
1101                  * The PMD path doesn't have an equivalent to
1102                  * dax_pfn_mkwrite(), though, so for a read followed by a
1103                  * write we traverse all the way through dax_pmd_fault()
1104                  * twice.  This means we can just skip inserting a radix tree
1105                  * entry completely on the initial read and just wait until
1106                  * the write to insert a dirty entry.
1107                  */
1108                 if (write) {
1109                         /*
1110                          * We should insert radix-tree entry and dirty it here.
1111                          * For now this is broken...
1112                          */
1113                 }
1114
1115                 dev_dbg(part_to_dev(bdev->bd_part),
1116                                 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
1117                                 __func__, current->comm, address,
1118                                 pfn_t_to_pfn(dax.pfn),
1119                                 (unsigned long long) dax.sector);
1120                 result |= vmf_insert_pfn_pmd(vma, address, pmd,
1121                                 dax.pfn, write);
1122         }
1123
1124  out:
1125         return result;
1126
1127  fallback:
1128         count_vm_event(THP_FAULT_FALLBACK);
1129         result = VM_FAULT_FALLBACK;
1130         goto out;
1131 }
1132 EXPORT_SYMBOL_GPL(dax_pmd_fault);
1133 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1134
1135 /**
1136  * dax_pfn_mkwrite - handle first write to DAX page
1137  * @vma: The virtual memory area where the fault occurred
1138  * @vmf: The description of the fault
1139  */
1140 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1141 {
1142         struct file *file = vma->vm_file;
1143         struct address_space *mapping = file->f_mapping;
1144         void *entry;
1145         pgoff_t index = vmf->pgoff;
1146
1147         spin_lock_irq(&mapping->tree_lock);
1148         entry = get_unlocked_mapping_entry(mapping, index, NULL);
1149         if (!entry || !radix_tree_exceptional_entry(entry))
1150                 goto out;
1151         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
1152         put_unlocked_mapping_entry(mapping, index, entry);
1153 out:
1154         spin_unlock_irq(&mapping->tree_lock);
1155         return VM_FAULT_NOPAGE;
1156 }
1157 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
1158
1159 static bool dax_range_is_aligned(struct block_device *bdev,
1160                                  unsigned int offset, unsigned int length)
1161 {
1162         unsigned short sector_size = bdev_logical_block_size(bdev);
1163
1164         if (!IS_ALIGNED(offset, sector_size))
1165                 return false;
1166         if (!IS_ALIGNED(length, sector_size))
1167                 return false;
1168
1169         return true;
1170 }
1171
1172 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
1173                 unsigned int offset, unsigned int length)
1174 {
1175         struct blk_dax_ctl dax = {
1176                 .sector         = sector,
1177                 .size           = PAGE_SIZE,
1178         };
1179
1180         if (dax_range_is_aligned(bdev, offset, length)) {
1181                 sector_t start_sector = dax.sector + (offset >> 9);
1182
1183                 return blkdev_issue_zeroout(bdev, start_sector,
1184                                 length >> 9, GFP_NOFS, true);
1185         } else {
1186                 if (dax_map_atomic(bdev, &dax) < 0)
1187                         return PTR_ERR(dax.addr);
1188                 clear_pmem(dax.addr + offset, length);
1189                 dax_unmap_atomic(bdev, &dax);
1190         }
1191         return 0;
1192 }
1193 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
1194
1195 /**
1196  * dax_zero_page_range - zero a range within a page of a DAX file
1197  * @inode: The file being truncated
1198  * @from: The file offset that is being truncated to
1199  * @length: The number of bytes to zero
1200  * @get_block: The filesystem method used to translate file offsets to blocks
1201  *
1202  * This function can be called by a filesystem when it is zeroing part of a
1203  * page in a DAX file.  This is intended for hole-punch operations.  If
1204  * you are truncating a file, the helper function dax_truncate_page() may be
1205  * more convenient.
1206  */
1207 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
1208                                                         get_block_t get_block)
1209 {
1210         struct buffer_head bh;
1211         pgoff_t index = from >> PAGE_SHIFT;
1212         unsigned offset = from & (PAGE_SIZE-1);
1213         int err;
1214
1215         /* Block boundary? Nothing to do */
1216         if (!length)
1217                 return 0;
1218         BUG_ON((offset + length) > PAGE_SIZE);
1219
1220         memset(&bh, 0, sizeof(bh));
1221         bh.b_bdev = inode->i_sb->s_bdev;
1222         bh.b_size = PAGE_SIZE;
1223         err = get_block(inode, index, &bh, 0);
1224         if (err < 0 || !buffer_written(&bh))
1225                 return err;
1226
1227         return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode),
1228                         offset, length);
1229 }
1230 EXPORT_SYMBOL_GPL(dax_zero_page_range);
1231
1232 /**
1233  * dax_truncate_page - handle a partial page being truncated in a DAX file
1234  * @inode: The file being truncated
1235  * @from: The file offset that is being truncated to
1236  * @get_block: The filesystem method used to translate file offsets to blocks
1237  *
1238  * Similar to block_truncate_page(), this function can be called by a
1239  * filesystem when it is truncating a DAX file to handle the partial page.
1240  */
1241 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1242 {
1243         unsigned length = PAGE_ALIGN(from) - from;
1244         return dax_zero_page_range(inode, from, length, get_block);
1245 }
1246 EXPORT_SYMBOL_GPL(dax_truncate_page);
1247
1248 #ifdef CONFIG_FS_IOMAP
1249 static loff_t
1250 iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
1251                 struct iomap *iomap)
1252 {
1253         struct iov_iter *iter = data;
1254         loff_t end = pos + length, done = 0;
1255         ssize_t ret = 0;
1256
1257         if (iov_iter_rw(iter) == READ) {
1258                 end = min(end, i_size_read(inode));
1259                 if (pos >= end)
1260                         return 0;
1261
1262                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1263                         return iov_iter_zero(min(length, end - pos), iter);
1264         }
1265
1266         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
1267                 return -EIO;
1268
1269         /*
1270          * Write can allocate block for an area which has a hole page mapped
1271          * into page tables. We have to tear down these mappings so that data
1272          * written by write(2) is visible in mmap.
1273          */
1274         if ((iomap->flags & IOMAP_F_NEW) && inode->i_mapping->nrpages) {
1275                 invalidate_inode_pages2_range(inode->i_mapping,
1276                                               pos >> PAGE_SHIFT,
1277                                               (end - 1) >> PAGE_SHIFT);
1278         }
1279
1280         while (pos < end) {
1281                 unsigned offset = pos & (PAGE_SIZE - 1);
1282                 struct blk_dax_ctl dax = { 0 };
1283                 ssize_t map_len;
1284
1285                 if (fatal_signal_pending(current)) {
1286                         ret = -EINTR;
1287                         break;
1288                 }
1289
1290                 dax.sector = iomap->blkno +
1291                         (((pos & PAGE_MASK) - iomap->offset) >> 9);
1292                 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
1293                 map_len = dax_map_atomic(iomap->bdev, &dax);
1294                 if (map_len < 0) {
1295                         ret = map_len;
1296                         break;
1297                 }
1298
1299                 dax.addr += offset;
1300                 map_len -= offset;
1301                 if (map_len > end - pos)
1302                         map_len = end - pos;
1303
1304                 if (iov_iter_rw(iter) == WRITE)
1305                         map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
1306                 else
1307                         map_len = copy_to_iter(dax.addr, map_len, iter);
1308                 dax_unmap_atomic(iomap->bdev, &dax);
1309                 if (map_len <= 0) {
1310                         ret = map_len ? map_len : -EFAULT;
1311                         break;
1312                 }
1313
1314                 pos += map_len;
1315                 length -= map_len;
1316                 done += map_len;
1317         }
1318
1319         return done ? done : ret;
1320 }
1321
1322 /**
1323  * iomap_dax_rw - Perform I/O to a DAX file
1324  * @iocb:       The control block for this I/O
1325  * @iter:       The addresses to do I/O from or to
1326  * @ops:        iomap ops passed from the file system
1327  *
1328  * This function performs read and write operations to directly mapped
1329  * persistent memory.  The callers needs to take care of read/write exclusion
1330  * and evicting any page cache pages in the region under I/O.
1331  */
1332 ssize_t
1333 iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
1334                 struct iomap_ops *ops)
1335 {
1336         struct address_space *mapping = iocb->ki_filp->f_mapping;
1337         struct inode *inode = mapping->host;
1338         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1339         unsigned flags = 0;
1340
1341         if (iov_iter_rw(iter) == WRITE)
1342                 flags |= IOMAP_WRITE;
1343
1344         while (iov_iter_count(iter)) {
1345                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1346                                 iter, iomap_dax_actor);
1347                 if (ret <= 0)
1348                         break;
1349                 pos += ret;
1350                 done += ret;
1351         }
1352
1353         iocb->ki_pos += done;
1354         return done ? done : ret;
1355 }
1356 EXPORT_SYMBOL_GPL(iomap_dax_rw);
1357
1358 /**
1359  * iomap_dax_fault - handle a page fault on a DAX file
1360  * @vma: The virtual memory area where the fault occurred
1361  * @vmf: The description of the fault
1362  * @ops: iomap ops passed from the file system
1363  *
1364  * When a page fault occurs, filesystems may call this helper in their fault
1365  * or mkwrite handler for DAX files. Assumes the caller has done all the
1366  * necessary locking for the page fault to proceed successfully.
1367  */
1368 int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
1369                         struct iomap_ops *ops)
1370 {
1371         struct address_space *mapping = vma->vm_file->f_mapping;
1372         struct inode *inode = mapping->host;
1373         unsigned long vaddr = (unsigned long)vmf->virtual_address;
1374         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1375         sector_t sector;
1376         struct iomap iomap = { 0 };
1377         unsigned flags = 0;
1378         int error, major = 0;
1379         void *entry;
1380
1381         /*
1382          * Check whether offset isn't beyond end of file now. Caller is supposed
1383          * to hold locks serializing us with truncate / punch hole so this is
1384          * a reliable test.
1385          */
1386         if (pos >= i_size_read(inode))
1387                 return VM_FAULT_SIGBUS;
1388
1389         entry = grab_mapping_entry(mapping, vmf->pgoff);
1390         if (IS_ERR(entry)) {
1391                 error = PTR_ERR(entry);
1392                 goto out;
1393         }
1394
1395         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
1396                 flags |= IOMAP_WRITE;
1397
1398         /*
1399          * Note that we don't bother to use iomap_apply here: DAX required
1400          * the file system block size to be equal the page size, which means
1401          * that we never have to deal with more than a single extent here.
1402          */
1403         error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1404         if (error)
1405                 goto unlock_entry;
1406         if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1407                 error = -EIO;           /* fs corruption? */
1408                 goto unlock_entry;
1409         }
1410
1411         sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
1412
1413         if (vmf->cow_page) {
1414                 switch (iomap.type) {
1415                 case IOMAP_HOLE:
1416                 case IOMAP_UNWRITTEN:
1417                         clear_user_highpage(vmf->cow_page, vaddr);
1418                         break;
1419                 case IOMAP_MAPPED:
1420                         error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
1421                                         vmf->cow_page, vaddr);
1422                         break;
1423                 default:
1424                         WARN_ON_ONCE(1);
1425                         error = -EIO;
1426                         break;
1427                 }
1428
1429                 if (error)
1430                         goto unlock_entry;
1431                 if (!radix_tree_exceptional_entry(entry)) {
1432                         vmf->page = entry;
1433                         return VM_FAULT_LOCKED;
1434                 }
1435                 vmf->entry = entry;
1436                 return VM_FAULT_DAX_LOCKED;
1437         }
1438
1439         switch (iomap.type) {
1440         case IOMAP_MAPPED:
1441                 if (iomap.flags & IOMAP_F_NEW) {
1442                         count_vm_event(PGMAJFAULT);
1443                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1444                         major = VM_FAULT_MAJOR;
1445                 }
1446                 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1447                                 PAGE_SIZE, &entry, vma, vmf);
1448                 break;
1449         case IOMAP_UNWRITTEN:
1450         case IOMAP_HOLE:
1451                 if (!(vmf->flags & FAULT_FLAG_WRITE))
1452                         return dax_load_hole(mapping, entry, vmf);
1453                 /*FALLTHRU*/
1454         default:
1455                 WARN_ON_ONCE(1);
1456                 error = -EIO;
1457                 break;
1458         }
1459
1460  unlock_entry:
1461         put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1462  out:
1463         if (error == -ENOMEM)
1464                 return VM_FAULT_OOM | major;
1465         /* -EBUSY is fine, somebody else faulted on the same PTE */
1466         if (error < 0 && error != -EBUSY)
1467                 return VM_FAULT_SIGBUS | major;
1468         return VM_FAULT_NOPAGE | major;
1469 }
1470 EXPORT_SYMBOL_GPL(iomap_dax_fault);
1471 #endif /* CONFIG_FS_IOMAP */