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1/*
2 * fs/dax.c - Direct Access filesystem code
3 * Copyright (c) 2013-2014 Intel Corporation
4 * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
5 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms and conditions of the GNU General Public License,
9 * version 2, as published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 * more details.
15 */
16
17#include <linux/atomic.h>
18#include <linux/blkdev.h>
19#include <linux/buffer_head.h>
20#include <linux/dax.h>
21#include <linux/fs.h>
22#include <linux/genhd.h>
23#include <linux/highmem.h>
24#include <linux/memcontrol.h>
25#include <linux/mm.h>
26#include <linux/mutex.h>
27#include <linux/pagevec.h>
28#include <linux/pmem.h>
29#include <linux/sched.h>
30#include <linux/uio.h>
31#include <linux/vmstat.h>
32#include <linux/pfn_t.h>
33#include <linux/sizes.h>
34
35static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
36{
37 struct request_queue *q = bdev->bd_queue;
38 long rc = -EIO;
39
40 dax->addr = (void __pmem *) ERR_PTR(-EIO);
41 if (blk_queue_enter(q, true) != 0)
42 return rc;
43
44 rc = bdev_direct_access(bdev, dax);
45 if (rc < 0) {
46 dax->addr = (void __pmem *) ERR_PTR(rc);
47 blk_queue_exit(q);
48 return rc;
49 }
50 return rc;
51}
52
53static void dax_unmap_atomic(struct block_device *bdev,
54 const struct blk_dax_ctl *dax)
55{
56 if (IS_ERR(dax->addr))
57 return;
58 blk_queue_exit(bdev->bd_queue);
59}
60
61struct page *read_dax_sector(struct block_device *bdev, sector_t n)
62{
63 struct page *page = alloc_pages(GFP_KERNEL, 0);
64 struct blk_dax_ctl dax = {
65 .size = PAGE_SIZE,
66 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
67 };
68 long rc;
69
70 if (!page)
71 return ERR_PTR(-ENOMEM);
72
73 rc = dax_map_atomic(bdev, &dax);
74 if (rc < 0)
75 return ERR_PTR(rc);
76 memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
77 dax_unmap_atomic(bdev, &dax);
78 return page;
79}
80
81/*
82 * dax_clear_sectors() is called from within transaction context from XFS,
83 * and hence this means the stack from this point must follow GFP_NOFS
84 * semantics for all operations.
85 */
86int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size)
87{
88 struct blk_dax_ctl dax = {
89 .sector = _sector,
90 .size = _size,
91 };
92
93 might_sleep();
94 do {
95 long count, sz;
96
97 count = dax_map_atomic(bdev, &dax);
98 if (count < 0)
99 return count;
100 sz = min_t(long, count, SZ_128K);
101 clear_pmem(dax.addr, sz);
102 dax.size -= sz;
103 dax.sector += sz / 512;
104 dax_unmap_atomic(bdev, &dax);
105 cond_resched();
106 } while (dax.size);
107
108 wmb_pmem();
109 return 0;
110}
111EXPORT_SYMBOL_GPL(dax_clear_sectors);
112
113/* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
114static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
115 loff_t pos, loff_t end)
116{
117 loff_t final = end - pos + first; /* The final byte of the buffer */
118
119 if (first > 0)
120 clear_pmem(addr, first);
121 if (final < size)
122 clear_pmem(addr + final, size - final);
123}
124
125static bool buffer_written(struct buffer_head *bh)
126{
127 return buffer_mapped(bh) && !buffer_unwritten(bh);
128}
129
130/*
131 * When ext4 encounters a hole, it returns without modifying the buffer_head
132 * which means that we can't trust b_size. To cope with this, we set b_state
133 * to 0 before calling get_block and, if any bit is set, we know we can trust
134 * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is
135 * and would save us time calling get_block repeatedly.
136 */
137static bool buffer_size_valid(struct buffer_head *bh)
138{
139 return bh->b_state != 0;
140}
141
142
143static sector_t to_sector(const struct buffer_head *bh,
144 const struct inode *inode)
145{
146 sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
147
148 return sector;
149}
150
151static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
152 loff_t start, loff_t end, get_block_t get_block,
153 struct buffer_head *bh)
154{
155 loff_t pos = start, max = start, bh_max = start;
156 bool hole = false, need_wmb = false;
157 struct block_device *bdev = NULL;
158 int rw = iov_iter_rw(iter), rc;
159 long map_len = 0;
160 struct blk_dax_ctl dax = {
161 .addr = (void __pmem *) ERR_PTR(-EIO),
162 };
163
164 if (rw == READ)
165 end = min(end, i_size_read(inode));
166
167 while (pos < end) {
168 size_t len;
169 if (pos == max) {
170 unsigned blkbits = inode->i_blkbits;
171 long page = pos >> PAGE_SHIFT;
172 sector_t block = page << (PAGE_SHIFT - blkbits);
173 unsigned first = pos - (block << blkbits);
174 long size;
175
176 if (pos == bh_max) {
177 bh->b_size = PAGE_ALIGN(end - pos);
178 bh->b_state = 0;
179 rc = get_block(inode, block, bh, rw == WRITE);
180 if (rc)
181 break;
182 if (!buffer_size_valid(bh))
183 bh->b_size = 1 << blkbits;
184 bh_max = pos - first + bh->b_size;
185 bdev = bh->b_bdev;
186 } else {
187 unsigned done = bh->b_size -
188 (bh_max - (pos - first));
189 bh->b_blocknr += done >> blkbits;
190 bh->b_size -= done;
191 }
192
193 hole = rw == READ && !buffer_written(bh);
194 if (hole) {
195 size = bh->b_size - first;
196 } else {
197 dax_unmap_atomic(bdev, &dax);
198 dax.sector = to_sector(bh, inode);
199 dax.size = bh->b_size;
200 map_len = dax_map_atomic(bdev, &dax);
201 if (map_len < 0) {
202 rc = map_len;
203 break;
204 }
205 if (buffer_unwritten(bh) || buffer_new(bh)) {
206 dax_new_buf(dax.addr, map_len, first,
207 pos, end);
208 need_wmb = true;
209 }
210 dax.addr += first;
211 size = map_len - first;
212 }
213 max = min(pos + size, end);
214 }
215
216 if (iov_iter_rw(iter) == WRITE) {
217 len = copy_from_iter_pmem(dax.addr, max - pos, iter);
218 need_wmb = true;
219 } else if (!hole)
220 len = copy_to_iter((void __force *) dax.addr, max - pos,
221 iter);
222 else
223 len = iov_iter_zero(max - pos, iter);
224
225 if (!len) {
226 rc = -EFAULT;
227 break;
228 }
229
230 pos += len;
231 if (!IS_ERR(dax.addr))
232 dax.addr += len;
233 }
234
235 if (need_wmb)
236 wmb_pmem();
237 dax_unmap_atomic(bdev, &dax);
238
239 return (pos == start) ? rc : pos - start;
240}
241
242/**
243 * dax_do_io - Perform I/O to a DAX file
244 * @iocb: The control block for this I/O
245 * @inode: The file which the I/O is directed at
246 * @iter: The addresses to do I/O from or to
247 * @pos: The file offset where the I/O starts
248 * @get_block: The filesystem method used to translate file offsets to blocks
249 * @end_io: A filesystem callback for I/O completion
250 * @flags: See below
251 *
252 * This function uses the same locking scheme as do_blockdev_direct_IO:
253 * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
254 * caller for writes. For reads, we take and release the i_mutex ourselves.
255 * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
256 * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
257 * is in progress.
258 */
259ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
260 struct iov_iter *iter, loff_t pos, get_block_t get_block,
261 dio_iodone_t end_io, int flags)
262{
263 struct buffer_head bh;
264 ssize_t retval = -EINVAL;
265 loff_t end = pos + iov_iter_count(iter);
266
267 memset(&bh, 0, sizeof(bh));
268 bh.b_bdev = inode->i_sb->s_bdev;
269
270 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
271 struct address_space *mapping = inode->i_mapping;
272 inode_lock(inode);
273 retval = filemap_write_and_wait_range(mapping, pos, end - 1);
274 if (retval) {
275 inode_unlock(inode);
276 goto out;
277 }
278 }
279
280 /* Protects against truncate */
281 if (!(flags & DIO_SKIP_DIO_COUNT))
282 inode_dio_begin(inode);
283
284 retval = dax_io(inode, iter, pos, end, get_block, &bh);
285
286 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
287 inode_unlock(inode);
288
289 if (end_io) {
290 int err;
291
292 err = end_io(iocb, pos, retval, bh.b_private);
293 if (err)
294 retval = err;
295 }
296
297 if (!(flags & DIO_SKIP_DIO_COUNT))
298 inode_dio_end(inode);
299 out:
300 return retval;
301}
302EXPORT_SYMBOL_GPL(dax_do_io);
303
304/*
305 * The user has performed a load from a hole in the file. Allocating
306 * a new page in the file would cause excessive storage usage for
307 * workloads with sparse files. We allocate a page cache page instead.
308 * We'll kick it out of the page cache if it's ever written to,
309 * otherwise it will simply fall out of the page cache under memory
310 * pressure without ever having been dirtied.
311 */
312static int dax_load_hole(struct address_space *mapping, struct page *page,
313 struct vm_fault *vmf)
314{
315 unsigned long size;
316 struct inode *inode = mapping->host;
317 if (!page)
318 page = find_or_create_page(mapping, vmf->pgoff,
319 GFP_KERNEL | __GFP_ZERO);
320 if (!page)
321 return VM_FAULT_OOM;
322 /* Recheck i_size under page lock to avoid truncate race */
323 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
324 if (vmf->pgoff >= size) {
325 unlock_page(page);
326 put_page(page);
327 return VM_FAULT_SIGBUS;
328 }
329
330 vmf->page = page;
331 return VM_FAULT_LOCKED;
332}
333
334static int copy_user_bh(struct page *to, struct inode *inode,
335 struct buffer_head *bh, unsigned long vaddr)
336{
337 struct blk_dax_ctl dax = {
338 .sector = to_sector(bh, inode),
339 .size = bh->b_size,
340 };
341 struct block_device *bdev = bh->b_bdev;
342 void *vto;
343
344 if (dax_map_atomic(bdev, &dax) < 0)
345 return PTR_ERR(dax.addr);
346 vto = kmap_atomic(to);
347 copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
348 kunmap_atomic(vto);
349 dax_unmap_atomic(bdev, &dax);
350 return 0;
351}
352
353#define NO_SECTOR -1
354#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
355
356static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
357 sector_t sector, bool pmd_entry, bool dirty)
358{
359 struct radix_tree_root *page_tree = &mapping->page_tree;
360 pgoff_t pmd_index = DAX_PMD_INDEX(index);
361 int type, error = 0;
362 void *entry;
363
364 WARN_ON_ONCE(pmd_entry && !dirty);
365 if (dirty)
366 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
367
368 spin_lock_irq(&mapping->tree_lock);
369
370 entry = radix_tree_lookup(page_tree, pmd_index);
371 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) {
372 index = pmd_index;
373 goto dirty;
374 }
375
376 entry = radix_tree_lookup(page_tree, index);
377 if (entry) {
378 type = RADIX_DAX_TYPE(entry);
379 if (WARN_ON_ONCE(type != RADIX_DAX_PTE &&
380 type != RADIX_DAX_PMD)) {
381 error = -EIO;
382 goto unlock;
383 }
384
385 if (!pmd_entry || type == RADIX_DAX_PMD)
386 goto dirty;
387
388 /*
389 * We only insert dirty PMD entries into the radix tree. This
390 * means we don't need to worry about removing a dirty PTE
391 * entry and inserting a clean PMD entry, thus reducing the
392 * range we would flush with a follow-up fsync/msync call.
393 */
394 radix_tree_delete(&mapping->page_tree, index);
395 mapping->nrexceptional--;
396 }
397
398 if (sector == NO_SECTOR) {
399 /*
400 * This can happen during correct operation if our pfn_mkwrite
401 * fault raced against a hole punch operation. If this
402 * happens the pte that was hole punched will have been
403 * unmapped and the radix tree entry will have been removed by
404 * the time we are called, but the call will still happen. We
405 * will return all the way up to wp_pfn_shared(), where the
406 * pte_same() check will fail, eventually causing page fault
407 * to be retried by the CPU.
408 */
409 goto unlock;
410 }
411
412 error = radix_tree_insert(page_tree, index,
413 RADIX_DAX_ENTRY(sector, pmd_entry));
414 if (error)
415 goto unlock;
416
417 mapping->nrexceptional++;
418 dirty:
419 if (dirty)
420 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
421 unlock:
422 spin_unlock_irq(&mapping->tree_lock);
423 return error;
424}
425
426static int dax_writeback_one(struct block_device *bdev,
427 struct address_space *mapping, pgoff_t index, void *entry)
428{
429 struct radix_tree_root *page_tree = &mapping->page_tree;
430 int type = RADIX_DAX_TYPE(entry);
431 struct radix_tree_node *node;
432 struct blk_dax_ctl dax;
433 void **slot;
434 int ret = 0;
435
436 spin_lock_irq(&mapping->tree_lock);
437 /*
438 * Regular page slots are stabilized by the page lock even
439 * without the tree itself locked. These unlocked entries
440 * need verification under the tree lock.
441 */
442 if (!__radix_tree_lookup(page_tree, index, &node, &slot))
443 goto unlock;
444 if (*slot != entry)
445 goto unlock;
446
447 /* another fsync thread may have already written back this entry */
448 if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
449 goto unlock;
450
451 if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
452 ret = -EIO;
453 goto unlock;
454 }
455
456 dax.sector = RADIX_DAX_SECTOR(entry);
457 dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
458 spin_unlock_irq(&mapping->tree_lock);
459
460 /*
461 * We cannot hold tree_lock while calling dax_map_atomic() because it
462 * eventually calls cond_resched().
463 */
464 ret = dax_map_atomic(bdev, &dax);
465 if (ret < 0)
466 return ret;
467
468 if (WARN_ON_ONCE(ret < dax.size)) {
469 ret = -EIO;
470 goto unmap;
471 }
472
473 wb_cache_pmem(dax.addr, dax.size);
474
475 spin_lock_irq(&mapping->tree_lock);
476 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
477 spin_unlock_irq(&mapping->tree_lock);
478 unmap:
479 dax_unmap_atomic(bdev, &dax);
480 return ret;
481
482 unlock:
483 spin_unlock_irq(&mapping->tree_lock);
484 return ret;
485}
486
487/*
488 * Flush the mapping to the persistent domain within the byte range of [start,
489 * end]. This is required by data integrity operations to ensure file data is
490 * on persistent storage prior to completion of the operation.
491 */
492int dax_writeback_mapping_range(struct address_space *mapping,
493 struct block_device *bdev, struct writeback_control *wbc)
494{
495 struct inode *inode = mapping->host;
496 pgoff_t start_index, end_index, pmd_index;
497 pgoff_t indices[PAGEVEC_SIZE];
498 struct pagevec pvec;
499 bool done = false;
500 int i, ret = 0;
501 void *entry;
502
503 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
504 return -EIO;
505
506 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
507 return 0;
508
509 start_index = wbc->range_start >> PAGE_SHIFT;
510 end_index = wbc->range_end >> PAGE_SHIFT;
511 pmd_index = DAX_PMD_INDEX(start_index);
512
513 rcu_read_lock();
514 entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
515 rcu_read_unlock();
516
517 /* see if the start of our range is covered by a PMD entry */
518 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
519 start_index = pmd_index;
520
521 tag_pages_for_writeback(mapping, start_index, end_index);
522
523 pagevec_init(&pvec, 0);
524 while (!done) {
525 pvec.nr = find_get_entries_tag(mapping, start_index,
526 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
527 pvec.pages, indices);
528
529 if (pvec.nr == 0)
530 break;
531
532 for (i = 0; i < pvec.nr; i++) {
533 if (indices[i] > end_index) {
534 done = true;
535 break;
536 }
537
538 ret = dax_writeback_one(bdev, mapping, indices[i],
539 pvec.pages[i]);
540 if (ret < 0)
541 return ret;
542 }
543 }
544 wmb_pmem();
545 return 0;
546}
547EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
548
549static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
550 struct vm_area_struct *vma, struct vm_fault *vmf)
551{
552 unsigned long vaddr = (unsigned long)vmf->virtual_address;
553 struct address_space *mapping = inode->i_mapping;
554 struct block_device *bdev = bh->b_bdev;
555 struct blk_dax_ctl dax = {
556 .sector = to_sector(bh, inode),
557 .size = bh->b_size,
558 };
559 pgoff_t size;
560 int error;
561
562 i_mmap_lock_read(mapping);
563
564 /*
565 * Check truncate didn't happen while we were allocating a block.
566 * If it did, this block may or may not be still allocated to the
567 * file. We can't tell the filesystem to free it because we can't
568 * take i_mutex here. In the worst case, the file still has blocks
569 * allocated past the end of the file.
570 */
571 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
572 if (unlikely(vmf->pgoff >= size)) {
573 error = -EIO;
574 goto out;
575 }
576
577 if (dax_map_atomic(bdev, &dax) < 0) {
578 error = PTR_ERR(dax.addr);
579 goto out;
580 }
581
582 if (buffer_unwritten(bh) || buffer_new(bh)) {
583 clear_pmem(dax.addr, PAGE_SIZE);
584 wmb_pmem();
585 }
586 dax_unmap_atomic(bdev, &dax);
587
588 error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
589 vmf->flags & FAULT_FLAG_WRITE);
590 if (error)
591 goto out;
592
593 error = vm_insert_mixed(vma, vaddr, dax.pfn);
594
595 out:
596 i_mmap_unlock_read(mapping);
597
598 return error;
599}
600
601/**
602 * __dax_fault - handle a page fault on a DAX file
603 * @vma: The virtual memory area where the fault occurred
604 * @vmf: The description of the fault
605 * @get_block: The filesystem method used to translate file offsets to blocks
606 * @complete_unwritten: The filesystem method used to convert unwritten blocks
607 * to written so the data written to them is exposed. This is required for
608 * required by write faults for filesystems that will return unwritten
609 * extent mappings from @get_block, but it is optional for reads as
610 * dax_insert_mapping() will always zero unwritten blocks. If the fs does
611 * not support unwritten extents, the it should pass NULL.
612 *
613 * When a page fault occurs, filesystems may call this helper in their
614 * fault handler for DAX files. __dax_fault() assumes the caller has done all
615 * the necessary locking for the page fault to proceed successfully.
616 */
617int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
618 get_block_t get_block, dax_iodone_t complete_unwritten)
619{
620 struct file *file = vma->vm_file;
621 struct address_space *mapping = file->f_mapping;
622 struct inode *inode = mapping->host;
623 struct page *page;
624 struct buffer_head bh;
625 unsigned long vaddr = (unsigned long)vmf->virtual_address;
626 unsigned blkbits = inode->i_blkbits;
627 sector_t block;
628 pgoff_t size;
629 int error;
630 int major = 0;
631
632 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
633 if (vmf->pgoff >= size)
634 return VM_FAULT_SIGBUS;
635
636 memset(&bh, 0, sizeof(bh));
637 block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
638 bh.b_bdev = inode->i_sb->s_bdev;
639 bh.b_size = PAGE_SIZE;
640
641 repeat:
642 page = find_get_page(mapping, vmf->pgoff);
643 if (page) {
644 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
645 put_page(page);
646 return VM_FAULT_RETRY;
647 }
648 if (unlikely(page->mapping != mapping)) {
649 unlock_page(page);
650 put_page(page);
651 goto repeat;
652 }
653 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
654 if (unlikely(vmf->pgoff >= size)) {
655 /*
656 * We have a struct page covering a hole in the file
657 * from a read fault and we've raced with a truncate
658 */
659 error = -EIO;
660 goto unlock_page;
661 }
662 }
663
664 error = get_block(inode, block, &bh, 0);
665 if (!error && (bh.b_size < PAGE_SIZE))
666 error = -EIO; /* fs corruption? */
667 if (error)
668 goto unlock_page;
669
670 if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
671 if (vmf->flags & FAULT_FLAG_WRITE) {
672 error = get_block(inode, block, &bh, 1);
673 count_vm_event(PGMAJFAULT);
674 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
675 major = VM_FAULT_MAJOR;
676 if (!error && (bh.b_size < PAGE_SIZE))
677 error = -EIO;
678 if (error)
679 goto unlock_page;
680 } else {
681 return dax_load_hole(mapping, page, vmf);
682 }
683 }
684
685 if (vmf->cow_page) {
686 struct page *new_page = vmf->cow_page;
687 if (buffer_written(&bh))
688 error = copy_user_bh(new_page, inode, &bh, vaddr);
689 else
690 clear_user_highpage(new_page, vaddr);
691 if (error)
692 goto unlock_page;
693 vmf->page = page;
694 if (!page) {
695 i_mmap_lock_read(mapping);
696 /* Check we didn't race with truncate */
697 size = (i_size_read(inode) + PAGE_SIZE - 1) >>
698 PAGE_SHIFT;
699 if (vmf->pgoff >= size) {
700 i_mmap_unlock_read(mapping);
701 error = -EIO;
702 goto out;
703 }
704 }
705 return VM_FAULT_LOCKED;
706 }
707
708 /* Check we didn't race with a read fault installing a new page */
709 if (!page && major)
710 page = find_lock_page(mapping, vmf->pgoff);
711
712 if (page) {
713 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
714 PAGE_SIZE, 0);
715 delete_from_page_cache(page);
716 unlock_page(page);
717 put_page(page);
718 page = NULL;
719 }
720
721 /*
722 * If we successfully insert the new mapping over an unwritten extent,
723 * we need to ensure we convert the unwritten extent. If there is an
724 * error inserting the mapping, the filesystem needs to leave it as
725 * unwritten to prevent exposure of the stale underlying data to
726 * userspace, but we still need to call the completion function so
727 * the private resources on the mapping buffer can be released. We
728 * indicate what the callback should do via the uptodate variable, same
729 * as for normal BH based IO completions.
730 */
731 error = dax_insert_mapping(inode, &bh, vma, vmf);
732 if (buffer_unwritten(&bh)) {
733 if (complete_unwritten)
734 complete_unwritten(&bh, !error);
735 else
736 WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
737 }
738
739 out:
740 if (error == -ENOMEM)
741 return VM_FAULT_OOM | major;
742 /* -EBUSY is fine, somebody else faulted on the same PTE */
743 if ((error < 0) && (error != -EBUSY))
744 return VM_FAULT_SIGBUS | major;
745 return VM_FAULT_NOPAGE | major;
746
747 unlock_page:
748 if (page) {
749 unlock_page(page);
750 put_page(page);
751 }
752 goto out;
753}
754EXPORT_SYMBOL(__dax_fault);
755
756/**
757 * dax_fault - handle a page fault on a DAX file
758 * @vma: The virtual memory area where the fault occurred
759 * @vmf: The description of the fault
760 * @get_block: The filesystem method used to translate file offsets to blocks
761 *
762 * When a page fault occurs, filesystems may call this helper in their
763 * fault handler for DAX files.
764 */
765int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
766 get_block_t get_block, dax_iodone_t complete_unwritten)
767{
768 int result;
769 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
770
771 if (vmf->flags & FAULT_FLAG_WRITE) {
772 sb_start_pagefault(sb);
773 file_update_time(vma->vm_file);
774 }
775 result = __dax_fault(vma, vmf, get_block, complete_unwritten);
776 if (vmf->flags & FAULT_FLAG_WRITE)
777 sb_end_pagefault(sb);
778
779 return result;
780}
781EXPORT_SYMBOL_GPL(dax_fault);
782
783#ifdef CONFIG_TRANSPARENT_HUGEPAGE
784/*
785 * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
786 * more often than one might expect in the below function.
787 */
788#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
789
790static void __dax_dbg(struct buffer_head *bh, unsigned long address,
791 const char *reason, const char *fn)
792{
793 if (bh) {
794 char bname[BDEVNAME_SIZE];
795 bdevname(bh->b_bdev, bname);
796 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
797 "length %zd fallback: %s\n", fn, current->comm,
798 address, bname, bh->b_state, (u64)bh->b_blocknr,
799 bh->b_size, reason);
800 } else {
801 pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
802 current->comm, address, reason);
803 }
804}
805
806#define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd")
807
808int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
809 pmd_t *pmd, unsigned int flags, get_block_t get_block,
810 dax_iodone_t complete_unwritten)
811{
812 struct file *file = vma->vm_file;
813 struct address_space *mapping = file->f_mapping;
814 struct inode *inode = mapping->host;
815 struct buffer_head bh;
816 unsigned blkbits = inode->i_blkbits;
817 unsigned long pmd_addr = address & PMD_MASK;
818 bool write = flags & FAULT_FLAG_WRITE;
819 struct block_device *bdev;
820 pgoff_t size, pgoff;
821 sector_t block;
822 int error, result = 0;
823 bool alloc = false;
824
825 /* dax pmd mappings require pfn_t_devmap() */
826 if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
827 return VM_FAULT_FALLBACK;
828
829 /* Fall back to PTEs if we're going to COW */
830 if (write && !(vma->vm_flags & VM_SHARED)) {
831 split_huge_pmd(vma, pmd, address);
832 dax_pmd_dbg(NULL, address, "cow write");
833 return VM_FAULT_FALLBACK;
834 }
835 /* If the PMD would extend outside the VMA */
836 if (pmd_addr < vma->vm_start) {
837 dax_pmd_dbg(NULL, address, "vma start unaligned");
838 return VM_FAULT_FALLBACK;
839 }
840 if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
841 dax_pmd_dbg(NULL, address, "vma end unaligned");
842 return VM_FAULT_FALLBACK;
843 }
844
845 pgoff = linear_page_index(vma, pmd_addr);
846 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
847 if (pgoff >= size)
848 return VM_FAULT_SIGBUS;
849 /* If the PMD would cover blocks out of the file */
850 if ((pgoff | PG_PMD_COLOUR) >= size) {
851 dax_pmd_dbg(NULL, address,
852 "offset + huge page size > file size");
853 return VM_FAULT_FALLBACK;
854 }
855
856 memset(&bh, 0, sizeof(bh));
857 bh.b_bdev = inode->i_sb->s_bdev;
858 block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
859
860 bh.b_size = PMD_SIZE;
861
862 if (get_block(inode, block, &bh, 0) != 0)
863 return VM_FAULT_SIGBUS;
864
865 if (!buffer_mapped(&bh) && write) {
866 if (get_block(inode, block, &bh, 1) != 0)
867 return VM_FAULT_SIGBUS;
868 alloc = true;
869 }
870
871 bdev = bh.b_bdev;
872
873 /*
874 * If the filesystem isn't willing to tell us the length of a hole,
875 * just fall back to PTEs. Calling get_block 512 times in a loop
876 * would be silly.
877 */
878 if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
879 dax_pmd_dbg(&bh, address, "allocated block too small");
880 return VM_FAULT_FALLBACK;
881 }
882
883 /*
884 * If we allocated new storage, make sure no process has any
885 * zero pages covering this hole
886 */
887 if (alloc) {
888 loff_t lstart = pgoff << PAGE_SHIFT;
889 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
890
891 truncate_pagecache_range(inode, lstart, lend);
892 }
893
894 i_mmap_lock_read(mapping);
895
896 /*
897 * If a truncate happened while we were allocating blocks, we may
898 * leave blocks allocated to the file that are beyond EOF. We can't
899 * take i_mutex here, so just leave them hanging; they'll be freed
900 * when the file is deleted.
901 */
902 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
903 if (pgoff >= size) {
904 result = VM_FAULT_SIGBUS;
905 goto out;
906 }
907 if ((pgoff | PG_PMD_COLOUR) >= size) {
908 dax_pmd_dbg(&bh, address,
909 "offset + huge page size > file size");
910 goto fallback;
911 }
912
913 if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
914 spinlock_t *ptl;
915 pmd_t entry;
916 struct page *zero_page = get_huge_zero_page();
917
918 if (unlikely(!zero_page)) {
919 dax_pmd_dbg(&bh, address, "no zero page");
920 goto fallback;
921 }
922
923 ptl = pmd_lock(vma->vm_mm, pmd);
924 if (!pmd_none(*pmd)) {
925 spin_unlock(ptl);
926 dax_pmd_dbg(&bh, address, "pmd already present");
927 goto fallback;
928 }
929
930 dev_dbg(part_to_dev(bdev->bd_part),
931 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
932 __func__, current->comm, address,
933 (unsigned long long) to_sector(&bh, inode));
934
935 entry = mk_pmd(zero_page, vma->vm_page_prot);
936 entry = pmd_mkhuge(entry);
937 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
938 result = VM_FAULT_NOPAGE;
939 spin_unlock(ptl);
940 } else {
941 struct blk_dax_ctl dax = {
942 .sector = to_sector(&bh, inode),
943 .size = PMD_SIZE,
944 };
945 long length = dax_map_atomic(bdev, &dax);
946
947 if (length < 0) {
948 result = VM_FAULT_SIGBUS;
949 goto out;
950 }
951 if (length < PMD_SIZE) {
952 dax_pmd_dbg(&bh, address, "dax-length too small");
953 dax_unmap_atomic(bdev, &dax);
954 goto fallback;
955 }
956 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
957 dax_pmd_dbg(&bh, address, "pfn unaligned");
958 dax_unmap_atomic(bdev, &dax);
959 goto fallback;
960 }
961
962 if (!pfn_t_devmap(dax.pfn)) {
963 dax_unmap_atomic(bdev, &dax);
964 dax_pmd_dbg(&bh, address, "pfn not in memmap");
965 goto fallback;
966 }
967
968 if (buffer_unwritten(&bh) || buffer_new(&bh)) {
969 clear_pmem(dax.addr, PMD_SIZE);
970 wmb_pmem();
971 count_vm_event(PGMAJFAULT);
972 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
973 result |= VM_FAULT_MAJOR;
974 }
975 dax_unmap_atomic(bdev, &dax);
976
977 /*
978 * For PTE faults we insert a radix tree entry for reads, and
979 * leave it clean. Then on the first write we dirty the radix
980 * tree entry via the dax_pfn_mkwrite() path. This sequence
981 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
982 * call into get_block() to translate the pgoff to a sector in
983 * order to be able to create a new radix tree entry.
984 *
985 * The PMD path doesn't have an equivalent to
986 * dax_pfn_mkwrite(), though, so for a read followed by a
987 * write we traverse all the way through __dax_pmd_fault()
988 * twice. This means we can just skip inserting a radix tree
989 * entry completely on the initial read and just wait until
990 * the write to insert a dirty entry.
991 */
992 if (write) {
993 error = dax_radix_entry(mapping, pgoff, dax.sector,
994 true, true);
995 if (error) {
996 dax_pmd_dbg(&bh, address,
997 "PMD radix insertion failed");
998 goto fallback;
999 }
1000 }
1001
1002 dev_dbg(part_to_dev(bdev->bd_part),
1003 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
1004 __func__, current->comm, address,
1005 pfn_t_to_pfn(dax.pfn),
1006 (unsigned long long) dax.sector);
1007 result |= vmf_insert_pfn_pmd(vma, address, pmd,
1008 dax.pfn, write);
1009 }
1010
1011 out:
1012 i_mmap_unlock_read(mapping);
1013
1014 if (buffer_unwritten(&bh))
1015 complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
1016
1017 return result;
1018
1019 fallback:
1020 count_vm_event(THP_FAULT_FALLBACK);
1021 result = VM_FAULT_FALLBACK;
1022 goto out;
1023}
1024EXPORT_SYMBOL_GPL(__dax_pmd_fault);
1025
1026/**
1027 * dax_pmd_fault - handle a PMD fault on a DAX file
1028 * @vma: The virtual memory area where the fault occurred
1029 * @vmf: The description of the fault
1030 * @get_block: The filesystem method used to translate file offsets to blocks
1031 *
1032 * When a page fault occurs, filesystems may call this helper in their
1033 * pmd_fault handler for DAX files.
1034 */
1035int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1036 pmd_t *pmd, unsigned int flags, get_block_t get_block,
1037 dax_iodone_t complete_unwritten)
1038{
1039 int result;
1040 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
1041
1042 if (flags & FAULT_FLAG_WRITE) {
1043 sb_start_pagefault(sb);
1044 file_update_time(vma->vm_file);
1045 }
1046 result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
1047 complete_unwritten);
1048 if (flags & FAULT_FLAG_WRITE)
1049 sb_end_pagefault(sb);
1050
1051 return result;
1052}
1053EXPORT_SYMBOL_GPL(dax_pmd_fault);
1054#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1055
1056/**
1057 * dax_pfn_mkwrite - handle first write to DAX page
1058 * @vma: The virtual memory area where the fault occurred
1059 * @vmf: The description of the fault
1060 */
1061int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1062{
1063 struct file *file = vma->vm_file;
1064 int error;
1065
1066 /*
1067 * We pass NO_SECTOR to dax_radix_entry() because we expect that a
1068 * RADIX_DAX_PTE entry already exists in the radix tree from a
1069 * previous call to __dax_fault(). We just want to look up that PTE
1070 * entry using vmf->pgoff and make sure the dirty tag is set. This
1071 * saves us from having to make a call to get_block() here to look
1072 * up the sector.
1073 */
1074 error = dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false,
1075 true);
1076
1077 if (error == -ENOMEM)
1078 return VM_FAULT_OOM;
1079 if (error)
1080 return VM_FAULT_SIGBUS;
1081 return VM_FAULT_NOPAGE;
1082}
1083EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
1084
1085/**
1086 * dax_zero_page_range - zero a range within a page of a DAX file
1087 * @inode: The file being truncated
1088 * @from: The file offset that is being truncated to
1089 * @length: The number of bytes to zero
1090 * @get_block: The filesystem method used to translate file offsets to blocks
1091 *
1092 * This function can be called by a filesystem when it is zeroing part of a
1093 * page in a DAX file. This is intended for hole-punch operations. If
1094 * you are truncating a file, the helper function dax_truncate_page() may be
1095 * more convenient.
1096 *
1097 * We work in terms of PAGE_SIZE here for commonality with
1098 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1099 * took care of disposing of the unnecessary blocks. Even if the filesystem
1100 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1101 * since the file might be mmapped.
1102 */
1103int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
1104 get_block_t get_block)
1105{
1106 struct buffer_head bh;
1107 pgoff_t index = from >> PAGE_SHIFT;
1108 unsigned offset = from & (PAGE_SIZE-1);
1109 int err;
1110
1111 /* Block boundary? Nothing to do */
1112 if (!length)
1113 return 0;
1114 BUG_ON((offset + length) > PAGE_SIZE);
1115
1116 memset(&bh, 0, sizeof(bh));
1117 bh.b_bdev = inode->i_sb->s_bdev;
1118 bh.b_size = PAGE_SIZE;
1119 err = get_block(inode, index, &bh, 0);
1120 if (err < 0)
1121 return err;
1122 if (buffer_written(&bh)) {
1123 struct block_device *bdev = bh.b_bdev;
1124 struct blk_dax_ctl dax = {
1125 .sector = to_sector(&bh, inode),
1126 .size = PAGE_SIZE,
1127 };
1128
1129 if (dax_map_atomic(bdev, &dax) < 0)
1130 return PTR_ERR(dax.addr);
1131 clear_pmem(dax.addr + offset, length);
1132 wmb_pmem();
1133 dax_unmap_atomic(bdev, &dax);
1134 }
1135
1136 return 0;
1137}
1138EXPORT_SYMBOL_GPL(dax_zero_page_range);
1139
1140/**
1141 * dax_truncate_page - handle a partial page being truncated in a DAX file
1142 * @inode: The file being truncated
1143 * @from: The file offset that is being truncated to
1144 * @get_block: The filesystem method used to translate file offsets to blocks
1145 *
1146 * Similar to block_truncate_page(), this function can be called by a
1147 * filesystem when it is truncating a DAX file to handle the partial page.
1148 *
1149 * We work in terms of PAGE_SIZE here for commonality with
1150 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1151 * took care of disposing of the unnecessary blocks. Even if the filesystem
1152 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1153 * since the file might be mmapped.
1154 */
1155int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1156{
1157 unsigned length = PAGE_ALIGN(from) - from;
1158 return dax_zero_page_range(inode, from, length, get_block);
1159}
1160EXPORT_SYMBOL_GPL(dax_truncate_page);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/dax.c - Direct Access filesystem code
4 * Copyright (c) 2013-2014 Intel Corporation
5 * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
6 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
7 */
8
9#include <linux/atomic.h>
10#include <linux/blkdev.h>
11#include <linux/buffer_head.h>
12#include <linux/dax.h>
13#include <linux/fs.h>
14#include <linux/genhd.h>
15#include <linux/highmem.h>
16#include <linux/memcontrol.h>
17#include <linux/mm.h>
18#include <linux/mutex.h>
19#include <linux/pagevec.h>
20#include <linux/sched.h>
21#include <linux/sched/signal.h>
22#include <linux/uio.h>
23#include <linux/vmstat.h>
24#include <linux/pfn_t.h>
25#include <linux/sizes.h>
26#include <linux/mmu_notifier.h>
27#include <linux/iomap.h>
28#include <asm/pgalloc.h>
29
30#define CREATE_TRACE_POINTS
31#include <trace/events/fs_dax.h>
32
33static inline unsigned int pe_order(enum page_entry_size pe_size)
34{
35 if (pe_size == PE_SIZE_PTE)
36 return PAGE_SHIFT - PAGE_SHIFT;
37 if (pe_size == PE_SIZE_PMD)
38 return PMD_SHIFT - PAGE_SHIFT;
39 if (pe_size == PE_SIZE_PUD)
40 return PUD_SHIFT - PAGE_SHIFT;
41 return ~0;
42}
43
44/* We choose 4096 entries - same as per-zone page wait tables */
45#define DAX_WAIT_TABLE_BITS 12
46#define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
47
48/* The 'colour' (ie low bits) within a PMD of a page offset. */
49#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
50#define PG_PMD_NR (PMD_SIZE >> PAGE_SHIFT)
51
52/* The order of a PMD entry */
53#define PMD_ORDER (PMD_SHIFT - PAGE_SHIFT)
54
55static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
56
57static int __init init_dax_wait_table(void)
58{
59 int i;
60
61 for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
62 init_waitqueue_head(wait_table + i);
63 return 0;
64}
65fs_initcall(init_dax_wait_table);
66
67/*
68 * DAX pagecache entries use XArray value entries so they can't be mistaken
69 * for pages. We use one bit for locking, one bit for the entry size (PMD)
70 * and two more to tell us if the entry is a zero page or an empty entry that
71 * is just used for locking. In total four special bits.
72 *
73 * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE
74 * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem
75 * block allocation.
76 */
77#define DAX_SHIFT (4)
78#define DAX_LOCKED (1UL << 0)
79#define DAX_PMD (1UL << 1)
80#define DAX_ZERO_PAGE (1UL << 2)
81#define DAX_EMPTY (1UL << 3)
82
83static unsigned long dax_to_pfn(void *entry)
84{
85 return xa_to_value(entry) >> DAX_SHIFT;
86}
87
88static void *dax_make_entry(pfn_t pfn, unsigned long flags)
89{
90 return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT));
91}
92
93static bool dax_is_locked(void *entry)
94{
95 return xa_to_value(entry) & DAX_LOCKED;
96}
97
98static unsigned int dax_entry_order(void *entry)
99{
100 if (xa_to_value(entry) & DAX_PMD)
101 return PMD_ORDER;
102 return 0;
103}
104
105static unsigned long dax_is_pmd_entry(void *entry)
106{
107 return xa_to_value(entry) & DAX_PMD;
108}
109
110static bool dax_is_pte_entry(void *entry)
111{
112 return !(xa_to_value(entry) & DAX_PMD);
113}
114
115static int dax_is_zero_entry(void *entry)
116{
117 return xa_to_value(entry) & DAX_ZERO_PAGE;
118}
119
120static int dax_is_empty_entry(void *entry)
121{
122 return xa_to_value(entry) & DAX_EMPTY;
123}
124
125/*
126 * true if the entry that was found is of a smaller order than the entry
127 * we were looking for
128 */
129static bool dax_is_conflict(void *entry)
130{
131 return entry == XA_RETRY_ENTRY;
132}
133
134/*
135 * DAX page cache entry locking
136 */
137struct exceptional_entry_key {
138 struct xarray *xa;
139 pgoff_t entry_start;
140};
141
142struct wait_exceptional_entry_queue {
143 wait_queue_entry_t wait;
144 struct exceptional_entry_key key;
145};
146
147static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
148 void *entry, struct exceptional_entry_key *key)
149{
150 unsigned long hash;
151 unsigned long index = xas->xa_index;
152
153 /*
154 * If 'entry' is a PMD, align the 'index' that we use for the wait
155 * queue to the start of that PMD. This ensures that all offsets in
156 * the range covered by the PMD map to the same bit lock.
157 */
158 if (dax_is_pmd_entry(entry))
159 index &= ~PG_PMD_COLOUR;
160 key->xa = xas->xa;
161 key->entry_start = index;
162
163 hash = hash_long((unsigned long)xas->xa ^ index, DAX_WAIT_TABLE_BITS);
164 return wait_table + hash;
165}
166
167static int wake_exceptional_entry_func(wait_queue_entry_t *wait,
168 unsigned int mode, int sync, void *keyp)
169{
170 struct exceptional_entry_key *key = keyp;
171 struct wait_exceptional_entry_queue *ewait =
172 container_of(wait, struct wait_exceptional_entry_queue, wait);
173
174 if (key->xa != ewait->key.xa ||
175 key->entry_start != ewait->key.entry_start)
176 return 0;
177 return autoremove_wake_function(wait, mode, sync, NULL);
178}
179
180/*
181 * @entry may no longer be the entry at the index in the mapping.
182 * The important information it's conveying is whether the entry at
183 * this index used to be a PMD entry.
184 */
185static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all)
186{
187 struct exceptional_entry_key key;
188 wait_queue_head_t *wq;
189
190 wq = dax_entry_waitqueue(xas, entry, &key);
191
192 /*
193 * Checking for locked entry and prepare_to_wait_exclusive() happens
194 * under the i_pages lock, ditto for entry handling in our callers.
195 * So at this point all tasks that could have seen our entry locked
196 * must be in the waitqueue and the following check will see them.
197 */
198 if (waitqueue_active(wq))
199 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
200}
201
202/*
203 * Look up entry in page cache, wait for it to become unlocked if it
204 * is a DAX entry and return it. The caller must subsequently call
205 * put_unlocked_entry() if it did not lock the entry or dax_unlock_entry()
206 * if it did. The entry returned may have a larger order than @order.
207 * If @order is larger than the order of the entry found in i_pages, this
208 * function returns a dax_is_conflict entry.
209 *
210 * Must be called with the i_pages lock held.
211 */
212static void *get_unlocked_entry(struct xa_state *xas, unsigned int order)
213{
214 void *entry;
215 struct wait_exceptional_entry_queue ewait;
216 wait_queue_head_t *wq;
217
218 init_wait(&ewait.wait);
219 ewait.wait.func = wake_exceptional_entry_func;
220
221 for (;;) {
222 entry = xas_find_conflict(xas);
223 if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
224 return entry;
225 if (dax_entry_order(entry) < order)
226 return XA_RETRY_ENTRY;
227 if (!dax_is_locked(entry))
228 return entry;
229
230 wq = dax_entry_waitqueue(xas, entry, &ewait.key);
231 prepare_to_wait_exclusive(wq, &ewait.wait,
232 TASK_UNINTERRUPTIBLE);
233 xas_unlock_irq(xas);
234 xas_reset(xas);
235 schedule();
236 finish_wait(wq, &ewait.wait);
237 xas_lock_irq(xas);
238 }
239}
240
241/*
242 * The only thing keeping the address space around is the i_pages lock
243 * (it's cycled in clear_inode() after removing the entries from i_pages)
244 * After we call xas_unlock_irq(), we cannot touch xas->xa.
245 */
246static void wait_entry_unlocked(struct xa_state *xas, void *entry)
247{
248 struct wait_exceptional_entry_queue ewait;
249 wait_queue_head_t *wq;
250
251 init_wait(&ewait.wait);
252 ewait.wait.func = wake_exceptional_entry_func;
253
254 wq = dax_entry_waitqueue(xas, entry, &ewait.key);
255 /*
256 * Unlike get_unlocked_entry() there is no guarantee that this
257 * path ever successfully retrieves an unlocked entry before an
258 * inode dies. Perform a non-exclusive wait in case this path
259 * never successfully performs its own wake up.
260 */
261 prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);
262 xas_unlock_irq(xas);
263 schedule();
264 finish_wait(wq, &ewait.wait);
265}
266
267static void put_unlocked_entry(struct xa_state *xas, void *entry)
268{
269 /* If we were the only waiter woken, wake the next one */
270 if (entry && !dax_is_conflict(entry))
271 dax_wake_entry(xas, entry, false);
272}
273
274/*
275 * We used the xa_state to get the entry, but then we locked the entry and
276 * dropped the xa_lock, so we know the xa_state is stale and must be reset
277 * before use.
278 */
279static void dax_unlock_entry(struct xa_state *xas, void *entry)
280{
281 void *old;
282
283 BUG_ON(dax_is_locked(entry));
284 xas_reset(xas);
285 xas_lock_irq(xas);
286 old = xas_store(xas, entry);
287 xas_unlock_irq(xas);
288 BUG_ON(!dax_is_locked(old));
289 dax_wake_entry(xas, entry, false);
290}
291
292/*
293 * Return: The entry stored at this location before it was locked.
294 */
295static void *dax_lock_entry(struct xa_state *xas, void *entry)
296{
297 unsigned long v = xa_to_value(entry);
298 return xas_store(xas, xa_mk_value(v | DAX_LOCKED));
299}
300
301static unsigned long dax_entry_size(void *entry)
302{
303 if (dax_is_zero_entry(entry))
304 return 0;
305 else if (dax_is_empty_entry(entry))
306 return 0;
307 else if (dax_is_pmd_entry(entry))
308 return PMD_SIZE;
309 else
310 return PAGE_SIZE;
311}
312
313static unsigned long dax_end_pfn(void *entry)
314{
315 return dax_to_pfn(entry) + dax_entry_size(entry) / PAGE_SIZE;
316}
317
318/*
319 * Iterate through all mapped pfns represented by an entry, i.e. skip
320 * 'empty' and 'zero' entries.
321 */
322#define for_each_mapped_pfn(entry, pfn) \
323 for (pfn = dax_to_pfn(entry); \
324 pfn < dax_end_pfn(entry); pfn++)
325
326/*
327 * TODO: for reflink+dax we need a way to associate a single page with
328 * multiple address_space instances at different linear_page_index()
329 * offsets.
330 */
331static void dax_associate_entry(void *entry, struct address_space *mapping,
332 struct vm_area_struct *vma, unsigned long address)
333{
334 unsigned long size = dax_entry_size(entry), pfn, index;
335 int i = 0;
336
337 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
338 return;
339
340 index = linear_page_index(vma, address & ~(size - 1));
341 for_each_mapped_pfn(entry, pfn) {
342 struct page *page = pfn_to_page(pfn);
343
344 WARN_ON_ONCE(page->mapping);
345 page->mapping = mapping;
346 page->index = index + i++;
347 }
348}
349
350static void dax_disassociate_entry(void *entry, struct address_space *mapping,
351 bool trunc)
352{
353 unsigned long pfn;
354
355 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
356 return;
357
358 for_each_mapped_pfn(entry, pfn) {
359 struct page *page = pfn_to_page(pfn);
360
361 WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
362 WARN_ON_ONCE(page->mapping && page->mapping != mapping);
363 page->mapping = NULL;
364 page->index = 0;
365 }
366}
367
368static struct page *dax_busy_page(void *entry)
369{
370 unsigned long pfn;
371
372 for_each_mapped_pfn(entry, pfn) {
373 struct page *page = pfn_to_page(pfn);
374
375 if (page_ref_count(page) > 1)
376 return page;
377 }
378 return NULL;
379}
380
381/*
382 * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page
383 * @page: The page whose entry we want to lock
384 *
385 * Context: Process context.
386 * Return: A cookie to pass to dax_unlock_page() or 0 if the entry could
387 * not be locked.
388 */
389dax_entry_t dax_lock_page(struct page *page)
390{
391 XA_STATE(xas, NULL, 0);
392 void *entry;
393
394 /* Ensure page->mapping isn't freed while we look at it */
395 rcu_read_lock();
396 for (;;) {
397 struct address_space *mapping = READ_ONCE(page->mapping);
398
399 entry = NULL;
400 if (!mapping || !dax_mapping(mapping))
401 break;
402
403 /*
404 * In the device-dax case there's no need to lock, a
405 * struct dev_pagemap pin is sufficient to keep the
406 * inode alive, and we assume we have dev_pagemap pin
407 * otherwise we would not have a valid pfn_to_page()
408 * translation.
409 */
410 entry = (void *)~0UL;
411 if (S_ISCHR(mapping->host->i_mode))
412 break;
413
414 xas.xa = &mapping->i_pages;
415 xas_lock_irq(&xas);
416 if (mapping != page->mapping) {
417 xas_unlock_irq(&xas);
418 continue;
419 }
420 xas_set(&xas, page->index);
421 entry = xas_load(&xas);
422 if (dax_is_locked(entry)) {
423 rcu_read_unlock();
424 wait_entry_unlocked(&xas, entry);
425 rcu_read_lock();
426 continue;
427 }
428 dax_lock_entry(&xas, entry);
429 xas_unlock_irq(&xas);
430 break;
431 }
432 rcu_read_unlock();
433 return (dax_entry_t)entry;
434}
435
436void dax_unlock_page(struct page *page, dax_entry_t cookie)
437{
438 struct address_space *mapping = page->mapping;
439 XA_STATE(xas, &mapping->i_pages, page->index);
440
441 if (S_ISCHR(mapping->host->i_mode))
442 return;
443
444 dax_unlock_entry(&xas, (void *)cookie);
445}
446
447/*
448 * Find page cache entry at given index. If it is a DAX entry, return it
449 * with the entry locked. If the page cache doesn't contain an entry at
450 * that index, add a locked empty entry.
451 *
452 * When requesting an entry with size DAX_PMD, grab_mapping_entry() will
453 * either return that locked entry or will return VM_FAULT_FALLBACK.
454 * This will happen if there are any PTE entries within the PMD range
455 * that we are requesting.
456 *
457 * We always favor PTE entries over PMD entries. There isn't a flow where we
458 * evict PTE entries in order to 'upgrade' them to a PMD entry. A PMD
459 * insertion will fail if it finds any PTE entries already in the tree, and a
460 * PTE insertion will cause an existing PMD entry to be unmapped and
461 * downgraded to PTE entries. This happens for both PMD zero pages as
462 * well as PMD empty entries.
463 *
464 * The exception to this downgrade path is for PMD entries that have
465 * real storage backing them. We will leave these real PMD entries in
466 * the tree, and PTE writes will simply dirty the entire PMD entry.
467 *
468 * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
469 * persistent memory the benefit is doubtful. We can add that later if we can
470 * show it helps.
471 *
472 * On error, this function does not return an ERR_PTR. Instead it returns
473 * a VM_FAULT code, encoded as an xarray internal entry. The ERR_PTR values
474 * overlap with xarray value entries.
475 */
476static void *grab_mapping_entry(struct xa_state *xas,
477 struct address_space *mapping, unsigned int order)
478{
479 unsigned long index = xas->xa_index;
480 bool pmd_downgrade = false; /* splitting PMD entry into PTE entries? */
481 void *entry;
482
483retry:
484 xas_lock_irq(xas);
485 entry = get_unlocked_entry(xas, order);
486
487 if (entry) {
488 if (dax_is_conflict(entry))
489 goto fallback;
490 if (!xa_is_value(entry)) {
491 xas_set_err(xas, -EIO);
492 goto out_unlock;
493 }
494
495 if (order == 0) {
496 if (dax_is_pmd_entry(entry) &&
497 (dax_is_zero_entry(entry) ||
498 dax_is_empty_entry(entry))) {
499 pmd_downgrade = true;
500 }
501 }
502 }
503
504 if (pmd_downgrade) {
505 /*
506 * Make sure 'entry' remains valid while we drop
507 * the i_pages lock.
508 */
509 dax_lock_entry(xas, entry);
510
511 /*
512 * Besides huge zero pages the only other thing that gets
513 * downgraded are empty entries which don't need to be
514 * unmapped.
515 */
516 if (dax_is_zero_entry(entry)) {
517 xas_unlock_irq(xas);
518 unmap_mapping_pages(mapping,
519 xas->xa_index & ~PG_PMD_COLOUR,
520 PG_PMD_NR, false);
521 xas_reset(xas);
522 xas_lock_irq(xas);
523 }
524
525 dax_disassociate_entry(entry, mapping, false);
526 xas_store(xas, NULL); /* undo the PMD join */
527 dax_wake_entry(xas, entry, true);
528 mapping->nrexceptional--;
529 entry = NULL;
530 xas_set(xas, index);
531 }
532
533 if (entry) {
534 dax_lock_entry(xas, entry);
535 } else {
536 unsigned long flags = DAX_EMPTY;
537
538 if (order > 0)
539 flags |= DAX_PMD;
540 entry = dax_make_entry(pfn_to_pfn_t(0), flags);
541 dax_lock_entry(xas, entry);
542 if (xas_error(xas))
543 goto out_unlock;
544 mapping->nrexceptional++;
545 }
546
547out_unlock:
548 xas_unlock_irq(xas);
549 if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
550 goto retry;
551 if (xas->xa_node == XA_ERROR(-ENOMEM))
552 return xa_mk_internal(VM_FAULT_OOM);
553 if (xas_error(xas))
554 return xa_mk_internal(VM_FAULT_SIGBUS);
555 return entry;
556fallback:
557 xas_unlock_irq(xas);
558 return xa_mk_internal(VM_FAULT_FALLBACK);
559}
560
561/**
562 * dax_layout_busy_page - find first pinned page in @mapping
563 * @mapping: address space to scan for a page with ref count > 1
564 *
565 * DAX requires ZONE_DEVICE mapped pages. These pages are never
566 * 'onlined' to the page allocator so they are considered idle when
567 * page->count == 1. A filesystem uses this interface to determine if
568 * any page in the mapping is busy, i.e. for DMA, or other
569 * get_user_pages() usages.
570 *
571 * It is expected that the filesystem is holding locks to block the
572 * establishment of new mappings in this address_space. I.e. it expects
573 * to be able to run unmap_mapping_range() and subsequently not race
574 * mapping_mapped() becoming true.
575 */
576struct page *dax_layout_busy_page(struct address_space *mapping)
577{
578 XA_STATE(xas, &mapping->i_pages, 0);
579 void *entry;
580 unsigned int scanned = 0;
581 struct page *page = NULL;
582
583 /*
584 * In the 'limited' case get_user_pages() for dax is disabled.
585 */
586 if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
587 return NULL;
588
589 if (!dax_mapping(mapping) || !mapping_mapped(mapping))
590 return NULL;
591
592 /*
593 * If we race get_user_pages_fast() here either we'll see the
594 * elevated page count in the iteration and wait, or
595 * get_user_pages_fast() will see that the page it took a reference
596 * against is no longer mapped in the page tables and bail to the
597 * get_user_pages() slow path. The slow path is protected by
598 * pte_lock() and pmd_lock(). New references are not taken without
599 * holding those locks, and unmap_mapping_range() will not zero the
600 * pte or pmd without holding the respective lock, so we are
601 * guaranteed to either see new references or prevent new
602 * references from being established.
603 */
604 unmap_mapping_range(mapping, 0, 0, 0);
605
606 xas_lock_irq(&xas);
607 xas_for_each(&xas, entry, ULONG_MAX) {
608 if (WARN_ON_ONCE(!xa_is_value(entry)))
609 continue;
610 if (unlikely(dax_is_locked(entry)))
611 entry = get_unlocked_entry(&xas, 0);
612 if (entry)
613 page = dax_busy_page(entry);
614 put_unlocked_entry(&xas, entry);
615 if (page)
616 break;
617 if (++scanned % XA_CHECK_SCHED)
618 continue;
619
620 xas_pause(&xas);
621 xas_unlock_irq(&xas);
622 cond_resched();
623 xas_lock_irq(&xas);
624 }
625 xas_unlock_irq(&xas);
626 return page;
627}
628EXPORT_SYMBOL_GPL(dax_layout_busy_page);
629
630static int __dax_invalidate_entry(struct address_space *mapping,
631 pgoff_t index, bool trunc)
632{
633 XA_STATE(xas, &mapping->i_pages, index);
634 int ret = 0;
635 void *entry;
636
637 xas_lock_irq(&xas);
638 entry = get_unlocked_entry(&xas, 0);
639 if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
640 goto out;
641 if (!trunc &&
642 (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY) ||
643 xas_get_mark(&xas, PAGECACHE_TAG_TOWRITE)))
644 goto out;
645 dax_disassociate_entry(entry, mapping, trunc);
646 xas_store(&xas, NULL);
647 mapping->nrexceptional--;
648 ret = 1;
649out:
650 put_unlocked_entry(&xas, entry);
651 xas_unlock_irq(&xas);
652 return ret;
653}
654
655/*
656 * Delete DAX entry at @index from @mapping. Wait for it
657 * to be unlocked before deleting it.
658 */
659int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
660{
661 int ret = __dax_invalidate_entry(mapping, index, true);
662
663 /*
664 * This gets called from truncate / punch_hole path. As such, the caller
665 * must hold locks protecting against concurrent modifications of the
666 * page cache (usually fs-private i_mmap_sem for writing). Since the
667 * caller has seen a DAX entry for this index, we better find it
668 * at that index as well...
669 */
670 WARN_ON_ONCE(!ret);
671 return ret;
672}
673
674/*
675 * Invalidate DAX entry if it is clean.
676 */
677int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
678 pgoff_t index)
679{
680 return __dax_invalidate_entry(mapping, index, false);
681}
682
683static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_dev,
684 sector_t sector, struct page *to, unsigned long vaddr)
685{
686 void *vto, *kaddr;
687 pgoff_t pgoff;
688 long rc;
689 int id;
690
691 rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
692 if (rc)
693 return rc;
694
695 id = dax_read_lock();
696 rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(PAGE_SIZE), &kaddr, NULL);
697 if (rc < 0) {
698 dax_read_unlock(id);
699 return rc;
700 }
701 vto = kmap_atomic(to);
702 copy_user_page(vto, (void __force *)kaddr, vaddr, to);
703 kunmap_atomic(vto);
704 dax_read_unlock(id);
705 return 0;
706}
707
708/*
709 * By this point grab_mapping_entry() has ensured that we have a locked entry
710 * of the appropriate size so we don't have to worry about downgrading PMDs to
711 * PTEs. If we happen to be trying to insert a PTE and there is a PMD
712 * already in the tree, we will skip the insertion and just dirty the PMD as
713 * appropriate.
714 */
715static void *dax_insert_entry(struct xa_state *xas,
716 struct address_space *mapping, struct vm_fault *vmf,
717 void *entry, pfn_t pfn, unsigned long flags, bool dirty)
718{
719 void *new_entry = dax_make_entry(pfn, flags);
720
721 if (dirty)
722 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
723
724 if (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE)) {
725 unsigned long index = xas->xa_index;
726 /* we are replacing a zero page with block mapping */
727 if (dax_is_pmd_entry(entry))
728 unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
729 PG_PMD_NR, false);
730 else /* pte entry */
731 unmap_mapping_pages(mapping, index, 1, false);
732 }
733
734 xas_reset(xas);
735 xas_lock_irq(xas);
736 if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
737 void *old;
738
739 dax_disassociate_entry(entry, mapping, false);
740 dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address);
741 /*
742 * Only swap our new entry into the page cache if the current
743 * entry is a zero page or an empty entry. If a normal PTE or
744 * PMD entry is already in the cache, we leave it alone. This
745 * means that if we are trying to insert a PTE and the
746 * existing entry is a PMD, we will just leave the PMD in the
747 * tree and dirty it if necessary.
748 */
749 old = dax_lock_entry(xas, new_entry);
750 WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) |
751 DAX_LOCKED));
752 entry = new_entry;
753 } else {
754 xas_load(xas); /* Walk the xa_state */
755 }
756
757 if (dirty)
758 xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
759
760 xas_unlock_irq(xas);
761 return entry;
762}
763
764static inline
765unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
766{
767 unsigned long address;
768
769 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
770 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
771 return address;
772}
773
774/* Walk all mappings of a given index of a file and writeprotect them */
775static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
776 unsigned long pfn)
777{
778 struct vm_area_struct *vma;
779 pte_t pte, *ptep = NULL;
780 pmd_t *pmdp = NULL;
781 spinlock_t *ptl;
782
783 i_mmap_lock_read(mapping);
784 vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
785 struct mmu_notifier_range range;
786 unsigned long address;
787
788 cond_resched();
789
790 if (!(vma->vm_flags & VM_SHARED))
791 continue;
792
793 address = pgoff_address(index, vma);
794
795 /*
796 * Note because we provide range to follow_pte_pmd it will
797 * call mmu_notifier_invalidate_range_start() on our behalf
798 * before taking any lock.
799 */
800 if (follow_pte_pmd(vma->vm_mm, address, &range,
801 &ptep, &pmdp, &ptl))
802 continue;
803
804 /*
805 * No need to call mmu_notifier_invalidate_range() as we are
806 * downgrading page table protection not changing it to point
807 * to a new page.
808 *
809 * See Documentation/vm/mmu_notifier.rst
810 */
811 if (pmdp) {
812#ifdef CONFIG_FS_DAX_PMD
813 pmd_t pmd;
814
815 if (pfn != pmd_pfn(*pmdp))
816 goto unlock_pmd;
817 if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
818 goto unlock_pmd;
819
820 flush_cache_page(vma, address, pfn);
821 pmd = pmdp_invalidate(vma, address, pmdp);
822 pmd = pmd_wrprotect(pmd);
823 pmd = pmd_mkclean(pmd);
824 set_pmd_at(vma->vm_mm, address, pmdp, pmd);
825unlock_pmd:
826#endif
827 spin_unlock(ptl);
828 } else {
829 if (pfn != pte_pfn(*ptep))
830 goto unlock_pte;
831 if (!pte_dirty(*ptep) && !pte_write(*ptep))
832 goto unlock_pte;
833
834 flush_cache_page(vma, address, pfn);
835 pte = ptep_clear_flush(vma, address, ptep);
836 pte = pte_wrprotect(pte);
837 pte = pte_mkclean(pte);
838 set_pte_at(vma->vm_mm, address, ptep, pte);
839unlock_pte:
840 pte_unmap_unlock(ptep, ptl);
841 }
842
843 mmu_notifier_invalidate_range_end(&range);
844 }
845 i_mmap_unlock_read(mapping);
846}
847
848static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
849 struct address_space *mapping, void *entry)
850{
851 unsigned long pfn, index, count;
852 long ret = 0;
853
854 /*
855 * A page got tagged dirty in DAX mapping? Something is seriously
856 * wrong.
857 */
858 if (WARN_ON(!xa_is_value(entry)))
859 return -EIO;
860
861 if (unlikely(dax_is_locked(entry))) {
862 void *old_entry = entry;
863
864 entry = get_unlocked_entry(xas, 0);
865
866 /* Entry got punched out / reallocated? */
867 if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
868 goto put_unlocked;
869 /*
870 * Entry got reallocated elsewhere? No need to writeback.
871 * We have to compare pfns as we must not bail out due to
872 * difference in lockbit or entry type.
873 */
874 if (dax_to_pfn(old_entry) != dax_to_pfn(entry))
875 goto put_unlocked;
876 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
877 dax_is_zero_entry(entry))) {
878 ret = -EIO;
879 goto put_unlocked;
880 }
881
882 /* Another fsync thread may have already done this entry */
883 if (!xas_get_mark(xas, PAGECACHE_TAG_TOWRITE))
884 goto put_unlocked;
885 }
886
887 /* Lock the entry to serialize with page faults */
888 dax_lock_entry(xas, entry);
889
890 /*
891 * We can clear the tag now but we have to be careful so that concurrent
892 * dax_writeback_one() calls for the same index cannot finish before we
893 * actually flush the caches. This is achieved as the calls will look
894 * at the entry only under the i_pages lock and once they do that
895 * they will see the entry locked and wait for it to unlock.
896 */
897 xas_clear_mark(xas, PAGECACHE_TAG_TOWRITE);
898 xas_unlock_irq(xas);
899
900 /*
901 * If dax_writeback_mapping_range() was given a wbc->range_start
902 * in the middle of a PMD, the 'index' we use needs to be
903 * aligned to the start of the PMD.
904 * This allows us to flush for PMD_SIZE and not have to worry about
905 * partial PMD writebacks.
906 */
907 pfn = dax_to_pfn(entry);
908 count = 1UL << dax_entry_order(entry);
909 index = xas->xa_index & ~(count - 1);
910
911 dax_entry_mkclean(mapping, index, pfn);
912 dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_SIZE);
913 /*
914 * After we have flushed the cache, we can clear the dirty tag. There
915 * cannot be new dirty data in the pfn after the flush has completed as
916 * the pfn mappings are writeprotected and fault waits for mapping
917 * entry lock.
918 */
919 xas_reset(xas);
920 xas_lock_irq(xas);
921 xas_store(xas, entry);
922 xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
923 dax_wake_entry(xas, entry, false);
924
925 trace_dax_writeback_one(mapping->host, index, count);
926 return ret;
927
928 put_unlocked:
929 put_unlocked_entry(xas, entry);
930 return ret;
931}
932
933/*
934 * Flush the mapping to the persistent domain within the byte range of [start,
935 * end]. This is required by data integrity operations to ensure file data is
936 * on persistent storage prior to completion of the operation.
937 */
938int dax_writeback_mapping_range(struct address_space *mapping,
939 struct dax_device *dax_dev, struct writeback_control *wbc)
940{
941 XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
942 struct inode *inode = mapping->host;
943 pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
944 void *entry;
945 int ret = 0;
946 unsigned int scanned = 0;
947
948 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
949 return -EIO;
950
951 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
952 return 0;
953
954 trace_dax_writeback_range(inode, xas.xa_index, end_index);
955
956 tag_pages_for_writeback(mapping, xas.xa_index, end_index);
957
958 xas_lock_irq(&xas);
959 xas_for_each_marked(&xas, entry, end_index, PAGECACHE_TAG_TOWRITE) {
960 ret = dax_writeback_one(&xas, dax_dev, mapping, entry);
961 if (ret < 0) {
962 mapping_set_error(mapping, ret);
963 break;
964 }
965 if (++scanned % XA_CHECK_SCHED)
966 continue;
967
968 xas_pause(&xas);
969 xas_unlock_irq(&xas);
970 cond_resched();
971 xas_lock_irq(&xas);
972 }
973 xas_unlock_irq(&xas);
974 trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
975 return ret;
976}
977EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
978
979static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
980{
981 return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
982}
983
984static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
985 pfn_t *pfnp)
986{
987 const sector_t sector = dax_iomap_sector(iomap, pos);
988 pgoff_t pgoff;
989 int id, rc;
990 long length;
991
992 rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff);
993 if (rc)
994 return rc;
995 id = dax_read_lock();
996 length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
997 NULL, pfnp);
998 if (length < 0) {
999 rc = length;
1000 goto out;
1001 }
1002 rc = -EINVAL;
1003 if (PFN_PHYS(length) < size)
1004 goto out;
1005 if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1))
1006 goto out;
1007 /* For larger pages we need devmap */
1008 if (length > 1 && !pfn_t_devmap(*pfnp))
1009 goto out;
1010 rc = 0;
1011out:
1012 dax_read_unlock(id);
1013 return rc;
1014}
1015
1016/*
1017 * The user has performed a load from a hole in the file. Allocating a new
1018 * page in the file would cause excessive storage usage for workloads with
1019 * sparse files. Instead we insert a read-only mapping of the 4k zero page.
1020 * If this page is ever written to we will re-fault and change the mapping to
1021 * point to real DAX storage instead.
1022 */
1023static vm_fault_t dax_load_hole(struct xa_state *xas,
1024 struct address_space *mapping, void **entry,
1025 struct vm_fault *vmf)
1026{
1027 struct inode *inode = mapping->host;
1028 unsigned long vaddr = vmf->address;
1029 pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
1030 vm_fault_t ret;
1031
1032 *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn,
1033 DAX_ZERO_PAGE, false);
1034
1035 ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
1036 trace_dax_load_hole(inode, vmf, ret);
1037 return ret;
1038}
1039
1040int dax_iomap_zero(loff_t pos, unsigned offset, unsigned size,
1041 struct iomap *iomap)
1042{
1043 sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
1044 pgoff_t pgoff;
1045 long rc, id;
1046 void *kaddr;
1047 bool page_aligned = false;
1048
1049
1050 if (IS_ALIGNED(sector << SECTOR_SHIFT, PAGE_SIZE) &&
1051 IS_ALIGNED(size, PAGE_SIZE))
1052 page_aligned = true;
1053
1054 rc = bdev_dax_pgoff(iomap->bdev, sector, PAGE_SIZE, &pgoff);
1055 if (rc)
1056 return rc;
1057
1058 id = dax_read_lock();
1059
1060 if (page_aligned)
1061 rc = dax_zero_page_range(iomap->dax_dev, pgoff,
1062 size >> PAGE_SHIFT);
1063 else
1064 rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
1065 if (rc < 0) {
1066 dax_read_unlock(id);
1067 return rc;
1068 }
1069
1070 if (!page_aligned) {
1071 memset(kaddr + offset, 0, size);
1072 dax_flush(iomap->dax_dev, kaddr + offset, size);
1073 }
1074 dax_read_unlock(id);
1075 return 0;
1076}
1077
1078static loff_t
1079dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
1080 struct iomap *iomap, struct iomap *srcmap)
1081{
1082 struct block_device *bdev = iomap->bdev;
1083 struct dax_device *dax_dev = iomap->dax_dev;
1084 struct iov_iter *iter = data;
1085 loff_t end = pos + length, done = 0;
1086 ssize_t ret = 0;
1087 size_t xfer;
1088 int id;
1089
1090 if (iov_iter_rw(iter) == READ) {
1091 end = min(end, i_size_read(inode));
1092 if (pos >= end)
1093 return 0;
1094
1095 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1096 return iov_iter_zero(min(length, end - pos), iter);
1097 }
1098
1099 if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
1100 return -EIO;
1101
1102 /*
1103 * Write can allocate block for an area which has a hole page mapped
1104 * into page tables. We have to tear down these mappings so that data
1105 * written by write(2) is visible in mmap.
1106 */
1107 if (iomap->flags & IOMAP_F_NEW) {
1108 invalidate_inode_pages2_range(inode->i_mapping,
1109 pos >> PAGE_SHIFT,
1110 (end - 1) >> PAGE_SHIFT);
1111 }
1112
1113 id = dax_read_lock();
1114 while (pos < end) {
1115 unsigned offset = pos & (PAGE_SIZE - 1);
1116 const size_t size = ALIGN(length + offset, PAGE_SIZE);
1117 const sector_t sector = dax_iomap_sector(iomap, pos);
1118 ssize_t map_len;
1119 pgoff_t pgoff;
1120 void *kaddr;
1121
1122 if (fatal_signal_pending(current)) {
1123 ret = -EINTR;
1124 break;
1125 }
1126
1127 ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
1128 if (ret)
1129 break;
1130
1131 map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
1132 &kaddr, NULL);
1133 if (map_len < 0) {
1134 ret = map_len;
1135 break;
1136 }
1137
1138 map_len = PFN_PHYS(map_len);
1139 kaddr += offset;
1140 map_len -= offset;
1141 if (map_len > end - pos)
1142 map_len = end - pos;
1143
1144 /*
1145 * The userspace address for the memory copy has already been
1146 * validated via access_ok() in either vfs_read() or
1147 * vfs_write(), depending on which operation we are doing.
1148 */
1149 if (iov_iter_rw(iter) == WRITE)
1150 xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr,
1151 map_len, iter);
1152 else
1153 xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr,
1154 map_len, iter);
1155
1156 pos += xfer;
1157 length -= xfer;
1158 done += xfer;
1159
1160 if (xfer == 0)
1161 ret = -EFAULT;
1162 if (xfer < map_len)
1163 break;
1164 }
1165 dax_read_unlock(id);
1166
1167 return done ? done : ret;
1168}
1169
1170/**
1171 * dax_iomap_rw - Perform I/O to a DAX file
1172 * @iocb: The control block for this I/O
1173 * @iter: The addresses to do I/O from or to
1174 * @ops: iomap ops passed from the file system
1175 *
1176 * This function performs read and write operations to directly mapped
1177 * persistent memory. The callers needs to take care of read/write exclusion
1178 * and evicting any page cache pages in the region under I/O.
1179 */
1180ssize_t
1181dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1182 const struct iomap_ops *ops)
1183{
1184 struct address_space *mapping = iocb->ki_filp->f_mapping;
1185 struct inode *inode = mapping->host;
1186 loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1187 unsigned flags = 0;
1188
1189 if (iov_iter_rw(iter) == WRITE) {
1190 lockdep_assert_held_write(&inode->i_rwsem);
1191 flags |= IOMAP_WRITE;
1192 } else {
1193 lockdep_assert_held(&inode->i_rwsem);
1194 }
1195
1196 if (iocb->ki_flags & IOCB_NOWAIT)
1197 flags |= IOMAP_NOWAIT;
1198
1199 while (iov_iter_count(iter)) {
1200 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1201 iter, dax_iomap_actor);
1202 if (ret <= 0)
1203 break;
1204 pos += ret;
1205 done += ret;
1206 }
1207
1208 iocb->ki_pos += done;
1209 return done ? done : ret;
1210}
1211EXPORT_SYMBOL_GPL(dax_iomap_rw);
1212
1213static vm_fault_t dax_fault_return(int error)
1214{
1215 if (error == 0)
1216 return VM_FAULT_NOPAGE;
1217 return vmf_error(error);
1218}
1219
1220/*
1221 * MAP_SYNC on a dax mapping guarantees dirty metadata is
1222 * flushed on write-faults (non-cow), but not read-faults.
1223 */
1224static bool dax_fault_is_synchronous(unsigned long flags,
1225 struct vm_area_struct *vma, struct iomap *iomap)
1226{
1227 return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC)
1228 && (iomap->flags & IOMAP_F_DIRTY);
1229}
1230
1231static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
1232 int *iomap_errp, const struct iomap_ops *ops)
1233{
1234 struct vm_area_struct *vma = vmf->vma;
1235 struct address_space *mapping = vma->vm_file->f_mapping;
1236 XA_STATE(xas, &mapping->i_pages, vmf->pgoff);
1237 struct inode *inode = mapping->host;
1238 unsigned long vaddr = vmf->address;
1239 loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1240 struct iomap iomap = { .type = IOMAP_HOLE };
1241 struct iomap srcmap = { .type = IOMAP_HOLE };
1242 unsigned flags = IOMAP_FAULT;
1243 int error, major = 0;
1244 bool write = vmf->flags & FAULT_FLAG_WRITE;
1245 bool sync;
1246 vm_fault_t ret = 0;
1247 void *entry;
1248 pfn_t pfn;
1249
1250 trace_dax_pte_fault(inode, vmf, ret);
1251 /*
1252 * Check whether offset isn't beyond end of file now. Caller is supposed
1253 * to hold locks serializing us with truncate / punch hole so this is
1254 * a reliable test.
1255 */
1256 if (pos >= i_size_read(inode)) {
1257 ret = VM_FAULT_SIGBUS;
1258 goto out;
1259 }
1260
1261 if (write && !vmf->cow_page)
1262 flags |= IOMAP_WRITE;
1263
1264 entry = grab_mapping_entry(&xas, mapping, 0);
1265 if (xa_is_internal(entry)) {
1266 ret = xa_to_internal(entry);
1267 goto out;
1268 }
1269
1270 /*
1271 * It is possible, particularly with mixed reads & writes to private
1272 * mappings, that we have raced with a PMD fault that overlaps with
1273 * the PTE we need to set up. If so just return and the fault will be
1274 * retried.
1275 */
1276 if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
1277 ret = VM_FAULT_NOPAGE;
1278 goto unlock_entry;
1279 }
1280
1281 /*
1282 * Note that we don't bother to use iomap_apply here: DAX required
1283 * the file system block size to be equal the page size, which means
1284 * that we never have to deal with more than a single extent here.
1285 */
1286 error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap, &srcmap);
1287 if (iomap_errp)
1288 *iomap_errp = error;
1289 if (error) {
1290 ret = dax_fault_return(error);
1291 goto unlock_entry;
1292 }
1293 if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1294 error = -EIO; /* fs corruption? */
1295 goto error_finish_iomap;
1296 }
1297
1298 if (vmf->cow_page) {
1299 sector_t sector = dax_iomap_sector(&iomap, pos);
1300
1301 switch (iomap.type) {
1302 case IOMAP_HOLE:
1303 case IOMAP_UNWRITTEN:
1304 clear_user_highpage(vmf->cow_page, vaddr);
1305 break;
1306 case IOMAP_MAPPED:
1307 error = copy_cow_page_dax(iomap.bdev, iomap.dax_dev,
1308 sector, vmf->cow_page, vaddr);
1309 break;
1310 default:
1311 WARN_ON_ONCE(1);
1312 error = -EIO;
1313 break;
1314 }
1315
1316 if (error)
1317 goto error_finish_iomap;
1318
1319 __SetPageUptodate(vmf->cow_page);
1320 ret = finish_fault(vmf);
1321 if (!ret)
1322 ret = VM_FAULT_DONE_COW;
1323 goto finish_iomap;
1324 }
1325
1326 sync = dax_fault_is_synchronous(flags, vma, &iomap);
1327
1328 switch (iomap.type) {
1329 case IOMAP_MAPPED:
1330 if (iomap.flags & IOMAP_F_NEW) {
1331 count_vm_event(PGMAJFAULT);
1332 count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
1333 major = VM_FAULT_MAJOR;
1334 }
1335 error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
1336 if (error < 0)
1337 goto error_finish_iomap;
1338
1339 entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn,
1340 0, write && !sync);
1341
1342 /*
1343 * If we are doing synchronous page fault and inode needs fsync,
1344 * we can insert PTE into page tables only after that happens.
1345 * Skip insertion for now and return the pfn so that caller can
1346 * insert it after fsync is done.
1347 */
1348 if (sync) {
1349 if (WARN_ON_ONCE(!pfnp)) {
1350 error = -EIO;
1351 goto error_finish_iomap;
1352 }
1353 *pfnp = pfn;
1354 ret = VM_FAULT_NEEDDSYNC | major;
1355 goto finish_iomap;
1356 }
1357 trace_dax_insert_mapping(inode, vmf, entry);
1358 if (write)
1359 ret = vmf_insert_mixed_mkwrite(vma, vaddr, pfn);
1360 else
1361 ret = vmf_insert_mixed(vma, vaddr, pfn);
1362
1363 goto finish_iomap;
1364 case IOMAP_UNWRITTEN:
1365 case IOMAP_HOLE:
1366 if (!write) {
1367 ret = dax_load_hole(&xas, mapping, &entry, vmf);
1368 goto finish_iomap;
1369 }
1370 fallthrough;
1371 default:
1372 WARN_ON_ONCE(1);
1373 error = -EIO;
1374 break;
1375 }
1376
1377 error_finish_iomap:
1378 ret = dax_fault_return(error);
1379 finish_iomap:
1380 if (ops->iomap_end) {
1381 int copied = PAGE_SIZE;
1382
1383 if (ret & VM_FAULT_ERROR)
1384 copied = 0;
1385 /*
1386 * The fault is done by now and there's no way back (other
1387 * thread may be already happily using PTE we have installed).
1388 * Just ignore error from ->iomap_end since we cannot do much
1389 * with it.
1390 */
1391 ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
1392 }
1393 unlock_entry:
1394 dax_unlock_entry(&xas, entry);
1395 out:
1396 trace_dax_pte_fault_done(inode, vmf, ret);
1397 return ret | major;
1398}
1399
1400#ifdef CONFIG_FS_DAX_PMD
1401static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
1402 struct iomap *iomap, void **entry)
1403{
1404 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1405 unsigned long pmd_addr = vmf->address & PMD_MASK;
1406 struct vm_area_struct *vma = vmf->vma;
1407 struct inode *inode = mapping->host;
1408 pgtable_t pgtable = NULL;
1409 struct page *zero_page;
1410 spinlock_t *ptl;
1411 pmd_t pmd_entry;
1412 pfn_t pfn;
1413
1414 zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
1415
1416 if (unlikely(!zero_page))
1417 goto fallback;
1418
1419 pfn = page_to_pfn_t(zero_page);
1420 *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn,
1421 DAX_PMD | DAX_ZERO_PAGE, false);
1422
1423 if (arch_needs_pgtable_deposit()) {
1424 pgtable = pte_alloc_one(vma->vm_mm);
1425 if (!pgtable)
1426 return VM_FAULT_OOM;
1427 }
1428
1429 ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1430 if (!pmd_none(*(vmf->pmd))) {
1431 spin_unlock(ptl);
1432 goto fallback;
1433 }
1434
1435 if (pgtable) {
1436 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
1437 mm_inc_nr_ptes(vma->vm_mm);
1438 }
1439 pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot);
1440 pmd_entry = pmd_mkhuge(pmd_entry);
1441 set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry);
1442 spin_unlock(ptl);
1443 trace_dax_pmd_load_hole(inode, vmf, zero_page, *entry);
1444 return VM_FAULT_NOPAGE;
1445
1446fallback:
1447 if (pgtable)
1448 pte_free(vma->vm_mm, pgtable);
1449 trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, *entry);
1450 return VM_FAULT_FALLBACK;
1451}
1452
1453static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1454 const struct iomap_ops *ops)
1455{
1456 struct vm_area_struct *vma = vmf->vma;
1457 struct address_space *mapping = vma->vm_file->f_mapping;
1458 XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER);
1459 unsigned long pmd_addr = vmf->address & PMD_MASK;
1460 bool write = vmf->flags & FAULT_FLAG_WRITE;
1461 bool sync;
1462 unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1463 struct inode *inode = mapping->host;
1464 vm_fault_t result = VM_FAULT_FALLBACK;
1465 struct iomap iomap = { .type = IOMAP_HOLE };
1466 struct iomap srcmap = { .type = IOMAP_HOLE };
1467 pgoff_t max_pgoff;
1468 void *entry;
1469 loff_t pos;
1470 int error;
1471 pfn_t pfn;
1472
1473 /*
1474 * Check whether offset isn't beyond end of file now. Caller is
1475 * supposed to hold locks serializing us with truncate / punch hole so
1476 * this is a reliable test.
1477 */
1478 max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
1479
1480 trace_dax_pmd_fault(inode, vmf, max_pgoff, 0);
1481
1482 /*
1483 * Make sure that the faulting address's PMD offset (color) matches
1484 * the PMD offset from the start of the file. This is necessary so
1485 * that a PMD range in the page table overlaps exactly with a PMD
1486 * range in the page cache.
1487 */
1488 if ((vmf->pgoff & PG_PMD_COLOUR) !=
1489 ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR))
1490 goto fallback;
1491
1492 /* Fall back to PTEs if we're going to COW */
1493 if (write && !(vma->vm_flags & VM_SHARED))
1494 goto fallback;
1495
1496 /* If the PMD would extend outside the VMA */
1497 if (pmd_addr < vma->vm_start)
1498 goto fallback;
1499 if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1500 goto fallback;
1501
1502 if (xas.xa_index >= max_pgoff) {
1503 result = VM_FAULT_SIGBUS;
1504 goto out;
1505 }
1506
1507 /* If the PMD would extend beyond the file size */
1508 if ((xas.xa_index | PG_PMD_COLOUR) >= max_pgoff)
1509 goto fallback;
1510
1511 /*
1512 * grab_mapping_entry() will make sure we get an empty PMD entry,
1513 * a zero PMD entry or a DAX PMD. If it can't (because a PTE
1514 * entry is already in the array, for instance), it will return
1515 * VM_FAULT_FALLBACK.
1516 */
1517 entry = grab_mapping_entry(&xas, mapping, PMD_ORDER);
1518 if (xa_is_internal(entry)) {
1519 result = xa_to_internal(entry);
1520 goto fallback;
1521 }
1522
1523 /*
1524 * It is possible, particularly with mixed reads & writes to private
1525 * mappings, that we have raced with a PTE fault that overlaps with
1526 * the PMD we need to set up. If so just return and the fault will be
1527 * retried.
1528 */
1529 if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) &&
1530 !pmd_devmap(*vmf->pmd)) {
1531 result = 0;
1532 goto unlock_entry;
1533 }
1534
1535 /*
1536 * Note that we don't use iomap_apply here. We aren't doing I/O, only
1537 * setting up a mapping, so really we're using iomap_begin() as a way
1538 * to look up our filesystem block.
1539 */
1540 pos = (loff_t)xas.xa_index << PAGE_SHIFT;
1541 error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap,
1542 &srcmap);
1543 if (error)
1544 goto unlock_entry;
1545
1546 if (iomap.offset + iomap.length < pos + PMD_SIZE)
1547 goto finish_iomap;
1548
1549 sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap);
1550
1551 switch (iomap.type) {
1552 case IOMAP_MAPPED:
1553 error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
1554 if (error < 0)
1555 goto finish_iomap;
1556
1557 entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn,
1558 DAX_PMD, write && !sync);
1559
1560 /*
1561 * If we are doing synchronous page fault and inode needs fsync,
1562 * we can insert PMD into page tables only after that happens.
1563 * Skip insertion for now and return the pfn so that caller can
1564 * insert it after fsync is done.
1565 */
1566 if (sync) {
1567 if (WARN_ON_ONCE(!pfnp))
1568 goto finish_iomap;
1569 *pfnp = pfn;
1570 result = VM_FAULT_NEEDDSYNC;
1571 goto finish_iomap;
1572 }
1573
1574 trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
1575 result = vmf_insert_pfn_pmd(vmf, pfn, write);
1576 break;
1577 case IOMAP_UNWRITTEN:
1578 case IOMAP_HOLE:
1579 if (WARN_ON_ONCE(write))
1580 break;
1581 result = dax_pmd_load_hole(&xas, vmf, &iomap, &entry);
1582 break;
1583 default:
1584 WARN_ON_ONCE(1);
1585 break;
1586 }
1587
1588 finish_iomap:
1589 if (ops->iomap_end) {
1590 int copied = PMD_SIZE;
1591
1592 if (result == VM_FAULT_FALLBACK)
1593 copied = 0;
1594 /*
1595 * The fault is done by now and there's no way back (other
1596 * thread may be already happily using PMD we have installed).
1597 * Just ignore error from ->iomap_end since we cannot do much
1598 * with it.
1599 */
1600 ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
1601 &iomap);
1602 }
1603 unlock_entry:
1604 dax_unlock_entry(&xas, entry);
1605 fallback:
1606 if (result == VM_FAULT_FALLBACK) {
1607 split_huge_pmd(vma, vmf->pmd, vmf->address);
1608 count_vm_event(THP_FAULT_FALLBACK);
1609 }
1610out:
1611 trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result);
1612 return result;
1613}
1614#else
1615static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
1616 const struct iomap_ops *ops)
1617{
1618 return VM_FAULT_FALLBACK;
1619}
1620#endif /* CONFIG_FS_DAX_PMD */
1621
1622/**
1623 * dax_iomap_fault - handle a page fault on a DAX file
1624 * @vmf: The description of the fault
1625 * @pe_size: Size of the page to fault in
1626 * @pfnp: PFN to insert for synchronous faults if fsync is required
1627 * @iomap_errp: Storage for detailed error code in case of error
1628 * @ops: Iomap ops passed from the file system
1629 *
1630 * When a page fault occurs, filesystems may call this helper in
1631 * their fault handler for DAX files. dax_iomap_fault() assumes the caller
1632 * has done all the necessary locking for page fault to proceed
1633 * successfully.
1634 */
1635vm_fault_t dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
1636 pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
1637{
1638 switch (pe_size) {
1639 case PE_SIZE_PTE:
1640 return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops);
1641 case PE_SIZE_PMD:
1642 return dax_iomap_pmd_fault(vmf, pfnp, ops);
1643 default:
1644 return VM_FAULT_FALLBACK;
1645 }
1646}
1647EXPORT_SYMBOL_GPL(dax_iomap_fault);
1648
1649/*
1650 * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables
1651 * @vmf: The description of the fault
1652 * @pfn: PFN to insert
1653 * @order: Order of entry to insert.
1654 *
1655 * This function inserts a writeable PTE or PMD entry into the page tables
1656 * for an mmaped DAX file. It also marks the page cache entry as dirty.
1657 */
1658static vm_fault_t
1659dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order)
1660{
1661 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
1662 XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, order);
1663 void *entry;
1664 vm_fault_t ret;
1665
1666 xas_lock_irq(&xas);
1667 entry = get_unlocked_entry(&xas, order);
1668 /* Did we race with someone splitting entry or so? */
1669 if (!entry || dax_is_conflict(entry) ||
1670 (order == 0 && !dax_is_pte_entry(entry))) {
1671 put_unlocked_entry(&xas, entry);
1672 xas_unlock_irq(&xas);
1673 trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
1674 VM_FAULT_NOPAGE);
1675 return VM_FAULT_NOPAGE;
1676 }
1677 xas_set_mark(&xas, PAGECACHE_TAG_DIRTY);
1678 dax_lock_entry(&xas, entry);
1679 xas_unlock_irq(&xas);
1680 if (order == 0)
1681 ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
1682#ifdef CONFIG_FS_DAX_PMD
1683 else if (order == PMD_ORDER)
1684 ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE);
1685#endif
1686 else
1687 ret = VM_FAULT_FALLBACK;
1688 dax_unlock_entry(&xas, entry);
1689 trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret);
1690 return ret;
1691}
1692
1693/**
1694 * dax_finish_sync_fault - finish synchronous page fault
1695 * @vmf: The description of the fault
1696 * @pe_size: Size of entry to be inserted
1697 * @pfn: PFN to insert
1698 *
1699 * This function ensures that the file range touched by the page fault is
1700 * stored persistently on the media and handles inserting of appropriate page
1701 * table entry.
1702 */
1703vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
1704 enum page_entry_size pe_size, pfn_t pfn)
1705{
1706 int err;
1707 loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
1708 unsigned int order = pe_order(pe_size);
1709 size_t len = PAGE_SIZE << order;
1710
1711 err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1);
1712 if (err)
1713 return VM_FAULT_SIGBUS;
1714 return dax_insert_pfn_mkwrite(vmf, pfn, order);
1715}
1716EXPORT_SYMBOL_GPL(dax_finish_sync_fault);