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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);