Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[deliverable/linux.git] / fs / dax.c
1 /*
2 * fs/dax.c - Direct Access filesystem code
3 * Copyright (c) 2013-2014 Intel Corporation
4 * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
5 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms and conditions of the GNU General Public License,
9 * version 2, as published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 * more details.
15 */
16
17 #include <linux/atomic.h>
18 #include <linux/blkdev.h>
19 #include <linux/buffer_head.h>
20 #include <linux/dax.h>
21 #include <linux/fs.h>
22 #include <linux/genhd.h>
23 #include <linux/highmem.h>
24 #include <linux/memcontrol.h>
25 #include <linux/mm.h>
26 #include <linux/mutex.h>
27 #include <linux/pagevec.h>
28 #include <linux/pmem.h>
29 #include <linux/sched.h>
30 #include <linux/uio.h>
31 #include <linux/vmstat.h>
32 #include <linux/pfn_t.h>
33 #include <linux/sizes.h>
34
35 static 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
53 static 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
61 struct 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 */
86 int 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 }
111 EXPORT_SYMBOL_GPL(dax_clear_sectors);
112
113 /* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
114 static 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
125 static 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 */
137 static bool buffer_size_valid(struct buffer_head *bh)
138 {
139 return bh->b_state != 0;
140 }
141
142
143 static 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
151 static 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 */
259 ssize_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 ((retval > 0) && end_io)
290 end_io(iocb, pos, retval, bh.b_private);
291
292 if (!(flags & DIO_SKIP_DIO_COUNT))
293 inode_dio_end(inode);
294 out:
295 return retval;
296 }
297 EXPORT_SYMBOL_GPL(dax_do_io);
298
299 /*
300 * The user has performed a load from a hole in the file. Allocating
301 * a new page in the file would cause excessive storage usage for
302 * workloads with sparse files. We allocate a page cache page instead.
303 * We'll kick it out of the page cache if it's ever written to,
304 * otherwise it will simply fall out of the page cache under memory
305 * pressure without ever having been dirtied.
306 */
307 static int dax_load_hole(struct address_space *mapping, struct page *page,
308 struct vm_fault *vmf)
309 {
310 unsigned long size;
311 struct inode *inode = mapping->host;
312 if (!page)
313 page = find_or_create_page(mapping, vmf->pgoff,
314 GFP_KERNEL | __GFP_ZERO);
315 if (!page)
316 return VM_FAULT_OOM;
317 /* Recheck i_size under page lock to avoid truncate race */
318 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
319 if (vmf->pgoff >= size) {
320 unlock_page(page);
321 page_cache_release(page);
322 return VM_FAULT_SIGBUS;
323 }
324
325 vmf->page = page;
326 return VM_FAULT_LOCKED;
327 }
328
329 static int copy_user_bh(struct page *to, struct inode *inode,
330 struct buffer_head *bh, unsigned long vaddr)
331 {
332 struct blk_dax_ctl dax = {
333 .sector = to_sector(bh, inode),
334 .size = bh->b_size,
335 };
336 struct block_device *bdev = bh->b_bdev;
337 void *vto;
338
339 if (dax_map_atomic(bdev, &dax) < 0)
340 return PTR_ERR(dax.addr);
341 vto = kmap_atomic(to);
342 copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
343 kunmap_atomic(vto);
344 dax_unmap_atomic(bdev, &dax);
345 return 0;
346 }
347
348 #define NO_SECTOR -1
349 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_CACHE_SHIFT))
350
351 static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
352 sector_t sector, bool pmd_entry, bool dirty)
353 {
354 struct radix_tree_root *page_tree = &mapping->page_tree;
355 pgoff_t pmd_index = DAX_PMD_INDEX(index);
356 int type, error = 0;
357 void *entry;
358
359 WARN_ON_ONCE(pmd_entry && !dirty);
360 if (dirty)
361 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
362
363 spin_lock_irq(&mapping->tree_lock);
364
365 entry = radix_tree_lookup(page_tree, pmd_index);
366 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) {
367 index = pmd_index;
368 goto dirty;
369 }
370
371 entry = radix_tree_lookup(page_tree, index);
372 if (entry) {
373 type = RADIX_DAX_TYPE(entry);
374 if (WARN_ON_ONCE(type != RADIX_DAX_PTE &&
375 type != RADIX_DAX_PMD)) {
376 error = -EIO;
377 goto unlock;
378 }
379
380 if (!pmd_entry || type == RADIX_DAX_PMD)
381 goto dirty;
382
383 /*
384 * We only insert dirty PMD entries into the radix tree. This
385 * means we don't need to worry about removing a dirty PTE
386 * entry and inserting a clean PMD entry, thus reducing the
387 * range we would flush with a follow-up fsync/msync call.
388 */
389 radix_tree_delete(&mapping->page_tree, index);
390 mapping->nrexceptional--;
391 }
392
393 if (sector == NO_SECTOR) {
394 /*
395 * This can happen during correct operation if our pfn_mkwrite
396 * fault raced against a hole punch operation. If this
397 * happens the pte that was hole punched will have been
398 * unmapped and the radix tree entry will have been removed by
399 * the time we are called, but the call will still happen. We
400 * will return all the way up to wp_pfn_shared(), where the
401 * pte_same() check will fail, eventually causing page fault
402 * to be retried by the CPU.
403 */
404 goto unlock;
405 }
406
407 error = radix_tree_insert(page_tree, index,
408 RADIX_DAX_ENTRY(sector, pmd_entry));
409 if (error)
410 goto unlock;
411
412 mapping->nrexceptional++;
413 dirty:
414 if (dirty)
415 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
416 unlock:
417 spin_unlock_irq(&mapping->tree_lock);
418 return error;
419 }
420
421 static int dax_writeback_one(struct block_device *bdev,
422 struct address_space *mapping, pgoff_t index, void *entry)
423 {
424 struct radix_tree_root *page_tree = &mapping->page_tree;
425 int type = RADIX_DAX_TYPE(entry);
426 struct radix_tree_node *node;
427 struct blk_dax_ctl dax;
428 void **slot;
429 int ret = 0;
430
431 spin_lock_irq(&mapping->tree_lock);
432 /*
433 * Regular page slots are stabilized by the page lock even
434 * without the tree itself locked. These unlocked entries
435 * need verification under the tree lock.
436 */
437 if (!__radix_tree_lookup(page_tree, index, &node, &slot))
438 goto unlock;
439 if (*slot != entry)
440 goto unlock;
441
442 /* another fsync thread may have already written back this entry */
443 if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
444 goto unlock;
445
446 if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
447 ret = -EIO;
448 goto unlock;
449 }
450
451 dax.sector = RADIX_DAX_SECTOR(entry);
452 dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
453 spin_unlock_irq(&mapping->tree_lock);
454
455 /*
456 * We cannot hold tree_lock while calling dax_map_atomic() because it
457 * eventually calls cond_resched().
458 */
459 ret = dax_map_atomic(bdev, &dax);
460 if (ret < 0)
461 return ret;
462
463 if (WARN_ON_ONCE(ret < dax.size)) {
464 ret = -EIO;
465 goto unmap;
466 }
467
468 wb_cache_pmem(dax.addr, dax.size);
469
470 spin_lock_irq(&mapping->tree_lock);
471 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
472 spin_unlock_irq(&mapping->tree_lock);
473 unmap:
474 dax_unmap_atomic(bdev, &dax);
475 return ret;
476
477 unlock:
478 spin_unlock_irq(&mapping->tree_lock);
479 return ret;
480 }
481
482 /*
483 * Flush the mapping to the persistent domain within the byte range of [start,
484 * end]. This is required by data integrity operations to ensure file data is
485 * on persistent storage prior to completion of the operation.
486 */
487 int dax_writeback_mapping_range(struct address_space *mapping,
488 struct block_device *bdev, struct writeback_control *wbc)
489 {
490 struct inode *inode = mapping->host;
491 pgoff_t start_index, end_index, pmd_index;
492 pgoff_t indices[PAGEVEC_SIZE];
493 struct pagevec pvec;
494 bool done = false;
495 int i, ret = 0;
496 void *entry;
497
498 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
499 return -EIO;
500
501 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
502 return 0;
503
504 start_index = wbc->range_start >> PAGE_CACHE_SHIFT;
505 end_index = wbc->range_end >> PAGE_CACHE_SHIFT;
506 pmd_index = DAX_PMD_INDEX(start_index);
507
508 rcu_read_lock();
509 entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
510 rcu_read_unlock();
511
512 /* see if the start of our range is covered by a PMD entry */
513 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
514 start_index = pmd_index;
515
516 tag_pages_for_writeback(mapping, start_index, end_index);
517
518 pagevec_init(&pvec, 0);
519 while (!done) {
520 pvec.nr = find_get_entries_tag(mapping, start_index,
521 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
522 pvec.pages, indices);
523
524 if (pvec.nr == 0)
525 break;
526
527 for (i = 0; i < pvec.nr; i++) {
528 if (indices[i] > end_index) {
529 done = true;
530 break;
531 }
532
533 ret = dax_writeback_one(bdev, mapping, indices[i],
534 pvec.pages[i]);
535 if (ret < 0)
536 return ret;
537 }
538 }
539 wmb_pmem();
540 return 0;
541 }
542 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
543
544 static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
545 struct vm_area_struct *vma, struct vm_fault *vmf)
546 {
547 unsigned long vaddr = (unsigned long)vmf->virtual_address;
548 struct address_space *mapping = inode->i_mapping;
549 struct block_device *bdev = bh->b_bdev;
550 struct blk_dax_ctl dax = {
551 .sector = to_sector(bh, inode),
552 .size = bh->b_size,
553 };
554 pgoff_t size;
555 int error;
556
557 i_mmap_lock_read(mapping);
558
559 /*
560 * Check truncate didn't happen while we were allocating a block.
561 * If it did, this block may or may not be still allocated to the
562 * file. We can't tell the filesystem to free it because we can't
563 * take i_mutex here. In the worst case, the file still has blocks
564 * allocated past the end of the file.
565 */
566 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
567 if (unlikely(vmf->pgoff >= size)) {
568 error = -EIO;
569 goto out;
570 }
571
572 if (dax_map_atomic(bdev, &dax) < 0) {
573 error = PTR_ERR(dax.addr);
574 goto out;
575 }
576
577 if (buffer_unwritten(bh) || buffer_new(bh)) {
578 clear_pmem(dax.addr, PAGE_SIZE);
579 wmb_pmem();
580 }
581 dax_unmap_atomic(bdev, &dax);
582
583 error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
584 vmf->flags & FAULT_FLAG_WRITE);
585 if (error)
586 goto out;
587
588 error = vm_insert_mixed(vma, vaddr, dax.pfn);
589
590 out:
591 i_mmap_unlock_read(mapping);
592
593 return error;
594 }
595
596 /**
597 * __dax_fault - handle a page fault on a DAX file
598 * @vma: The virtual memory area where the fault occurred
599 * @vmf: The description of the fault
600 * @get_block: The filesystem method used to translate file offsets to blocks
601 * @complete_unwritten: The filesystem method used to convert unwritten blocks
602 * to written so the data written to them is exposed. This is required for
603 * required by write faults for filesystems that will return unwritten
604 * extent mappings from @get_block, but it is optional for reads as
605 * dax_insert_mapping() will always zero unwritten blocks. If the fs does
606 * not support unwritten extents, the it should pass NULL.
607 *
608 * When a page fault occurs, filesystems may call this helper in their
609 * fault handler for DAX files. __dax_fault() assumes the caller has done all
610 * the necessary locking for the page fault to proceed successfully.
611 */
612 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
613 get_block_t get_block, dax_iodone_t complete_unwritten)
614 {
615 struct file *file = vma->vm_file;
616 struct address_space *mapping = file->f_mapping;
617 struct inode *inode = mapping->host;
618 struct page *page;
619 struct buffer_head bh;
620 unsigned long vaddr = (unsigned long)vmf->virtual_address;
621 unsigned blkbits = inode->i_blkbits;
622 sector_t block;
623 pgoff_t size;
624 int error;
625 int major = 0;
626
627 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
628 if (vmf->pgoff >= size)
629 return VM_FAULT_SIGBUS;
630
631 memset(&bh, 0, sizeof(bh));
632 block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
633 bh.b_bdev = inode->i_sb->s_bdev;
634 bh.b_size = PAGE_SIZE;
635
636 repeat:
637 page = find_get_page(mapping, vmf->pgoff);
638 if (page) {
639 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
640 page_cache_release(page);
641 return VM_FAULT_RETRY;
642 }
643 if (unlikely(page->mapping != mapping)) {
644 unlock_page(page);
645 page_cache_release(page);
646 goto repeat;
647 }
648 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
649 if (unlikely(vmf->pgoff >= size)) {
650 /*
651 * We have a struct page covering a hole in the file
652 * from a read fault and we've raced with a truncate
653 */
654 error = -EIO;
655 goto unlock_page;
656 }
657 }
658
659 error = get_block(inode, block, &bh, 0);
660 if (!error && (bh.b_size < PAGE_SIZE))
661 error = -EIO; /* fs corruption? */
662 if (error)
663 goto unlock_page;
664
665 if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
666 if (vmf->flags & FAULT_FLAG_WRITE) {
667 error = get_block(inode, block, &bh, 1);
668 count_vm_event(PGMAJFAULT);
669 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
670 major = VM_FAULT_MAJOR;
671 if (!error && (bh.b_size < PAGE_SIZE))
672 error = -EIO;
673 if (error)
674 goto unlock_page;
675 } else {
676 return dax_load_hole(mapping, page, vmf);
677 }
678 }
679
680 if (vmf->cow_page) {
681 struct page *new_page = vmf->cow_page;
682 if (buffer_written(&bh))
683 error = copy_user_bh(new_page, inode, &bh, vaddr);
684 else
685 clear_user_highpage(new_page, vaddr);
686 if (error)
687 goto unlock_page;
688 vmf->page = page;
689 if (!page) {
690 i_mmap_lock_read(mapping);
691 /* Check we didn't race with truncate */
692 size = (i_size_read(inode) + PAGE_SIZE - 1) >>
693 PAGE_SHIFT;
694 if (vmf->pgoff >= size) {
695 i_mmap_unlock_read(mapping);
696 error = -EIO;
697 goto out;
698 }
699 }
700 return VM_FAULT_LOCKED;
701 }
702
703 /* Check we didn't race with a read fault installing a new page */
704 if (!page && major)
705 page = find_lock_page(mapping, vmf->pgoff);
706
707 if (page) {
708 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
709 PAGE_CACHE_SIZE, 0);
710 delete_from_page_cache(page);
711 unlock_page(page);
712 page_cache_release(page);
713 page = NULL;
714 }
715
716 /*
717 * If we successfully insert the new mapping over an unwritten extent,
718 * we need to ensure we convert the unwritten extent. If there is an
719 * error inserting the mapping, the filesystem needs to leave it as
720 * unwritten to prevent exposure of the stale underlying data to
721 * userspace, but we still need to call the completion function so
722 * the private resources on the mapping buffer can be released. We
723 * indicate what the callback should do via the uptodate variable, same
724 * as for normal BH based IO completions.
725 */
726 error = dax_insert_mapping(inode, &bh, vma, vmf);
727 if (buffer_unwritten(&bh)) {
728 if (complete_unwritten)
729 complete_unwritten(&bh, !error);
730 else
731 WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
732 }
733
734 out:
735 if (error == -ENOMEM)
736 return VM_FAULT_OOM | major;
737 /* -EBUSY is fine, somebody else faulted on the same PTE */
738 if ((error < 0) && (error != -EBUSY))
739 return VM_FAULT_SIGBUS | major;
740 return VM_FAULT_NOPAGE | major;
741
742 unlock_page:
743 if (page) {
744 unlock_page(page);
745 page_cache_release(page);
746 }
747 goto out;
748 }
749 EXPORT_SYMBOL(__dax_fault);
750
751 /**
752 * dax_fault - handle a page fault on a DAX file
753 * @vma: The virtual memory area where the fault occurred
754 * @vmf: The description of the fault
755 * @get_block: The filesystem method used to translate file offsets to blocks
756 *
757 * When a page fault occurs, filesystems may call this helper in their
758 * fault handler for DAX files.
759 */
760 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
761 get_block_t get_block, dax_iodone_t complete_unwritten)
762 {
763 int result;
764 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
765
766 if (vmf->flags & FAULT_FLAG_WRITE) {
767 sb_start_pagefault(sb);
768 file_update_time(vma->vm_file);
769 }
770 result = __dax_fault(vma, vmf, get_block, complete_unwritten);
771 if (vmf->flags & FAULT_FLAG_WRITE)
772 sb_end_pagefault(sb);
773
774 return result;
775 }
776 EXPORT_SYMBOL_GPL(dax_fault);
777
778 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
779 /*
780 * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
781 * more often than one might expect in the below function.
782 */
783 #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
784
785 static void __dax_dbg(struct buffer_head *bh, unsigned long address,
786 const char *reason, const char *fn)
787 {
788 if (bh) {
789 char bname[BDEVNAME_SIZE];
790 bdevname(bh->b_bdev, bname);
791 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
792 "length %zd fallback: %s\n", fn, current->comm,
793 address, bname, bh->b_state, (u64)bh->b_blocknr,
794 bh->b_size, reason);
795 } else {
796 pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
797 current->comm, address, reason);
798 }
799 }
800
801 #define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd")
802
803 int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
804 pmd_t *pmd, unsigned int flags, get_block_t get_block,
805 dax_iodone_t complete_unwritten)
806 {
807 struct file *file = vma->vm_file;
808 struct address_space *mapping = file->f_mapping;
809 struct inode *inode = mapping->host;
810 struct buffer_head bh;
811 unsigned blkbits = inode->i_blkbits;
812 unsigned long pmd_addr = address & PMD_MASK;
813 bool write = flags & FAULT_FLAG_WRITE;
814 struct block_device *bdev;
815 pgoff_t size, pgoff;
816 sector_t block;
817 int error, result = 0;
818 bool alloc = false;
819
820 /* dax pmd mappings require pfn_t_devmap() */
821 if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
822 return VM_FAULT_FALLBACK;
823
824 /* Fall back to PTEs if we're going to COW */
825 if (write && !(vma->vm_flags & VM_SHARED)) {
826 split_huge_pmd(vma, pmd, address);
827 dax_pmd_dbg(NULL, address, "cow write");
828 return VM_FAULT_FALLBACK;
829 }
830 /* If the PMD would extend outside the VMA */
831 if (pmd_addr < vma->vm_start) {
832 dax_pmd_dbg(NULL, address, "vma start unaligned");
833 return VM_FAULT_FALLBACK;
834 }
835 if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
836 dax_pmd_dbg(NULL, address, "vma end unaligned");
837 return VM_FAULT_FALLBACK;
838 }
839
840 pgoff = linear_page_index(vma, pmd_addr);
841 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
842 if (pgoff >= size)
843 return VM_FAULT_SIGBUS;
844 /* If the PMD would cover blocks out of the file */
845 if ((pgoff | PG_PMD_COLOUR) >= size) {
846 dax_pmd_dbg(NULL, address,
847 "offset + huge page size > file size");
848 return VM_FAULT_FALLBACK;
849 }
850
851 memset(&bh, 0, sizeof(bh));
852 bh.b_bdev = inode->i_sb->s_bdev;
853 block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
854
855 bh.b_size = PMD_SIZE;
856
857 if (get_block(inode, block, &bh, 0) != 0)
858 return VM_FAULT_SIGBUS;
859
860 if (!buffer_mapped(&bh) && write) {
861 if (get_block(inode, block, &bh, 1) != 0)
862 return VM_FAULT_SIGBUS;
863 alloc = true;
864 }
865
866 bdev = bh.b_bdev;
867
868 /*
869 * If the filesystem isn't willing to tell us the length of a hole,
870 * just fall back to PTEs. Calling get_block 512 times in a loop
871 * would be silly.
872 */
873 if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
874 dax_pmd_dbg(&bh, address, "allocated block too small");
875 return VM_FAULT_FALLBACK;
876 }
877
878 /*
879 * If we allocated new storage, make sure no process has any
880 * zero pages covering this hole
881 */
882 if (alloc) {
883 loff_t lstart = pgoff << PAGE_SHIFT;
884 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
885
886 truncate_pagecache_range(inode, lstart, lend);
887 }
888
889 i_mmap_lock_read(mapping);
890
891 /*
892 * If a truncate happened while we were allocating blocks, we may
893 * leave blocks allocated to the file that are beyond EOF. We can't
894 * take i_mutex here, so just leave them hanging; they'll be freed
895 * when the file is deleted.
896 */
897 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
898 if (pgoff >= size) {
899 result = VM_FAULT_SIGBUS;
900 goto out;
901 }
902 if ((pgoff | PG_PMD_COLOUR) >= size) {
903 dax_pmd_dbg(&bh, address,
904 "offset + huge page size > file size");
905 goto fallback;
906 }
907
908 if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
909 spinlock_t *ptl;
910 pmd_t entry;
911 struct page *zero_page = get_huge_zero_page();
912
913 if (unlikely(!zero_page)) {
914 dax_pmd_dbg(&bh, address, "no zero page");
915 goto fallback;
916 }
917
918 ptl = pmd_lock(vma->vm_mm, pmd);
919 if (!pmd_none(*pmd)) {
920 spin_unlock(ptl);
921 dax_pmd_dbg(&bh, address, "pmd already present");
922 goto fallback;
923 }
924
925 dev_dbg(part_to_dev(bdev->bd_part),
926 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
927 __func__, current->comm, address,
928 (unsigned long long) to_sector(&bh, inode));
929
930 entry = mk_pmd(zero_page, vma->vm_page_prot);
931 entry = pmd_mkhuge(entry);
932 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
933 result = VM_FAULT_NOPAGE;
934 spin_unlock(ptl);
935 } else {
936 struct blk_dax_ctl dax = {
937 .sector = to_sector(&bh, inode),
938 .size = PMD_SIZE,
939 };
940 long length = dax_map_atomic(bdev, &dax);
941
942 if (length < 0) {
943 result = VM_FAULT_SIGBUS;
944 goto out;
945 }
946 if (length < PMD_SIZE) {
947 dax_pmd_dbg(&bh, address, "dax-length too small");
948 dax_unmap_atomic(bdev, &dax);
949 goto fallback;
950 }
951 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
952 dax_pmd_dbg(&bh, address, "pfn unaligned");
953 dax_unmap_atomic(bdev, &dax);
954 goto fallback;
955 }
956
957 if (!pfn_t_devmap(dax.pfn)) {
958 dax_unmap_atomic(bdev, &dax);
959 dax_pmd_dbg(&bh, address, "pfn not in memmap");
960 goto fallback;
961 }
962
963 if (buffer_unwritten(&bh) || buffer_new(&bh)) {
964 clear_pmem(dax.addr, PMD_SIZE);
965 wmb_pmem();
966 count_vm_event(PGMAJFAULT);
967 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
968 result |= VM_FAULT_MAJOR;
969 }
970 dax_unmap_atomic(bdev, &dax);
971
972 /*
973 * For PTE faults we insert a radix tree entry for reads, and
974 * leave it clean. Then on the first write we dirty the radix
975 * tree entry via the dax_pfn_mkwrite() path. This sequence
976 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
977 * call into get_block() to translate the pgoff to a sector in
978 * order to be able to create a new radix tree entry.
979 *
980 * The PMD path doesn't have an equivalent to
981 * dax_pfn_mkwrite(), though, so for a read followed by a
982 * write we traverse all the way through __dax_pmd_fault()
983 * twice. This means we can just skip inserting a radix tree
984 * entry completely on the initial read and just wait until
985 * the write to insert a dirty entry.
986 */
987 if (write) {
988 error = dax_radix_entry(mapping, pgoff, dax.sector,
989 true, true);
990 if (error) {
991 dax_pmd_dbg(&bh, address,
992 "PMD radix insertion failed");
993 goto fallback;
994 }
995 }
996
997 dev_dbg(part_to_dev(bdev->bd_part),
998 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
999 __func__, current->comm, address,
1000 pfn_t_to_pfn(dax.pfn),
1001 (unsigned long long) dax.sector);
1002 result |= vmf_insert_pfn_pmd(vma, address, pmd,
1003 dax.pfn, write);
1004 }
1005
1006 out:
1007 i_mmap_unlock_read(mapping);
1008
1009 if (buffer_unwritten(&bh))
1010 complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
1011
1012 return result;
1013
1014 fallback:
1015 count_vm_event(THP_FAULT_FALLBACK);
1016 result = VM_FAULT_FALLBACK;
1017 goto out;
1018 }
1019 EXPORT_SYMBOL_GPL(__dax_pmd_fault);
1020
1021 /**
1022 * dax_pmd_fault - handle a PMD fault on a DAX file
1023 * @vma: The virtual memory area where the fault occurred
1024 * @vmf: The description of the fault
1025 * @get_block: The filesystem method used to translate file offsets to blocks
1026 *
1027 * When a page fault occurs, filesystems may call this helper in their
1028 * pmd_fault handler for DAX files.
1029 */
1030 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1031 pmd_t *pmd, unsigned int flags, get_block_t get_block,
1032 dax_iodone_t complete_unwritten)
1033 {
1034 int result;
1035 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
1036
1037 if (flags & FAULT_FLAG_WRITE) {
1038 sb_start_pagefault(sb);
1039 file_update_time(vma->vm_file);
1040 }
1041 result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
1042 complete_unwritten);
1043 if (flags & FAULT_FLAG_WRITE)
1044 sb_end_pagefault(sb);
1045
1046 return result;
1047 }
1048 EXPORT_SYMBOL_GPL(dax_pmd_fault);
1049 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1050
1051 /**
1052 * dax_pfn_mkwrite - handle first write to DAX page
1053 * @vma: The virtual memory area where the fault occurred
1054 * @vmf: The description of the fault
1055 */
1056 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1057 {
1058 struct file *file = vma->vm_file;
1059 int error;
1060
1061 /*
1062 * We pass NO_SECTOR to dax_radix_entry() because we expect that a
1063 * RADIX_DAX_PTE entry already exists in the radix tree from a
1064 * previous call to __dax_fault(). We just want to look up that PTE
1065 * entry using vmf->pgoff and make sure the dirty tag is set. This
1066 * saves us from having to make a call to get_block() here to look
1067 * up the sector.
1068 */
1069 error = dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false,
1070 true);
1071
1072 if (error == -ENOMEM)
1073 return VM_FAULT_OOM;
1074 if (error)
1075 return VM_FAULT_SIGBUS;
1076 return VM_FAULT_NOPAGE;
1077 }
1078 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
1079
1080 /**
1081 * dax_zero_page_range - zero a range within a page of a DAX file
1082 * @inode: The file being truncated
1083 * @from: The file offset that is being truncated to
1084 * @length: The number of bytes to zero
1085 * @get_block: The filesystem method used to translate file offsets to blocks
1086 *
1087 * This function can be called by a filesystem when it is zeroing part of a
1088 * page in a DAX file. This is intended for hole-punch operations. If
1089 * you are truncating a file, the helper function dax_truncate_page() may be
1090 * more convenient.
1091 *
1092 * We work in terms of PAGE_CACHE_SIZE here for commonality with
1093 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1094 * took care of disposing of the unnecessary blocks. Even if the filesystem
1095 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1096 * since the file might be mmapped.
1097 */
1098 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
1099 get_block_t get_block)
1100 {
1101 struct buffer_head bh;
1102 pgoff_t index = from >> PAGE_CACHE_SHIFT;
1103 unsigned offset = from & (PAGE_CACHE_SIZE-1);
1104 int err;
1105
1106 /* Block boundary? Nothing to do */
1107 if (!length)
1108 return 0;
1109 BUG_ON((offset + length) > PAGE_CACHE_SIZE);
1110
1111 memset(&bh, 0, sizeof(bh));
1112 bh.b_bdev = inode->i_sb->s_bdev;
1113 bh.b_size = PAGE_CACHE_SIZE;
1114 err = get_block(inode, index, &bh, 0);
1115 if (err < 0)
1116 return err;
1117 if (buffer_written(&bh)) {
1118 struct block_device *bdev = bh.b_bdev;
1119 struct blk_dax_ctl dax = {
1120 .sector = to_sector(&bh, inode),
1121 .size = PAGE_CACHE_SIZE,
1122 };
1123
1124 if (dax_map_atomic(bdev, &dax) < 0)
1125 return PTR_ERR(dax.addr);
1126 clear_pmem(dax.addr + offset, length);
1127 wmb_pmem();
1128 dax_unmap_atomic(bdev, &dax);
1129 }
1130
1131 return 0;
1132 }
1133 EXPORT_SYMBOL_GPL(dax_zero_page_range);
1134
1135 /**
1136 * dax_truncate_page - handle a partial page being truncated in a DAX file
1137 * @inode: The file being truncated
1138 * @from: The file offset that is being truncated to
1139 * @get_block: The filesystem method used to translate file offsets to blocks
1140 *
1141 * Similar to block_truncate_page(), this function can be called by a
1142 * filesystem when it is truncating a DAX file to handle the partial page.
1143 *
1144 * We work in terms of PAGE_CACHE_SIZE here for commonality with
1145 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1146 * took care of disposing of the unnecessary blocks. Even if the filesystem
1147 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1148 * since the file might be mmapped.
1149 */
1150 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1151 {
1152 unsigned length = PAGE_CACHE_ALIGN(from) - from;
1153 return dax_zero_page_range(inode, from, length, get_block);
1154 }
1155 EXPORT_SYMBOL_GPL(dax_truncate_page);
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