blob: c3e21ccfc358b2da1170c15f09a5946afad0ff16 [file] [log] [blame]
Matthew Wilcoxd475c632015-02-16 15:58:56 -08001/*
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/fs.h>
21#include <linux/genhd.h>
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -080022#include <linux/highmem.h>
23#include <linux/memcontrol.h>
24#include <linux/mm.h>
Matthew Wilcoxd475c632015-02-16 15:58:56 -080025#include <linux/mutex.h>
Matthew Wilcox289c6ae2015-02-16 15:58:59 -080026#include <linux/sched.h>
Matthew Wilcoxd475c632015-02-16 15:58:56 -080027#include <linux/uio.h>
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -080028#include <linux/vmstat.h>
Matthew Wilcoxd475c632015-02-16 15:58:56 -080029
Matthew Wilcox289c6ae2015-02-16 15:58:59 -080030int dax_clear_blocks(struct inode *inode, sector_t block, long size)
31{
32 struct block_device *bdev = inode->i_sb->s_bdev;
33 sector_t sector = block << (inode->i_blkbits - 9);
34
35 might_sleep();
36 do {
37 void *addr;
38 unsigned long pfn;
39 long count;
40
41 count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
42 if (count < 0)
43 return count;
44 BUG_ON(size < count);
45 while (count > 0) {
46 unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
47 if (pgsz > count)
48 pgsz = count;
49 if (pgsz < PAGE_SIZE)
50 memset(addr, 0, pgsz);
51 else
52 clear_page(addr);
53 addr += pgsz;
54 size -= pgsz;
55 count -= pgsz;
56 BUG_ON(pgsz & 511);
57 sector += pgsz / 512;
58 cond_resched();
59 }
60 } while (size);
61
62 return 0;
63}
64EXPORT_SYMBOL_GPL(dax_clear_blocks);
65
Matthew Wilcoxd475c632015-02-16 15:58:56 -080066static long dax_get_addr(struct buffer_head *bh, void **addr, unsigned blkbits)
67{
68 unsigned long pfn;
69 sector_t sector = bh->b_blocknr << (blkbits - 9);
70 return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size);
71}
72
73static void dax_new_buf(void *addr, unsigned size, unsigned first, loff_t pos,
74 loff_t end)
75{
76 loff_t final = end - pos + first; /* The final byte of the buffer */
77
78 if (first > 0)
79 memset(addr, 0, first);
80 if (final < size)
81 memset(addr + final, 0, size - final);
82}
83
84static bool buffer_written(struct buffer_head *bh)
85{
86 return buffer_mapped(bh) && !buffer_unwritten(bh);
87}
88
89/*
90 * When ext4 encounters a hole, it returns without modifying the buffer_head
91 * which means that we can't trust b_size. To cope with this, we set b_state
92 * to 0 before calling get_block and, if any bit is set, we know we can trust
93 * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is
94 * and would save us time calling get_block repeatedly.
95 */
96static bool buffer_size_valid(struct buffer_head *bh)
97{
98 return bh->b_state != 0;
99}
100
Omar Sandovala95cd632015-03-16 04:33:51 -0700101static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
102 loff_t start, loff_t end, get_block_t get_block,
103 struct buffer_head *bh)
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800104{
105 ssize_t retval = 0;
106 loff_t pos = start;
107 loff_t max = start;
108 loff_t bh_max = start;
109 void *addr;
110 bool hole = false;
111
Omar Sandovala95cd632015-03-16 04:33:51 -0700112 if (iov_iter_rw(iter) != WRITE)
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800113 end = min(end, i_size_read(inode));
114
115 while (pos < end) {
116 unsigned len;
117 if (pos == max) {
118 unsigned blkbits = inode->i_blkbits;
119 sector_t block = pos >> blkbits;
120 unsigned first = pos - (block << blkbits);
121 long size;
122
123 if (pos == bh_max) {
124 bh->b_size = PAGE_ALIGN(end - pos);
125 bh->b_state = 0;
126 retval = get_block(inode, block, bh,
Omar Sandovala95cd632015-03-16 04:33:51 -0700127 iov_iter_rw(iter) == WRITE);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800128 if (retval)
129 break;
130 if (!buffer_size_valid(bh))
131 bh->b_size = 1 << blkbits;
132 bh_max = pos - first + bh->b_size;
133 } else {
134 unsigned done = bh->b_size -
135 (bh_max - (pos - first));
136 bh->b_blocknr += done >> blkbits;
137 bh->b_size -= done;
138 }
139
Omar Sandovala95cd632015-03-16 04:33:51 -0700140 hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800141 if (hole) {
142 addr = NULL;
143 size = bh->b_size - first;
144 } else {
145 retval = dax_get_addr(bh, &addr, blkbits);
146 if (retval < 0)
147 break;
148 if (buffer_unwritten(bh) || buffer_new(bh))
149 dax_new_buf(addr, retval, first, pos,
150 end);
151 addr += first;
152 size = retval - first;
153 }
154 max = min(pos + size, end);
155 }
156
Omar Sandovala95cd632015-03-16 04:33:51 -0700157 if (iov_iter_rw(iter) == WRITE)
Matthew Wilcox872eb122015-07-03 10:40:39 -0400158 len = copy_from_iter_nocache(addr, max - pos, iter);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800159 else if (!hole)
160 len = copy_to_iter(addr, max - pos, iter);
161 else
162 len = iov_iter_zero(max - pos, iter);
163
164 if (!len)
165 break;
166
167 pos += len;
168 addr += len;
169 }
170
171 return (pos == start) ? retval : pos - start;
172}
173
174/**
175 * dax_do_io - Perform I/O to a DAX file
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800176 * @iocb: The control block for this I/O
177 * @inode: The file which the I/O is directed at
178 * @iter: The addresses to do I/O from or to
179 * @pos: The file offset where the I/O starts
180 * @get_block: The filesystem method used to translate file offsets to blocks
181 * @end_io: A filesystem callback for I/O completion
182 * @flags: See below
183 *
184 * This function uses the same locking scheme as do_blockdev_direct_IO:
185 * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
186 * caller for writes. For reads, we take and release the i_mutex ourselves.
187 * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
188 * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
189 * is in progress.
190 */
Omar Sandovala95cd632015-03-16 04:33:51 -0700191ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
192 struct iov_iter *iter, loff_t pos, get_block_t get_block,
193 dio_iodone_t end_io, int flags)
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800194{
195 struct buffer_head bh;
196 ssize_t retval = -EINVAL;
197 loff_t end = pos + iov_iter_count(iter);
198
199 memset(&bh, 0, sizeof(bh));
200
Omar Sandovala95cd632015-03-16 04:33:51 -0700201 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800202 struct address_space *mapping = inode->i_mapping;
203 mutex_lock(&inode->i_mutex);
204 retval = filemap_write_and_wait_range(mapping, pos, end - 1);
205 if (retval) {
206 mutex_unlock(&inode->i_mutex);
207 goto out;
208 }
209 }
210
211 /* Protects against truncate */
Matthew Wilcoxbbab37d2015-07-03 10:40:42 -0400212 if (!(flags & DIO_SKIP_DIO_COUNT))
213 inode_dio_begin(inode);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800214
Omar Sandovala95cd632015-03-16 04:33:51 -0700215 retval = dax_io(inode, iter, pos, end, get_block, &bh);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800216
Omar Sandovala95cd632015-03-16 04:33:51 -0700217 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800218 mutex_unlock(&inode->i_mutex);
219
220 if ((retval > 0) && end_io)
221 end_io(iocb, pos, retval, bh.b_private);
222
Matthew Wilcoxbbab37d2015-07-03 10:40:42 -0400223 if (!(flags & DIO_SKIP_DIO_COUNT))
224 inode_dio_end(inode);
Matthew Wilcoxd475c632015-02-16 15:58:56 -0800225 out:
226 return retval;
227}
228EXPORT_SYMBOL_GPL(dax_do_io);
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800229
230/*
231 * The user has performed a load from a hole in the file. Allocating
232 * a new page in the file would cause excessive storage usage for
233 * workloads with sparse files. We allocate a page cache page instead.
234 * We'll kick it out of the page cache if it's ever written to,
235 * otherwise it will simply fall out of the page cache under memory
236 * pressure without ever having been dirtied.
237 */
238static int dax_load_hole(struct address_space *mapping, struct page *page,
239 struct vm_fault *vmf)
240{
241 unsigned long size;
242 struct inode *inode = mapping->host;
243 if (!page)
244 page = find_or_create_page(mapping, vmf->pgoff,
245 GFP_KERNEL | __GFP_ZERO);
246 if (!page)
247 return VM_FAULT_OOM;
248 /* Recheck i_size under page lock to avoid truncate race */
249 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
250 if (vmf->pgoff >= size) {
251 unlock_page(page);
252 page_cache_release(page);
253 return VM_FAULT_SIGBUS;
254 }
255
256 vmf->page = page;
257 return VM_FAULT_LOCKED;
258}
259
260static int copy_user_bh(struct page *to, struct buffer_head *bh,
261 unsigned blkbits, unsigned long vaddr)
262{
263 void *vfrom, *vto;
264 if (dax_get_addr(bh, &vfrom, blkbits) < 0)
265 return -EIO;
266 vto = kmap_atomic(to);
267 copy_user_page(vto, vfrom, vaddr, to);
268 kunmap_atomic(vto);
269 return 0;
270}
271
272static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
273 struct vm_area_struct *vma, struct vm_fault *vmf)
274{
275 struct address_space *mapping = inode->i_mapping;
276 sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
277 unsigned long vaddr = (unsigned long)vmf->virtual_address;
278 void *addr;
279 unsigned long pfn;
280 pgoff_t size;
281 int error;
282
283 i_mmap_lock_read(mapping);
284
285 /*
286 * Check truncate didn't happen while we were allocating a block.
287 * If it did, this block may or may not be still allocated to the
288 * file. We can't tell the filesystem to free it because we can't
289 * take i_mutex here. In the worst case, the file still has blocks
290 * allocated past the end of the file.
291 */
292 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
293 if (unlikely(vmf->pgoff >= size)) {
294 error = -EIO;
295 goto out;
296 }
297
298 error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size);
299 if (error < 0)
300 goto out;
301 if (error < PAGE_SIZE) {
302 error = -EIO;
303 goto out;
304 }
305
306 if (buffer_unwritten(bh) || buffer_new(bh))
307 clear_page(addr);
308
309 error = vm_insert_mixed(vma, vaddr, pfn);
310
311 out:
312 i_mmap_unlock_read(mapping);
313
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800314 return error;
315}
316
Dave Chinnerce5c5d52015-06-04 09:18:18 +1000317/**
318 * __dax_fault - handle a page fault on a DAX file
319 * @vma: The virtual memory area where the fault occurred
320 * @vmf: The description of the fault
321 * @get_block: The filesystem method used to translate file offsets to blocks
322 *
323 * When a page fault occurs, filesystems may call this helper in their
324 * fault handler for DAX files. __dax_fault() assumes the caller has done all
325 * the necessary locking for the page fault to proceed successfully.
326 */
327int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
Dave Chinnere842f292015-06-04 09:18:18 +1000328 get_block_t get_block, dax_iodone_t complete_unwritten)
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800329{
330 struct file *file = vma->vm_file;
331 struct address_space *mapping = file->f_mapping;
332 struct inode *inode = mapping->host;
333 struct page *page;
334 struct buffer_head bh;
335 unsigned long vaddr = (unsigned long)vmf->virtual_address;
336 unsigned blkbits = inode->i_blkbits;
337 sector_t block;
338 pgoff_t size;
339 int error;
340 int major = 0;
341
342 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
343 if (vmf->pgoff >= size)
344 return VM_FAULT_SIGBUS;
345
346 memset(&bh, 0, sizeof(bh));
347 block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
348 bh.b_size = PAGE_SIZE;
349
350 repeat:
351 page = find_get_page(mapping, vmf->pgoff);
352 if (page) {
353 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
354 page_cache_release(page);
355 return VM_FAULT_RETRY;
356 }
357 if (unlikely(page->mapping != mapping)) {
358 unlock_page(page);
359 page_cache_release(page);
360 goto repeat;
361 }
362 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
363 if (unlikely(vmf->pgoff >= size)) {
364 /*
365 * We have a struct page covering a hole in the file
366 * from a read fault and we've raced with a truncate
367 */
368 error = -EIO;
369 goto unlock_page;
370 }
371 }
372
373 error = get_block(inode, block, &bh, 0);
374 if (!error && (bh.b_size < PAGE_SIZE))
375 error = -EIO; /* fs corruption? */
376 if (error)
377 goto unlock_page;
378
379 if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
380 if (vmf->flags & FAULT_FLAG_WRITE) {
381 error = get_block(inode, block, &bh, 1);
382 count_vm_event(PGMAJFAULT);
383 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
384 major = VM_FAULT_MAJOR;
385 if (!error && (bh.b_size < PAGE_SIZE))
386 error = -EIO;
387 if (error)
388 goto unlock_page;
389 } else {
390 return dax_load_hole(mapping, page, vmf);
391 }
392 }
393
394 if (vmf->cow_page) {
395 struct page *new_page = vmf->cow_page;
396 if (buffer_written(&bh))
397 error = copy_user_bh(new_page, &bh, blkbits, vaddr);
398 else
399 clear_user_highpage(new_page, vaddr);
400 if (error)
401 goto unlock_page;
402 vmf->page = page;
403 if (!page) {
404 i_mmap_lock_read(mapping);
405 /* Check we didn't race with truncate */
406 size = (i_size_read(inode) + PAGE_SIZE - 1) >>
407 PAGE_SHIFT;
408 if (vmf->pgoff >= size) {
409 i_mmap_unlock_read(mapping);
410 error = -EIO;
411 goto out;
412 }
413 }
414 return VM_FAULT_LOCKED;
415 }
416
417 /* Check we didn't race with a read fault installing a new page */
418 if (!page && major)
419 page = find_lock_page(mapping, vmf->pgoff);
420
421 if (page) {
422 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
423 PAGE_CACHE_SIZE, 0);
424 delete_from_page_cache(page);
425 unlock_page(page);
426 page_cache_release(page);
427 }
428
Dave Chinnere842f292015-06-04 09:18:18 +1000429 /*
430 * If we successfully insert the new mapping over an unwritten extent,
431 * we need to ensure we convert the unwritten extent. If there is an
432 * error inserting the mapping, the filesystem needs to leave it as
433 * unwritten to prevent exposure of the stale underlying data to
434 * userspace, but we still need to call the completion function so
435 * the private resources on the mapping buffer can be released. We
436 * indicate what the callback should do via the uptodate variable, same
437 * as for normal BH based IO completions.
438 */
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800439 error = dax_insert_mapping(inode, &bh, vma, vmf);
Dave Chinnere842f292015-06-04 09:18:18 +1000440 if (buffer_unwritten(&bh))
441 complete_unwritten(&bh, !error);
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800442
443 out:
444 if (error == -ENOMEM)
445 return VM_FAULT_OOM | major;
446 /* -EBUSY is fine, somebody else faulted on the same PTE */
447 if ((error < 0) && (error != -EBUSY))
448 return VM_FAULT_SIGBUS | major;
449 return VM_FAULT_NOPAGE | major;
450
451 unlock_page:
452 if (page) {
453 unlock_page(page);
454 page_cache_release(page);
455 }
456 goto out;
457}
Dave Chinnerce5c5d52015-06-04 09:18:18 +1000458EXPORT_SYMBOL(__dax_fault);
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800459
460/**
461 * dax_fault - handle a page fault on a DAX file
462 * @vma: The virtual memory area where the fault occurred
463 * @vmf: The description of the fault
464 * @get_block: The filesystem method used to translate file offsets to blocks
465 *
466 * When a page fault occurs, filesystems may call this helper in their
467 * fault handler for DAX files.
468 */
469int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
Dave Chinnere842f292015-06-04 09:18:18 +1000470 get_block_t get_block, dax_iodone_t complete_unwritten)
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800471{
472 int result;
473 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
474
475 if (vmf->flags & FAULT_FLAG_WRITE) {
476 sb_start_pagefault(sb);
477 file_update_time(vma->vm_file);
478 }
Dave Chinnerce5c5d52015-06-04 09:18:18 +1000479 result = __dax_fault(vma, vmf, get_block, complete_unwritten);
Matthew Wilcoxf7ca90b2015-02-16 15:59:02 -0800480 if (vmf->flags & FAULT_FLAG_WRITE)
481 sb_end_pagefault(sb);
482
483 return result;
484}
485EXPORT_SYMBOL_GPL(dax_fault);
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800486
487/**
Boaz Harrosh0e3b2102015-04-15 16:15:14 -0700488 * dax_pfn_mkwrite - handle first write to DAX page
489 * @vma: The virtual memory area where the fault occurred
490 * @vmf: The description of the fault
491 *
492 */
493int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
494{
495 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
496
497 sb_start_pagefault(sb);
498 file_update_time(vma->vm_file);
499 sb_end_pagefault(sb);
500 return VM_FAULT_NOPAGE;
501}
502EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
503
504/**
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800505 * dax_zero_page_range - zero a range within a page of a DAX file
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800506 * @inode: The file being truncated
507 * @from: The file offset that is being truncated to
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800508 * @length: The number of bytes to zero
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800509 * @get_block: The filesystem method used to translate file offsets to blocks
510 *
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800511 * This function can be called by a filesystem when it is zeroing part of a
512 * page in a DAX file. This is intended for hole-punch operations. If
513 * you are truncating a file, the helper function dax_truncate_page() may be
514 * more convenient.
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800515 *
516 * We work in terms of PAGE_CACHE_SIZE here for commonality with
517 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
518 * took care of disposing of the unnecessary blocks. Even if the filesystem
519 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800520 * since the file might be mmapped.
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800521 */
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800522int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
523 get_block_t get_block)
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800524{
525 struct buffer_head bh;
526 pgoff_t index = from >> PAGE_CACHE_SHIFT;
527 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800528 int err;
529
530 /* Block boundary? Nothing to do */
531 if (!length)
532 return 0;
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800533 BUG_ON((offset + length) > PAGE_CACHE_SIZE);
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800534
535 memset(&bh, 0, sizeof(bh));
536 bh.b_size = PAGE_CACHE_SIZE;
537 err = get_block(inode, index, &bh, 0);
538 if (err < 0)
539 return err;
540 if (buffer_written(&bh)) {
541 void *addr;
542 err = dax_get_addr(&bh, &addr, inode->i_blkbits);
543 if (err < 0)
544 return err;
545 memset(addr + offset, 0, length);
546 }
547
548 return 0;
549}
Matthew Wilcox25726bc2015-02-16 15:59:35 -0800550EXPORT_SYMBOL_GPL(dax_zero_page_range);
551
552/**
553 * dax_truncate_page - handle a partial page being truncated in a DAX file
554 * @inode: The file being truncated
555 * @from: The file offset that is being truncated to
556 * @get_block: The filesystem method used to translate file offsets to blocks
557 *
558 * Similar to block_truncate_page(), this function can be called by a
559 * filesystem when it is truncating a DAX file to handle the partial page.
560 *
561 * We work in terms of PAGE_CACHE_SIZE here for commonality with
562 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
563 * took care of disposing of the unnecessary blocks. Even if the filesystem
564 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
565 * since the file might be mmapped.
566 */
567int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
568{
569 unsigned length = PAGE_CACHE_ALIGN(from) - from;
570 return dax_zero_page_range(inode, from, length, get_block);
571}
Matthew Wilcox4c0ccfe2015-02-16 15:59:06 -0800572EXPORT_SYMBOL_GPL(dax_truncate_page);