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1 /*
2 * Copyright (C) 2010 Red Hat, Inc.
3 * Copyright (c) 2016 Christoph Hellwig.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 */
14 #include <linux/module.h>
15 #include <linux/compiler.h>
16 #include <linux/fs.h>
17 #include <linux/iomap.h>
18 #include <linux/uaccess.h>
19 #include <linux/gfp.h>
20 #include <linux/mm.h>
21 #include <linux/swap.h>
22 #include <linux/pagemap.h>
23 #include <linux/file.h>
24 #include <linux/uio.h>
25 #include <linux/backing-dev.h>
26 #include <linux/buffer_head.h>
27 #include <linux/dax.h>
28 #include "internal.h"
29
30 /*
31 * Execute a iomap write on a segment of the mapping that spans a
32 * contiguous range of pages that have identical block mapping state.
33 *
34 * This avoids the need to map pages individually, do individual allocations
35 * for each page and most importantly avoid the need for filesystem specific
36 * locking per page. Instead, all the operations are amortised over the entire
37 * range of pages. It is assumed that the filesystems will lock whatever
38 * resources they require in the iomap_begin call, and release them in the
39 * iomap_end call.
40 */
41 loff_t
42 iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
43 struct iomap_ops *ops, void *data, iomap_actor_t actor)
44 {
45 struct iomap iomap = { 0 };
46 loff_t written = 0, ret;
47
48 /*
49 * Need to map a range from start position for length bytes. This can
50 * span multiple pages - it is only guaranteed to return a range of a
51 * single type of pages (e.g. all into a hole, all mapped or all
52 * unwritten). Failure at this point has nothing to undo.
53 *
54 * If allocation is required for this range, reserve the space now so
55 * that the allocation is guaranteed to succeed later on. Once we copy
56 * the data into the page cache pages, then we cannot fail otherwise we
57 * expose transient stale data. If the reserve fails, we can safely
58 * back out at this point as there is nothing to undo.
59 */
60 ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
61 if (ret)
62 return ret;
63 if (WARN_ON(iomap.offset > pos))
64 return -EIO;
65
66 /*
67 * Cut down the length to the one actually provided by the filesystem,
68 * as it might not be able to give us the whole size that we requested.
69 */
70 if (iomap.offset + iomap.length < pos + length)
71 length = iomap.offset + iomap.length - pos;
72
73 /*
74 * Now that we have guaranteed that the space allocation will succeed.
75 * we can do the copy-in page by page without having to worry about
76 * failures exposing transient data.
77 */
78 written = actor(inode, pos, length, data, &iomap);
79
80 /*
81 * Now the data has been copied, commit the range we've copied. This
82 * should not fail unless the filesystem has had a fatal error.
83 */
84 if (ops->iomap_end) {
85 ret = ops->iomap_end(inode, pos, length,
86 written > 0 ? written : 0,
87 flags, &iomap);
88 }
89
90 return written ? written : ret;
91 }
92
93 static void
94 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
95 {
96 loff_t i_size = i_size_read(inode);
97
98 /*
99 * Only truncate newly allocated pages beyoned EOF, even if the
100 * write started inside the existing inode size.
101 */
102 if (pos + len > i_size)
103 truncate_pagecache_range(inode, max(pos, i_size), pos + len);
104 }
105
106 static int
107 iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
108 struct page **pagep, struct iomap *iomap)
109 {
110 pgoff_t index = pos >> PAGE_SHIFT;
111 struct page *page;
112 int status = 0;
113
114 BUG_ON(pos + len > iomap->offset + iomap->length);
115
116 page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
117 if (!page)
118 return -ENOMEM;
119
120 status = __block_write_begin_int(page, pos, len, NULL, iomap);
121 if (unlikely(status)) {
122 unlock_page(page);
123 put_page(page);
124 page = NULL;
125
126 iomap_write_failed(inode, pos, len);
127 }
128
129 *pagep = page;
130 return status;
131 }
132
133 static int
134 iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
135 unsigned copied, struct page *page)
136 {
137 int ret;
138
139 ret = generic_write_end(NULL, inode->i_mapping, pos, len,
140 copied, page, NULL);
141 if (ret < len)
142 iomap_write_failed(inode, pos, len);
143 return ret;
144 }
145
146 static loff_t
147 iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
148 struct iomap *iomap)
149 {
150 struct iov_iter *i = data;
151 long status = 0;
152 ssize_t written = 0;
153 unsigned int flags = AOP_FLAG_NOFS;
154
155 /*
156 * Copies from kernel address space cannot fail (NFSD is a big user).
157 */
158 if (!iter_is_iovec(i))
159 flags |= AOP_FLAG_UNINTERRUPTIBLE;
160
161 do {
162 struct page *page;
163 unsigned long offset; /* Offset into pagecache page */
164 unsigned long bytes; /* Bytes to write to page */
165 size_t copied; /* Bytes copied from user */
166
167 offset = (pos & (PAGE_SIZE - 1));
168 bytes = min_t(unsigned long, PAGE_SIZE - offset,
169 iov_iter_count(i));
170 again:
171 if (bytes > length)
172 bytes = length;
173
174 /*
175 * Bring in the user page that we will copy from _first_.
176 * Otherwise there's a nasty deadlock on copying from the
177 * same page as we're writing to, without it being marked
178 * up-to-date.
179 *
180 * Not only is this an optimisation, but it is also required
181 * to check that the address is actually valid, when atomic
182 * usercopies are used, below.
183 */
184 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
185 status = -EFAULT;
186 break;
187 }
188
189 status = iomap_write_begin(inode, pos, bytes, flags, &page,
190 iomap);
191 if (unlikely(status))
192 break;
193
194 if (mapping_writably_mapped(inode->i_mapping))
195 flush_dcache_page(page);
196
197 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
198
199 flush_dcache_page(page);
200
201 status = iomap_write_end(inode, pos, bytes, copied, page);
202 if (unlikely(status < 0))
203 break;
204 copied = status;
205
206 cond_resched();
207
208 iov_iter_advance(i, copied);
209 if (unlikely(copied == 0)) {
210 /*
211 * If we were unable to copy any data at all, we must
212 * fall back to a single segment length write.
213 *
214 * If we didn't fallback here, we could livelock
215 * because not all segments in the iov can be copied at
216 * once without a pagefault.
217 */
218 bytes = min_t(unsigned long, PAGE_SIZE - offset,
219 iov_iter_single_seg_count(i));
220 goto again;
221 }
222 pos += copied;
223 written += copied;
224 length -= copied;
225
226 balance_dirty_pages_ratelimited(inode->i_mapping);
227 } while (iov_iter_count(i) && length);
228
229 return written ? written : status;
230 }
231
232 ssize_t
233 iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
234 struct iomap_ops *ops)
235 {
236 struct inode *inode = iocb->ki_filp->f_mapping->host;
237 loff_t pos = iocb->ki_pos, ret = 0, written = 0;
238
239 while (iov_iter_count(iter)) {
240 ret = iomap_apply(inode, pos, iov_iter_count(iter),
241 IOMAP_WRITE, ops, iter, iomap_write_actor);
242 if (ret <= 0)
243 break;
244 pos += ret;
245 written += ret;
246 }
247
248 return written ? written : ret;
249 }
250 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
251
252 static struct page *
253 __iomap_read_page(struct inode *inode, loff_t offset)
254 {
255 struct address_space *mapping = inode->i_mapping;
256 struct page *page;
257
258 page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
259 if (IS_ERR(page))
260 return page;
261 if (!PageUptodate(page)) {
262 put_page(page);
263 return ERR_PTR(-EIO);
264 }
265 return page;
266 }
267
268 static loff_t
269 iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
270 struct iomap *iomap)
271 {
272 long status = 0;
273 ssize_t written = 0;
274
275 do {
276 struct page *page, *rpage;
277 unsigned long offset; /* Offset into pagecache page */
278 unsigned long bytes; /* Bytes to write to page */
279
280 offset = (pos & (PAGE_SIZE - 1));
281 bytes = min_t(unsigned long, PAGE_SIZE - offset, length);
282
283 rpage = __iomap_read_page(inode, pos);
284 if (IS_ERR(rpage))
285 return PTR_ERR(rpage);
286
287 status = iomap_write_begin(inode, pos, bytes,
288 AOP_FLAG_NOFS | AOP_FLAG_UNINTERRUPTIBLE,
289 &page, iomap);
290 put_page(rpage);
291 if (unlikely(status))
292 return status;
293
294 WARN_ON_ONCE(!PageUptodate(page));
295
296 status = iomap_write_end(inode, pos, bytes, bytes, page);
297 if (unlikely(status <= 0)) {
298 if (WARN_ON_ONCE(status == 0))
299 return -EIO;
300 return status;
301 }
302
303 cond_resched();
304
305 pos += status;
306 written += status;
307 length -= status;
308
309 balance_dirty_pages_ratelimited(inode->i_mapping);
310 } while (length);
311
312 return written;
313 }
314
315 int
316 iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
317 struct iomap_ops *ops)
318 {
319 loff_t ret;
320
321 while (len) {
322 ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
323 iomap_dirty_actor);
324 if (ret <= 0)
325 return ret;
326 pos += ret;
327 len -= ret;
328 }
329
330 return 0;
331 }
332 EXPORT_SYMBOL_GPL(iomap_file_dirty);
333
334 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
335 unsigned bytes, struct iomap *iomap)
336 {
337 struct page *page;
338 int status;
339
340 status = iomap_write_begin(inode, pos, bytes,
341 AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
342 if (status)
343 return status;
344
345 zero_user(page, offset, bytes);
346 mark_page_accessed(page);
347
348 return iomap_write_end(inode, pos, bytes, bytes, page);
349 }
350
351 static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
352 struct iomap *iomap)
353 {
354 sector_t sector = iomap->blkno +
355 (((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);
356
357 return __dax_zero_page_range(iomap->bdev, sector, offset, bytes);
358 }
359
360 static loff_t
361 iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
362 void *data, struct iomap *iomap)
363 {
364 bool *did_zero = data;
365 loff_t written = 0;
366 int status;
367
368 /* already zeroed? we're done. */
369 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
370 return count;
371
372 do {
373 unsigned offset, bytes;
374
375 offset = pos & (PAGE_SIZE - 1); /* Within page */
376 bytes = min_t(unsigned, PAGE_SIZE - offset, count);
377
378 if (IS_DAX(inode))
379 status = iomap_dax_zero(pos, offset, bytes, iomap);
380 else
381 status = iomap_zero(inode, pos, offset, bytes, iomap);
382 if (status < 0)
383 return status;
384
385 pos += bytes;
386 count -= bytes;
387 written += bytes;
388 if (did_zero)
389 *did_zero = true;
390 } while (count > 0);
391
392 return written;
393 }
394
395 int
396 iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
397 struct iomap_ops *ops)
398 {
399 loff_t ret;
400
401 while (len > 0) {
402 ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
403 ops, did_zero, iomap_zero_range_actor);
404 if (ret <= 0)
405 return ret;
406
407 pos += ret;
408 len -= ret;
409 }
410
411 return 0;
412 }
413 EXPORT_SYMBOL_GPL(iomap_zero_range);
414
415 int
416 iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
417 struct iomap_ops *ops)
418 {
419 unsigned blocksize = (1 << inode->i_blkbits);
420 unsigned off = pos & (blocksize - 1);
421
422 /* Block boundary? Nothing to do */
423 if (!off)
424 return 0;
425 return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
426 }
427 EXPORT_SYMBOL_GPL(iomap_truncate_page);
428
429 static loff_t
430 iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
431 void *data, struct iomap *iomap)
432 {
433 struct page *page = data;
434 int ret;
435
436 ret = __block_write_begin_int(page, pos, length, NULL, iomap);
437 if (ret)
438 return ret;
439
440 block_commit_write(page, 0, length);
441 return length;
442 }
443
444 int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
445 struct iomap_ops *ops)
446 {
447 struct page *page = vmf->page;
448 struct inode *inode = file_inode(vma->vm_file);
449 unsigned long length;
450 loff_t offset, size;
451 ssize_t ret;
452
453 lock_page(page);
454 size = i_size_read(inode);
455 if ((page->mapping != inode->i_mapping) ||
456 (page_offset(page) > size)) {
457 /* We overload EFAULT to mean page got truncated */
458 ret = -EFAULT;
459 goto out_unlock;
460 }
461
462 /* page is wholly or partially inside EOF */
463 if (((page->index + 1) << PAGE_SHIFT) > size)
464 length = size & ~PAGE_MASK;
465 else
466 length = PAGE_SIZE;
467
468 offset = page_offset(page);
469 while (length > 0) {
470 ret = iomap_apply(inode, offset, length, IOMAP_WRITE,
471 ops, page, iomap_page_mkwrite_actor);
472 if (unlikely(ret <= 0))
473 goto out_unlock;
474 offset += ret;
475 length -= ret;
476 }
477
478 set_page_dirty(page);
479 wait_for_stable_page(page);
480 return 0;
481 out_unlock:
482 unlock_page(page);
483 return ret;
484 }
485 EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
486
487 struct fiemap_ctx {
488 struct fiemap_extent_info *fi;
489 struct iomap prev;
490 };
491
492 static int iomap_to_fiemap(struct fiemap_extent_info *fi,
493 struct iomap *iomap, u32 flags)
494 {
495 switch (iomap->type) {
496 case IOMAP_HOLE:
497 /* skip holes */
498 return 0;
499 case IOMAP_DELALLOC:
500 flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
501 break;
502 case IOMAP_UNWRITTEN:
503 flags |= FIEMAP_EXTENT_UNWRITTEN;
504 break;
505 case IOMAP_MAPPED:
506 break;
507 }
508
509 if (iomap->flags & IOMAP_F_MERGED)
510 flags |= FIEMAP_EXTENT_MERGED;
511 if (iomap->flags & IOMAP_F_SHARED)
512 flags |= FIEMAP_EXTENT_SHARED;
513
514 return fiemap_fill_next_extent(fi, iomap->offset,
515 iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
516 iomap->length, flags);
517
518 }
519
520 static loff_t
521 iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
522 struct iomap *iomap)
523 {
524 struct fiemap_ctx *ctx = data;
525 loff_t ret = length;
526
527 if (iomap->type == IOMAP_HOLE)
528 return length;
529
530 ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
531 ctx->prev = *iomap;
532 switch (ret) {
533 case 0: /* success */
534 return length;
535 case 1: /* extent array full */
536 return 0;
537 default:
538 return ret;
539 }
540 }
541
542 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
543 loff_t start, loff_t len, struct iomap_ops *ops)
544 {
545 struct fiemap_ctx ctx;
546 loff_t ret;
547
548 memset(&ctx, 0, sizeof(ctx));
549 ctx.fi = fi;
550 ctx.prev.type = IOMAP_HOLE;
551
552 ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
553 if (ret)
554 return ret;
555
556 if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
557 ret = filemap_write_and_wait(inode->i_mapping);
558 if (ret)
559 return ret;
560 }
561
562 while (len > 0) {
563 ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx,
564 iomap_fiemap_actor);
565 /* inode with no (attribute) mapping will give ENOENT */
566 if (ret == -ENOENT)
567 break;
568 if (ret < 0)
569 return ret;
570 if (ret == 0)
571 break;
572
573 start += ret;
574 len -= ret;
575 }
576
577 if (ctx.prev.type != IOMAP_HOLE) {
578 ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
579 if (ret < 0)
580 return ret;
581 }
582
583 return 0;
584 }
585 EXPORT_SYMBOL_GPL(iomap_fiemap);