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TOMOYO Linux Cross Reference
Linux/fs/iomap.c

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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/task_io_accounting_ops.h>
 28 #include <linux/dax.h>
 29 #include <linux/sched/signal.h>
 30 
 31 #include "internal.h"
 32 
 33 /*
 34  * Execute a iomap write on a segment of the mapping that spans a
 35  * contiguous range of pages that have identical block mapping state.
 36  *
 37  * This avoids the need to map pages individually, do individual allocations
 38  * for each page and most importantly avoid the need for filesystem specific
 39  * locking per page. Instead, all the operations are amortised over the entire
 40  * range of pages. It is assumed that the filesystems will lock whatever
 41  * resources they require in the iomap_begin call, and release them in the
 42  * iomap_end call.
 43  */
 44 loff_t
 45 iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
 46                 const struct iomap_ops *ops, void *data, iomap_actor_t actor)
 47 {
 48         struct iomap iomap = { 0 };
 49         loff_t written = 0, ret;
 50 
 51         /*
 52          * Need to map a range from start position for length bytes. This can
 53          * span multiple pages - it is only guaranteed to return a range of a
 54          * single type of pages (e.g. all into a hole, all mapped or all
 55          * unwritten). Failure at this point has nothing to undo.
 56          *
 57          * If allocation is required for this range, reserve the space now so
 58          * that the allocation is guaranteed to succeed later on. Once we copy
 59          * the data into the page cache pages, then we cannot fail otherwise we
 60          * expose transient stale data. If the reserve fails, we can safely
 61          * back out at this point as there is nothing to undo.
 62          */
 63         ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
 64         if (ret)
 65                 return ret;
 66         if (WARN_ON(iomap.offset > pos))
 67                 return -EIO;
 68         if (WARN_ON(iomap.length == 0))
 69                 return -EIO;
 70 
 71         /*
 72          * Cut down the length to the one actually provided by the filesystem,
 73          * as it might not be able to give us the whole size that we requested.
 74          */
 75         if (iomap.offset + iomap.length < pos + length)
 76                 length = iomap.offset + iomap.length - pos;
 77 
 78         /*
 79          * Now that we have guaranteed that the space allocation will succeed.
 80          * we can do the copy-in page by page without having to worry about
 81          * failures exposing transient data.
 82          */
 83         written = actor(inode, pos, length, data, &iomap);
 84 
 85         /*
 86          * Now the data has been copied, commit the range we've copied.  This
 87          * should not fail unless the filesystem has had a fatal error.
 88          */
 89         if (ops->iomap_end) {
 90                 ret = ops->iomap_end(inode, pos, length,
 91                                      written > 0 ? written : 0,
 92                                      flags, &iomap);
 93         }
 94 
 95         return written ? written : ret;
 96 }
 97 
 98 static void
 99 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
100 {
101         loff_t i_size = i_size_read(inode);
102 
103         /*
104          * Only truncate newly allocated pages beyoned EOF, even if the
105          * write started inside the existing inode size.
106          */
107         if (pos + len > i_size)
108                 truncate_pagecache_range(inode, max(pos, i_size), pos + len);
109 }
110 
111 static int
112 iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
113                 struct page **pagep, struct iomap *iomap)
114 {
115         pgoff_t index = pos >> PAGE_SHIFT;
116         struct page *page;
117         int status = 0;
118 
119         BUG_ON(pos + len > iomap->offset + iomap->length);
120 
121         if (fatal_signal_pending(current))
122                 return -EINTR;
123 
124         page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
125         if (!page)
126                 return -ENOMEM;
127 
128         status = __block_write_begin_int(page, pos, len, NULL, iomap);
129         if (unlikely(status)) {
130                 unlock_page(page);
131                 put_page(page);
132                 page = NULL;
133 
134                 iomap_write_failed(inode, pos, len);
135         }
136 
137         *pagep = page;
138         return status;
139 }
140 
141 static int
142 iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
143                 unsigned copied, struct page *page)
144 {
145         int ret;
146 
147         ret = generic_write_end(NULL, inode->i_mapping, pos, len,
148                         copied, page, NULL);
149         if (ret < len)
150                 iomap_write_failed(inode, pos, len);
151         return ret;
152 }
153 
154 static loff_t
155 iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
156                 struct iomap *iomap)
157 {
158         struct iov_iter *i = data;
159         long status = 0;
160         ssize_t written = 0;
161         unsigned int flags = AOP_FLAG_NOFS;
162 
163         do {
164                 struct page *page;
165                 unsigned long offset;   /* Offset into pagecache page */
166                 unsigned long bytes;    /* Bytes to write to page */
167                 size_t copied;          /* Bytes copied from user */
168 
169                 offset = (pos & (PAGE_SIZE - 1));
170                 bytes = min_t(unsigned long, PAGE_SIZE - offset,
171                                                 iov_iter_count(i));
172 again:
173                 if (bytes > length)
174                         bytes = length;
175 
176                 /*
177                  * Bring in the user page that we will copy from _first_.
178                  * Otherwise there's a nasty deadlock on copying from the
179                  * same page as we're writing to, without it being marked
180                  * up-to-date.
181                  *
182                  * Not only is this an optimisation, but it is also required
183                  * to check that the address is actually valid, when atomic
184                  * usercopies are used, below.
185                  */
186                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
187                         status = -EFAULT;
188                         break;
189                 }
190 
191                 status = iomap_write_begin(inode, pos, bytes, flags, &page,
192                                 iomap);
193                 if (unlikely(status))
194                         break;
195 
196                 if (mapping_writably_mapped(inode->i_mapping))
197                         flush_dcache_page(page);
198 
199                 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
200 
201                 flush_dcache_page(page);
202 
203                 status = iomap_write_end(inode, pos, bytes, copied, page);
204                 if (unlikely(status < 0))
205                         break;
206                 copied = status;
207 
208                 cond_resched();
209 
210                 iov_iter_advance(i, copied);
211                 if (unlikely(copied == 0)) {
212                         /*
213                          * If we were unable to copy any data at all, we must
214                          * fall back to a single segment length write.
215                          *
216                          * If we didn't fallback here, we could livelock
217                          * because not all segments in the iov can be copied at
218                          * once without a pagefault.
219                          */
220                         bytes = min_t(unsigned long, PAGE_SIZE - offset,
221                                                 iov_iter_single_seg_count(i));
222                         goto again;
223                 }
224                 pos += copied;
225                 written += copied;
226                 length -= copied;
227 
228                 balance_dirty_pages_ratelimited(inode->i_mapping);
229         } while (iov_iter_count(i) && length);
230 
231         return written ? written : status;
232 }
233 
234 ssize_t
235 iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
236                 const struct iomap_ops *ops)
237 {
238         struct inode *inode = iocb->ki_filp->f_mapping->host;
239         loff_t pos = iocb->ki_pos, ret = 0, written = 0;
240 
241         while (iov_iter_count(iter)) {
242                 ret = iomap_apply(inode, pos, iov_iter_count(iter),
243                                 IOMAP_WRITE, ops, iter, iomap_write_actor);
244                 if (ret <= 0)
245                         break;
246                 pos += ret;
247                 written += ret;
248         }
249 
250         return written ? written : ret;
251 }
252 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
253 
254 static struct page *
255 __iomap_read_page(struct inode *inode, loff_t offset)
256 {
257         struct address_space *mapping = inode->i_mapping;
258         struct page *page;
259 
260         page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
261         if (IS_ERR(page))
262                 return page;
263         if (!PageUptodate(page)) {
264                 put_page(page);
265                 return ERR_PTR(-EIO);
266         }
267         return page;
268 }
269 
270 static loff_t
271 iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
272                 struct iomap *iomap)
273 {
274         long status = 0;
275         ssize_t written = 0;
276 
277         do {
278                 struct page *page, *rpage;
279                 unsigned long offset;   /* Offset into pagecache page */
280                 unsigned long bytes;    /* Bytes to write to page */
281 
282                 offset = (pos & (PAGE_SIZE - 1));
283                 bytes = min_t(loff_t, PAGE_SIZE - offset, length);
284 
285                 rpage = __iomap_read_page(inode, pos);
286                 if (IS_ERR(rpage))
287                         return PTR_ERR(rpage);
288 
289                 status = iomap_write_begin(inode, pos, bytes,
290                                            AOP_FLAG_NOFS, &page, iomap);
291                 put_page(rpage);
292                 if (unlikely(status))
293                         return status;
294 
295                 WARN_ON_ONCE(!PageUptodate(page));
296 
297                 status = iomap_write_end(inode, pos, bytes, bytes, page);
298                 if (unlikely(status <= 0)) {
299                         if (WARN_ON_ONCE(status == 0))
300                                 return -EIO;
301                         return status;
302                 }
303 
304                 cond_resched();
305 
306                 pos += status;
307                 written += status;
308                 length -= status;
309 
310                 balance_dirty_pages_ratelimited(inode->i_mapping);
311         } while (length);
312 
313         return written;
314 }
315 
316 int
317 iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
318                 const struct iomap_ops *ops)
319 {
320         loff_t ret;
321 
322         while (len) {
323                 ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
324                                 iomap_dirty_actor);
325                 if (ret <= 0)
326                         return ret;
327                 pos += ret;
328                 len -= ret;
329         }
330 
331         return 0;
332 }
333 EXPORT_SYMBOL_GPL(iomap_file_dirty);
334 
335 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
336                 unsigned bytes, struct iomap *iomap)
337 {
338         struct page *page;
339         int status;
340 
341         status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
342                                    iomap);
343         if (status)
344                 return status;
345 
346         zero_user(page, offset, bytes);
347         mark_page_accessed(page);
348 
349         return iomap_write_end(inode, pos, bytes, bytes, page);
350 }
351 
352 static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
353                 struct iomap *iomap)
354 {
355         sector_t sector = (iomap->addr +
356                            (pos & PAGE_MASK) - iomap->offset) >> 9;
357 
358         return __dax_zero_page_range(iomap->bdev, iomap->dax_dev, sector,
359                         offset, bytes);
360 }
361 
362 static loff_t
363 iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
364                 void *data, struct iomap *iomap)
365 {
366         bool *did_zero = data;
367         loff_t written = 0;
368         int status;
369 
370         /* already zeroed?  we're done. */
371         if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
372                 return count;
373 
374         do {
375                 unsigned offset, bytes;
376 
377                 offset = pos & (PAGE_SIZE - 1); /* Within page */
378                 bytes = min_t(loff_t, PAGE_SIZE - offset, count);
379 
380                 if (IS_DAX(inode))
381                         status = iomap_dax_zero(pos, offset, bytes, iomap);
382                 else
383                         status = iomap_zero(inode, pos, offset, bytes, iomap);
384                 if (status < 0)
385                         return status;
386 
387                 pos += bytes;
388                 count -= bytes;
389                 written += bytes;
390                 if (did_zero)
391                         *did_zero = true;
392         } while (count > 0);
393 
394         return written;
395 }
396 
397 int
398 iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
399                 const struct iomap_ops *ops)
400 {
401         loff_t ret;
402 
403         while (len > 0) {
404                 ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
405                                 ops, did_zero, iomap_zero_range_actor);
406                 if (ret <= 0)
407                         return ret;
408 
409                 pos += ret;
410                 len -= ret;
411         }
412 
413         return 0;
414 }
415 EXPORT_SYMBOL_GPL(iomap_zero_range);
416 
417 int
418 iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
419                 const struct iomap_ops *ops)
420 {
421         unsigned int blocksize = i_blocksize(inode);
422         unsigned int off = pos & (blocksize - 1);
423 
424         /* Block boundary? Nothing to do */
425         if (!off)
426                 return 0;
427         return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
428 }
429 EXPORT_SYMBOL_GPL(iomap_truncate_page);
430 
431 static loff_t
432 iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
433                 void *data, struct iomap *iomap)
434 {
435         struct page *page = data;
436         int ret;
437 
438         ret = __block_write_begin_int(page, pos, length, NULL, iomap);
439         if (ret)
440                 return ret;
441 
442         block_commit_write(page, 0, length);
443         return length;
444 }
445 
446 int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
447 {
448         struct page *page = vmf->page;
449         struct inode *inode = file_inode(vmf->vma->vm_file);
450         unsigned long length;
451         loff_t offset, size;
452         ssize_t ret;
453 
454         lock_page(page);
455         size = i_size_read(inode);
456         if ((page->mapping != inode->i_mapping) ||
457             (page_offset(page) > size)) {
458                 /* We overload EFAULT to mean page got truncated */
459                 ret = -EFAULT;
460                 goto out_unlock;
461         }
462 
463         /* page is wholly or partially inside EOF */
464         if (((page->index + 1) << PAGE_SHIFT) > size)
465                 length = size & ~PAGE_MASK;
466         else
467                 length = PAGE_SIZE;
468 
469         offset = page_offset(page);
470         while (length > 0) {
471                 ret = iomap_apply(inode, offset, length,
472                                 IOMAP_WRITE | IOMAP_FAULT, ops, page,
473                                 iomap_page_mkwrite_actor);
474                 if (unlikely(ret <= 0))
475                         goto out_unlock;
476                 offset += ret;
477                 length -= ret;
478         }
479 
480         set_page_dirty(page);
481         wait_for_stable_page(page);
482         return VM_FAULT_LOCKED;
483 out_unlock:
484         unlock_page(page);
485         return block_page_mkwrite_return(ret);
486 }
487 EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
488 
489 struct fiemap_ctx {
490         struct fiemap_extent_info *fi;
491         struct iomap prev;
492 };
493 
494 static int iomap_to_fiemap(struct fiemap_extent_info *fi,
495                 struct iomap *iomap, u32 flags)
496 {
497         switch (iomap->type) {
498         case IOMAP_HOLE:
499                 /* skip holes */
500                 return 0;
501         case IOMAP_DELALLOC:
502                 flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
503                 break;
504         case IOMAP_UNWRITTEN:
505                 flags |= FIEMAP_EXTENT_UNWRITTEN;
506                 break;
507         case IOMAP_MAPPED:
508                 break;
509         }
510 
511         if (iomap->flags & IOMAP_F_MERGED)
512                 flags |= FIEMAP_EXTENT_MERGED;
513         if (iomap->flags & IOMAP_F_SHARED)
514                 flags |= FIEMAP_EXTENT_SHARED;
515         if (iomap->flags & IOMAP_F_DATA_INLINE)
516                 flags |= FIEMAP_EXTENT_DATA_INLINE;
517 
518         return fiemap_fill_next_extent(fi, iomap->offset,
519                         iomap->addr != IOMAP_NULL_ADDR ? iomap->addr : 0,
520                         iomap->length, flags);
521 }
522 
523 static loff_t
524 iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
525                 struct iomap *iomap)
526 {
527         struct fiemap_ctx *ctx = data;
528         loff_t ret = length;
529 
530         if (iomap->type == IOMAP_HOLE)
531                 return length;
532 
533         ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
534         ctx->prev = *iomap;
535         switch (ret) {
536         case 0:         /* success */
537                 return length;
538         case 1:         /* extent array full */
539                 return 0;
540         default:
541                 return ret;
542         }
543 }
544 
545 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
546                 loff_t start, loff_t len, const struct iomap_ops *ops)
547 {
548         struct fiemap_ctx ctx;
549         loff_t ret;
550 
551         memset(&ctx, 0, sizeof(ctx));
552         ctx.fi = fi;
553         ctx.prev.type = IOMAP_HOLE;
554 
555         ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
556         if (ret)
557                 return ret;
558 
559         if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
560                 ret = filemap_write_and_wait(inode->i_mapping);
561                 if (ret)
562                         return ret;
563         }
564 
565         while (len > 0) {
566                 ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx,
567                                 iomap_fiemap_actor);
568                 /* inode with no (attribute) mapping will give ENOENT */
569                 if (ret == -ENOENT)
570                         break;
571                 if (ret < 0)
572                         return ret;
573                 if (ret == 0)
574                         break;
575 
576                 start += ret;
577                 len -= ret;
578         }
579 
580         if (ctx.prev.type != IOMAP_HOLE) {
581                 ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
582                 if (ret < 0)
583                         return ret;
584         }
585 
586         return 0;
587 }
588 EXPORT_SYMBOL_GPL(iomap_fiemap);
589 
590 static loff_t
591 iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
592                       void *data, struct iomap *iomap)
593 {
594         switch (iomap->type) {
595         case IOMAP_UNWRITTEN:
596                 offset = page_cache_seek_hole_data(inode, offset, length,
597                                                    SEEK_HOLE);
598                 if (offset < 0)
599                         return length;
600                 /* fall through */
601         case IOMAP_HOLE:
602                 *(loff_t *)data = offset;
603                 return 0;
604         default:
605                 return length;
606         }
607 }
608 
609 loff_t
610 iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
611 {
612         loff_t size = i_size_read(inode);
613         loff_t length = size - offset;
614         loff_t ret;
615 
616         /* Nothing to be found before or beyond the end of the file. */
617         if (offset < 0 || offset >= size)
618                 return -ENXIO;
619 
620         while (length > 0) {
621                 ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
622                                   &offset, iomap_seek_hole_actor);
623                 if (ret < 0)
624                         return ret;
625                 if (ret == 0)
626                         break;
627 
628                 offset += ret;
629                 length -= ret;
630         }
631 
632         return offset;
633 }
634 EXPORT_SYMBOL_GPL(iomap_seek_hole);
635 
636 static loff_t
637 iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
638                       void *data, struct iomap *iomap)
639 {
640         switch (iomap->type) {
641         case IOMAP_HOLE:
642                 return length;
643         case IOMAP_UNWRITTEN:
644                 offset = page_cache_seek_hole_data(inode, offset, length,
645                                                    SEEK_DATA);
646                 if (offset < 0)
647                         return length;
648                 /*FALLTHRU*/
649         default:
650                 *(loff_t *)data = offset;
651                 return 0;
652         }
653 }
654 
655 loff_t
656 iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
657 {
658         loff_t size = i_size_read(inode);
659         loff_t length = size - offset;
660         loff_t ret;
661 
662         /* Nothing to be found before or beyond the end of the file. */
663         if (offset < 0 || offset >= size)
664                 return -ENXIO;
665 
666         while (length > 0) {
667                 ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
668                                   &offset, iomap_seek_data_actor);
669                 if (ret < 0)
670                         return ret;
671                 if (ret == 0)
672                         break;
673 
674                 offset += ret;
675                 length -= ret;
676         }
677 
678         if (length <= 0)
679                 return -ENXIO;
680         return offset;
681 }
682 EXPORT_SYMBOL_GPL(iomap_seek_data);
683 
684 /*
685  * Private flags for iomap_dio, must not overlap with the public ones in
686  * iomap.h:
687  */
688 #define IOMAP_DIO_WRITE         (1 << 30)
689 #define IOMAP_DIO_DIRTY         (1 << 31)
690 
691 struct iomap_dio {
692         struct kiocb            *iocb;
693         iomap_dio_end_io_t      *end_io;
694         loff_t                  i_size;
695         loff_t                  size;
696         atomic_t                ref;
697         unsigned                flags;
698         int                     error;
699 
700         union {
701                 /* used during submission and for synchronous completion: */
702                 struct {
703                         struct iov_iter         *iter;
704                         struct task_struct      *waiter;
705                         struct request_queue    *last_queue;
706                         blk_qc_t                cookie;
707                 } submit;
708 
709                 /* used for aio completion: */
710                 struct {
711                         struct work_struct      work;
712                 } aio;
713         };
714 };
715 
716 static ssize_t iomap_dio_complete(struct iomap_dio *dio)
717 {
718         struct kiocb *iocb = dio->iocb;
719         struct inode *inode = file_inode(iocb->ki_filp);
720         loff_t offset = iocb->ki_pos;
721         ssize_t ret;
722 
723         if (dio->end_io) {
724                 ret = dio->end_io(iocb,
725                                 dio->error ? dio->error : dio->size,
726                                 dio->flags);
727         } else {
728                 ret = dio->error;
729         }
730 
731         if (likely(!ret)) {
732                 ret = dio->size;
733                 /* check for short read */
734                 if (offset + ret > dio->i_size &&
735                     !(dio->flags & IOMAP_DIO_WRITE))
736                         ret = dio->i_size - offset;
737                 iocb->ki_pos += ret;
738         }
739 
740         /*
741          * Try again to invalidate clean pages which might have been cached by
742          * non-direct readahead, or faulted in by get_user_pages() if the source
743          * of the write was an mmap'ed region of the file we're writing.  Either
744          * one is a pretty crazy thing to do, so we don't support it 100%.  If
745          * this invalidation fails, tough, the write still worked...
746          *
747          * And this page cache invalidation has to be after dio->end_io(), as
748          * some filesystems convert unwritten extents to real allocations in
749          * end_io() when necessary, otherwise a racing buffer read would cache
750          * zeros from unwritten extents.
751          */
752         if (!dio->error &&
753             (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
754                 int err;
755                 err = invalidate_inode_pages2_range(inode->i_mapping,
756                                 offset >> PAGE_SHIFT,
757                                 (offset + dio->size - 1) >> PAGE_SHIFT);
758                 if (err)
759                         dio_warn_stale_pagecache(iocb->ki_filp);
760         }
761 
762         inode_dio_end(file_inode(iocb->ki_filp));
763         kfree(dio);
764 
765         return ret;
766 }
767 
768 static void iomap_dio_complete_work(struct work_struct *work)
769 {
770         struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
771         struct kiocb *iocb = dio->iocb;
772         bool is_write = (dio->flags & IOMAP_DIO_WRITE);
773         ssize_t ret;
774 
775         ret = iomap_dio_complete(dio);
776         if (is_write && ret > 0)
777                 ret = generic_write_sync(iocb, ret);
778         iocb->ki_complete(iocb, ret, 0);
779 }
780 
781 /*
782  * Set an error in the dio if none is set yet.  We have to use cmpxchg
783  * as the submission context and the completion context(s) can race to
784  * update the error.
785  */
786 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
787 {
788         cmpxchg(&dio->error, 0, ret);
789 }
790 
791 static void iomap_dio_bio_end_io(struct bio *bio)
792 {
793         struct iomap_dio *dio = bio->bi_private;
794         bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
795 
796         if (bio->bi_status)
797                 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
798 
799         if (atomic_dec_and_test(&dio->ref)) {
800                 if (is_sync_kiocb(dio->iocb)) {
801                         struct task_struct *waiter = dio->submit.waiter;
802 
803                         WRITE_ONCE(dio->submit.waiter, NULL);
804                         wake_up_process(waiter);
805                 } else if (dio->flags & IOMAP_DIO_WRITE) {
806                         struct inode *inode = file_inode(dio->iocb->ki_filp);
807 
808                         INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
809                         queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
810                 } else {
811                         iomap_dio_complete_work(&dio->aio.work);
812                 }
813         }
814 
815         if (should_dirty) {
816                 bio_check_pages_dirty(bio);
817         } else {
818                 struct bio_vec *bvec;
819                 int i;
820 
821                 bio_for_each_segment_all(bvec, bio, i)
822                         put_page(bvec->bv_page);
823                 bio_put(bio);
824         }
825 }
826 
827 static blk_qc_t
828 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
829                 unsigned len)
830 {
831         struct page *page = ZERO_PAGE(0);
832         struct bio *bio;
833 
834         bio = bio_alloc(GFP_KERNEL, 1);
835         bio_set_dev(bio, iomap->bdev);
836         bio->bi_iter.bi_sector =
837                 (iomap->addr + pos - iomap->offset) >> 9;
838         bio->bi_private = dio;
839         bio->bi_end_io = iomap_dio_bio_end_io;
840 
841         get_page(page);
842         if (bio_add_page(bio, page, len, 0) != len)
843                 BUG();
844         bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
845 
846         atomic_inc(&dio->ref);
847         return submit_bio(bio);
848 }
849 
850 static loff_t
851 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
852                 void *data, struct iomap *iomap)
853 {
854         struct iomap_dio *dio = data;
855         unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
856         unsigned int fs_block_size = i_blocksize(inode), pad;
857         unsigned int align = iov_iter_alignment(dio->submit.iter);
858         struct iov_iter iter;
859         struct bio *bio;
860         bool need_zeroout = false;
861         int nr_pages, ret;
862         size_t copied = 0;
863 
864         if ((pos | length | align) & ((1 << blkbits) - 1))
865                 return -EINVAL;
866 
867         switch (iomap->type) {
868         case IOMAP_HOLE:
869                 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
870                         return -EIO;
871                 /*FALLTHRU*/
872         case IOMAP_UNWRITTEN:
873                 if (!(dio->flags & IOMAP_DIO_WRITE)) {
874                         length = iov_iter_zero(length, dio->submit.iter);
875                         dio->size += length;
876                         return length;
877                 }
878                 dio->flags |= IOMAP_DIO_UNWRITTEN;
879                 need_zeroout = true;
880                 break;
881         case IOMAP_MAPPED:
882                 if (iomap->flags & IOMAP_F_SHARED)
883                         dio->flags |= IOMAP_DIO_COW;
884                 if (iomap->flags & IOMAP_F_NEW)
885                         need_zeroout = true;
886                 break;
887         default:
888                 WARN_ON_ONCE(1);
889                 return -EIO;
890         }
891 
892         /*
893          * Operate on a partial iter trimmed to the extent we were called for.
894          * We'll update the iter in the dio once we're done with this extent.
895          */
896         iter = *dio->submit.iter;
897         iov_iter_truncate(&iter, length);
898 
899         nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
900         if (nr_pages <= 0)
901                 return nr_pages;
902 
903         if (need_zeroout) {
904                 /* zero out from the start of the block to the write offset */
905                 pad = pos & (fs_block_size - 1);
906                 if (pad)
907                         iomap_dio_zero(dio, iomap, pos - pad, pad);
908         }
909 
910         do {
911                 size_t n;
912                 if (dio->error) {
913                         iov_iter_revert(dio->submit.iter, copied);
914                         return 0;
915                 }
916 
917                 bio = bio_alloc(GFP_KERNEL, nr_pages);
918                 bio_set_dev(bio, iomap->bdev);
919                 bio->bi_iter.bi_sector =
920                         (iomap->addr + pos - iomap->offset) >> 9;
921                 bio->bi_write_hint = dio->iocb->ki_hint;
922                 bio->bi_private = dio;
923                 bio->bi_end_io = iomap_dio_bio_end_io;
924 
925                 ret = bio_iov_iter_get_pages(bio, &iter);
926                 if (unlikely(ret)) {
927                         bio_put(bio);
928                         return copied ? copied : ret;
929                 }
930 
931                 n = bio->bi_iter.bi_size;
932                 if (dio->flags & IOMAP_DIO_WRITE) {
933                         bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
934                         task_io_account_write(n);
935                 } else {
936                         bio_set_op_attrs(bio, REQ_OP_READ, 0);
937                         if (dio->flags & IOMAP_DIO_DIRTY)
938                                 bio_set_pages_dirty(bio);
939                 }
940 
941                 iov_iter_advance(dio->submit.iter, n);
942 
943                 dio->size += n;
944                 pos += n;
945                 copied += n;
946 
947                 nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
948 
949                 atomic_inc(&dio->ref);
950 
951                 dio->submit.last_queue = bdev_get_queue(iomap->bdev);
952                 dio->submit.cookie = submit_bio(bio);
953         } while (nr_pages);
954 
955         if (need_zeroout) {
956                 /* zero out from the end of the write to the end of the block */
957                 pad = pos & (fs_block_size - 1);
958                 if (pad)
959                         iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
960         }
961         return copied;
962 }
963 
964 ssize_t
965 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
966                 const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
967 {
968         struct address_space *mapping = iocb->ki_filp->f_mapping;
969         struct inode *inode = file_inode(iocb->ki_filp);
970         size_t count = iov_iter_count(iter);
971         loff_t pos = iocb->ki_pos, start = pos;
972         loff_t end = iocb->ki_pos + count - 1, ret = 0;
973         unsigned int flags = IOMAP_DIRECT;
974         struct blk_plug plug;
975         struct iomap_dio *dio;
976 
977         lockdep_assert_held(&inode->i_rwsem);
978 
979         if (!count)
980                 return 0;
981 
982         dio = kmalloc(sizeof(*dio), GFP_KERNEL);
983         if (!dio)
984                 return -ENOMEM;
985 
986         dio->iocb = iocb;
987         atomic_set(&dio->ref, 1);
988         dio->size = 0;
989         dio->i_size = i_size_read(inode);
990         dio->end_io = end_io;
991         dio->error = 0;
992         dio->flags = 0;
993 
994         dio->submit.iter = iter;
995         if (is_sync_kiocb(iocb)) {
996                 dio->submit.waiter = current;
997                 dio->submit.cookie = BLK_QC_T_NONE;
998                 dio->submit.last_queue = NULL;
999         }
1000 
1001         if (iov_iter_rw(iter) == READ) {
1002                 if (pos >= dio->i_size)
1003                         goto out_free_dio;
1004 
1005                 if (iter->type == ITER_IOVEC)
1006                         dio->flags |= IOMAP_DIO_DIRTY;
1007         } else {
1008                 dio->flags |= IOMAP_DIO_WRITE;
1009                 flags |= IOMAP_WRITE;
1010         }
1011 
1012         if (iocb->ki_flags & IOCB_NOWAIT) {
1013                 if (filemap_range_has_page(mapping, start, end)) {
1014                         ret = -EAGAIN;
1015                         goto out_free_dio;
1016                 }
1017                 flags |= IOMAP_NOWAIT;
1018         }
1019 
1020         ret = filemap_write_and_wait_range(mapping, start, end);
1021         if (ret)
1022                 goto out_free_dio;
1023 
1024         /*
1025          * Try to invalidate cache pages for the range we're direct
1026          * writing.  If this invalidation fails, tough, the write will
1027          * still work, but racing two incompatible write paths is a
1028          * pretty crazy thing to do, so we don't support it 100%.
1029          */
1030         ret = invalidate_inode_pages2_range(mapping,
1031                         start >> PAGE_SHIFT, end >> PAGE_SHIFT);
1032         if (ret)
1033                 dio_warn_stale_pagecache(iocb->ki_filp);
1034         ret = 0;
1035 
1036         if (iov_iter_rw(iter) == WRITE && !is_sync_kiocb(iocb) &&
1037             !inode->i_sb->s_dio_done_wq) {
1038                 ret = sb_init_dio_done_wq(inode->i_sb);
1039                 if (ret < 0)
1040                         goto out_free_dio;
1041         }
1042 
1043         inode_dio_begin(inode);
1044 
1045         blk_start_plug(&plug);
1046         do {
1047                 ret = iomap_apply(inode, pos, count, flags, ops, dio,
1048                                 iomap_dio_actor);
1049                 if (ret <= 0) {
1050                         /* magic error code to fall back to buffered I/O */
1051                         if (ret == -ENOTBLK)
1052                                 ret = 0;
1053                         break;
1054                 }
1055                 pos += ret;
1056 
1057                 if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
1058                         break;
1059         } while ((count = iov_iter_count(iter)) > 0);
1060         blk_finish_plug(&plug);
1061 
1062         if (ret < 0)
1063                 iomap_dio_set_error(dio, ret);
1064 
1065         if (!atomic_dec_and_test(&dio->ref)) {
1066                 if (!is_sync_kiocb(iocb))
1067                         return -EIOCBQUEUED;
1068 
1069                 for (;;) {
1070                         set_current_state(TASK_UNINTERRUPTIBLE);
1071                         if (!READ_ONCE(dio->submit.waiter))
1072                                 break;
1073 
1074                         if (!(iocb->ki_flags & IOCB_HIPRI) ||
1075                             !dio->submit.last_queue ||
1076                             !blk_poll(dio->submit.last_queue,
1077                                          dio->submit.cookie))
1078                                 io_schedule();
1079                 }
1080                 __set_current_state(TASK_RUNNING);
1081         }
1082 
1083         ret = iomap_dio_complete(dio);
1084 
1085         return ret;
1086 
1087 out_free_dio:
1088         kfree(dio);
1089         return ret;
1090 }
1091 EXPORT_SYMBOL_GPL(iomap_dio_rw);
1092 

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