1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/slab.h>
7 #include "btrfs_inode.h"
10 * Subpage (sectorsize < PAGE_SIZE) support overview:
14 * - Only support 64K page size for now
15 * This is to make metadata handling easier, as 64K page would ensure
16 * all nodesize would fit inside one page, thus we don't need to handle
17 * cases where a tree block crosses several pages.
19 * - Only metadata read-write for now
20 * The data read-write part is in development.
22 * - Metadata can't cross 64K page boundary
23 * btrfs-progs and kernel have done that for a while, thus only ancient
24 * filesystems could have such problem. For such case, do a graceful
30 * Metadata read is fully supported.
31 * Meaning when reading one tree block will only trigger the read for the
32 * needed range, other unrelated range in the same page will not be touched.
34 * Metadata write support is partial.
35 * The writeback is still for the full page, but we will only submit
36 * the dirty extent buffers in the page.
38 * This means, if we have a metadata page like this:
42 * |/////////| |///////////|
43 * \- Tree block A \- Tree block B
45 * Even if we just want to writeback tree block A, we will also writeback
46 * tree block B if it's also dirty.
48 * This may cause extra metadata writeback which results more COW.
53 * Both metadata and data will use a new structure, btrfs_subpage, to
54 * record the status of each sector inside a page. This provides the extra
58 * Since we have multiple tree blocks inside one page, we can't rely on page
59 * locking anymore, or we will have greatly reduced concurrency or even
60 * deadlocks (hold one tree lock while trying to lock another tree lock in
63 * Thus for metadata locking, subpage support relies on io_tree locking only.
64 * This means a slightly higher tree locking latency.
67 bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping)
69 if (fs_info->sectorsize >= PAGE_SIZE)
73 * Only data pages (either through DIO or compression) can have no
74 * mapping. And if page->mapping->host is data inode, it's subpage.
75 * As we have ruled our sectorsize >= PAGE_SIZE case already.
77 if (!mapping || !mapping->host || is_data_inode(mapping->host))
81 * Now the only remaining case is metadata, which we only go subpage
82 * routine if nodesize < PAGE_SIZE.
84 if (fs_info->nodesize < PAGE_SIZE)
89 void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize)
94 ASSERT(IS_ALIGNED(PAGE_SIZE, sectorsize));
96 nr_bits = PAGE_SIZE / sectorsize;
97 subpage_info->bitmap_nr_bits = nr_bits;
99 subpage_info->uptodate_offset = cur;
102 subpage_info->dirty_offset = cur;
105 subpage_info->writeback_offset = cur;
108 subpage_info->ordered_offset = cur;
111 subpage_info->checked_offset = cur;
114 subpage_info->total_nr_bits = cur;
117 int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
118 struct folio *folio, enum btrfs_subpage_type type)
120 struct btrfs_subpage *subpage;
123 * We have cases like a dummy extent buffer page, which is not mapped
124 * and doesn't need to be locked.
127 ASSERT(folio_test_locked(folio));
129 /* Either not subpage, or the folio already has private attached. */
130 if (!btrfs_is_subpage(fs_info, folio->mapping) || folio_test_private(folio))
133 subpage = btrfs_alloc_subpage(fs_info, type);
135 return PTR_ERR(subpage);
137 folio_attach_private(folio, subpage);
141 void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *folio)
143 struct btrfs_subpage *subpage;
145 /* Either not subpage, or the folio already has private attached. */
146 if (!btrfs_is_subpage(fs_info, folio->mapping) || !folio_test_private(folio))
149 subpage = folio_detach_private(folio);
151 btrfs_free_subpage(subpage);
154 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
155 enum btrfs_subpage_type type)
157 struct btrfs_subpage *ret;
158 unsigned int real_size;
160 ASSERT(fs_info->sectorsize < PAGE_SIZE);
162 real_size = struct_size(ret, bitmaps,
163 BITS_TO_LONGS(fs_info->subpage_info->total_nr_bits));
164 ret = kzalloc(real_size, GFP_NOFS);
166 return ERR_PTR(-ENOMEM);
168 spin_lock_init(&ret->lock);
169 if (type == BTRFS_SUBPAGE_METADATA) {
170 atomic_set(&ret->eb_refs, 0);
172 atomic_set(&ret->readers, 0);
173 atomic_set(&ret->writers, 0);
178 void btrfs_free_subpage(struct btrfs_subpage *subpage)
184 * Increase the eb_refs of current subpage.
186 * This is important for eb allocation, to prevent race with last eb freeing
188 * With the eb_refs increased before the eb inserted into radix tree,
189 * detach_extent_buffer_page() won't detach the folio private while we're still
190 * allocating the extent buffer.
192 void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
194 struct btrfs_subpage *subpage;
196 if (!btrfs_is_subpage(fs_info, folio->mapping))
199 ASSERT(folio_test_private(folio) && folio->mapping);
200 lockdep_assert_held(&folio->mapping->i_private_lock);
202 subpage = folio_get_private(folio);
203 atomic_inc(&subpage->eb_refs);
206 void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
208 struct btrfs_subpage *subpage;
210 if (!btrfs_is_subpage(fs_info, folio->mapping))
213 ASSERT(folio_test_private(folio) && folio->mapping);
214 lockdep_assert_held(&folio->mapping->i_private_lock);
216 subpage = folio_get_private(folio);
217 ASSERT(atomic_read(&subpage->eb_refs));
218 atomic_dec(&subpage->eb_refs);
221 static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info,
222 struct folio *folio, u64 start, u32 len)
224 /* For subpage support, the folio must be single page. */
225 ASSERT(folio_order(folio) == 0);
228 ASSERT(folio_test_private(folio) && folio_get_private(folio));
229 ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
230 IS_ALIGNED(len, fs_info->sectorsize));
232 * The range check only works for mapped page, we can still have
233 * unmapped page like dummy extent buffer pages.
236 ASSERT(folio_pos(folio) <= start &&
237 start + len <= folio_pos(folio) + PAGE_SIZE);
240 void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
241 struct folio *folio, u64 start, u32 len)
243 struct btrfs_subpage *subpage = folio_get_private(folio);
244 const int nbits = len >> fs_info->sectorsize_bits;
246 btrfs_subpage_assert(fs_info, folio, start, len);
248 atomic_add(nbits, &subpage->readers);
251 void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
252 struct folio *folio, u64 start, u32 len)
254 struct btrfs_subpage *subpage = folio_get_private(folio);
255 const int nbits = len >> fs_info->sectorsize_bits;
259 btrfs_subpage_assert(fs_info, folio, start, len);
260 is_data = is_data_inode(folio->mapping->host);
261 ASSERT(atomic_read(&subpage->readers) >= nbits);
262 last = atomic_sub_and_test(nbits, &subpage->readers);
265 * For data we need to unlock the page if the last read has finished.
267 * And please don't replace @last with atomic_sub_and_test() call
268 * inside if () condition.
269 * As we want the atomic_sub_and_test() to be always executed.
275 static void btrfs_subpage_clamp_range(struct folio *folio, u64 *start, u32 *len)
277 u64 orig_start = *start;
280 *start = max_t(u64, folio_pos(folio), orig_start);
282 * For certain call sites like btrfs_drop_pages(), we may have pages
283 * beyond the target range. In that case, just set @len to 0, subpage
284 * helpers can handle @len == 0 without any problem.
286 if (folio_pos(folio) >= orig_start + orig_len)
289 *len = min_t(u64, folio_pos(folio) + PAGE_SIZE,
290 orig_start + orig_len) - *start;
293 void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
294 struct folio *folio, u64 start, u32 len)
296 struct btrfs_subpage *subpage = folio_get_private(folio);
297 const int nbits = (len >> fs_info->sectorsize_bits);
300 btrfs_subpage_assert(fs_info, folio, start, len);
302 ASSERT(atomic_read(&subpage->readers) == 0);
303 ret = atomic_add_return(nbits, &subpage->writers);
304 ASSERT(ret == nbits);
307 bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
308 struct folio *folio, u64 start, u32 len)
310 struct btrfs_subpage *subpage = folio_get_private(folio);
311 const int nbits = (len >> fs_info->sectorsize_bits);
313 btrfs_subpage_assert(fs_info, folio, start, len);
316 * We have call sites passing @lock_page into
317 * extent_clear_unlock_delalloc() for compression path.
319 * This @locked_page is locked by plain lock_page(), thus its
320 * subpage::writers is 0. Handle them in a special way.
322 if (atomic_read(&subpage->writers) == 0)
325 ASSERT(atomic_read(&subpage->writers) >= nbits);
326 return atomic_sub_and_test(nbits, &subpage->writers);
330 * Lock a folio for delalloc page writeback.
332 * Return -EAGAIN if the page is not properly initialized.
333 * Return 0 with the page locked, and writer counter updated.
335 * Even with 0 returned, the page still need extra check to make sure
336 * it's really the correct page, as the caller is using
337 * filemap_get_folios_contig(), which can race with page invalidating.
339 int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
340 struct folio *folio, u64 start, u32 len)
342 if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) {
347 if (!folio_test_private(folio) || !folio_get_private(folio)) {
351 btrfs_subpage_clamp_range(folio, &start, &len);
352 btrfs_subpage_start_writer(fs_info, folio, start, len);
356 void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
357 struct folio *folio, u64 start, u32 len)
359 if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) {
363 btrfs_subpage_clamp_range(folio, &start, &len);
364 if (btrfs_subpage_end_and_test_writer(fs_info, folio, start, len))
368 #define subpage_calc_start_bit(fs_info, folio, name, start, len) \
370 unsigned int start_bit; \
372 btrfs_subpage_assert(fs_info, folio, start, len); \
373 start_bit = offset_in_page(start) >> fs_info->sectorsize_bits; \
374 start_bit += fs_info->subpage_info->name##_offset; \
378 #define subpage_test_bitmap_all_set(fs_info, subpage, name) \
379 bitmap_test_range_all_set(subpage->bitmaps, \
380 fs_info->subpage_info->name##_offset, \
381 fs_info->subpage_info->bitmap_nr_bits)
383 #define subpage_test_bitmap_all_zero(fs_info, subpage, name) \
384 bitmap_test_range_all_zero(subpage->bitmaps, \
385 fs_info->subpage_info->name##_offset, \
386 fs_info->subpage_info->bitmap_nr_bits)
388 void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info,
389 struct folio *folio, u64 start, u32 len)
391 struct btrfs_subpage *subpage = folio_get_private(folio);
392 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
393 uptodate, start, len);
396 spin_lock_irqsave(&subpage->lock, flags);
397 bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
398 if (subpage_test_bitmap_all_set(fs_info, subpage, uptodate))
399 folio_mark_uptodate(folio);
400 spin_unlock_irqrestore(&subpage->lock, flags);
403 void btrfs_subpage_clear_uptodate(const struct btrfs_fs_info *fs_info,
404 struct folio *folio, u64 start, u32 len)
406 struct btrfs_subpage *subpage = folio_get_private(folio);
407 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
408 uptodate, start, len);
411 spin_lock_irqsave(&subpage->lock, flags);
412 bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
413 folio_clear_uptodate(folio);
414 spin_unlock_irqrestore(&subpage->lock, flags);
417 void btrfs_subpage_set_dirty(const struct btrfs_fs_info *fs_info,
418 struct folio *folio, u64 start, u32 len)
420 struct btrfs_subpage *subpage = folio_get_private(folio);
421 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
425 spin_lock_irqsave(&subpage->lock, flags);
426 bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
427 spin_unlock_irqrestore(&subpage->lock, flags);
428 folio_mark_dirty(folio);
432 * Extra clear_and_test function for subpage dirty bitmap.
434 * Return true if we're the last bits in the dirty_bitmap and clear the
436 * Return false otherwise.
438 * NOTE: Callers should manually clear page dirty for true case, as we have
439 * extra handling for tree blocks.
441 bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
442 struct folio *folio, u64 start, u32 len)
444 struct btrfs_subpage *subpage = folio_get_private(folio);
445 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
450 spin_lock_irqsave(&subpage->lock, flags);
451 bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
452 if (subpage_test_bitmap_all_zero(fs_info, subpage, dirty))
454 spin_unlock_irqrestore(&subpage->lock, flags);
458 void btrfs_subpage_clear_dirty(const struct btrfs_fs_info *fs_info,
459 struct folio *folio, u64 start, u32 len)
463 last = btrfs_subpage_clear_and_test_dirty(fs_info, folio, start, len);
465 folio_clear_dirty_for_io(folio);
468 void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info,
469 struct folio *folio, u64 start, u32 len)
471 struct btrfs_subpage *subpage = folio_get_private(folio);
472 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
473 writeback, start, len);
476 spin_lock_irqsave(&subpage->lock, flags);
477 bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
478 folio_start_writeback(folio);
479 spin_unlock_irqrestore(&subpage->lock, flags);
482 void btrfs_subpage_clear_writeback(const struct btrfs_fs_info *fs_info,
483 struct folio *folio, u64 start, u32 len)
485 struct btrfs_subpage *subpage = folio_get_private(folio);
486 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
487 writeback, start, len);
490 spin_lock_irqsave(&subpage->lock, flags);
491 bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
492 if (subpage_test_bitmap_all_zero(fs_info, subpage, writeback)) {
493 ASSERT(folio_test_writeback(folio));
494 folio_end_writeback(folio);
496 spin_unlock_irqrestore(&subpage->lock, flags);
499 void btrfs_subpage_set_ordered(const struct btrfs_fs_info *fs_info,
500 struct folio *folio, u64 start, u32 len)
502 struct btrfs_subpage *subpage = folio_get_private(folio);
503 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
504 ordered, start, len);
507 spin_lock_irqsave(&subpage->lock, flags);
508 bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
509 folio_set_ordered(folio);
510 spin_unlock_irqrestore(&subpage->lock, flags);
513 void btrfs_subpage_clear_ordered(const struct btrfs_fs_info *fs_info,
514 struct folio *folio, u64 start, u32 len)
516 struct btrfs_subpage *subpage = folio_get_private(folio);
517 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
518 ordered, start, len);
521 spin_lock_irqsave(&subpage->lock, flags);
522 bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
523 if (subpage_test_bitmap_all_zero(fs_info, subpage, ordered))
524 folio_clear_ordered(folio);
525 spin_unlock_irqrestore(&subpage->lock, flags);
528 void btrfs_subpage_set_checked(const struct btrfs_fs_info *fs_info,
529 struct folio *folio, u64 start, u32 len)
531 struct btrfs_subpage *subpage = folio_get_private(folio);
532 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
533 checked, start, len);
536 spin_lock_irqsave(&subpage->lock, flags);
537 bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
538 if (subpage_test_bitmap_all_set(fs_info, subpage, checked))
539 folio_set_checked(folio);
540 spin_unlock_irqrestore(&subpage->lock, flags);
543 void btrfs_subpage_clear_checked(const struct btrfs_fs_info *fs_info,
544 struct folio *folio, u64 start, u32 len)
546 struct btrfs_subpage *subpage = folio_get_private(folio);
547 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
548 checked, start, len);
551 spin_lock_irqsave(&subpage->lock, flags);
552 bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
553 folio_clear_checked(folio);
554 spin_unlock_irqrestore(&subpage->lock, flags);
558 * Unlike set/clear which is dependent on each page status, for test all bits
559 * are tested in the same way.
561 #define IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(name) \
562 bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
563 struct folio *folio, u64 start, u32 len) \
565 struct btrfs_subpage *subpage = folio_get_private(folio); \
566 unsigned int start_bit = subpage_calc_start_bit(fs_info, folio, \
568 unsigned long flags; \
571 spin_lock_irqsave(&subpage->lock, flags); \
572 ret = bitmap_test_range_all_set(subpage->bitmaps, start_bit, \
573 len >> fs_info->sectorsize_bits); \
574 spin_unlock_irqrestore(&subpage->lock, flags); \
577 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate);
578 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(dirty);
579 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(writeback);
580 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(ordered);
581 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(checked);
584 * Note that, in selftests (extent-io-tests), we can have empty fs_info passed
585 * in. We only test sectorsize == PAGE_SIZE cases so far, thus we can fall
586 * back to regular sectorsize branch.
588 #define IMPLEMENT_BTRFS_PAGE_OPS(name, folio_set_func, \
589 folio_clear_func, folio_test_func) \
590 void btrfs_folio_set_##name(const struct btrfs_fs_info *fs_info, \
591 struct folio *folio, u64 start, u32 len) \
593 if (unlikely(!fs_info) || \
594 !btrfs_is_subpage(fs_info, folio->mapping)) { \
595 folio_set_func(folio); \
598 btrfs_subpage_set_##name(fs_info, folio, start, len); \
600 void btrfs_folio_clear_##name(const struct btrfs_fs_info *fs_info, \
601 struct folio *folio, u64 start, u32 len) \
603 if (unlikely(!fs_info) || \
604 !btrfs_is_subpage(fs_info, folio->mapping)) { \
605 folio_clear_func(folio); \
608 btrfs_subpage_clear_##name(fs_info, folio, start, len); \
610 bool btrfs_folio_test_##name(const struct btrfs_fs_info *fs_info, \
611 struct folio *folio, u64 start, u32 len) \
613 if (unlikely(!fs_info) || \
614 !btrfs_is_subpage(fs_info, folio->mapping)) \
615 return folio_test_func(folio); \
616 return btrfs_subpage_test_##name(fs_info, folio, start, len); \
618 void btrfs_folio_clamp_set_##name(const struct btrfs_fs_info *fs_info, \
619 struct folio *folio, u64 start, u32 len) \
621 if (unlikely(!fs_info) || \
622 !btrfs_is_subpage(fs_info, folio->mapping)) { \
623 folio_set_func(folio); \
626 btrfs_subpage_clamp_range(folio, &start, &len); \
627 btrfs_subpage_set_##name(fs_info, folio, start, len); \
629 void btrfs_folio_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
630 struct folio *folio, u64 start, u32 len) \
632 if (unlikely(!fs_info) || \
633 !btrfs_is_subpage(fs_info, folio->mapping)) { \
634 folio_clear_func(folio); \
637 btrfs_subpage_clamp_range(folio, &start, &len); \
638 btrfs_subpage_clear_##name(fs_info, folio, start, len); \
640 bool btrfs_folio_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
641 struct folio *folio, u64 start, u32 len) \
643 if (unlikely(!fs_info) || \
644 !btrfs_is_subpage(fs_info, folio->mapping)) \
645 return folio_test_func(folio); \
646 btrfs_subpage_clamp_range(folio, &start, &len); \
647 return btrfs_subpage_test_##name(fs_info, folio, start, len); \
649 IMPLEMENT_BTRFS_PAGE_OPS(uptodate, folio_mark_uptodate, folio_clear_uptodate,
650 folio_test_uptodate);
651 IMPLEMENT_BTRFS_PAGE_OPS(dirty, folio_mark_dirty, folio_clear_dirty_for_io,
653 IMPLEMENT_BTRFS_PAGE_OPS(writeback, folio_start_writeback, folio_end_writeback,
654 folio_test_writeback);
655 IMPLEMENT_BTRFS_PAGE_OPS(ordered, folio_set_ordered, folio_clear_ordered,
657 IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
661 * Make sure not only the page dirty bit is cleared, but also subpage dirty bit
664 void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info, struct folio *folio)
666 struct btrfs_subpage *subpage = folio_get_private(folio);
668 if (!IS_ENABLED(CONFIG_BTRFS_ASSERT))
671 ASSERT(!folio_test_dirty(folio));
672 if (!btrfs_is_subpage(fs_info, folio->mapping))
675 ASSERT(folio_test_private(folio) && folio_get_private(folio));
676 ASSERT(subpage_test_bitmap_all_zero(fs_info, subpage, dirty));
680 * Handle different locked pages with different page sizes:
682 * - Page locked by plain lock_page()
683 * It should not have any subpage::writers count.
684 * Can be unlocked by unlock_page().
685 * This is the most common locked page for __extent_writepage() called
686 * inside extent_write_cache_pages().
687 * Rarer cases include the @locked_page from extent_write_locked_range().
689 * - Page locked by lock_delalloc_pages()
690 * There is only one caller, all pages except @locked_page for
691 * extent_write_locked_range().
692 * In this case, we have to call subpage helper to handle the case.
694 void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
695 struct folio *folio, u64 start, u32 len)
697 struct btrfs_subpage *subpage;
699 ASSERT(folio_test_locked(folio));
700 /* For non-subpage case, we just unlock the page */
701 if (!btrfs_is_subpage(fs_info, folio->mapping)) {
706 ASSERT(folio_test_private(folio) && folio_get_private(folio));
707 subpage = folio_get_private(folio);
710 * For subpage case, there are two types of locked page. With or
711 * without writers number.
713 * Since we own the page lock, no one else could touch subpage::writers
714 * and we are safe to do several atomic operations without spinlock.
716 if (atomic_read(&subpage->writers) == 0) {
717 /* No writers, locked by plain lock_page() */
722 /* Have writers, use proper subpage helper to end it */
723 btrfs_folio_end_writer_lock(fs_info, folio, start, len);
726 #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst) \
727 bitmap_cut(dst, subpage->bitmaps, 0, \
728 subpage_info->name##_offset, subpage_info->bitmap_nr_bits)
730 void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
731 struct folio *folio, u64 start, u32 len)
733 struct btrfs_subpage_info *subpage_info = fs_info->subpage_info;
734 struct btrfs_subpage *subpage;
735 unsigned long uptodate_bitmap;
736 unsigned long error_bitmap;
737 unsigned long dirty_bitmap;
738 unsigned long writeback_bitmap;
739 unsigned long ordered_bitmap;
740 unsigned long checked_bitmap;
743 ASSERT(folio_test_private(folio) && folio_get_private(folio));
744 ASSERT(subpage_info);
745 subpage = folio_get_private(folio);
747 spin_lock_irqsave(&subpage->lock, flags);
748 GET_SUBPAGE_BITMAP(subpage, subpage_info, uptodate, &uptodate_bitmap);
749 GET_SUBPAGE_BITMAP(subpage, subpage_info, dirty, &dirty_bitmap);
750 GET_SUBPAGE_BITMAP(subpage, subpage_info, writeback, &writeback_bitmap);
751 GET_SUBPAGE_BITMAP(subpage, subpage_info, ordered, &ordered_bitmap);
752 GET_SUBPAGE_BITMAP(subpage, subpage_info, checked, &checked_bitmap);
753 spin_unlock_irqrestore(&subpage->lock, flags);
755 dump_page(folio_page(folio, 0), "btrfs subpage dump");
757 "start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl error=%*pbl dirty=%*pbl writeback=%*pbl ordered=%*pbl checked=%*pbl",
758 start, len, folio_pos(folio),
759 subpage_info->bitmap_nr_bits, &uptodate_bitmap,
760 subpage_info->bitmap_nr_bits, &error_bitmap,
761 subpage_info->bitmap_nr_bits, &dirty_bitmap,
762 subpage_info->bitmap_nr_bits, &writeback_bitmap,
763 subpage_info->bitmap_nr_bits, &ordered_bitmap,
764 subpage_info->bitmap_nr_bits, &checked_bitmap);