From bca707e54276de828a8cad82b723192374e73e00 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 19 Feb 2024 13:13:24 +1030 Subject: [PATCH] btrfs: subpage: introduce helpers to handle subpage delalloc locking Three new helpers are introduced for the incoming subpage delalloc locking change. - btrfs_folio_set_writer_lock() This is to mark specified range with subpage specific writer lock. After calling this, the subpage range can be proper unlocked by btrfs_folio_end_writer_lock() - btrfs_subpage_find_writer_locked() This is to find the writer locked subpage range in a page. With the help of btrfs_folio_set_writer_lock(), it can allow us to record and find previously locked subpage range without extra memory allocation. - btrfs_folio_end_all_writers() This is for the locked_page of __extent_writepage(), as there may be multiple subpage delalloc ranges locked. Reviewed-by: Johannes Thumshirn Reviewed-by: Naohiro Aota Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/subpage.c | 118 +++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/subpage.h | 6 +++ 2 files changed, 124 insertions(+) diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 6947a6f3d9d8..93ae7b7367d5 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -775,6 +775,124 @@ void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info, btrfs_folio_end_writer_lock(fs_info, folio, start, len); } +/* + * This is for folio already locked by plain lock_page()/folio_lock(), which + * doesn't have any subpage awareness. + * + * This populates the involved subpage ranges so that subpage helpers can + * properly unlock them. + */ +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info, + struct folio *folio, u64 start, u32 len) +{ + struct btrfs_subpage *subpage; + unsigned long flags; + unsigned int start_bit; + unsigned int nbits; + int ret; + + ASSERT(folio_test_locked(folio)); + if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping)) + return; + + subpage = folio_get_private(folio); + start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len); + nbits = len >> fs_info->sectorsize_bits; + spin_lock_irqsave(&subpage->lock, flags); + /* Target range should not yet be locked. */ + ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits)); + bitmap_set(subpage->bitmaps, start_bit, nbits); + ret = atomic_add_return(nbits, &subpage->writers); + ASSERT(ret <= fs_info->subpage_info->bitmap_nr_bits); + spin_unlock_irqrestore(&subpage->lock, flags); +} + +/* + * Find any subpage writer locked range inside @folio, starting at file offset + * @search_start. The caller should ensure the folio is locked. + * + * Return true and update @found_start_ret and @found_len_ret to the first + * writer locked range. + * Return false if there is no writer locked range. + */ +bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info, + struct folio *folio, u64 search_start, + u64 *found_start_ret, u32 *found_len_ret) +{ + struct btrfs_subpage_info *subpage_info = fs_info->subpage_info; + struct btrfs_subpage *subpage = folio_get_private(folio); + const unsigned int len = PAGE_SIZE - offset_in_page(search_start); + const unsigned int start_bit = subpage_calc_start_bit(fs_info, folio, + locked, search_start, len); + const unsigned int locked_bitmap_start = subpage_info->locked_offset; + const unsigned int locked_bitmap_end = locked_bitmap_start + + subpage_info->bitmap_nr_bits; + unsigned long flags; + int first_zero; + int first_set; + bool found = false; + + ASSERT(folio_test_locked(folio)); + spin_lock_irqsave(&subpage->lock, flags); + first_set = find_next_bit(subpage->bitmaps, locked_bitmap_end, start_bit); + if (first_set >= locked_bitmap_end) + goto out; + + found = true; + + *found_start_ret = folio_pos(folio) + + ((first_set - locked_bitmap_start) << fs_info->sectorsize_bits); + /* + * Since @first_set is ensured to be smaller than locked_bitmap_end + * here, @found_start_ret should be inside the folio. + */ + ASSERT(*found_start_ret < folio_pos(folio) + PAGE_SIZE); + + first_zero = find_next_zero_bit(subpage->bitmaps, locked_bitmap_end, first_set); + *found_len_ret = (first_zero - first_set) << fs_info->sectorsize_bits; +out: + spin_unlock_irqrestore(&subpage->lock, flags); + return found; +} + +/* + * Unlike btrfs_folio_end_writer_lock() which unlocks a specified subpage range, + * this ends all writer locked ranges of a page. + * + * This is for the locked page of __extent_writepage(), as the locked page + * can contain several locked subpage ranges. + */ +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio) +{ + u64 folio_start = folio_pos(folio); + u64 cur = folio_start; + + ASSERT(folio_test_locked(folio)); + if (!btrfs_is_subpage(fs_info, folio->mapping)) { + folio_unlock(folio); + return; + } + + while (cur < folio_start + PAGE_SIZE) { + u64 found_start; + u32 found_len; + bool found; + bool last; + + found = btrfs_subpage_find_writer_locked(fs_info, folio, cur, + &found_start, &found_len); + if (!found) + break; + last = btrfs_subpage_end_and_test_writer(fs_info, folio, + found_start, found_len); + if (last) { + folio_unlock(folio); + break; + } + cur = found_start + found_len; + } +} + #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst) \ bitmap_cut(dst, subpage->bitmaps, 0, \ subpage_info->name##_offset, subpage_info->bitmap_nr_bits) diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h index 4b363d9453af..249396e118d0 100644 --- a/fs/btrfs/subpage.h +++ b/fs/btrfs/subpage.h @@ -112,6 +112,12 @@ int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len); void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len); +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info, + struct folio *folio, u64 start, u32 len); +bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info, + struct folio *folio, u64 search_start, + u64 *found_start_ret, u32 *found_len_ret); +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio); /* * Template for subpage related operations.