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Wed, 13 May 2026 04:36:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QO4sJ93/A2r1SQAAD6G6ig (envelope-from ) for ; Wed, 13 May 2026 04:36:45 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH 2/4] btrfs: prepare subpage operations to support >= BITS_PER_LONG sub-bitmaps Date: Wed, 13 May 2026 14:06:19 +0930 Message-ID: <78b3cc42dc86e23de803bb1bc1d0004ed7b231a2.1778646753.git.wqu@suse.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Spam-Score: -2.80 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.com:email,suse.com:mid]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[linux-btrfs@vger.kernel.org]; RCVD_TLS_ALL(0.00)[] X-Spam-Level: [CURRENT LIMIT] Btrfs currently only supports sub-bitmaps (e.g. dirty bitmap) no larger than BITS_PER_LONG. That limit allows us to easily grab an unsigned long without the need to properly allocate memory for a larger bitmap. Unfortunately that limit prevents us from supporting huge folios. For 4K page size and block size, a huge folio (order 9) means 512 blocks inside a 2M folio. [ENHANCEMENT] To allow direct bitmap operations without allocating new memory, introduce two different ways to access the subpage bitmaps: - Return an unsigned long value This only happens if blocks_per_folio <= BITS_PER_LONG. We read out the sub-bitmap into an unsigned long, and return the value. This is the old existing method. This involves get_bitmap_value_##name() helper functions. And this time the helper functions are defined as inline functions instead of macros to provide better type checks. - Return a pointer where the sub-bitmap starts This only happens if blocks_per_folio >= BITS_PER_LONG. This is the new method for sub-bitmaps larger than BITS_PER_LONG. Since the sizes of sub-bitmaps are all aligned to BITS_PER_LONG, we can directly access the start word of the sub-bitmap. This involves get_bitmap_pointer_##name() helper functions. Then change the existing sub-bitmaps users to use the new helpers: - Bitmap dumping Switch between get_bitmap_value_##name() and get_bitmap_pointer_##name() depending on the sub-bitmap size. - btrfs_get_subpage_dirty_bitmap() Rename it to btrfs_get_subpage_dirty_bitmap_value() to follow the new value/pointer naming. Since we do not support huge folios yet, there is no pointer version for the dirty bitmap. Furthermore, add the support for bs == ps cases for btrfs_get_subpage_dirty_bitmap_value(), so that the caller no longer needs to check if the folio needs subpage handling. Signed-off-by: Qu Wenruo --- fs/btrfs/extent_io.c | 7 +-- fs/btrfs/subpage.c | 118 ++++++++++++++++++++++++++++++------------- fs/btrfs/subpage.h | 5 +- 3 files changed, 87 insertions(+), 43 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 8cf1e4c5105f..1dfa3152e4bd 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1492,12 +1492,7 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, int ret = 0; /* Save the dirty bitmap as our submission bitmap will be a subset of it. */ - if (btrfs_is_subpage(fs_info, folio)) { - ASSERT(blocks_per_folio > 1); - btrfs_get_subpage_dirty_bitmap(fs_info, folio, &bio_ctrl->submit_bitmap); - } else { - bio_ctrl->submit_bitmap = 1; - } + bio_ctrl->submit_bitmap = btrfs_get_subpage_dirty_bitmap_value(fs_info, folio); for_each_set_bitrange(start_bit, end_bit, &bio_ctrl->submit_bitmap, blocks_per_folio) { diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 99ae53656dba..fb56eaf52325 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -555,25 +555,54 @@ IMPLEMENT_BTRFS_PAGE_OPS(dirty, folio_mark_dirty, folio_clear_dirty_for_io, IMPLEMENT_BTRFS_PAGE_OPS(writeback, folio_start_writeback, folio_end_writeback, folio_test_writeback); -#define GET_SUBPAGE_BITMAP(fs_info, folio, name, dst) \ -{ \ - const unsigned int __bpf = btrfs_blocks_per_folio(fs_info, folio); \ - const struct btrfs_folio_state *__bfs = folio_get_private(folio); \ - \ - ASSERT(__bpf <= BITS_PER_LONG); \ - *dst = bitmap_read(__bfs->bitmaps, \ - __bpf * btrfs_bitmap_nr_##name, __bpf); \ +#define DEFINE_GET_SUBPAGE_BITMAP(name) \ +static inline unsigned long get_bitmap_value_##name( \ + const struct btrfs_fs_info *fs_info, \ + struct folio *folio) \ +{ \ + const unsigned int __bpf = btrfs_blocks_per_folio(fs_info, folio); \ + const struct btrfs_folio_state *__bfs = folio_get_private(folio); \ + unsigned long value; \ + \ + ASSERT(__bpf <= BITS_PER_LONG); \ + value = bitmap_read(__bfs->bitmaps, __bpf * btrfs_bitmap_nr_##name, \ + __bpf); \ + return value; \ +} \ +static inline const unsigned long *get_bitmap_pointer_##name( \ + const struct btrfs_fs_info *fs_info, \ + struct folio *folio) \ +{ \ + const unsigned int __bpf = btrfs_blocks_per_folio(fs_info, folio); \ + struct btrfs_folio_state *__bfs = folio_get_private(folio); \ + unsigned long *pointer; \ + \ + ASSERT(__bpf >= BITS_PER_LONG); \ + ASSERT(IS_ALIGNED(__bpf, BITS_PER_LONG)); \ + pointer = __bfs->bitmaps + (BIT_WORD(__bpf) * btrfs_bitmap_nr_##name); \ + return pointer; \ } -#define SUBPAGE_DUMP_BITMAP(fs_info, folio, name, start, len) \ -{ \ - unsigned long bitmap; \ - const unsigned int __bpf = btrfs_blocks_per_folio(fs_info, folio); \ - \ - GET_SUBPAGE_BITMAP(fs_info, folio, name, &bitmap); \ - btrfs_warn(fs_info, \ - "dumping bitmap start=%llu len=%u folio=%llu " #name "_bitmap=%*pbl", \ - start, len, folio_pos(folio), __bpf, &bitmap); \ +DEFINE_GET_SUBPAGE_BITMAP(uptodate); +DEFINE_GET_SUBPAGE_BITMAP(dirty); +DEFINE_GET_SUBPAGE_BITMAP(writeback); + +#define SUBPAGE_DUMP_BITMAP(fs_info, folio, name, start, len) \ +{ \ + const unsigned int __bpf = btrfs_blocks_per_folio(fs_info, folio); \ + \ + if (__bpf <= BITS_PER_LONG) { \ + unsigned long bitmap = get_bitmap_value_##name(fs_info, folio); \ + \ + btrfs_warn(fs_info, \ + "dumping bitmap start=%llu len=%u folio=%llu " #name "_bitmap=%*pbl", \ + start, len, folio_pos(folio), __bpf, &bitmap); \ + } else { \ + btrfs_warn(fs_info, \ + "dumping bitmap start=%llu len=%u folio=%llu " #name "_bitmap=%*pbl", \ + start, len, folio_pos(folio), __bpf, \ + get_bitmap_pointer_##name(fs_info, folio)); \ + } \ } /* @@ -663,42 +692,63 @@ void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info, { struct btrfs_folio_state *bfs; const unsigned int blocks_per_folio = btrfs_blocks_per_folio(fs_info, folio); - unsigned long uptodate_bitmap; - unsigned long dirty_bitmap; - unsigned long writeback_bitmap; unsigned long flags; ASSERT(folio_test_private(folio) && folio_get_private(folio)); ASSERT(blocks_per_folio > 1); bfs = folio_get_private(folio); - spin_lock_irqsave(&bfs->lock, flags); - GET_SUBPAGE_BITMAP(fs_info, folio, uptodate, &uptodate_bitmap); - GET_SUBPAGE_BITMAP(fs_info, folio, dirty, &dirty_bitmap); - GET_SUBPAGE_BITMAP(fs_info, folio, writeback, &writeback_bitmap); - spin_unlock_irqrestore(&bfs->lock, flags); - dump_page(folio_page(folio, 0), "btrfs folio state dump"); + + if (blocks_per_folio <= BITS_PER_LONG) { + unsigned long uptodate; + unsigned long dirty; + unsigned long writeback; + + spin_lock_irqsave(&bfs->lock, flags); + uptodate = get_bitmap_value_uptodate(fs_info, folio); + dirty = get_bitmap_value_dirty(fs_info, folio); + writeback = get_bitmap_value_writeback(fs_info, folio); + + spin_unlock_irqrestore(&bfs->lock, flags); + + btrfs_warn(fs_info, +"start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl dirty=%*pbl writeback=%*pbl", + start, len, folio_pos(folio), + blocks_per_folio, &uptodate, + blocks_per_folio, &dirty, + blocks_per_folio, &writeback); + return; + } + + spin_lock_irqsave(&bfs->lock, flags); btrfs_warn(fs_info, "start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl dirty=%*pbl writeback=%*pbl", start, len, folio_pos(folio), - blocks_per_folio, &uptodate_bitmap, - blocks_per_folio, &dirty_bitmap, - blocks_per_folio, &writeback_bitmap); + blocks_per_folio, get_bitmap_pointer_uptodate(fs_info, folio), + blocks_per_folio, get_bitmap_pointer_dirty(fs_info, folio), + blocks_per_folio, get_bitmap_pointer_writeback(fs_info, folio)); + spin_unlock_irqrestore(&bfs->lock, flags); } -void btrfs_get_subpage_dirty_bitmap(struct btrfs_fs_info *fs_info, - struct folio *folio, - unsigned long *ret_bitmap) +unsigned long btrfs_get_subpage_dirty_bitmap_value(struct btrfs_fs_info *fs_info, + struct folio *folio) { struct btrfs_folio_state *bfs; + const unsigned int blocks_per_folio = btrfs_blocks_per_folio(fs_info, folio); unsigned long flags; + unsigned long value; + + if (blocks_per_folio == 1) + return 1; ASSERT(folio_test_private(folio) && folio_get_private(folio)); - ASSERT(btrfs_blocks_per_folio(fs_info, folio) > 1); + ASSERT(blocks_per_folio > 1); + ASSERT(blocks_per_folio <= BITS_PER_LONG); bfs = folio_get_private(folio); spin_lock_irqsave(&bfs->lock, flags); - GET_SUBPAGE_BITMAP(fs_info, folio, dirty, ret_bitmap); + value = get_bitmap_value_dirty(fs_info, folio); spin_unlock_irqrestore(&bfs->lock, flags); + return value; } diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h index b30eb4abae64..756c05c89c11 100644 --- a/fs/btrfs/subpage.h +++ b/fs/btrfs/subpage.h @@ -184,9 +184,8 @@ bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info, void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len); bool btrfs_meta_folio_clear_and_test_dirty(struct folio *folio, const struct extent_buffer *eb); -void btrfs_get_subpage_dirty_bitmap(struct btrfs_fs_info *fs_info, - struct folio *folio, - unsigned long *ret_bitmap); +unsigned long btrfs_get_subpage_dirty_bitmap_value(struct btrfs_fs_info *fs_info, + struct folio *folio); void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len); -- 2.54.0