btrfs: remove folio checked subpage bitmap tracking

The folio checked flag is only utilized by the COW fixup mechanism
inside btrfs.

Since the COW fixup is already removed from non-experimental builds,
there is no need to keep the checked subpage bitmap.

This will saves us some space for large folios, for example for a single
256K sized large folio on 4K page sized systems:

 Old bitmap size = 6 * (256K / 4K / 8) = 48 bytes
 New bitmap size = 5 * (256K / 4K / 8) = 40 bytes

This will be more obvious when we're going to support huge folios (order
= 9).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/defrag.c

@@ -1179,7 +1179,6 @@ static int defrag_one_locked_target(struct btrfs_inode *inode,
 		if (start >= folio_next_pos(folio) ||
 		    start + len <= folio_pos(folio))
 			continue;
-		btrfs_folio_clamp_clear_checked(fs_info, folio, start, len);
 		btrfs_folio_clamp_set_dirty(fs_info, folio, start, len);
 	}
 	btrfs_delalloc_release_extents(inode, len);

fs/btrfs/file.c

@@ -49,14 +49,6 @@ static void btrfs_drop_folio(struct btrfs_fs_info *fs_info, struct folio *folio,
 	u64 block_len = round_up(pos + copied, fs_info->sectorsize) - block_start;
 
 	ASSERT(block_len <= U32_MAX);
-	/*
-	 * Folio checked is some magic around finding folios that have been
-	 * modified without going through btrfs_dirty_folio().  Clear it here.
-	 * There should be no need to mark the pages accessed as
-	 * prepare_one_folio() should have marked them accessed in
-	 * prepare_one_folio() via find_or_create_page()
-	 */
-	btrfs_folio_clamp_clear_checked(fs_info, folio, block_start, block_len);
 	folio_unlock(folio);
 	folio_put(folio);
 }
@@ -65,7 +57,7 @@ static void btrfs_drop_folio(struct btrfs_fs_info *fs_info, struct folio *folio,
  * After copy_folio_from_iter_atomic(), update the following things for delalloc:
  * - Mark newly dirtied folio as DELALLOC in the io tree.
  *   Used to advise which range is to be written back.
- * - Mark modified folio as Uptodate/Dirty and not needing COW fixup
+ * - Mark modified folio as Uptodate/Dirty
  * - Update inode size for past EOF write
  */
 int btrfs_dirty_folio(struct btrfs_inode *inode, struct folio *folio, loff_t pos,
@@ -107,7 +99,6 @@ int btrfs_dirty_folio(struct btrfs_inode *inode, struct folio *folio, loff_t pos
 		return ret;
 
 	btrfs_folio_clamp_set_uptodate(fs_info, folio, start_pos, num_bytes);
-	btrfs_folio_clamp_clear_checked(fs_info, folio, start_pos, num_bytes);
 	btrfs_folio_clamp_set_dirty(fs_info, folio, start_pos, num_bytes);
 
 	/*
@@ -1992,7 +1983,6 @@ again:
 	if (zero_start != fsize)
 		folio_zero_range(folio, zero_start, folio_size(folio) - zero_start);
 
-	btrfs_folio_clear_checked(fs_info, folio, page_start, fsize);
 	btrfs_folio_set_dirty(fs_info, folio, page_start, end + 1 - page_start);
 	btrfs_folio_set_uptodate(fs_info, folio, page_start, end + 1 - page_start);
 

fs/btrfs/free-space-cache.c

@@ -433,10 +433,6 @@ static void io_ctl_drop_pages(struct btrfs_io_ctl *io_ctl)
 
 	for (i = 0; i < io_ctl->num_pages; i++) {
 		if (io_ctl->pages[i]) {
-			btrfs_folio_clear_checked(io_ctl->fs_info,
-					page_folio(io_ctl->pages[i]),
-					page_offset(io_ctl->pages[i]),
-					PAGE_SIZE);
 			unlock_page(io_ctl->pages[i]);
 			put_page(io_ctl->pages[i]);
 		}

fs/btrfs/inode.c

@@ -5009,8 +5009,6 @@ again:
 	folio_zero_range(folio, zero_start - folio_pos(folio),
 			 zero_end - zero_start + 1);
 
-	btrfs_folio_clear_checked(fs_info, folio, block_start,
-				  block_end + 1 - block_start);
 	btrfs_folio_set_dirty(fs_info, folio, block_start,
 			      block_end + 1 - block_start);
 
@@ -7627,7 +7625,6 @@ next:
 	 * did something wrong.
 	 */
 	ASSERT(!folio_test_ordered(folio));
-	btrfs_folio_clear_checked(fs_info, folio, folio_pos(folio), folio_size(folio));
 	if (!inode_evicting)
 		__btrfs_release_folio(folio, GFP_NOFS);
 	clear_folio_extent_mapped(folio);

fs/btrfs/reflink.c

@@ -141,7 +141,6 @@ static int copy_inline_to_page(struct btrfs_inode *inode,
 		folio_zero_range(folio, datal, block_size - datal);
 
 	btrfs_folio_set_uptodate(fs_info, folio, file_offset, block_size);
-	btrfs_folio_clear_checked(fs_info, folio, file_offset, block_size);
 	btrfs_folio_set_dirty(fs_info, folio, file_offset, block_size);
 out_unlock:
 	if (!IS_ERR(folio)) {

fs/btrfs/subpage.c

@@ -508,35 +508,6 @@ void btrfs_subpage_clear_ordered(const struct btrfs_fs_info *fs_info,
 	spin_unlock_irqrestore(&bfs->lock, flags);
 }
 
-void btrfs_subpage_set_checked(const struct btrfs_fs_info *fs_info,
-			       struct folio *folio, u64 start, u32 len)
-{
-	struct btrfs_folio_state *bfs = folio_get_private(folio);
-	unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
-							checked, start, len);
-	unsigned long flags;
-
-	spin_lock_irqsave(&bfs->lock, flags);
-	bitmap_set(bfs->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
-	if (subpage_test_bitmap_all_set(fs_info, folio, checked))
-		folio_set_checked(folio);
-	spin_unlock_irqrestore(&bfs->lock, flags);
-}
-
-void btrfs_subpage_clear_checked(const struct btrfs_fs_info *fs_info,
-				 struct folio *folio, u64 start, u32 len)
-{
-	struct btrfs_folio_state *bfs = folio_get_private(folio);
-	unsigned int start_bit = subpage_calc_start_bit(fs_info, folio,
-							checked, start, len);
-	unsigned long flags;
-
-	spin_lock_irqsave(&bfs->lock, flags);
-	bitmap_clear(bfs->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
-	folio_clear_checked(folio);
-	spin_unlock_irqrestore(&bfs->lock, flags);
-}
-
 /*
  * Unlike set/clear which is dependent on each page status, for test all bits
  * are tested in the same way.
@@ -561,7 +532,6 @@ IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate);
 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(dirty);
 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(writeback);
 IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(ordered);
-IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(checked);
 
 /*
  * Note that, in selftests (extent-io-tests), we can have empty fs_info passed
@@ -659,8 +629,6 @@ IMPLEMENT_BTRFS_PAGE_OPS(writeback, folio_start_writeback, folio_end_writeback,
 			 folio_test_writeback);
 IMPLEMENT_BTRFS_PAGE_OPS(ordered, folio_set_ordered, folio_clear_ordered,
 			 folio_test_ordered);
-IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
-			 folio_test_checked);
 
 #define GET_SUBPAGE_BITMAP(fs_info, folio, name, dst)			\
 {									\
@@ -782,7 +750,6 @@ void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
 	unsigned long dirty_bitmap;
 	unsigned long writeback_bitmap;
 	unsigned long ordered_bitmap;
-	unsigned long checked_bitmap;
 	unsigned long locked_bitmap;
 	unsigned long flags;
 
@@ -795,20 +762,18 @@ void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
 	GET_SUBPAGE_BITMAP(fs_info, folio, dirty, &dirty_bitmap);
 	GET_SUBPAGE_BITMAP(fs_info, folio, writeback, &writeback_bitmap);
 	GET_SUBPAGE_BITMAP(fs_info, folio, ordered, &ordered_bitmap);
-	GET_SUBPAGE_BITMAP(fs_info, folio, checked, &checked_bitmap);
 	GET_SUBPAGE_BITMAP(fs_info, folio, locked, &locked_bitmap);
 	spin_unlock_irqrestore(&bfs->lock, flags);
 
 	dump_page(folio_page(folio, 0), "btrfs folio state dump");
 	btrfs_warn(fs_info,
-"start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl dirty=%*pbl locked=%*pbl writeback=%*pbl ordered=%*pbl checked=%*pbl",
+"start=%llu len=%u page=%llu, bitmaps uptodate=%*pbl dirty=%*pbl locked=%*pbl writeback=%*pbl ordered=%*pbl",
 		    start, len, folio_pos(folio),
 		    blocks_per_folio, &uptodate_bitmap,
 		    blocks_per_folio, &dirty_bitmap,
 		    blocks_per_folio, &locked_bitmap,
 		    blocks_per_folio, &writeback_bitmap,
-		    blocks_per_folio, &ordered_bitmap,
-		    blocks_per_folio, &checked_bitmap);
+		    blocks_per_folio, &ordered_bitmap);
 }
 
 void btrfs_get_subpage_dirty_bitmap(struct btrfs_fs_info *fs_info,

fs/btrfs/subpage.h

@@ -41,11 +41,9 @@ enum {
 	btrfs_bitmap_nr_writeback,
 
 	/*
-	 * The ordered and checked flags are for COW fixup, already marked
-	 * deprecated, and will be removed eventually.
+	 * The ordered flags shows if the range has an ordered extent.
 	 */
 	btrfs_bitmap_nr_ordered,
-	btrfs_bitmap_nr_checked,
 
 	/*
 	 * The locked bit is for async delalloc range (compression), currently
@@ -182,7 +180,6 @@ DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
 DECLARE_BTRFS_SUBPAGE_OPS(dirty);
 DECLARE_BTRFS_SUBPAGE_OPS(writeback);
 DECLARE_BTRFS_SUBPAGE_OPS(ordered);
-DECLARE_BTRFS_SUBPAGE_OPS(checked);
 
 /*
  * Helper for error cleanup, where a folio will have its dirty flag cleared,