btrfs: simplify subpage handling of btrfs_clear_buffer_dirty()

The function btrfs_clear_buffer_dirty() is called on dirty extent buffer
that will not be written back.

The function will call btree_clear_folio_dirty() to clear the folio
dirty flag and also clear PAGECACHE_TAG_DIRTY flag.

And we split the subpage and regular handling, as for subpage cases we
should only clear PAGECACHE_TAG_DIRTY if the last dirty extent buffer in
the page is cleared.

So here we can simplify the function by:

- Use the newly introduced btrfs_meta_folio_clear_and_test_dirty() helper
  The helper will return true if we cleared the folio dirty flag.
  With that we can use the same helper for both subpage and regular
  cases.

- Rename btree_clear_folio_dirty() to btree_clear_folio_dirty_tag()
  As we move the folio dirty clearing in the btrfs_clear_buffer_dirty().

- Call btrfs_meta_folio_clear_and_test_dirty() to clear the dirty flags
  for both regular and subpage metadata cases

- Only call btree_clear_folio_dirty_tag() when the folio is no longer
  dirty

- Update the comment inside set_extent_buffer_dirty()
  As there is no separate clear_subpage_extent_buffer_dirty() anymore.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index ee118bb2c22f..6a2dd208eeae 100644
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -186,6 +186,8 @@ 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(const struct btrfs_fs_info *fs_info,
+					   struct folio *folio, u64 start, u32 len);
 void btrfs_get_subpage_dirty_bitmap(struct btrfs_fs_info *fs_info,
 				    struct folio *folio,
 				    unsigned long *ret_bitmap);