btrfs: convert try_release_subpage_extent_buffer() to take a folio

The old page API is being gradually replaced and converted to use folio
to improve code readability and avoid repeated conversion between page
and folio. And use folio_pos instead of page_offset, which is more
consistent with folio usage. At the same time, folio_test_private() can
handle folio directly without converting from page to folio first.

Signed-off-by: Li Zetao <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: Li Zetao

fs/btrfs/extent_io.c

@@ -4077,11 +4077,11 @@ static struct extent_buffer *get_next_extent_buffer(
 	return found;
 }
 
-static int try_release_subpage_extent_buffer(struct page *page)
+static int try_release_subpage_extent_buffer(struct folio *folio)
 {
-	struct btrfs_fs_info *fs_info = page_to_fs_info(page);
-	u64 cur = page_offset(page);
-	const u64 end = page_offset(page) + PAGE_SIZE;
+	struct btrfs_fs_info *fs_info = folio_to_fs_info(folio);
+	u64 cur = folio_pos(folio);
+	const u64 end = cur + PAGE_SIZE;
 	int ret;
 
 	while (cur < end) {
@@ -4096,7 +4096,7 @@ static int try_release_subpage_extent_buffer(struct page *page)
 		 * with spinlock rather than RCU.
 		 */
 		spin_lock(&fs_info->buffer_lock);
-		eb = get_next_extent_buffer(fs_info, page_folio(page), cur);
+		eb = get_next_extent_buffer(fs_info, folio, cur);
 		if (!eb) {
 			/* No more eb in the page range after or at cur */
 			spin_unlock(&fs_info->buffer_lock);
@@ -4137,12 +4137,12 @@ static int try_release_subpage_extent_buffer(struct page *page)
 	 * Finally to check if we have cleared folio private, as if we have
 	 * released all ebs in the page, the folio private should be cleared now.
 	 */
-	spin_lock(&page->mapping->i_private_lock);
-	if (!folio_test_private(page_folio(page)))
+	spin_lock(&folio->mapping->i_private_lock);
+	if (!folio_test_private(folio))
 		ret = 1;
 	else
 		ret = 0;
-	spin_unlock(&page->mapping->i_private_lock);
+	spin_unlock(&folio->mapping->i_private_lock);
 	return ret;
 
 }
@@ -4153,7 +4153,7 @@ int try_release_extent_buffer(struct page *page)
 	struct extent_buffer *eb;
 
 	if (page_to_fs_info(page)->nodesize < PAGE_SIZE)
-		return try_release_subpage_extent_buffer(page);
+		return try_release_subpage_extent_buffer(page_folio(page));
 
 	/*
 	 * We need to make sure nobody is changing folio private, as we rely on