btrfs: convert get_next_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. Use folio_pos instead of page_offset, which is more
consistent with folio usage.
Signed-off-by: Li Zetao <lizetao1@huawei.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4041,17 +4041,17 @@ void memmove_extent_buffer(const struct extent_buffer *dst,
 
 #define GANG_LOOKUP_SIZE	16
 static struct extent_buffer *get_next_extent_buffer(
-		const struct btrfs_fs_info *fs_info, struct page *page, u64 bytenr)
+		const struct btrfs_fs_info *fs_info, struct folio *folio, u64 bytenr)
 {
 	struct extent_buffer *gang[GANG_LOOKUP_SIZE];
 	struct extent_buffer *found = NULL;
-	u64 page_start = page_offset(page);
-	u64 cur = page_start;
+	u64 folio_start = folio_pos(folio);
+	u64 cur = folio_start;
 
-	ASSERT(in_range(bytenr, page_start, PAGE_SIZE));
+	ASSERT(in_range(bytenr, folio_start, PAGE_SIZE));
 	lockdep_assert_held(&fs_info->buffer_lock);
 
-	while (cur < page_start + PAGE_SIZE) {
+	while (cur < folio_start + PAGE_SIZE) {
 		int ret;
 		int i;
 
@@ -4063,7 +4063,7 @@ static struct extent_buffer *get_next_extent_buffer(
 			goto out;
 		for (i = 0; i < ret; i++) {
 			/* Already beyond page end */
-			if (gang[i]->start >= page_start + PAGE_SIZE)
+			if (gang[i]->start >= folio_start + PAGE_SIZE)
 				goto out;
 			/* Found one */
 			if (gang[i]->start >= bytenr) {
@@ -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, cur);
+		eb = get_next_extent_buffer(fs_info, page_folio(page), cur);
 		if (!eb) {
 			/* No more eb in the page range after or at cur */
 			spin_unlock(&fs_info->buffer_lock);