btrfs: extend btrfs_cleanup_ordered_extents for NULL locked_page

btrfs_cleanup_ordered_extents() assumes locked_page to be non-NULL, so it
is not usable for submit_uncompressed_range() which can have NULL
locked_page.

Add support supports locked_page == NULL case. Also, it rewrites
redundant "page_offset(locked_page)".
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -190,11 +190,14 @@ static inline void btrfs_cleanup_ordered_extents(struct btrfs_inode *inode,
 {
 	unsigned long index = offset >> PAGE_SHIFT;
 	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
-	u64 page_start = page_offset(locked_page);
-	u64 page_end = page_start + PAGE_SIZE - 1;
-
+	u64 page_start, page_end;
 	struct page *page;
 
+	if (locked_page) {
+		page_start = page_offset(locked_page);
+		page_end = page_start + PAGE_SIZE - 1;
+	}
+
 	while (index <= end_index) {
 		/*
 		 * For locked page, we will call end_extent_writepage() on it
@@ -207,7 +210,7 @@ static inline void btrfs_cleanup_ordered_extents(struct btrfs_inode *inode,
 		 * btrfs_mark_ordered_io_finished() would skip the accounting
 		 * for the page range, and the ordered extent will never finish.
 		 */
-		if (index == (page_offset(locked_page) >> PAGE_SHIFT)) {
+		if (locked_page && index == (page_start >> PAGE_SHIFT)) {
 			index++;
 			continue;
 		}
@@ -226,18 +229,21 @@ static inline void btrfs_cleanup_ordered_extents(struct btrfs_inode *inode,
 		put_page(page);
 	}
 
+	if (locked_page) {
 		/* The locked page covers the full range, nothing needs to be done */
-	if (bytes + offset <= page_offset(locked_page) + PAGE_SIZE)
+		if (bytes + offset <= page_start + PAGE_SIZE)
 			return;
 		/*
-	 * In case this page belongs to the delalloc range being instantiated
-	 * then skip it, since the first page of a range is going to be
-	 * properly cleaned up by the caller of run_delalloc_range
+		 * In case this page belongs to the delalloc range being
+		 * instantiated then skip it, since the first page of a range is
+		 * going to be properly cleaned up by the caller of
+		 * run_delalloc_range
 		 */
 		if (page_start >= offset && page_end <= (offset + bytes - 1)) {
 			bytes = offset + bytes - page_offset(locked_page) - PAGE_SIZE;
 			offset = page_offset(locked_page) + PAGE_SIZE;
 		}
+	}
 
 	return btrfs_mark_ordered_io_finished(inode, NULL, offset, bytes, false);
 }