ext4: delete redundant calculations in ext4_mb_get_buddy_page_lock()

'blocks_per_page' is always 1 after 'if (blocks_per_page >= 2)',
'pnum' and 'block' are equal in this case.
Signed-off-by: Gou Hao <gouhao@uniontech.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231024035215.29474-1-gouhao@uniontech.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -1456,9 +1456,8 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
 		return 0;
 	}
 
-	block++;
-	pnum = block / blocks_per_page;
-	page = find_or_create_page(inode->i_mapping, pnum, gfp);
+	/* blocks_per_page == 1, hence we need another page for the buddy */
+	page = find_or_create_page(inode->i_mapping, block + 1, gfp);
 	if (!page)
 		return -ENOMEM;
 	BUG_ON(page->mapping != inode->i_mapping);