btrfs: use file_offset to limit bios size in calc_bio_boundaries

btrfs_ordered_extent->disk_bytenr can be rewritten by the zoned I/O
completion handler, and thus in general is not a good idea to limit I/O
size.  But the maximum bio size calculation can easily be done using the
file_offset fields in the btrfs_ordered_extent and btrfs_bio structures,
so switch to that instead.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -964,8 +964,8 @@ static void calc_bio_boundaries(struct btrfs_bio_ctrl *bio_ctrl,
 		ordered = btrfs_lookup_ordered_extent(inode, file_offset);
 		if (ordered) {
 			bio_ctrl->len_to_oe_boundary = min_t(u32, U32_MAX,
-					ordered->disk_bytenr +
-					ordered->disk_num_bytes - logical);
+					ordered->file_offset +
+					ordered->disk_num_bytes - file_offset);
 			btrfs_put_ordered_extent(ordered);
 			return;
 		}