bcachefs: Don't unnecessarily decrypt data when moving

There's various checks for "are we going to compress this" - but we're
not going to compress if we know it's incompressible.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/io_write.c

@@ -940,6 +940,9 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
 	bool page_alloc_failed = false;
 	int ret, more = 0;
 
+	if (op->incompressible)
+		op->compression_opt = 0;
+
 	BUG_ON(!bio_sectors(src));
 
 	ec_buf = bch2_writepoint_ec_buf(c, wp);