block: Improve bio_set_op_attrs() robustness

Since REQ_OP_BITS == 3 and __REQ_NR_BITS == 30 it is not that hard
to pass an op_flags argument to bio_set_op_attrs() that is larger
than the number of bits reserved for the op_flags argument. Complain
if this happens. Additionally, ensure that negative arguments trigger
a complaint (1 << ... is signed while 1U << ... is unsigned; adding
0U to an integer expression causes it to be promoted to an unsigned
type).
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <damien.lemoal@hgst.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

include/linux/blk_types.h

@@ -94,10 +94,17 @@ struct bio {
 #define bio_op(bio)	((bio)->bi_opf >> BIO_OP_SHIFT)
 
 #define bio_set_op_attrs(bio, op, op_flags) do {			\
-	WARN_ON(op >= (1 << REQ_OP_BITS));			\
+	if (__builtin_constant_p(op))					\
+		BUILD_BUG_ON((op) + 0U >= (1U << REQ_OP_BITS));		\
+	else								\
+		WARN_ON_ONCE((op) + 0U >= (1U << REQ_OP_BITS));		\
+	if (__builtin_constant_p(op_flags))				\
+		BUILD_BUG_ON((op_flags) + 0U >= (1U << BIO_OP_SHIFT));	\
+	else								\
+		WARN_ON_ONCE((op_flags) + 0U >= (1U << BIO_OP_SHIFT));	\
 	(bio)->bi_opf = bio_flags(bio);					\
-	(bio)->bi_opf |= ((unsigned int) (op) << BIO_OP_SHIFT);	\
-	(bio)->bi_opf |= op_flags;				\
+	(bio)->bi_opf |= (((op) + 0U) << BIO_OP_SHIFT);			\
+	(bio)->bi_opf |= (op_flags);					\
 } while (0)
 
 #define BIO_RESET_BYTES		offsetof(struct bio, bi_max_vecs)