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>

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 311fa2f..53ee1a2 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -93,11 +93,18 @@ struct bio {
 #define bio_flags(bio) ((bio)->bi_opf & ((1 << BIO_OP_SHIFT) - 1))
 #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));                      \
-       (bio)->bi_opf = bio_flags(bio);                         \
-       (bio)->bi_opf |= ((unsigned int) (op) << BIO_OP_SHIFT); \
-       (bio)->bi_opf |= op_flags;                              \
+#define bio_set_op_attrs(bio, op, op_flags) do {                       \
+       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 |= (((op) + 0U) << BIO_OP_SHIFT);                 \
+       (bio)->bi_opf |= (op_flags);                                    \
 } while (0)
 
 #define BIO_RESET_BYTES                offsetof(struct bio, bi_max_vecs)