block: Catch possible entries missing from cmd_flag_name[]

Add a BUILD_BUG_ON() call to ensure that we are not missing entries in
cmd_flag_name[].

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20240719112912.3830443-13-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-debugfs.c

@@ -281,6 +281,8 @@ int __blk_mq_debugfs_rq_show(struct seq_file *m, struct request *rq)
 	const enum req_op op = req_op(rq);
 	const char *op_str = blk_op_str(op);
 
+	BUILD_BUG_ON(ARRAY_SIZE(cmd_flag_name) != __REQ_NR_BITS);
+
 	seq_printf(m, "%p {.op=", rq);
 	if (strcmp(op_str, "UNKNOWN") == 0)
 		seq_printf(m, "%u", op);

include/linux/blk_types.h

@@ -354,6 +354,7 @@ enum req_op {
 	REQ_OP_LAST		= (__force blk_opf_t)36,
 };
 
+/* Keep cmd_flag_name[] in sync with the definitions below */
 enum req_flag_bits {
 	__REQ_FAILFAST_DEV =	/* no driver retries of device errors */
 		REQ_OP_BITS,