block: Provide blk_status_t decoding for path errors

This patch provides a common decoder for block status path related errors
that may be retried so various entities wishing to consult this do not
have to duplicate this decision.
Acked-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blk_types.h

@@ -39,6 +39,34 @@ typedef u8 __bitwise blk_status_t;
 
 #define BLK_STS_AGAIN		((__force blk_status_t)12)
 
+/**
+ * blk_path_error - returns true if error may be path related
+ * @error: status the request was completed with
+ *
+ * Description:
+ *     This classifies block error status into non-retryable errors and ones
+ *     that may be successful if retried on a failover path.
+ *
+ * Return:
+ *     %false - retrying failover path will not help
+ *     %true  - may succeed if retried
+ */
+static inline bool blk_path_error(blk_status_t error)
+{
+	switch (error) {
+	case BLK_STS_NOTSUPP:
+	case BLK_STS_NOSPC:
+	case BLK_STS_TARGET:
+	case BLK_STS_NEXUS:
+	case BLK_STS_MEDIUM:
+	case BLK_STS_PROTECTION:
+		return false;
+	}
+
+	/* Anything else could be a path failure, so should be retried */
+	return true;
+}
+
 struct blk_issue_stat {
 	u64 stat;
 };