scsi: scsi-mq-debugfs: Show more information

Show the request result, request timeout and SCSI command flags.  This
information is very helpful when trying to figure out why a queue got
stuck. An example of the information that is exported through debugfs:

$ (cd /sys/kernel/debug/block && find -type f -print0 | xargs -0 grep ago)
./sda/hctx0/busy:ffff8804a4523300 {.op=READ, .cmd_flags=FAILFAST_DEV|FAILFAST_TRANSPORT|FAILFAST_DRIVER|RAHEAD, .rq_flags=MQ_INFLIGHT|DONTPREP|IO_STAT|STATS, .atomic_flags=STARTED, .tag=24, .internal_tag=-1, .cmd=Read(10) 28 00 06 80 1c c8 00 00 08 00, .retries=0, .result = 0x0, .flags=TAGGED|INITIALIZED, .timeout=90.000, allocated 0.010 s ago}

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: James E.J. Bottomley <jejb@linux.vnet.ibm.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_debugfs.c

@@ -4,15 +4,50 @@
 #include <scsi/scsi_dbg.h>
 #include "scsi_debugfs.h"
 
+#define SCSI_CMD_FLAG_NAME(name) [ilog2(SCMD_##name)] = #name
+static const char *const scsi_cmd_flags[] = {
+	SCSI_CMD_FLAG_NAME(TAGGED),
+	SCSI_CMD_FLAG_NAME(UNCHECKED_ISA_DMA),
+	SCSI_CMD_FLAG_NAME(ZONE_WRITE_LOCK),
+	SCSI_CMD_FLAG_NAME(INITIALIZED),
+};
+#undef SCSI_CMD_FLAG_NAME
+
+static int scsi_flags_show(struct seq_file *m, const unsigned long flags,
+			   const char *const *flag_name, int flag_name_count)
+{
+	bool sep = false;
+	int i;
+
+	for (i = 0; i < sizeof(flags) * BITS_PER_BYTE; i++) {
+		if (!(flags & BIT(i)))
+			continue;
+		if (sep)
+			seq_puts(m, "|");
+		sep = true;
+		if (i < flag_name_count && flag_name[i])
+			seq_puts(m, flag_name[i]);
+		else
+			seq_printf(m, "%d", i);
+	}
+	return 0;
+}
+
 void scsi_show_rq(struct seq_file *m, struct request *rq)
 {
 	struct scsi_cmnd *cmd = container_of(scsi_req(rq), typeof(*cmd), req);
-	int msecs = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc);
+	int alloc_ms = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc);
+	int timeout_ms = jiffies_to_msecs(rq->timeout);
 	const u8 *const cdb = READ_ONCE(cmd->cmnd);
 	char buf[80] = "(?)";
 
 	if (cdb)
 		__scsi_format_command(buf, sizeof(buf), cdb, cmd->cmd_len);
-	seq_printf(m, ", .cmd=%s, .retries=%d, allocated %d.%03d s ago", buf,
-		   cmd->retries, msecs / 1000, msecs % 1000);
+	seq_printf(m, ", .cmd=%s, .retries=%d, .result = %#x, .flags=", buf,
+		   cmd->retries, cmd->result);
+	scsi_flags_show(m, cmd->flags, scsi_cmd_flags,
+			ARRAY_SIZE(scsi_cmd_flags));
+	seq_printf(m, ", .timeout=%d.%03d, allocated %d.%03d s ago",
+		   timeout_ms / 1000, timeout_ms % 1000,
+		   alloc_ms / 1000, alloc_ms % 1000);
 }