scsi: lpfc: use monotonic timestamps for statistics

The get_seconds() function suffers from a possible overflow in 2038 or
2106, as well as jitter due to settimeofday or leap second updates, and is
deprecated.

As we are interested in elapsed time only, using ktime_get_seconds() to
read the CLOCK_MONOTONIC timebase is ideal here. This also lets us remove
the hack that tries to deal with get_seconds() going slightly backwards,
which cannot happen with montonic timestamps.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_attr.c

@@ -5891,7 +5891,6 @@ lpfc_get_stats(struct Scsi_Host *shost)
 	struct lpfc_lnk_stat * lso = &psli->lnk_stat_offsets;
 	LPFC_MBOXQ_t *pmboxq;
 	MAILBOX_t *pmb;
-	unsigned long seconds;
 	int rc = 0;
 
 	/*
@@ -5992,12 +5991,7 @@ lpfc_get_stats(struct Scsi_Host *shost)
 
 	hs->dumped_frames = -1;
 
-	seconds = get_seconds();
-	if (seconds < psli->stats_start)
-		hs->seconds_since_last_reset = seconds +
-				((unsigned long)-1 - psli->stats_start);
-	else
-		hs->seconds_since_last_reset = seconds - psli->stats_start;
+	hs->seconds_since_last_reset = ktime_get_seconds() - psli->stats_start;
 
 	mempool_free(pmboxq, phba->mbox_mem_pool);
 
@@ -6076,7 +6070,7 @@ lpfc_reset_stats(struct Scsi_Host *shost)
 	else
 		lso->link_events = (phba->fc_eventTag >> 1);
 
-	psli->stats_start = get_seconds();
+	psli->stats_start = ktime_get_seconds();
 
 	mempool_free(pmboxq, phba->mbox_mem_pool);
 

drivers/scsi/lpfc/lpfc_sli.c

@@ -4591,7 +4591,7 @@ lpfc_sli_brdrestart_s3(struct lpfc_hba *phba)
 	spin_unlock_irq(&phba->hbalock);
 
 	memset(&psli->lnk_stat_offsets, 0, sizeof(psli->lnk_stat_offsets));
-	psli->stats_start = get_seconds();
+	psli->stats_start = ktime_get_seconds();
 
 	/* Give the INITFF and Post time to settle. */
 	mdelay(100);
@@ -4638,7 +4638,7 @@ lpfc_sli_brdrestart_s4(struct lpfc_hba *phba)
 	spin_unlock_irq(&phba->hbalock);
 
 	memset(&psli->lnk_stat_offsets, 0, sizeof(psli->lnk_stat_offsets));
-	psli->stats_start = get_seconds();
+	psli->stats_start = ktime_get_seconds();
 
 	/* Reset HBA AER if it was enabled, note hba_flag was reset above */
 	if (hba_aer_enabled)

drivers/scsi/lpfc/lpfc_sli.h

@@ -339,7 +339,7 @@ struct lpfc_sli {
 	struct lpfc_iocbq ** iocbq_lookup; /* array to lookup IOCB by IOTAG */
 	size_t iocbq_lookup_len;           /* current lengs of the array */
 	uint16_t  last_iotag;              /* last allocated IOTAG */
-	unsigned long  stats_start;        /* in seconds */
+	time64_t  stats_start;		   /* in seconds */
 	struct lpfc_lnk_stat lnk_stat_offsets;
 };