scsi: libfc: fix seconds_since_last_reset calculation

The fc_get_host_stats() function contains a complex conversion from
jiffies to timespec to seconds. As we try to get rid of uses of struct
timespec, we can clean this up and replace it with a simpler
computation.

Simply dividing the difference in jiffies by HZ is not only much more
efficient, it also avoids a problem that causes the
seconds_since_last_reset value to be incorrect if jiffies has overrun
since the 'boot_time' value was recorded.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index b9b44daff159f1f92d86ad7d31a9fe945d1a4d98..04ce7cfb6d1b6272d26ce138a9b11ee952a20d6f 100644 (file)
--- a/drivers/scsi/libfc/fc_lport.c
+++ b/drivers/scsi/libfc/fc_lport.c
@@ -301,7 +301,6 @@ struct fc_host_statistics *fc_get_host_stats(struct Scsi_Host *shost)
 {
        struct fc_host_statistics *fc_stats;
        struct fc_lport *lport = shost_priv(shost);
-       struct timespec v0, v1;
        unsigned int cpu;
        u64 fcp_in_bytes = 0;
        u64 fcp_out_bytes = 0;
@@ -309,9 +308,7 @@ struct fc_host_statistics *fc_get_host_stats(struct Scsi_Host *shost)
        fc_stats = &lport->host_stats;
        memset(fc_stats, 0, sizeof(struct fc_host_statistics));
 
-       jiffies_to_timespec(jiffies, &v0);
-       jiffies_to_timespec(lport->boot_time, &v1);
-       fc_stats->seconds_since_last_reset = (v0.tv_sec - v1.tv_sec);
+       fc_stats->seconds_since_last_reset = (lport->boot_time - jiffies) / HZ;
 
        for_each_possible_cpu(cpu) {
                struct fc_stats *stats;