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scsi: libfc: fix seconds_since_last_reset calculation

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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>
This commit is contained in:
Arnd Bergmann 2016-06-17 17:47:25 +02:00 committed by Martin K. Petersen
parent 0da21c4417
commit 540eb1eef0
1 changed files with 1 additions and 4 deletions
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5
drivers/scsi/libfc/fc_lport.c
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@ -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;