* [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
@ 2016-06-17 15:47 ` Arnd Bergmann
0 siblings, 0 replies; 9+ messages in thread
From: Arnd Bergmann @ 2016-06-17 15:47 UTC (permalink / raw)
To: Vasu Dev, James E.J. Bottomley, Martin K. Petersen
Cc: y2038, Arnd Bergmann, fcoe-devel, linux-scsi, linux-kernel
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>
---
drivers/scsi/libfc/fc_lport.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index e01a29863c38..99c6d9251404 100644
--- 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;
--
2.9.0
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
@ 2016-06-17 15:47 ` Arnd Bergmann
0 siblings, 0 replies; 9+ messages in thread
From: Arnd Bergmann @ 2016-06-17 15:47 UTC (permalink / raw)
To: Vasu Dev, James E.J. Bottomley, Martin K. Petersen
Cc: y2038, fcoe-devel, linux-scsi, Arnd Bergmann, linux-kernel
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>
---
drivers/scsi/libfc/fc_lport.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index e01a29863c38..99c6d9251404 100644
--- 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;
--
2.9.0
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
2016-06-17 15:47 ` Arnd Bergmann
@ 2016-06-20 13:54 ` Bart Van Assche
-1 siblings, 0 replies; 9+ messages in thread
From: Bart Van Assche @ 2016-06-20 13:54 UTC (permalink / raw)
To: Arnd Bergmann, Vasu Dev, James E.J. Bottomley, Martin K. Petersen
Cc: y2038, fcoe-devel, linux-scsi, linux-kernel
On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
> - 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;
Does this patch introduce a 64-bit division? There might still be 32-bit
users of this code.
Bart.
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
@ 2016-06-20 13:54 ` Bart Van Assche
0 siblings, 0 replies; 9+ messages in thread
From: Bart Van Assche @ 2016-06-20 13:54 UTC (permalink / raw)
To: Arnd Bergmann, Vasu Dev, James E.J. Bottomley, Martin K. Petersen
Cc: y2038, fcoe-devel, linux-kernel, linux-scsi
On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
> - 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;
Does this patch introduce a 64-bit division? There might still be 32-bit
users of this code.
Bart.
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Y2038 mailing list
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https://lists.linaro.org/mailman/listinfo/y2038
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
2016-06-20 13:54 ` Bart Van Assche
@ 2016-06-20 14:50 ` Arnd Bergmann
-1 siblings, 0 replies; 9+ messages in thread
From: Arnd Bergmann @ 2016-06-20 14:50 UTC (permalink / raw)
To: Bart Van Assche
Cc: Vasu Dev, James E.J. Bottomley, Martin K. Petersen, y2038,
fcoe-devel, linux-scsi, linux-kernel
On Monday, June 20, 2016 3:54:06 PM CEST Bart Van Assche wrote:
> On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
> > - 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;
>
> Does this patch introduce a 64-bit division? There might still be 32-bit
> users of this code.
No, both lport->boot_time and jiffies are 'unsigned long'.
Arnd
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
@ 2016-06-20 14:50 ` Arnd Bergmann
0 siblings, 0 replies; 9+ messages in thread
From: Arnd Bergmann @ 2016-06-20 14:50 UTC (permalink / raw)
To: Bart Van Assche
Cc: James E.J. Bottomley, Martin K. Petersen, linux-scsi, Vasu Dev,
y2038, linux-kernel, fcoe-devel
On Monday, June 20, 2016 3:54:06 PM CEST Bart Van Assche wrote:
> On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
> > - 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;
>
> Does this patch introduce a 64-bit division? There might still be 32-bit
> users of this code.
No, both lport->boot_time and jiffies are 'unsigned long'.
Arnd
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
2016-06-20 14:50 ` Arnd Bergmann
@ 2016-06-20 14:58 ` Bart Van Assche
-1 siblings, 0 replies; 9+ messages in thread
From: Bart Van Assche @ 2016-06-20 14:58 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Vasu Dev, James E.J. Bottomley, Martin K. Petersen, y2038,
fcoe-devel, linux-scsi, linux-kernel
On 06/20/2016 04:48 PM, Arnd Bergmann wrote:
> On Monday, June 20, 2016 3:54:06 PM CEST Bart Van Assche wrote:
>> On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
>>> - 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;
>>
>> Does this patch introduce a 64-bit division? There might still be 32-bit
>> users of this code.
>
> No, both lport->boot_time and jiffies are 'unsigned long'.
Ah, you're right. Hence:
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
@ 2016-06-20 14:58 ` Bart Van Assche
0 siblings, 0 replies; 9+ messages in thread
From: Bart Van Assche @ 2016-06-20 14:58 UTC (permalink / raw)
To: Arnd Bergmann
Cc: James E.J. Bottomley, Martin K. Petersen, linux-scsi, Vasu Dev,
y2038, linux-kernel, fcoe-devel
On 06/20/2016 04:48 PM, Arnd Bergmann wrote:
> On Monday, June 20, 2016 3:54:06 PM CEST Bart Van Assche wrote:
>> On 06/17/2016 05:47 PM, Arnd Bergmann wrote:
>>> - 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;
>>
>> Does this patch introduce a 64-bit division? There might still be 32-bit
>> users of this code.
>
> No, both lport->boot_time and jiffies are 'unsigned long'.
Ah, you're right. Hence:
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
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Y2038 mailing list
Y2038@lists.linaro.org
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] scsi: libfc: fix seconds_since_last_reset calculation
2016-06-17 15:47 ` Arnd Bergmann
(?)
(?)
@ 2016-06-21 2:05 ` Martin K. Petersen
-1 siblings, 0 replies; 9+ messages in thread
From: Martin K. Petersen @ 2016-06-21 2:05 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Vasu Dev, James E.J. Bottomley, Martin K. Petersen, y2038,
fcoe-devel, linux-scsi, linux-kernel
>>>>> "Arnd" == Arnd Bergmann <arnd@arndb.de> writes:
Arnd> The fc_get_host_stats() function contains a complex conversion
Arnd> from jiffies to timespec to seconds. As we try to get rid of uses
Arnd> of struct timespec, we can clean this up and replace it with a
Arnd> simpler computation.
Arnd> Simply dividing the difference in jiffies by HZ is not only much
Arnd> more efficient, it also avoids a problem that causes the
Arnd> seconds_since_last_reset value to be incorrect if jiffies has
Arnd> overrun since the 'boot_time' value was recorded.
Applied to 4.8/scsi-queue.
--
Martin K. Petersen Oracle Linux Engineering
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2016-06-21 2:05 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-06-17 15:47 [PATCH] scsi: libfc: fix seconds_since_last_reset calculation Arnd Bergmann
2016-06-17 15:47 ` Arnd Bergmann
2016-06-20 13:54 ` Bart Van Assche
2016-06-20 13:54 ` Bart Van Assche
2016-06-20 14:50 ` Arnd Bergmann
2016-06-20 14:50 ` Arnd Bergmann
2016-06-20 14:58 ` Bart Van Assche
2016-06-20 14:58 ` Bart Van Assche
2016-06-21 2:05 ` Martin K. Petersen
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