Re: [PATCH] scsi: srp_transport: Fix 'always false comparison' in srp_tmo_valid()

2017-01-27 Thread Augusto Mecking Caringi 
On Thu, Jan 26, 2017 at 3:11 PM, Bart Van Assche
 wrote:
> This patch is wrong. The purpose of the dev_loss_tmo >= LONG_MAX / HZ check
> is to avoid that the expression 1UL * dev_loss_tmo * HZ further down
> overflows. Can you check whether changing the if-statement into if (1UL *
> dev_loss_tmo >= LONG_MAX / HZ) also suppresses the compiler warning?

Hi Bart,

Right, now a I see...

Doing your proposed change the warning go away...

Do you want me to send a new patch for that?

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Augusto Mecking Caringi
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Re: [PATCH] scsi: srp_transport: Fix 'always false comparison' in srp_tmo_valid()

2017-01-26 Thread Bart Van Assche 
On Thu, 2017-01-26 at 11:17 +, Augusto Mecking Caringi wrote:
> In a 64bit system (where long is 64bit wide), even dividing LONG_MAX by
> HZ will always be bigger than the max value that an int variable can
> hold.
> 
> This has been detected by building the driver with W=1:
> 
> drivers/scsi/scsi_transport_srp.c: In function ‘srp_tmo_valid’:
> drivers/scsi/scsi_transport_srp.c:92:19: warning: comparison is always
> false due to limited range of data type [-Wtype-limits]
> if (dev_loss_tmo >= LONG_MAX / HZ)
>^
> 
> Signed-off-by: Augusto Mecking Caringi 
> ---
>  drivers/scsi/scsi_transport_srp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_transport_srp.c 
> b/drivers/scsi/scsi_transport_srp.c
> index b87a786..d8c83f4 100644
> --- a/drivers/scsi/scsi_transport_srp.c
> +++ b/drivers/scsi/scsi_transport_srp.c
> @@ -89,7 +89,7 @@ int srp_tmo_valid(int reconnect_delay, int 
> fast_io_fail_tmo, int dev_loss_tmo)
>   if (fast_io_fail_tmo < 0 &&
>   dev_loss_tmo > SCSI_DEVICE_BLOCK_MAX_TIMEOUT)
>   return -EINVAL;
> - if (dev_loss_tmo >= LONG_MAX / HZ)
> + if (dev_loss_tmo >= INT_MAX / HZ)
>   return -EINVAL;
>   if (fast_io_fail_tmo >= 0 && dev_loss_tmo >= 0 &&
>   fast_io_fail_tmo >= dev_loss_tmo)

This patch is wrong. The purpose of the dev_loss_tmo >= LONG_MAX / HZ check
is to avoid that the expression 1UL * dev_loss_tmo * HZ further down
overflows. Can you check whether changing the if-statement into if (1UL *
dev_loss_tmo >= LONG_MAX / HZ) also suppresses the compiler warning?

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[PATCH] scsi: srp_transport: Fix 'always false comparison' in srp_tmo_valid()

2017-01-26 Thread Augusto Mecking Caringi 
In a 64bit system (where long is 64bit wide), even dividing LONG_MAX by
HZ will always be bigger than the max value that an int variable can
hold.

This has been detected by building the driver with W=1:

drivers/scsi/scsi_transport_srp.c: In function ‘srp_tmo_valid’:
drivers/scsi/scsi_transport_srp.c:92:19: warning: comparison is always
false due to limited range of data type [-Wtype-limits]
if (dev_loss_tmo >= LONG_MAX / HZ)
   ^

Signed-off-by: Augusto Mecking Caringi 
---
 drivers/scsi/scsi_transport_srp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_transport_srp.c 
b/drivers/scsi/scsi_transport_srp.c
index b87a786..d8c83f4 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -89,7 +89,7 @@ int srp_tmo_valid(int reconnect_delay, int fast_io_fail_tmo, 
int dev_loss_tmo)
if (fast_io_fail_tmo < 0 &&
dev_loss_tmo > SCSI_DEVICE_BLOCK_MAX_TIMEOUT)
return -EINVAL;
-   if (dev_loss_tmo >= LONG_MAX / HZ)
+   if (dev_loss_tmo >= INT_MAX / HZ)
return -EINVAL;
if (fast_io_fail_tmo >= 0 && dev_loss_tmo >= 0 &&
fast_io_fail_tmo >= dev_loss_tmo)
-- 
2.7.4

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