Re: [PATCH 17/19] scsi_transport_srp: Suppress a W=1 compiler warning

Christoph Hellwig
2017-08-24T09:11:58Z

On Wed, Aug 23, 2017 at 02:40:07PM -0700, Bart Van Assche wrote:
> Avoid that the following compiler warning is reported when building
> with W=1:
>
> drivers/scsi/scsi_transport_srp.c:92:19: warning: comparison is always false due to limited range of data type [-Wtype-limits]
>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Johannes Thumshirn <jthumshirn@suse.de>
> ---
> 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 698cc4681706..b8f5e4c47579 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 + 0UL >= LONG_MAX / HZ)
> return -EINVAL;

That's a weird change.. If we can to promote dev_loss_tmo to
long we should just cast it. And of course we should always ask
us why we got this warning. If long is 64-bit and int is 32-bit
the warning makes sense, as for every reasonable comparism
the 32-bit timeout can't be larger than LONG_MAX divided by 100 or 100.

But for 32-bit longs it can, so we should keep it, maybe with a comment.