linux-kernel - [RFC PATCH v1 27/50] drivers/s390/scsi/zcsp_fc.c: Use prandom_u32

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Message-Id: <202003281643.02SGhHN7015213@sdf.org>
Date:   Fri, 29 Nov 2019 15:39:41 -0500
From:   George Spelvin <lkml@....org>
To:     linux-kernel@...r.kernel.org, lkml@....org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        linux-s390@...r.kernel.org
Subject: [RFC PATCH v1 27/50] drivers/s390/scsi/zcsp_fc.c: Use
 prandom_u32_max() for backoff

We don't need crypto-grade random numbers for randomized backoffs.

(We could skip the if() if we wanted to rely on the undocumented fact
that prandom_u32_max(0) always returns 0.  That would be a net time
saving it port_scan_backoff == 0 is rare; if it's common, the if()
is false often enough to pay for itself. Not sure which applies here.)

Signed-off-by: George Spelvin <lkml@....org>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: linux-s390@...r.kernel.org
---
 drivers/s390/scsi/zfcp_fc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c
index b018b61bd168e..d24cafe02708f 100644
--- a/drivers/s390/scsi/zfcp_fc.c
+++ b/drivers/s390/scsi/zfcp_fc.c
@@ -48,7 +48,7 @@ unsigned int zfcp_fc_port_scan_backoff(void)
 {
 	if (!port_scan_backoff)
 		return 0;
-	return get_random_int() % port_scan_backoff;
+	return prandom_u32_max(port_scan_backoff);
 }
 
 static void zfcp_fc_port_scan_time(struct zfcp_adapter *adapter)
-- 
2.26.0