linux-kernel - [PATCH 5.10 051/132] scsi: qla2xxx: Format log strings only if needed

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Date:   Mon, 13 Dec 2021 10:29:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rajan Shanmugavelu <rajan.shanmugavelu@...cle.com>,
        Roman Bolshakov <r.bolshakov@...ro.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Subject: [PATCH 5.10 051/132] scsi: qla2xxx: Format log strings only if needed

From: Roman Bolshakov <r.bolshakov@...ro.com>

commit 69002c8ce914ef0ae22a6ea14b43bb30b9a9a6a8 upstream.

Commit 598a90f2002c ("scsi: qla2xxx: add ring buffer for tracing debug
logs") introduced unconditional log string formatting to ql_dbg() even if
ql_dbg_log event is disabled. It harms performance because some strings are
formatted in fastpath and/or interrupt context.

Link: https://lore.kernel.org/r/20211112145446.51210-1-r.bolshakov@yadro.com
Fixes: 598a90f2002c ("scsi: qla2xxx: add ring buffer for tracing debug logs")
Cc: Rajan Shanmugavelu <rajan.shanmugavelu@...cle.com>
Cc: stable@...r.kernel.org
Signed-off-by: Roman Bolshakov <r.bolshakov@...ro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/scsi/qla2xxx/qla_dbg.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/scsi/qla2xxx/qla_dbg.c
+++ b/drivers/scsi/qla2xxx/qla_dbg.c
@@ -2477,6 +2477,9 @@ ql_dbg(uint level, scsi_qla_host_t *vha,
 	struct va_format vaf;
 	char pbuf[64];
 
+	if (!ql_mask_match(level) && !trace_ql_dbg_log_enabled())
+		return;
+
 	va_start(va, fmt);
 
 	vaf.fmt = fmt;