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    Subject[PATCH 5.15 071/171] scsi: qla2xxx: Format log strings only if needed
    Date
    From: Roman Bolshakov <r.bolshakov@yadro.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@oracle.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
    @@ -2491,6 +2491,9 @@ 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;

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