From cd464d838041b3a69464c0dd3938c1f912487bd3 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 15 Jan 2019 16:50:03 -0800 Subject: [PATCH] scsi: core: Remove an atomic instruction from the hot path From scsi_init_command(), a function called by scsi_mq_prep_fn(): /* zero out the cmd, except for the embedded scsi_request */ memset((char *)cmd + sizeof(cmd->req), 0, sizeof(*cmd) - sizeof(cmd->req) + dev->host->hostt->cmd_size); In other words, scsi_mq_prep_fn() clears scsi_cmnd.flags. Hence move the clear_bit() call into the else branch, the only branch in which this code is necessary. See also commit f1342709d18a ("scsi: Do not rely on blk-mq for double completions"). Cc: Keith Busch Cc: Christoph Hellwig Cc: Hannes Reinecke Signed-off-by: Bart Van Assche Reviewed-by: Keith Busch Signed-off-by: Martin K. Petersen --- drivers/scsi/scsi_lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index b13cc9288ba0..00cd365fb7d2 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1712,13 +1712,13 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, if (!scsi_host_queue_ready(q, shost, sdev)) goto out_dec_target_busy; - clear_bit(SCMD_STATE_COMPLETE, &cmd->state); if (!(req->rq_flags & RQF_DONTPREP)) { ret = scsi_mq_prep_fn(req); if (ret != BLK_STS_OK) goto out_dec_host_busy; req->rq_flags |= RQF_DONTPREP; } else { + clear_bit(SCMD_STATE_COMPLETE, &cmd->state); blk_mq_start_request(req); } -- 2.11.0