[PATCH 1/2] scsi: Add scsi_done_direct() for immediate completion.

From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
To: linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org,
	usb-storage@lists.one-eyed-alien.net
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Subject: [PATCH 1/2] scsi: Add scsi_done_direct() for immediate completion.
Date: Tue,  1 Feb 2022 22:09:53 +0100	[thread overview]
Message-ID: <20220201210954.570896-2-sebastian@breakpoint.cc> (raw)
In-Reply-To: <20220201210954.570896-1-sebastian@breakpoint.cc>

Add scsi_done_direct() which behaves like scsi_done() except that it
invokes blk_mq_complete_request_direct() in order to complete the
request.
Callers from process context can complete the request directly instead
waking ksoftirqd.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
---
 drivers/scsi/scsi_lib.c  | 27 +++++++++++++++++++++++----
 include/scsi/scsi_cmnd.h |  1 +
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0a70aa763a961..778ef6d09616f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1625,26 +1625,45 @@ static blk_status_t scsi_prepare_cmd(struct request *req)
 	return scsi_cmd_to_driver(cmd)->init_command(cmd);
 }
 
-void scsi_done(struct scsi_cmnd *cmd)
+static bool scsi_done_need_blk_compl(struct scsi_cmnd *cmd)
 {
 	switch (cmd->submitter) {
 	case SUBMITTED_BY_BLOCK_LAYER:
 		break;
 	case SUBMITTED_BY_SCSI_ERROR_HANDLER:
-		return scsi_eh_done(cmd);
+		scsi_eh_done(cmd);
+		return false;
 	case SUBMITTED_BY_SCSI_RESET_IOCTL:
-		return;
+		return false;
 	}
 
 	if (unlikely(blk_should_fake_timeout(scsi_cmd_to_rq(cmd)->q)))
-		return;
+		return false;
 	if (unlikely(test_and_set_bit(SCMD_STATE_COMPLETE, &cmd->state)))
+		return false;
+	return true;
+}
+
+void scsi_done(struct scsi_cmnd *cmd)
+{
+	if (!scsi_done_need_blk_compl(cmd))
 		return;
+
 	trace_scsi_dispatch_cmd_done(cmd);
 	blk_mq_complete_request(scsi_cmd_to_rq(cmd));
 }
 EXPORT_SYMBOL(scsi_done);
 
+void scsi_done_direct(struct scsi_cmnd *cmd)
+{
+	if (!scsi_done_need_blk_compl(cmd))
+		return;
+
+	trace_scsi_dispatch_cmd_done(cmd);
+	blk_mq_complete_request_direct(scsi_cmd_to_rq(cmd), scsi_complete);
+}
+EXPORT_SYMBOL(scsi_done_direct);
+
 static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
 {
 	struct scsi_device *sdev = q->queuedata;
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 6794d7322cbde..ff1c4b51f7aef 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -168,6 +168,7 @@ static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
 }
 
 void scsi_done(struct scsi_cmnd *cmd);
+void scsi_done_direct(struct scsi_cmnd *cmd);
 
 extern void scsi_finish_command(struct scsi_cmnd *cmd);
 
-- 
2.34.1

