From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Thu, 6 Jun 2013 08:44:48 +0000 (-0700)
Subject: vhost/scsi: Drop unnecessary wait_for_tasks=true usage with transport_generic_free_cmd
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=6c131d0c583cd5ceb2b497ae2dbeeae180d3573d;p=deliverable%2Flinux.git

vhost/scsi: Drop unnecessary wait_for_tasks=true usage with transport_generic_free_cmd

This patch changes vhost_scsi_free_cmd() to call transport_generic_free_cmd()
with wait_for_tasks=false in order to avoid the extra se_cmd->t_state_lock
access for the wait_for_tasks=true case.

This is unnecessary because vhost_scsi_free_cmd() is only ever called by
vhost_scsi_complete_cmd_work() after TCM completion handoff, and by
vhost_scsi_handle_vq() exception code before TCM submission handoff, so
there is never a case where se_cmd is still active from TCM's perspective
when transport_generic_free_cmd() is called.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@kernel.org>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Asias He <asias@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Moussa Ba <moussaba@micron.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 701420297225..aacf71ea001e 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -557,7 +557,7 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
 	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
 
 	/* TODO locking against target/backend threads? */
-	transport_generic_free_cmd(se_cmd, 1);
+	transport_generic_free_cmd(se_cmd, 0);
 
 	if (tv_cmd->tvc_sgl_count) {
 		u32 i;