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From: Mike Christie <michael.christie@oracle.com>
To: martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
	target-devel@vger.kernel.org, mst@redhat.com,
	jasowang@redhat.com, pbonzini@redhat.com, stefanha@redhat.com,
	virtualization@lists.linux-foundation.org
Subject: [PATCH 17/17] vhost scsi: drop submission workqueue
Date: Thu, 22 Oct 2020 00:35:03 +0000
Message-ID: <1603326903-27052-18-git-send-email-michael.christie@oracle.com> (raw)
In-Reply-To: <1603326903-27052-1-git-send-email-michael.christie@oracle.com>

We can't control a VM's vhost scsi IO right now because the vhost worker
is added to the VM's blk cgroup, but the vhost worker thread actually
just passes the cmd to a vhost-scsi driver workqueue which ends up
submitting the cmd to the block layer.

This patch has us submit from the vhost worker thread and removes the
work queue.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/vhost/scsi.c | 30 +++---------------------------
 1 file changed, 3 insertions(+), 27 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 4e91a90..3178bf54 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -101,8 +101,6 @@ struct vhost_scsi_cmd {
 	struct vhost_scsi_nexus *tvc_nexus;
 	/* The TCM I/O descriptor that is accessed via container_of() */
 	struct se_cmd tvc_se_cmd;
-	/* work item used for cmwq dispatch to vhost_scsi_submission_work() */
-	struct work_struct work;
 	/* Copy of the incoming SCSI command descriptor block (CDB) */
 	unsigned char tvc_cdb[VHOST_SCSI_MAX_CDB_SIZE];
 	/* Sense buffer that will be mapped into outgoing status */
@@ -240,8 +238,6 @@ struct vhost_scsi_ctx {
 	struct iov_iter out_iter;
 };
 
-static struct workqueue_struct *vhost_scsi_workqueue;
-
 /* Global spinlock to protect vhost_scsi TPG list for vhost IOCTL access */
 static DEFINE_MUTEX(vhost_scsi_mutex);
 static LIST_HEAD(vhost_scsi_list);
@@ -776,10 +772,8 @@ static int vhost_scsi_to_tcm_attr(int attr)
 	return TCM_SIMPLE_TAG;
 }
 
-static void vhost_scsi_submission_work(struct work_struct *work)
+static void vhost_scsi_target_submit(struct vhost_scsi_cmd *cmd)
 {
-	struct vhost_scsi_cmd *cmd -		container_of(work, struct vhost_scsi_cmd, work);
 	struct vhost_scsi_nexus *tv_nexus;
 	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;
 	struct scatterlist *sg_ptr, *sg_prot_ptr = NULL;
@@ -1126,14 +1120,7 @@ static u16 vhost_buf_to_lun(u8 *lun_buf)
 		 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()
 		 */
 		cmd->tvc_vq_desc = vc.head;
-		/*
-		 * Dispatch cmd descriptor for cmwq execution in process
-		 * context provided by vhost_scsi_workqueue.  This also ensures
-		 * cmd is executed on the same kworker CPU as this vhost
-		 * thread to gain positive L2 cache locality effects.
-		 */
-		INIT_WORK(&cmd->work, vhost_scsi_submission_work);
-		queue_work(vhost_scsi_workqueue, &cmd->work);
+		vhost_scsi_target_submit(cmd);
 		ret = 0;
 err:
 		/*
@@ -2511,17 +2498,9 @@ static int __init vhost_scsi_init(void)
 		" on "UTS_RELEASE"\n", VHOST_SCSI_VERSION, utsname()->sysname,
 		utsname()->machine);
 
-	/*
-	 * Use our own dedicated workqueue for submitting I/O into
-	 * target core to avoid contention within system_wq.
-	 */
-	vhost_scsi_workqueue = alloc_workqueue("vhost_scsi", 0, 0);
-	if (!vhost_scsi_workqueue)
-		goto out;
-
 	ret = vhost_scsi_register();
 	if (ret < 0)
-		goto out_destroy_workqueue;
+		goto out;
 
 	ret = target_register_template(&vhost_scsi_ops);
 	if (ret < 0)
@@ -2531,8 +2510,6 @@ static int __init vhost_scsi_init(void)
 
 out_vhost_scsi_deregister:
 	vhost_scsi_deregister();
-out_destroy_workqueue:
-	destroy_workqueue(vhost_scsi_workqueue);
 out:
 	return ret;
 };
@@ -2541,7 +2518,6 @@ static void vhost_scsi_exit(void)
 {
 	target_unregister_template(&vhost_scsi_ops);
 	vhost_scsi_deregister();
-	destroy_workqueue(vhost_scsi_workqueue);
 };
 
 MODULE_DESCRIPTION("VHOST_SCSI series fabric driver");
-- 
1.8.3.1

  parent reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-22  0:34 [PATCH 00/17 V3] vhost: fix scsi cmd handling and cgroup support Mike Christie
2020-10-22  0:34 ` [PATCH 01/17] vhost scsi: add lun parser helper Mike Christie
2020-10-26  3:33   ` Jason Wang
2020-10-22  0:34 ` [PATCH 02/17] vhost: remove work arg from vhost_work_flush Mike Christie
2020-10-22  0:51   ` Chaitanya Kulkarni
2020-10-22  0:34 ` [PATCH 03/17] vhost net: use goto error handling in open Mike Christie
2020-10-22  0:45   ` Chaitanya Kulkarni
2020-10-26  3:34   ` Jason Wang
2020-10-22  0:34 ` [PATCH 04/17] vhost: prep vhost_dev_init users to handle failures Mike Christie
2020-10-22  5:22   ` kernel test robot
2020-10-23 16:15   ` Mike Christie
2020-11-02  5:57   ` Jason Wang
2020-11-03 10:04   ` Dan Carpenter
2020-10-22  0:34 ` [PATCH 05/17] vhost: move vq iovec allocation to dev init time Mike Christie
2020-10-22  0:34 ` [PATCH 06/17] vhost: support delayed vq creation Mike Christie
2020-10-22  0:34 ` [PATCH 07/17] vhost scsi: support delayed IO " Mike Christie
2020-10-26  3:51   ` Jason Wang
2020-10-27  5:47     ` Mike Christie
2020-10-28  1:55       ` Jason Wang
2020-10-30  8:47       ` Michael S. Tsirkin
2020-10-30 16:30         ` Mike Christie
2020-10-30 17:26           ` Mike Christie
2020-11-01 22:06         ` Mike Christie
2020-11-02  6:36         ` Jason Wang
2020-11-02  6:49           ` Jason Wang
2020-11-02 16:19             ` Mike Christie
2020-10-22  0:34 ` [PATCH 08/17] vhost scsi: alloc cmds per vq instead of session Mike Christie
2020-10-22  0:34 ` [PATCH 09/17] vhost scsi: fix cmd completion race Mike Christie
2020-10-27 13:07   ` Maurizio Lombardi
2020-10-30  8:51   ` Michael S. Tsirkin
2020-10-30 16:04     ` Paolo Bonzini
2020-10-22  0:34 ` [PATCH 10/17] vhost scsi: Add support for LUN resets Mike Christie
2020-10-22  0:34 ` [PATCH 11/17] vhost scsi: remove extra flushes Mike Christie
2020-10-22  0:34 ` [PATCH 12/17] vhost poll: fix coding style Mike Christie
2020-10-22  0:39   ` Chaitanya Kulkarni
2020-10-22  0:34 ` [PATCH 13/17] vhost: support multiple worker threads Mike Christie
2020-10-22  0:35 ` [PATCH 14/17] vhost: poll support support multiple workers Mike Christie
2020-10-22  0:35 ` [PATCH 15/17] host: support delayed vq creation Mike Christie
2020-10-22  0:50   ` Mike Christie
2020-10-22  0:35 ` [PATCH 16/17] vhost scsi: multiple worker support Mike Christie
2020-10-22  0:35 ` Mike Christie [this message]
2020-10-29 21:47 ` [PATCH 00/17 V3] vhost: fix scsi cmd handling and cgroup support Michael S. Tsirkin
2020-10-29 22:19   ` Mike Christie

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