[3.13.y-ckt stable] Patch "vhost-scsi: Take configfs group dependency during VHOST_SCSI_SET_ENDPOINT" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    vhost-scsi: Take configfs group dependency during VHOST_SCSI_SET_ENDPOINT

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From bd68ddd2c6ef48252b631b119a2bc9e1f820b1bc Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab at linux-iscsi.org>
Date: Wed, 8 Oct 2014 06:19:20 +0000
Subject: vhost-scsi: Take configfs group dependency during
 VHOST_SCSI_SET_ENDPOINT

commit ab8edab132829b26dd13db6caca3c242cce35dc1 upstream.

This patch addresses a bug where individual vhost-scsi configfs endpoint
groups can be removed from below while active exports to QEMU userspace
still exist, resulting in an OOPs.

It adds a configfs_depend_item() in vhost_scsi_set_endpoint() to obtain
an explicit dependency on se_tpg->tpg_group in order to prevent individual
vhost-scsi WWPN endpoints from being released via normal configfs methods
while an QEMU ioctl reference still exists.

Also, add matching configfs_undepend_item() in vhost_scsi_clear_endpoint()
to release the dependency, once QEMU's reference to the individual group
at /sys/kernel/config/target/vhost/$WWPN/$TPGT is released.

(Fix up vhost_scsi_clear_endpoint() error path - DanC)

Cc: Michael S. Tsirkin <mst at redhat.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Stefan Hajnoczi <stefanha at redhat.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/vhost/scsi.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 1d0196e..bb52909 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1194,6 +1194,7 @@ static int
 vhost_scsi_set_endpoint(struct vhost_scsi *vs,
 			struct vhost_scsi_target *t)
 {
+	struct se_portal_group *se_tpg;
 	struct tcm_vhost_tport *tv_tport;
 	struct tcm_vhost_tpg *tpg;
 	struct tcm_vhost_tpg **vs_tpg;
@@ -1241,6 +1242,21 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
 				ret = -EEXIST;
 				goto out;
 			}
+			/*
+			 * In order to ensure individual vhost-scsi configfs
+			 * groups cannot be removed while in use by vhost ioctl,
+			 * go ahead and take an explicit se_tpg->tpg_group.cg_item
+			 * dependency now.
+			 */
+			se_tpg = &tpg->se_tpg;
+			ret = configfs_depend_item(se_tpg->se_tpg_tfo->tf_subsys,
+						   &se_tpg->tpg_group.cg_item);
+			if (ret) {
+				pr_warn("configfs_depend_item() failed: %d\n", ret);
+				kfree(vs_tpg);
+				mutex_unlock(&tpg->tv_tpg_mutex);
+				goto out;
+			}
 			tpg->tv_tpg_vhost_count++;
 			tpg->vhost_scsi = vs;
 			vs_tpg[tpg->tport_tpgt] = tpg;
@@ -1283,6 +1299,7 @@ static int
 vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
 			  struct vhost_scsi_target *t)
 {
+	struct se_portal_group *se_tpg;
 	struct tcm_vhost_tport *tv_tport;
 	struct tcm_vhost_tpg *tpg;
 	struct vhost_virtqueue *vq;
@@ -1331,6 +1348,13 @@ vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
 		vs->vs_tpg[target] = NULL;
 		match = true;
 		mutex_unlock(&tpg->tv_tpg_mutex);
+		/*
+		 * Release se_tpg->tpg_group.cg_item configfs dependency now
+		 * to allow vhost-scsi WWPN se_tpg->tpg_group shutdown to occur.
+		 */
+		se_tpg = &tpg->se_tpg;
+		configfs_undepend_item(se_tpg->se_tpg_tfo->tf_subsys,
+				       &se_tpg->tpg_group.cg_item);
 	}
 	if (match) {
 		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
--
1.9.1