tcm_vhost: Refactor the lock nesting rule

We want to use tcm_vhost_mutex to make sure hotplug/hotunplug will not
happen when set_endpoint/clear_endpoint is in process.

Signed-off-by: Asias He <asias@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 957a0b9..822cd1f 100644 (file)
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -808,6 +808,9 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
 /*
  * Called from vhost_scsi_ioctl() context to walk the list of available
  * tcm_vhost_tpg with an active struct tcm_vhost_nexus
+ *
+ *  The lock nesting rule is:
+ *    tcm_vhost_mutex -> vs->dev.mutex -> tpg->tv_tpg_mutex -> vq->mutex
  */
 static int vhost_scsi_set_endpoint(
        struct vhost_scsi *vs,
@@ -820,26 +823,27 @@ static int vhost_scsi_set_endpoint(
        int index, ret, i, len;
        bool match = false;
 
+       mutex_lock(&tcm_vhost_mutex);
        mutex_lock(&vs->dev.mutex);
+
        /* Verify that ring has been setup correctly. */
        for (index = 0; index < vs->dev.nvqs; ++index) {
                /* Verify that ring has been setup correctly. */
                if (!vhost_vq_access_ok(&vs->vqs[index])) {
-                       mutex_unlock(&vs->dev.mutex);
-                       return -EFAULT;
+                       ret = -EFAULT;
+                       goto out;
                }
        }
 
        len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET;
        vs_tpg = kzalloc(len, GFP_KERNEL);
        if (!vs_tpg) {
-               mutex_unlock(&vs->dev.mutex);
-               return -ENOMEM;
+               ret = -ENOMEM;
+               goto out;
        }
        if (vs->vs_tpg)
                memcpy(vs_tpg, vs->vs_tpg, len);
 
-       mutex_lock(&tcm_vhost_mutex);
        list_for_each_entry(tv_tpg, &tcm_vhost_list, tv_tpg_list) {
                mutex_lock(&tv_tpg->tv_tpg_mutex);
                if (!tv_tpg->tpg_nexus) {
@@ -854,11 +858,10 @@ static int vhost_scsi_set_endpoint(
 
                if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) {
                        if (vs->vs_tpg && vs->vs_tpg[tv_tpg->tport_tpgt]) {
-                               mutex_unlock(&tv_tpg->tv_tpg_mutex);
-                               mutex_unlock(&tcm_vhost_mutex);
-                               mutex_unlock(&vs->dev.mutex);
                                kfree(vs_tpg);
-                               return -EEXIST;
+                               mutex_unlock(&tv_tpg->tv_tpg_mutex);
+                               ret = -EEXIST;
+                               goto out;
                        }
                        tv_tpg->tv_tpg_vhost_count++;
                        vs_tpg[tv_tpg->tport_tpgt] = tv_tpg;
@@ -867,7 +870,6 @@ static int vhost_scsi_set_endpoint(
                }
                mutex_unlock(&tv_tpg->tv_tpg_mutex);
        }
-       mutex_unlock(&tcm_vhost_mutex);
 
        if (match) {
                memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,
@@ -893,7 +895,9 @@ static int vhost_scsi_set_endpoint(
        kfree(vs->vs_tpg);
        vs->vs_tpg = vs_tpg;
 
+out:
        mutex_unlock(&vs->dev.mutex);
+       mutex_unlock(&tcm_vhost_mutex);
        return ret;
 }
 
@@ -908,6 +912,7 @@ static int vhost_scsi_clear_endpoint(
        int index, ret, i;
        u8 target;
 
+       mutex_lock(&tcm_vhost_mutex);
        mutex_lock(&vs->dev.mutex);
        /* Verify that ring has been setup correctly. */
        for (index = 0; index < vs->dev.nvqs; ++index) {
@@ -918,8 +923,8 @@ static int vhost_scsi_clear_endpoint(
        }
 
        if (!vs->vs_tpg) {
-               mutex_unlock(&vs->dev.mutex);
-               return 0;
+               ret = 0;
+               goto err_dev;
        }
 
        for (i = 0; i < VHOST_SCSI_MAX_TARGET; i++) {
@@ -965,13 +970,14 @@ static int vhost_scsi_clear_endpoint(
        kfree(vs->vs_tpg);
        vs->vs_tpg = NULL;
        mutex_unlock(&vs->dev.mutex);
-
+       mutex_unlock(&tcm_vhost_mutex);
        return 0;
 
 err_tpg:
        mutex_unlock(&tv_tpg->tv_tpg_mutex);
 err_dev:
        mutex_unlock(&vs->dev.mutex);
+       mutex_unlock(&tcm_vhost_mutex);
        return ret;
 }