[libvirt] [RFC 3/3] lxc: Mount NBD devices before clone

[Radostin Stoyanov]

When user-namespace is enabled we are not allowed
to mount block/NBD devices.

Instead, mount /dev/nbdX to /run/libvirt/lxc/<domain>.root
and set:

	fs->src->path = /run/libvirt/lxc/<domain>.root
	fs->type = VIR_DOMAIN_FS_TYPE_MOUNT
---
 src/lxc/lxc_container.c  | 53 ------------------------------------------------
 src/lxc/lxc_controller.c | 49 +++++++++++++++++++++++++++++---------------
 2 files changed, 33 insertions(+), 69 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 3b8cb966e..420bb20ab 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -658,55 +658,6 @@ static int lxcContainerResolveSymlinks(virDomainFSDefPtr fs, bool gentle)
     return 0;
 }
 
-static int lxcContainerPrepareRoot(virDomainDefPtr def,
-                                   virDomainFSDefPtr root,
-                                   const char *sec_mount_options)
-{
-    char *dst;
-    char *tmp;
-
-    VIR_DEBUG("Prepare root %d", root->type);
-
-    if (root->type == VIR_DOMAIN_FS_TYPE_MOUNT)
-        return 0;
-
-    if (root->type == VIR_DOMAIN_FS_TYPE_FILE) {
-        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                       _("Unexpected root filesystem without loop device"));
-        return -1;
-    }
-
-    if (root->type != VIR_DOMAIN_FS_TYPE_BLOCK) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                       _("Unsupported root filesystem type %s"),
-                       virDomainFSTypeToString(root->type));
-        return -1;
-    }
-
-    if (lxcContainerResolveSymlinks(root, false) < 0)
-        return -1;
-
-    if (virAsprintf(&dst, "%s/%s.root",
-                    LXC_STATE_DIR, def->name) < 0)
-        return -1;
-
-    tmp = root->dst;
-    root->dst = dst;
-
-    if (lxcContainerMountFSBlock(root, "", sec_mount_options) < 0) {
-        root->dst = tmp;
-        VIR_FREE(dst);
-        return -1;
-    }
-
-    root->dst = tmp;
-    root->type = VIR_DOMAIN_FS_TYPE_MOUNT;
-    VIR_FREE(root->src->path);
-    root->src->path = dst;
-
-    return 0;
-}
-
 static int lxcContainerPivotRoot(virDomainFSDefPtr root)
 {
     int ret;
@@ -1755,10 +1706,6 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
     if (virFileResolveAllLinks(LXC_STATE_DIR, &stateDir) < 0)
         goto cleanup;
 
-    /* Ensure the root filesystem is mounted */
-    if (lxcContainerPrepareRoot(vmDef, root, sec_mount_options) < 0)
-        goto cleanup;
-
     /* Gives us a private root, leaving all parent OS mounts on /.oldroot */
     if (lxcContainerPivotRoot(root) < 0)
         goto cleanup;
diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
index 61d9ed07b..d1ae60b1d 100644
--- a/src/lxc/lxc_controller.c
+++ b/src/lxc/lxc_controller.c
@@ -530,9 +530,12 @@ static int virLXCControllerAppendNBDPids(virLXCControllerPtr ctrl,
 }
 
 
-static int virLXCControllerSetupNBDDeviceFS(virDomainFSDefPtr fs)
+static int virLXCControllerSetupNBDDeviceFS(virLXCControllerPtr ctrl,
+                                            virDomainFSDefPtr fs)
 {
-    char *dev;
+    char *dev, *dst, *tmp, *sec_mount_options;
+    virDomainDefPtr def = ctrl->def;
+    virSecurityManagerPtr securityDriver = ctrl->securityManager;
 
     if (fs->format <= VIR_STORAGE_FILE_NONE) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
@@ -540,22 +543,42 @@ static int virLXCControllerSetupNBDDeviceFS(virDomainFSDefPtr fs)
         return -1;
     }
 
+    if (virAsprintf(&dst, "%s/%s.root/",
+                    LXC_STATE_DIR, def->name) < 0)
+        return -1;
+
+    if (!(sec_mount_options = virSecurityManagerGetMountOptions(securityDriver, def)))
+        return -1;
+
     if (virFileNBDDeviceAssociate(fs->src->path,
                                   fs->format,
                                   fs->readonly,
                                   &dev) < 0)
         return -1;
 
-    VIR_DEBUG("Changing fs %s to use type=block for dev %s",
-              fs->src->path, dev);
-    /*
-     * We now change it into a block device type, so that
-     * the rest of container setup 'just works'
-     */
-    fs->type = VIR_DOMAIN_FS_TYPE_BLOCK;
     VIR_FREE(fs->src->path);
     fs->src->path = dev;
 
+    tmp = fs->dst;
+    fs->dst = dst;
+
+    if (lxcContainerMountFSBlock(fs, "", sec_mount_options) < 0) {
+        fs->dst = tmp;
+        VIR_FREE(dst);
+        return -1;
+    }
+
+    fs->dst = tmp;
+    fs->type = VIR_DOMAIN_FS_TYPE_MOUNT;
+
+    /* The NBD device will be cleaned up while the cgroup will end.
+     * For this we need to remember the qemu-nbd pid and add it to
+     * the cgroup*/
+    if (virLXCControllerAppendNBDPids(ctrl, fs->src->path) < 0)
+
+    VIR_FREE(fs->src->path);
+    fs->src->path = dst;
+
     return 0;
 }
 
@@ -637,13 +660,7 @@ static int virLXCControllerSetupLoopDevices(virLXCControllerPtr ctrl)
             }
             ctrl->loopDevFds[ctrl->nloopDevs - 1] = fd;
         } else if (fs->fsdriver == VIR_DOMAIN_FS_DRIVER_TYPE_NBD) {
-            if (virLXCControllerSetupNBDDeviceFS(fs) < 0)
-                goto cleanup;
-
-            /* The NBD device will be cleaned up while the cgroup will end.
-             * For this we need to remember the qemu-nbd pid and add it to
-             * the cgroup*/
-            if (virLXCControllerAppendNBDPids(ctrl, fs->src->path) < 0)
+            if (virLXCControllerSetupNBDDeviceFS(ctrl, fs) < 0)
                 goto cleanup;
         } else {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-- 
2.14.3