From cfa1a5723f0fc8eb6563fb1d19c206fd5e40cd41 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 4 May 2017 18:52:38 +0200
Subject: [PATCH] block: Drop permissions when migration completes

With image locking, permissions affect other qemu processes as well. We
want to be sure that the destination can run, so let's drop permissions
on the source when migration completes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 block.c                   | 12 +++++++++++-
 block/block-backend.c     | 25 +++++++++++++++++++++++++
 include/block/block_int.h |  7 ++++---
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/block.c b/block.c
index c8e6de29f07..444a52e331c 100644
--- a/block.c
+++ b/block.c
@@ -4019,7 +4019,7 @@ void bdrv_invalidate_cache_all(Error **errp)
 static int bdrv_inactivate_recurse(BlockDriverState *bs,
                                    bool setting_flag)
 {
-    BdrvChild *child;
+    BdrvChild *child, *parent;
     int ret;
 
     if (!setting_flag && bs->drv->bdrv_inactivate) {
@@ -4038,6 +4038,16 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs,
 
     if (setting_flag) {
         bs->open_flags |= BDRV_O_INACTIVE;
+
+        QLIST_FOREACH(parent, &bs->parents, next_parent) {
+            if (parent->role->inactivate) {
+                ret = parent->role->inactivate(parent);
+                if (ret < 0) {
+                    bs->open_flags &= ~BDRV_O_INACTIVE;
+                    return ret;
+                }
+            }
+        }
     }
     return 0;
 }
diff --git a/block/block-backend.c b/block/block-backend.c
index a7ce72b325e..f3a60081a76 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -156,6 +156,30 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
     }
 }
 
+static int blk_root_inactivate(BdrvChild *child)
+{
+    BlockBackend *blk = child->opaque;
+
+    if (blk->disable_perm) {
+        return 0;
+    }
+
+    /* Only inactivate BlockBackends for guest devices (which are inactive at
+     * this point because the VM is stopped) and unattached monitor-owned
+     * BlockBackends. If there is still any other user like a block job, then
+     * we simply can't inactivate the image. */
+    if (!blk->dev && !blk->name[0]) {
+        return -EPERM;
+    }
+
+    blk->disable_perm = true;
+    if (blk->root) {
+        bdrv_child_try_set_perm(blk->root, 0, BLK_PERM_ALL, &error_abort);
+    }
+
+    return 0;
+}
+
 static const BdrvChildRole child_root = {
     .inherit_options    = blk_root_inherit_options,
 
@@ -168,6 +192,7 @@ static const BdrvChildRole child_root = {
     .drained_end        = blk_root_drained_end,
 
     .activate           = blk_root_activate,
+    .inactivate         = blk_root_inactivate,
 };
 
 /*
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 563792580c2..5750a448a65 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -473,10 +473,11 @@ struct BdrvChildRole {
     void (*drained_begin)(BdrvChild *child);
     void (*drained_end)(BdrvChild *child);
 
-    /* Notifies the parent that the child has been activated (e.g. when
-     * migration is completing) and it can start requesting permissions and
-     * doing I/O on it. */
+    /* Notifies the parent that the child has been activated/inactivated (e.g.
+     * when migration is completing) and it can start/stop requesting
+     * permissions and doing I/O on it. */
     void (*activate)(BdrvChild *child, Error **errp);
+    int (*inactivate)(BdrvChild *child);
 
     void (*attach)(BdrvChild *child);
     void (*detach)(BdrvChild *child);
-- 
2.39.5