block: Update image size in bdrv_invalidate_cache()

After migration has completed, we call bdrv_invalidate_cache() so that
drivers which cache some data drop their stale copy of the data and
reread it from the image file to get a new version of data that the
source modified while the migration was running.

Reloading metadata from the image file is useless, though, if the size
of the image file stays stale (this is a value that is cached for all
image formats in block.c). Reads from (meta)data after the old EOF
return only zeroes, causing image corruption.

We need to update bs->total_sectors in all layers that could potentially
have changed their size (i.e. backing files are not a concern - if they
are changed, we're in bigger trouble)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

3 files changed, 14 insertions, 1 deletions

diff --git a/block.c b/block.c
index f1ef4b0109..7b306fb62f 100644
--- a/block.c
+++ b/block.c
@@ -4776,9 +4776,17 @@ flush_parent:
 
 void bdrv_invalidate_cache(BlockDriverState *bs)
 {
-    if (bs->drv && bs->drv->bdrv_invalidate_cache) {
+    if (!bs->drv)  {
+        return;
+    }
+
+    if (bs->drv->bdrv_invalidate_cache) {
         bs->drv->bdrv_invalidate_cache(bs);
+    } else if (bs->file) {
+        bdrv_invalidate_cache(bs->file);
     }
+
+    refresh_total_sectors(bs, bs->total_sectors);
 }
 
 void bdrv_invalidate_cache_all(void)
diff --git a/block/qcow2.c b/block/qcow2.c
index cfe80befa0..b5b1e8c1b9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1176,6 +1176,8 @@ static void qcow2_invalidate_cache(BlockDriverState *bs)
 
     qcow2_close(bs);
 
+    bdrv_invalidate_cache(bs->file);
+
     options = qdict_new();
     qdict_put(options, QCOW2_OPT_LAZY_REFCOUNTS,
               qbool_from_int(s->use_lazy_refcounts));
diff --git a/block/qed.c b/block/qed.c
index 8802ad3845..837accd39b 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1563,6 +1563,9 @@ static void bdrv_qed_invalidate_cache(BlockDriverState *bs)
     BDRVQEDState *s = bs->opaque;
 
     bdrv_qed_close(bs);
+
+    bdrv_invalidate_cache(bs->file);
+
     memset(s, 0, sizeof(BDRVQEDState));
     bdrv_qed_open(bs, NULL, bs->open_flags, NULL);
 }