block: Handle filter truncation like native impl.

Make the filter truncation (passing it through to bs->file) a
first-class citizen and handle it exactly as if it was the filter
driver's native implementation of .bdrv_co_truncate().

I do not see a reason not to, it makes the code a bit shorter, and may
be even more correct because this gets us to finish the write_req that
we prepared before (may be important to e.g. bring dirty bitmaps to the
correct size).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190918095144.955-2-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/block/io.c b/block/io.c
index f0b86c1..8ff3b47 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3347,20 +3347,19 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset,
         goto out;
     }
 
-    if (!drv->bdrv_co_truncate) {
-        if (bs->file && drv->is_filter) {
-            ret = bdrv_co_truncate(bs->file, offset, prealloc, errp);
-            goto out;
-        }
+    if (drv->bdrv_co_truncate) {
+        ret = drv->bdrv_co_truncate(bs, offset, prealloc, errp);
+    } else if (bs->file && drv->is_filter) {
+        ret = bdrv_co_truncate(bs->file, offset, prealloc, errp);
+    } else {
         error_setg(errp, "Image format driver does not support resize");
         ret = -ENOTSUP;
         goto out;
     }
-
-    ret = drv->bdrv_co_truncate(bs, offset, prealloc, errp);
     if (ret < 0) {
         goto out;
     }
+
     ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "Could not refresh total sector count");