[Qemu-devel] [PATCH] block: Use BDRV_O_NO_BACKING where appropriate

[Kevin Wolf <kwolf@redhat.com>]

If you open an image temporarily just because you want to check its size
or get it flushed, there's no real reason to open the whole backing file
chain.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c       | 3 ++-
 block/qcow2.c | 3 ++-
 block/vmdk.c  | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/block.c b/block.c
index 03e45fc..e2745a5 100644
--- a/block.c
+++ b/block.c
@@ -1061,7 +1061,8 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
         /* Get the required size from the image */
         bs1 = bdrv_new("");
         QINCREF(options);
-        ret = bdrv_open(bs1, filename, options, 0, drv, &local_err);
+        ret = bdrv_open(bs1, filename, options, BDRV_O_NO_BACKING,
+                        drv, &local_err);
         if (ret < 0) {
             bdrv_unref(bs1);
             goto fail;
diff --git a/block/qcow2.c b/block/qcow2.c
index 2fe37ed..8e2b6c7 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1588,7 +1588,8 @@ static int qcow2_create2(const char *filename, int64_t total_size,
 
     /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
     ret = bdrv_open(bs, filename, NULL,
-                    BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
+                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
+                    drv, &local_err);
     if (error_is_set(&local_err)) {
         error_propagate(errp, local_err);
         goto out;
diff --git a/block/vmdk.c b/block/vmdk.c
index 6555663..5fb6c81 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1690,7 +1690,7 @@ static int vmdk_create(const char *filename, QEMUOptionParameter *options,
     }
     if (backing_file) {
         BlockDriverState *bs = bdrv_new("");
-        ret = bdrv_open(bs, backing_file, NULL, 0, NULL, errp);
+        ret = bdrv_open(bs, backing_file, NULL, BDRV_O_NO_BACKING, NULL, errp);
         if (ret != 0) {
             bdrv_unref(bs);
             return ret;
-- 
1.8.1.4