[Qemu-block] [PATCH 02/19] block: Add BDS.backing_overridden

[Max Reitz]

If the backing file is overridden, this most probably does change the
guest-visible data of a BDS. Therefore, we will need to consider this in
bdrv_refresh_filename().

Adding a new field to the BDS is not nice, but it is very simple and
exactly keeps track of whether the backing file has been overridden.

Signed-off-by: Max Reitz <address@hidden>
---
 block.c                   | 2 ++
 include/block/block_int.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/block.c b/block.c
index e349e83..e178488 100644
--- a/block.c
+++ b/block.c
@@ -1299,6 +1299,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict 
*parent_options,
 
     reference = qdict_get_try_str(parent_options, bdref_key);
     if (reference || qdict_haskey(options, "file.filename")) {
+        bs->backing_overridden = true;
         backing_filename[0] = '\0';
     } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
         QDECREF(options);
@@ -1589,6 +1590,7 @@ static int bdrv_open_inherit(BlockDriverState **pbs, 
const char *filename,
     backing = qdict_get_try_str(options, "backing");
     if (backing && *backing == '\0') {
         flags |= BDRV_O_NO_BACKING;
+        bs->backing_overridden = true;
         qdict_del(options, "backing");
     }
 
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 10d8759..d73e9ce 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -409,6 +409,7 @@ struct BlockDriverState {
     char backing_file[PATH_MAX]; /* if non zero, the image is a diff of
                                     this file image */
     char backing_format[16]; /* if non-zero and backing_file exists */
+    bool backing_overridden; /* backing file has been specified by the user */
 
     QDict *full_open_options;
     char exact_filename[PATH_MAX];
-- 
2.8.0