block: Use bdrv_refresh_filename() to pull

Before this patch, bdrv_refresh_filename() is used in a pushing manner:
Whenever the BDS graph is modified, the parents of the modified edges
are supposed to be updated (recursively upwards).  However, that is
nonviable, considering that we want child changes not to concern
parents.

Also, in the long run we want a pull model anyway: Here, we would have a
bdrv_filename() function which returns a BDS's filename, freshly
constructed.

This patch is an intermediate step.  It adds bdrv_refresh_filename()
calls before every place a BDS.filename value is used.  The only
exceptions are protocol drivers that use their own filename, which
clearly would not profit from refreshing that filename before.

Also, bdrv_get_encrypted_filename() is removed along the way (as a user
of BDS.filename), since it is completely unused.

In turn, all of the calls to bdrv_refresh_filename() before this patch
are removed, because we no longer have to call this function on graph
changes.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190201192935.18394-2-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/qemu-img.c b/qemu-img.c
index eb5045c742..d2fc28c987 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2790,6 +2790,7 @@ static int get_block_status(BlockDriverState *bs, int64_t offset,
     BlockDriverState *file;
     bool has_offset;
     int64_t map;
+    char *filename = NULL;
 
     /* As an optimization, we could cache the current range of unallocated
      * clusters in each file of the chain, and avoid querying the same
@@ -2817,6 +2818,11 @@ static int get_block_status(BlockDriverState *bs, int64_t offset,
 
     has_offset = !!(ret & BDRV_BLOCK_OFFSET_VALID);
 
+    if (file && has_offset) {
+        bdrv_refresh_filename(file);
+        filename = file->filename;
+    }
+
     *e = (MapEntry) {
         .start = offset,
         .length = bytes,
@@ -2825,8 +2831,8 @@ static int get_block_status(BlockDriverState *bs, int64_t offset,
         .offset = map,
         .has_offset = has_offset,
         .depth = depth,
-        .has_filename = file && has_offset,
-        .filename = file && has_offset ? file->filename : NULL,
+        .has_filename = filename,
+        .filename = filename,
     };
 
     return 0;
@@ -3334,6 +3340,7 @@ static int img_rebase(int argc, char **argv)
                 qdict_put_bool(options, BDRV_OPT_FORCE_SHARE, true);
             }
 
+            bdrv_refresh_filename(bs);
             overlay_filename = bs->exact_filename[0] ? bs->exact_filename
                                                      : bs->filename;
             out_real_path = g_malloc(PATH_MAX);