[Qemu-devel] [PATCH v4 19/25] block: Add BlockDriver.bdrv_gather_child_options

[Max Reitz <mreitz@redhat.com>]

Some follow-up patches will rework the way bs->full_open_options is
refreshed in bdrv_refresh_filename(). The new implementation will remove
the need for the block drivers' bdrv_refresh_filename() implementations
to set bs->full_open_options; instead, it will be generic and use static
information from each block driver.

However, by implementing bdrv_gather_child_options(), block drivers will
still be able to override the way the full_open_options of their
children are incorporated into their own.

We need to implement this function for VMDK because we have to prevent
the generic implementation from gathering the options of all children:
It is not possible to specify options for the extents through the
runtime options.

For quorum, the child names that would be used by the generic
implementation and the ones that we actually want to use differ. See
quorum_gather_child_options() for more information.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 include/block/block_int.h |  1 +
 block/quorum.c            | 30 ++++++++++++++++++++++++++++++
 block/vmdk.c              | 13 +++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 799c892558..77f4121358 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -130,6 +130,7 @@ struct BlockDriver {
     int (*bdrv_make_empty)(BlockDriverState *bs);
 
     void (*bdrv_refresh_filename)(BlockDriverState *bs, QDict *options);
+    void (*bdrv_gather_child_options)(BlockDriverState *bs, QDict *target);
     char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);
 
     /* aio */
diff --git a/block/quorum.c b/block/quorum.c
index 878b8cfa9a..0a77ed44fd 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -1105,6 +1105,35 @@ static void quorum_refresh_filename(BlockDriverState *bs, QDict *options)
     bs->full_open_options = opts;
 }
 
+static void quorum_gather_child_options(BlockDriverState *bs, QDict *target)
+{
+    BDRVQuorumState *s = bs->opaque;
+    QList *children_list;
+    int i;
+
+    /* The generic implementation for gathering child options in
+     * bdrv_refresh_filename() would use the names of the children as specified
+     * for bdrv_open_child() or bdrv_attach_child(), which is "children.%u" with
+     * %u being a value (s->next_child_index) that is incremented each time a
+     * new child is added (and never decremented). Since children can be deleted
+     * at runtime, there may be gaps in that enumeration. When creating a new
+     * quorum BDS and specifying the children for it through runtime options,
+     * the enumeration used there may not have any gaps, though.
+     *
+     * Therefore, we have to create a new gap-less enumeration here (which we
+     * can achieve by simply putting all of the children's full_open_options
+     * into a QList).
+     */
+
+    children_list = qlist_new();
+    qdict_put(target, "children", children_list);
+
+    for (i = 0; i < s->num_children; i++) {
+        QINCREF(s->children[i]->bs->full_open_options);
+        qlist_append(children_list, s->children[i]->bs->full_open_options);
+    }
+}
+
 static char *quorum_dirname(BlockDriverState *bs, Error **errp)
 {
     /* In general, there are multiple BDSs with different dirnames below this
@@ -1124,6 +1153,7 @@ static BlockDriver bdrv_quorum = {
     .bdrv_file_open                     = quorum_open,
     .bdrv_close                         = quorum_close,
     .bdrv_refresh_filename              = quorum_refresh_filename,
+    .bdrv_gather_child_options          = quorum_gather_child_options,
     .bdrv_dirname                       = quorum_dirname,
 
     .bdrv_co_flush_to_disk              = quorum_co_flush,
diff --git a/block/vmdk.c b/block/vmdk.c
index 6f6932aa3f..87ac4f0e68 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -2287,6 +2287,18 @@ static int vmdk_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
     return 0;
 }
 
+static void vmdk_gather_child_options(BlockDriverState *bs, QDict *target)
+{
+    /* No children but file and backing can be explicitly specified */
+    QINCREF(bs->file->bs->full_open_options);
+    qdict_put(target, "file", bs->file->bs->full_open_options);
+
+    if (bs->backing_overridden) {
+        QINCREF(bs->backing->bs->full_open_options);
+        qdict_put(target, "backing", bs->backing->bs->full_open_options);
+    }
+}
+
 static QemuOptsList vmdk_create_opts = {
     .name = "vmdk-create-opts",
     .head = QTAILQ_HEAD_INITIALIZER(vmdk_create_opts.head),
@@ -2356,6 +2368,7 @@ static BlockDriver bdrv_vmdk = {
     .bdrv_get_specific_info       = vmdk_get_specific_info,
     .bdrv_refresh_limits          = vmdk_refresh_limits,
     .bdrv_get_info                = vmdk_get_info,
+    .bdrv_gather_child_options    = vmdk_gather_child_options,
 
     .supports_backing             = true,
     .create_opts                  = &vmdk_create_opts,
-- 
2.11.0