On 13.02.2017 18:22, Kevin Wolf wrote:
> For meaningful error messages in the permission system, we want to allow
> the parent of a BdrvChild to generate some kind of human-readable
> identifier for the link represented by the BdrvChild.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> ---
> block.c | 8 ++++++++
> block/block-backend.c | 20 ++++++++++++++++++++
> include/block/block_int.h | 4 ++++
> 3 files changed, 32 insertions(+)
>
> diff --git a/block.c b/block.c
> index fd06549..2116542 100644
> --- a/block.c
> +++ b/block.c
> @@ -800,6 +800,13 @@ const BdrvChildRole child_format = {
> .drained_end = bdrv_child_cb_drained_end,
> };
>
> +static char *bdrv_backing_link_name(BdrvChild *c)
> +{
> + BlockDriverState *parent = c->opaque;
> + return g_strdup_printf("backing file link from %s",
> + bdrv_get_device_or_node_name(parent));
So in this case it's really about the edge in the BDS graph.
> +}
> +
> /*
> * Returns the options and flags that bs->backing should get, based on the
> * given options and flags for the parent BDS
> @@ -825,6 +832,7 @@ static void bdrv_backing_options(int *child_flags, QDict
> *child_options,
> }
>
> static const BdrvChildRole child_backing = {
> + .get_link_name = bdrv_backing_link_name,
> .inherit_options = bdrv_backing_options,
> .drained_begin = bdrv_child_cb_drained_begin,
> .drained_end = bdrv_child_cb_drained_end,
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 0c23add..a314284 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -80,6 +80,7 @@ static const AIOCBInfo block_backend_aiocb_info = {
>
> static void drive_info_del(DriveInfo *dinfo);
> static BlockBackend *bdrv_first_blk(BlockDriverState *bs);
> +static char *blk_get_attached_dev_id(BlockBackend *blk);
>
> /* All BlockBackends */
> static QTAILQ_HEAD(, BlockBackend) block_backends =
> @@ -102,6 +103,24 @@ static void blk_root_drained_end(BdrvChild *child);
> static void blk_root_change_media(BdrvChild *child, bool load);
> static void blk_root_resize(BdrvChild *child);
>
> +static char *blk_root_get_link_name(BdrvChild *child)
> +{
> + BlockBackend *blk = child->opaque;
> + char *dev_id;
> +
> + if (blk->name) {
> + return g_strdup(blk->name);
This is considering the BB to be an edge in the BDS graph. I find that a
bit weird, and the fact that it makes complete and total sense after
thinking for some time doesn't change the fact that it is weird.
> + }
> +
> + dev_id = blk_get_attached_dev_id(blk);
> + if (*dev_id) {
> + return dev_id;
But the device model OTOH is definitely not an edge in the BDS graph.
> + } else {
> + g_free(dev_id);
> + return g_strdup("a block device");
> + }
> +}
> +
> static const char *blk_root_get_name(BdrvChild *child)
> {
> return blk_name(child->opaque);
[...]
Also, I'm curious what you are going to choose as a replacement if the
function pointer is not set. I have a couple of ideas, but most of them
are either not correct or would remove the need for
bdrv_backing_link_name()... Well, I'm curious. :-)
Max
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