+
+ /* Filtered child */
+ BDRV_CHILD_FILTERED = (1 << 2),
I'm not sure this comment does justice for what the flag represents, but
am not sure of what longer comment to put in its place.
You’re right. I thought I could just rely on our .is_filter
documentation (at least after
https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01721.html),
but that doesn’t really apply here.
For example, this series makes raw (without further parameters) have a
CHILD_FILTERED child, without raw being a filter itself.
So there should indeed be some definition here.
Maybe:
A child to which the parent forwards all reads and writes. Therefore,
this child presents exactly the same visible data as the parent.
On second thought, the “therefore” is wrong, because the first sentence
applies to quorum, but the logical conclusion does not.
So maybe rather:
A child to which the parent forwards all reads and writes. It must
present exactly the same visible data as the parent.
Any node may have at most one filtered child at a time.