quoted

But writes that have to fetch the non-cached data, will

unnecessarily

quoted

issue I/O to the fabric. These orphaned I/O's cause more pain in the
cleanup.
And if caching is enabled on the front-side then it's all the more
painful.

We can go one extra step and make FS fail read I/O for non-cached

data

quoted

too to avoid more orphan IOs.

I don't really see this as a useful state. Read-only without a real
backing file
system or LUN is hit or miss, that file system should go offline :)

Last year when I checked, I forget but I think xfs(or ext4) was going
read-only.
If this is still the case then you are basically asking FS's to modify
that behavior.