fuse-io-uring: We need to keep the tag/index

[Bernd Schubert <bernd.schubert@fastmail.fm>]

Hi Miklos,

in the discussion we had you asked to avoid an entry tag/index,
in the mean time I don't think we can. 
In fuse_uring_cmd(), i.e. the function that gets 
'struct io_uring_cmd *cmd' we need identify the corresponding fuse
data structure ('struct fuse_ring_ent'). Basically same as in
as in do_write(), which calls request_find() and does a list search.
With a large queue size that would be an issue (and even for smaller
queue sizes not beautiful, imho).

I'm now rewriting code to create an index in
FUSE_URING_REQ_FETCH and return that later on with the request
to userspace. That needs to do realloc the array as we do know the
exact queue size anymore.


Please let me know if you should have another suggestion.


Thanks,
Bernd


PS: In code review Joanne didn't like 'tag' too much (I took that 
over from ublk). I personally find index/idx too generic - any naming
suggestion is appreciated :)