Re: st.c update has broken dump multi-tape support

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Thu, Jun 10, 2021 at 11:10:23AM +0200, Frank Kardel wrote:
> Hi Brett,
> 
> I meant the section in ststart1 where error is set to zero followed by goto
> out inf the fixed blocksize part.

The biodone is missing, but also other parts.

We have 5 cases.

- I/O request is queued, error == 0.   -> will be finished in callback.
- I/O request is queued, error != 0.   -> ststart calls biodone.

- I/O request is not queued, error == EAGAIN  -> ststart requeues request
- I/O request is not queued, error != 0  -> ststart calls biodone.

and

- I/O request is not queued, error == 0  -> this is broken.


I would make the last case return error == -1 instead (!= any possible
errno value). In ststart errno is checked != 0, so it will
- finish the I/O request for iostat.
- call biodone

The latter needs an adjustment like:

bp->b_error = error < 0 ? 0 : error;

so that the fake errno is replaced with end-of-file.


If you don't like the fake errno, the function needs to return
two values, the error value and a boolean to finish the
unqueued request. Cleaner, but more changes.


Greetings,
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."