[PATCH] vfs_default: Fix passing of errno from async calls

[Christof Schmitt]

On Wed, Aug 23, 2017 at 03:54:58PM -0700, Jeremy Allison wrote:
> On Wed, Aug 23, 2017 at 03:12:26PM -0700, Christof Schmitt via samba-technical wrote:
> > I found this while testing with a system where the actual write() system
> > call returned an error. This led to Samba hanging and never continuing
> > with the result of the write. The attached patch fixes the problem. From
> > what i understand, errno was never passed correctly back to the callers.
> 
> Wow - good catch !!!!
> 
> Can we change the assignment:
> 
>  -     state->err = errno;
>  +     state->vfs_aio_state.error = errno;
> 
> to:
> 
>  -     state->err = errno;
>  +	if (state->ret == -1) {
>  +	     state->vfs_aio_state.error = errno;
>  +	}
> 
> on each of the hunks, as we need to make
> sure that the thread only assigns non-zero
> to state->vfs_aio_state.error in the fail
> case. It's (theoretically) possible that
> the first go around returns -1, errno = EINTR and
> the second go around returns 0, but
> doesn't set errno (leaving it as the
> previous EINTR value). We should only
> set state->vfs_aio_state.error on a
> *known* error return IMHO.
> 
> If you're happy with that RB+.

Yes, that makes sense. Let me test with the change and then send the
updated patch.

Christof