Re: [Qemu-stable] [PATCH v2 1/1] qemu-img: wait for convert coroutines to complete

[Anton Nefedov]

On 04/21/2017 01:44 PM, Peter Lieven wrote:
> Am 21.04.2017 um 12:04 schrieb Anton Nefedov:
> > On error path (like i/o error in one of the coroutines), it's required to
> >   - wait for coroutines completion before cleaning the common structures
> >   - reenter dependent coroutines so they ever finish
> >
> > Introduced in 2d9187bc65.
> >
> > Signed-off-by: Anton Nefedov <address@hidden>
> > ---
> > [..]
>
>
> And what if we error out in the read path? Wouldn't be something like this 
> easier?
>
>
> diff --git a/qemu-img.c b/qemu-img.c
> index 22f559a..4ff1085 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1903,6 +1903,16 @@ static int convert_do_copy(ImgConvertState *s)
>          main_loop_wait(false);
>      }
>
> +    /* on error path we need to enter all coroutines that are still
> +     * running before cleaning up common structures */
> +    if (s->ret) {
> +        for (i = 0; i < s->num_coroutines; i++) {
> +             if (s->co[i]) {
> +                 qemu_coroutine_enter(s->co[i]);
> +             }
> +        }
> +    }
> +
>      if (s->compressed && !s->ret) {
>          /* signal EOF to align */
>          ret = blk_pwrite_compressed(s->target, 0, NULL, 0);
>
>
> Peter

seemed a bit too daring to me to re-enter every coroutine potentially 
including the ones that yielded waiting for I/O completion.
If that's ok - that is for sure easier :)

Or maybe some intermediate variant, as you suggest but only enter the 
"wait_sector" coroutines (and main_loop_wait for the rest)?
Or do not even re-enter them, like just

-    while (s->ret == -EINPROGRESS) {
+    while (s->running_coroutines != s->waiting_coroutines) {
         main_loop_wait(false);
     }


/Anton