Re: [PATCH v2 9/9] block/io: expand in_flight inc/dec section: bdrv_make_zero

[Eric Blake <eblake@redhat.com>]

On 4/27/20 9:39 AM, Vladimir Sementsov-Ogievskiy wrote:
> It's safer to expand in_flight request to start before enter to
> coroutine in synchronous wrappers and end after BDRV_POLL_WHILE loop.
> Note that qemu_coroutine_enter may only schedule the coroutine in some
> circumstances.

See my wording suggestions earlier in the series.

> 
> bdrv_make_zero update includes refactoring: move the whole loop into
> coroutine, which has additional benefit of not create/enter new
> coroutine on each iteration.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   block/io.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 51 insertions(+), 3 deletions(-)
> 

> +int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
> +{
> +    int ret;
> +
> +    bdrv_inc_in_flight(child->bs);
> +
> +    if (qemu_in_coroutine()) {
> +        /* Fast-path if already in coroutine context */
> +        ret = bdrv_do_make_zero(child, flags);
> +    } else {
> +        BdrvDoMakeZeroData data = {
> +            .child = child,
> +            .flags = flags,
> +            .done = false,

Another case where the line '.done = false,' is optional, thanks to C 
semantics, but does not hurt to leave it in.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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