Re: [PATCH 2/2] nbd/server: Use drained block ops to quiesce the server

[Eric Blake <eblake@redhat.com>]

On Tue, Jun 01, 2021 at 07:57:28AM +0200, Sergio Lopez wrote:
> Before switching between AioContexts we need to make sure that we're
> fully quiesced ("nb_requests == 0" for every client) when entering the
> drained section.
> 
> To do this, we set "quiescing = true" for every client on
> ".drained_begin" to prevent new coroutines to be created, and check if

s/to be created/from being created/

> "nb_requests == 0" on ".drained_poll". Finally, once we're exiting the
> drained section, on ".drained_end" we set "quiescing = false" and
> call "nbd_client_receive_next_request()" to resume the processing of
> new requests.
> 
> With these changes, "blk_aio_attach()" and "blk_aio_detach()" can be
> reverted to be as simple as they were before f148ae7d36.

Is that reversion planned to be patch 3 of your series in v2?

> 
> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1960137
> Suggested-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
>  nbd/server.c | 99 +++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 75 insertions(+), 24 deletions(-)
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org