Re: [Qemu-devel] [PATCH v3 06/12] nbd-server: Clear "can_read" when "device io" blocker is set

[Max Reitz]

On 15.05.2015 08:04, Fam Zheng wrote:
> So that NBD export cannot submit IO during bdrv_drain_all().
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>   nbd.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)

But can_read is not cleared until nbd_update_can_read() is called, which 
is only in nbd_request_get(), nbd_request_put(), and 
nbd_co_receive_request(), which are all called from nbd_trip() - so the 
one request which clears can_read will most probably be itself processed.

Maybe we should call nbd_update_can_read() in nbd_op_blocker_changed(), 
for all clients of the export? Or just once somewhere at the beginning 
of processing a request, and if io_blocked is set, just yield...

Max