On 2/14/22 11:27, Emanuele Giuseppe Esposito wrote:
Anyways, I think that in addition to the fix in this patch, we should
also fix bdrv_parent_drained_begin_single(poll=true) in
bdrv_replace_child_noperm, with something similar to what is done in
bdrv_co_yield_to_drain? ie if we are in coroutine, schedule a BH that
runs the same logic but in the main loop, but then somehow wait that it
finishes before continuing?
Alternatively, we would forbid polling in coroutines at all. And the
only place I can see that is using the drain in coroutine is mirror (see
below).
I think you should first of all see what breaks if you forbid
bdrv_replace_child_noperm() from coroutine context.
Drain in coroutines does not poll, it gets out of the coroutine through
a bottom half before polling. So if bdrv_replace_child_noperm() doesn't
require it, polling in coroutines can still be forbidden.
This patch is correct nevertheless.
Paolo
