Peter Xu <pet...@redhat.com> writes: > On Mon, Sep 11, 2023 at 02:13:19PM -0300, Fabiano Rosas wrote: >> The core yank code is strict about balanced registering and >> unregistering of yank functions. >> >> This creates a difficulty because the migration code registers one >> yank function per QIOChannel, but each QIOChannel can be referenced by >> more than one QEMUFile. The yank function should not be removed until >> all QEMUFiles have been closed. >> >> Keep a reference count of how many QEMUFiles are using a QIOChannel >> that has a yank function. Only unregister the yank function when all >> QEMUFiles have been closed. >> >> This improves the current code by removing the need for the programmer >> to know which QEMUFile is the last one to be cleaned up and fixes the >> theoretical issue of removing the yank function while another QEMUFile >> could still be using the ioc and require a yank. >> >> Signed-off-by: Fabiano Rosas <faro...@suse.de> >> --- >> migration/yank_functions.c | 81 ++++++++++++++++++++++++++++++++++---- >> migration/yank_functions.h | 8 ++++ >> 2 files changed, 81 insertions(+), 8 deletions(-) > > I worry this over-complicate things.
It does. We ran out of simple options. > If you prefer the cleaness that we operate always on qemufile level, can we > just register each yank function per-qemufile? "just" hehe we could, but: i) the yank is a per-channel operation, so this is even more unintuitive; ii) multifd doesn't have a QEMUFile, so it will have to continue using the ioc; iii) we'll have to add a yank to every new QEMUFile created during the incoming migration (colo, rdma, etc), otherwise the incoming side will be left using iocs while the src uses the QEMUFile; iv) this is a functional change of the yank feature for which we have no tests. If that's all ok to you I'll go ahead and git it a try. > I think qmp yank will simply fail the 2nd call on the qemufile if the > iochannel is shared with the other one, but that's totally fine, IMHO. > > What do you think? > > In all cases, we should probably at least merge patch 1-8 if that can > resolve the CI issue. I think all of them are properly reviewed. I agree. Someone needs to queue this though since Juan has been busy.