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Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol
From: |
Daniel P . Berrangé |
Subject: |
Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol |
Date: |
Mon, 15 Apr 2019 11:47:25 +0100 |
User-agent: |
Mutt/1.11.3 (2019-02-01) |
On Mon, Apr 15, 2019 at 01:33:21PM +0300, Yury Kotov wrote:
> 15.04.2019, 13:25, "Daniel P. Berrangé" <address@hidden>:
> > On Mon, Apr 15, 2019 at 01:17:06PM +0300, Yury Kotov wrote:
> >> 15.04.2019, 13:11, "Daniel P. Berrangé" <address@hidden>:
> >> > On Mon, Apr 15, 2019 at 12:50:08PM +0300, Yury Kotov wrote:
> >> >> Hi,
> >> >>
> >> >> Just to clarify. I see two possible solutions:
> >> >>
> >> >> 1) Since the migration code doesn't receive fd, it isn't responsible
> >> for
> >> >> closing it. So, it may be better to use migrate_fd_param for both
> >> >> incoming/outgoing and add dupping for migrate_fd_param. Thus, clients
> >> must
> >> >> close the fd themselves. But existing clients will have a leak.
> >> >
> >> > We can't break existing clients in this way as they are correctly
> >> > using the monitor with its current semantics.
> >> >
> >> >> 2) If we don't duplicate fd, then at least we should remove fd from
> >> >> the corresponding list. Therefore, the solution is to fix qemu_close
> >> to find
> >> >> the list and remove fd from it. But qemu_close is currently
> >> consistent with
> >> >> qemu_open (which opens/dups fd), so adding additional logic might not
> >> be
> >> >> a very good idea.
> >> >
> >> > qemu_close is not appropriate place to deal with something speciifc
> >> > to the montor.
> >> >
> >> >> I don't see any other solution, but I might miss something.
> >> >> What do you think?
> >> >
> >> > All callers of monitor_get_fd() will close() the FD they get back.
> >> > Thus monitor_get_fd() should remove it from the list when it returns
> >> > it, and we should add API docs to monitor_get_fd() to explain this.
> >> >
> >> Ok, it sounds reasonable. But monitor_get_fd is only about outgoing
> >> migration.
> >> But what about the incoming migration? It doesn't use monitor_get_fd but
> >> just
> >> converts input string to int and use it as fd.
> >
> > The incoming migration expects the FD to be passed into QEMU by the mgmt
> > app when it is exec'ing the QEMU binary. It doesn't interact with the
> > monitor at all AFAIR.
> >
>
> Oh, sorry. This use case is not obvious. We used add-fd to pass fd for
> migrate-incoming and such way has described problems.
That's a bug in your usage of QEMU IMHO, as the incoming code is not
designed to use add-fd.
Regards,
Daniel
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- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, (continued)
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Daniel P . Berrangé, 2019/04/11
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/11
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Daniel P . Berrangé, 2019/04/11
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/11
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Daniel P . Berrangé, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Daniel P . Berrangé, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol,
Daniel P . Berrangé <=
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Dr. David Alan Gilbert, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Daniel P . Berrangé, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Dr. David Alan Gilbert, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/15
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/16
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/16
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Dr. David Alan Gilbert, 2019/04/18
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/18
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Dr. David Alan Gilbert, 2019/04/18
- Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol, Yury Kotov, 2019/04/18