Re: [Qemu-devel] [PATCH] migration: Fix handling fd protocol

[Yury Kotov]

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.

Regards,
Yury