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

[Daniel P . Berrangé]

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.


Regards,
Daniel
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