[libvirt] [Qemu-devel] [PATCH v4 0/7] file descriptor passing using pass-fd
Kevin Wolf
kwolf at redhat.com
Tue Jun 26 11:45:52 UTC 2012
Am 26.06.2012 11:10, schrieb Daniel P. Berrange:
> I was thinking about some of the sources complexity when using
> FD passing from libvirt and wanted to raise one idea for discussion
> before we continue.
>
> With this proposed series, we have usage akin to:
>
> 1. pass_fd FDSET={M} -> returns a string "/dev/fd/N" showing QEMU's
> view of the FD
> 2. drive_add file=/dev/fd/N
> 3. if failure:
> close_fd "/dev/fd/N"
In fact, there are more steps:
4. use it successfully
5. close_fd "/dev/fd/N"
I think it would well be possible that qemu just closes the fd when it's
not used internally any more. The point of close_fd is more that libvirt
still keeps a handle and can make use of this fd. One example where this
is necessary is reopening the FD of a backing file in order to perform a
live commit operation.
Kevin
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