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Re: [libvirt] [Qemu-devel] [PATCH v4 0/7] file descriptor passing using pass-fd



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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