[Qemu-devel] Re: [PATCH][RFC] Refactor AIO to allow multiple AIO implementations

[Gerd Hoffmann <kraxel@redhat.com>]

Anthony Liguori wrote:
> This patch refactors the AIO layer to allow multiple AIO implementations.  It's
> only possible because of the recent signalfd() patch.  
> 
> Right now, the AIO infrastructure is pretty specific to the block raw backend.
> For other block devices to implement AIO, the qemu_aio_wait function must support
> registration.  This patch introduces a new function, qmeu_aio_set_fd_handler, which
> can be used to register a file descriptor to be called back.  qemu_aio_wait() now
> polls a set of file descriptors registered with this function until one becomes
> readable or writable.

Hmm, what is the long-term plan for this?  Separating out the completion
notification is a nice first step.  Most of the aio infrastructure is
still in the block raw backend though.  IMHO it doesn't belong there.

The aio implementation(s) should be a separate entity usable by all
block backends to invoke aio requests, without having to care about how
this is actually implemented (threads, linux aio, posix aio, whatever).

cheers,
  Gerd