[dm-devel] Re: [RFC][PATCH 0/10] I/O context inheritance

[Dan Williams]

On Tue, Apr 22, 2008 at 7:54 AM, Jens Axboe <jens.axboe at oracle.com> wrote:
> On Tue, Apr 22 2008, Hirokazu Takahashi wrote:
>  > Hi,
>  >
>  > Sorry, these patches are for linux-2.6.25.
>  >
>  > > This series of patches make the block I/O layer and the I/O schedulers
>  > > be able to determine the right io_context of every I/O.
>  > >
>  > > The current implementation of the block I/O layer and the I/O schedulers
>  > > assume that the current process is the one which issued the given I/O,
>  > > then use the io_context of this process to control the I/O.
>  > > But this assumption isn't quite right because several kernel threads
>  > > will handle I/O requests on behalf of the processes which originated them.
>  > > This often happens when you want to use device mapper modules.
>  > >
>  > > The patches make every bio has a pointer to an io_context, which will
>  > > be set when it is allocated or cloned. So it makes it possible to find
>  > > the right io_context from any bio at any place.
>  > >
>  > > I'm waiting for your comments.
>
>  Can you give a brief summary of what you need this stuff for?
>

I am not sure if this the intended application, but I have been
looking at supporting ionice over software-raid and this series seems
like a necessary first step.

--
Dan