Re: [Patch 1/6] dm: endio method

Mike Christie
2004-02-23T22:15:27Z

Hey Joe,

Joe Thornber wrote:

> Mike,
>
> On Sat, Feb 21, 2004 at 01:58:38AM -0800, Mike Christie wrote:
>
>>Saving and restoring bi_bdev is going to break multipath.
>
>
> Yes, we'll have to fall back to plan A and use the map_context pointer
> to hold the path being used (attached patch for illustration only). I
> had been hoping we could keep the map_context unused so that we could
> allow the path selectors to use it. I should have spotted this.
>
> I'll also move the failed bio remap back to mpath_end_io(), so that
> the context can be reused there (it moved to the daemon when we were
> trying to do path testing in the kernel).
>

With this move if the path has to be activated first, will the daemon
have to call some sort of ps_path_is_initialized() function before it
calls generic_make_request?

It might be easier if mp's map_io call did not move so it or the ps
could send commands and wait for the response before selecting a path. I
guess this would mean you would have to add a access function for the
tio's map_info so it could be set from the daemon, or mp may need to
allocate its own io wrapper. It seems the latter may now be needed to
give ps's a a map_info, becuase dm-mpath needs to store the path in the
tio's map_info.

Mike