Re: NBD Cleanup patch and bugfix in ll_rw_blk.c

[Linus Torvalds]

In article <[e-mail]>, Jens Axboe  <[e-mail]> wrote:
>
>I think most of the "we want to disable plugging" behaviour stems
>from the way task queues behave. Once somebody starts a tq_disk
>run, the list is fried and walked one by one. Both old loop
>and nbd drop the io_request_lock and block, possibly waiting
>for I/O to be done (at least the loop case, don't know about
>ndb). But this I/O won't be done just because the target plug every
>now and then just happens to be queued behind the nbd/loop one and a new
>tq_disk run won't start it.

Ugh. 

How about loop/ndb intercepting the damn requests at the "elevator"
layer - that way you see every one of them, and the actual request
function might as well just be a no-op?

		Linus