[PATCH] xfs: re-enable xfsaild idle mode and fix associated races

[Mark Tinguely]

On 05/24/12 11:06, Brian Foster wrote:
> xfsaild idle mode logic currently leads to a couple hangs:
>
> 1.) If xfsaild is rescheduled in during an incremental scan
>      (i.e., tout != 0) and the target has been updated since
>      the previous run, we can hit the new target and go into
>      idle mode with a still populated ail.
> 2.) A wake up is only issued when the target is pushed forward.
>      The wake up can race with xfsaild if it is currently in the
>      process of entering idle mode, causing future wake up
>      events to be lost.
>
> Both hangs are reproducible by running xfstests 273 in a loop.
> Modify xfsaild to enter idle mode only when the ail is empty
> and the push target has not been moved forward since the last
> push.
>
> Signed-off-by: Brian Foster<bfoster at redhat.com>
> ---

I wouldn't mind keeping an large (a few minutes) wake up value for the
empty AIL case to be paranoid.

Reviewed-by: Mark Tinguely <tinguely at sgi.com>