Re: [PATCH v2] xen/page_alloc: Simplify domain_adjust_tot_pages

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Mar 04, 2025 at 11:10:00AM +0000, Alejandro Vallejo wrote:
> The logic has too many levels of indirection and it's very hard to
> understand it its current form. Split it between the corner case where
> the adjustment is bigger than the current claim and the rest to avoid 5
> auxiliary variables.
> 
> Add a functional change to prevent negative adjustments from
> re-increasing the claim. This has the nice side effect of avoiding
> taking the heap lock here on every free.
> 
> While at it, fix incorrect field name in nearby comment.
> 
> Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

I think it would be nice to also ensure that once the domain is
finished building (maybe when it's unpaused for the first
time?) d->outstanding_pages is set to 0.  IMO the claim system was
designed to avoid races during domain building, and shouldn't be used
once the domain is already running.

Thanks, Roger.