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SubjectRe: [PATCH v2 09/20] mm, hugetlb: protect region tracking via newly introduced resv_map lock
> > @@ -202,15 +199,27 @@ static long region_chg(struct resv_map *resv, long f, long t)
> > * Subtle, allocate a new region at the position but make it zero
> > * size such that we can guarantee to record the reservation. */
> > if (&rg->link == head || t < rg->from) {
> > - nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
> > - if (!nrg)
> > - return -ENOMEM;
> > + if (!nrg) {
> > + nrg = kmalloc(sizeof(*nrg), GFP_NOWAIT);
> > + if (!nrg) {
> > + spin_unlock(&resv->lock);
> > + nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
> > + if (!nrg) {
> > + chg = -ENOMEM;
> > + goto out;
>
> Just return -ENOMEM here.

Okay. It looks better!

>
> > + }
> > + goto retry;
> > + }
> > + }
> > +
>
> You seem to be right, at least in my workloads, the hold times for the
> region lock is quite small, so a spinlock is better than a sleeping
> lock.
>
> That said, this code is quite messy, but I cannot think of a
> better/cleaner approach right now.

Okay.

Thanks for review!


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