On Thu 18-03-21 10:59:10, Oscar Salvador wrote:
> On Thu, Mar 18, 2021 at 10:29:57AM +0100, Michal Hocko wrote:
> > On Thu 18-03-21 09:54:01, Oscar Salvador wrote:
> > [...]
> > > @@ -2287,10 +2288,12 @@ static int alloc_and_dissolve_huge_page(struct
> > > hstate *h, struct page *old_page)
> > > goto unlock;
> > > } else if (page_count(old_page)) {
> > > /*
> > > - * Someone has grabbed the page, fail for now.
> > > + * Someone has grabbed the page, try to isolate it here.
> > > + * Fail with -EBUSY if not possible.
> > > */
> > > - ret = -EBUSY;
> > > update_and_free_page(h, new_page);
> > > + if (!isolate_huge_page(old_page, list)
> > > + ret = -EBUSY;
> > > goto unlock;
> > > } else if (!HPageFreed(old_page)) {
> >
> > I do not think you want to call isolate_huge_page with hugetlb_lock
> > held. You would need to drop the lock before calling isolate_huge_page.
>
> Yeah, that was an oversight. As I said I did not compile it(let alone
> test it), otherwise the system would have screamed I guess.
>
> I was more interested in knowing whether how did it look wrt. retry
> concerns:
Yes this looks much more to my taste. If we need to retry then it could
just goto retry there. The caller doesn't really have to care.
> @@ -2287,10 +2288,14 @@ static int alloc_and_dissolve_huge_page(struct hstate
> *h, struct page *old_page)
> goto unlock;
> } else if (page_count(old_page)) {
> /*
> - * Someone has grabbed the page, fail for now.
> + * Someone has grabbed the page, try to isolate it here.
> + * Fail with -EBUSY if not possible.
> */
> - ret = -EBUSY;
> update_and_free_page(h, new_page);
> + spin_unlock(&hugetlb_lock);
> + if (!isolate_huge_page(old_page, list)
> + ret = -EBUSY;
> + spin_lock(&hugetlb_lock);
> goto unlock;
simply return ret; here
--
Michal Hocko
SUSE Labs
