On Tue, Jan 12, 2021 at 7:17 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Tue 12-01-21 18:13:02, Muchun Song wrote: > > On Tue, Jan 12, 2021 at 6:02 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Sun 10-01-21 20:40:14, Muchun Song wrote: > > > [...] > > > > @@ -1770,6 +1788,14 @@ int dissolve_free_huge_page(struct page *page) > > > > int nid = page_to_nid(head); > > > > if (h->free_huge_pages - h->resv_huge_pages == 0) > > > > goto out; > > > > + > > > > + /* > > > > + * We should make sure that the page is already on the free list > > > > + * when it is dissolved. > > > > + */ > > > > + if (unlikely(!PageHugeFreed(head))) > > > > + goto out; > > > > + > > > > > > Do you really want to report EBUSY in this case? This doesn't make much > > > sense to me TBH. I believe you want to return 0 same as when you race > > > and the page is no longer PageHuge. > > > > Return 0 is wrong. Because the page is not freed to the buddy allocator. > > IIUC, dissolve_free_huge_page returns 0 when the page is already freed > > to the buddy allocator. Right? > > 0 is return when the page is either dissolved or it doesn't need > dissolving. If there is a race with somebody else freeing the page then > there is nothing to dissolve. Under which condition it makes sense to > report the failure and/or retry dissolving? If there is a race with somebody else freeing the page, the page can be freed to the hugepage pool not the buddy allocator. Do you think that this page is dissolved? > -- > Michal Hocko > SUSE Labs
