Messages in this thread | | | Date | Mon, 9 Jan 2023 10:26:07 -0600 | Subject | Re: [PATCH mm-unstable 6/8] mm/hugetlb: convert alloc_migrate_huge_page to folios | From | Sidhartha Kumar <> |
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On 1/6/23 6:54 PM, Mike Kravetz wrote: > On 01/03/23 13:13, Sidhartha Kumar wrote: >> Change alloc_huge_page_nodemask() to alloc_hugetlb_folio_nodemask() and >> alloc_migrate_huge_page() to alloc_migrate_hugetlb_folio(). Both functions >> now return a folio rather than a page. > >> /* mempolicy aware migration callback */ >> @@ -2357,16 +2357,16 @@ struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, >> { >> struct mempolicy *mpol; >> nodemask_t *nodemask; >> - struct page *page; >> + struct folio *folio; >> gfp_t gfp_mask; >> int node; >> >> gfp_mask = htlb_alloc_mask(h); >> node = huge_node(vma, address, gfp_mask, &mpol, &nodemask); >> - page = alloc_huge_page_nodemask(h, node, nodemask, gfp_mask); >> + folio = alloc_hugetlb_folio_nodemask(h, node, nodemask, gfp_mask); >> mpol_cond_put(mpol); >> >> - return page; >> + return &folio->page; > > Is it possible that folio could be NULL here and cause addressing exception? > >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 6932b3d5a9dd..fab706b78be1 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1622,6 +1622,7 @@ struct page *alloc_migration_target(struct page *page, unsigned long private) >> struct migration_target_control *mtc; >> gfp_t gfp_mask; >> unsigned int order = 0; >> + struct folio *hugetlb_folio = NULL; >> struct folio *new_folio = NULL; >> int nid; >> int zidx; >> @@ -1636,7 +1637,9 @@ struct page *alloc_migration_target(struct page *page, unsigned long private) >> struct hstate *h = folio_hstate(folio); >> >> gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); >> - return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask); >> + hugetlb_folio = alloc_hugetlb_folio_nodemask(h, nid, >> + mtc->nmask, gfp_mask); >> + return &hugetlb_folio->page; > > and, here as well?
Hi Mike,
It is possible that the folio could be null but I believe these instances would not cause an addressing exception because as described in [1], &folio->page is safe even if the folio is NULL as the page offset is at 0.
[1] https://lore.kernel.org/lkml/Y7h4jsv6jl0XSIsk@casper.infradead.org/T/
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