Messages in this thread | | | Date | Fri, 20 Jan 2023 14:05:57 -0800 | Subject | Re: [PATCH 4/9] mm/rmap: change hugepage_add_new_anon_rmap to take in a folio | From | Sidhartha Kumar <> |
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On 1/20/23 1:17 PM, Matthew Wilcox wrote: > On Fri, Jan 20, 2023 at 12:45:38PM -0800, Sidhartha Kumar wrote: >>>> @@ -6176,6 +6186,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, >>>> spinlock_t *ptl; >>>> int ret = -ENOMEM; >>>> struct page *page; >>>> + struct folio *folio = NULL; >>>> int writable; >>>> bool page_in_pagecache = false; >>>> @@ -6251,12 +6262,15 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, >>>> *pagep = NULL; >>>> } >>>> + if (page) >>>> + folio = page_folio(page); >>>> + >>>> /* >>>> - * The memory barrier inside __SetPageUptodate makes sure that >>>> + * The memory barrier inside __folio_mark_uptodate makes sure that >>>> * preceding stores to the page contents become visible before >>>> * the set_pte_at() write. >>>> */ >>>> - __SetPageUptodate(page); >>>> + __folio_mark_uptodate(folio); >>> >> >> Hi Matthew, >> >> In the snippet: >> >> page = alloc_huge_page(dst_vma, dst_addr, 0); >> if (IS_ERR(page)) { >> put_page(*pagep); >> ret = -ENOMEM; >> *pagep = NULL; >> goto out; >> } >> copy_user_huge_page(page, *pagep, dst_addr, dst_vma, >> pages_per_huge_page(h)); >> >> I thought the IS_ERR() call does not handle the NULL case and is a check for >> high memory addresses, and copy_user_huge_page() path does not seem to >> handle the NULL case as well but alloc_huge_page() can possibly return NULL >> so I was unsure about how to handle the folio conversion. > > I'm not sure how alloc_huge_page() can return NULL. It seems like it > returns ERR_PTR(-ENOSPC) or ERR_PTR(-ENOMEM) if it cannot allocate memory? > I see now, I agree that page cannot be NULL at the return from alloc_huge_page, I will make that change in v2.
Thanks, Sidhartha Kumar
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