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?
