| Date | Mon, 10 Jan 2022 17:47:29 -0800 | Subject | Re: [PATCH v2 06/28] gup: Fix some contiguous memmap assumptions | From | John Hubbard <> |
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On 1/9/22 20:23, Matthew Wilcox (Oracle) wrote: > Several functions in gup.c assume that a compound page has virtually > contiguous page structs. This isn't true for SPARSEMEM configs unless > SPARSEMEM_VMEMMAP is also set. Fix them by using nth_page() instead of > plain pointer arithmetic. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > mm/gup.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-)
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
thanks, -- John Hubbard NVIDIA
> > diff --git a/mm/gup.c b/mm/gup.c > index 8a0ea220ced1..9c0a702a4e03 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -235,7 +235,7 @@ static inline struct page *compound_range_next(unsigned long i, > struct page *next, *page; > unsigned int nr = 1; > > - next = start + i; > + next = nth_page(start, i); > page = compound_head(next); > if (PageHead(page)) > nr = min_t(unsigned int, > @@ -2430,8 +2430,8 @@ static int record_subpages(struct page *page, unsigned long addr, > { > int nr; > > - for (nr = 0; addr != end; addr += PAGE_SIZE) > - pages[nr++] = page++; > + for (nr = 0; addr != end; nr++, addr += PAGE_SIZE) > + pages[nr] = nth_page(page, nr); > > return nr; > } > @@ -2466,7 +2466,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > > head = pte_page(pte); > - page = head + ((addr & (sz-1)) >> PAGE_SHIFT); > + page = nth_page(head, (addr & (sz-1)) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > head = try_grab_compound_head(head, refs, flags); > @@ -2526,7 +2526,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > pages, nr); > } > > - page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > + page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > head = try_grab_compound_head(pmd_page(orig), refs, flags); > @@ -2560,7 +2560,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > pages, nr); > } > > - page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > + page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > head = try_grab_compound_head(pud_page(orig), refs, flags); > @@ -2589,7 +2589,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, > > BUILD_BUG_ON(pgd_devmap(orig)); > > - page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); > + page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT); > refs = record_subpages(page, addr, end, pages + *nr); > > head = try_grab_compound_head(pgd_page(orig), refs, flags);
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