| Message ID | 1578552280-5703-1-git-send-email-lixinhai.lxh@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/page_vma_mapped.c: Exactly compare hugetlbfs page's pfn in pfn_in_hpage() | expand |
On Thu, Jan 09, 2020 at 06:44:40AM +0000, Li Xinhai wrote: > check_pte is called for hugetlbfs page and comparing pfn in pfn_in_page, > where pfn is compared in range [hpage_pfn, hpage_pfn+HPAGE_PMD_NR). Now > change it to match exactly for hugetlbfs page to avoid hiding any > potential problems. Hm. What potential problems do you talk about? I understand that for hugetlb pages pfn is always has to be equal hpage_pfn, but returning false for pfn in the range of the hugetlb page just because it's not head is not helpful. I would rather have VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage); there. > > Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > mm/page_vma_mapped.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > index eff4b45..434978b 100644 > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -55,6 +55,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) > static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) > { > unsigned long hpage_pfn = page_to_pfn(hpage); > + if (unlikely(PageHuge(hpage))) > + return pfn == hpage_pfn; > > /* THP can be referenced by any subpage */ > return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); > -- > 1.8.3.1 > >
On 2020-01-09 at 20:30 Kirill A. Shutemov wrote: >On Thu, Jan 09, 2020 at 06:44:40AM +0000, Li Xinhai wrote: >> check_pte is called for hugetlbfs page and comparing pfn in pfn_in_page, >> where pfn is compared in range [hpage_pfn, hpage_pfn+HPAGE_PMD_NR). Now >> change it to match exactly for hugetlbfs page to avoid hiding any >> potential problems. > >Hm. What potential problems do you talk about? > >I understand that for hugetlb pages pfn is always has to be equal >hpage_pfn, but returning false for pfn in the range of the hugetlb page >just because it's not head is not helpful. > >I would rather have > > VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage); > >there. Yes, that is better to report BUG as we already catch it. >> >> Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com> >> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> >> --- >> mm/page_vma_mapped.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c >> index eff4b45..434978b 100644 >> --- a/mm/page_vma_mapped.c >> +++ b/mm/page_vma_mapped.c >> @@ -55,6 +55,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) >> static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) >> { >> unsigned long hpage_pfn = page_to_pfn(hpage); >> + if (unlikely(PageHuge(hpage))) >> + return pfn == hpage_pfn; >> >> /* THP can be referenced by any subpage */ >> return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); >> -- >> 1.8.3.1 >> >> > >-- > Kirill A. Shutemov
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index eff4b45..434978b 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -55,6 +55,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw) static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) { unsigned long hpage_pfn = page_to_pfn(hpage); + if (unlikely(PageHuge(hpage))) + return pfn == hpage_pfn; /* THP can be referenced by any subpage */ return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage);
check_pte is called for hugetlbfs page and comparing pfn in pfn_in_page, where pfn is compared in range [hpage_pfn, hpage_pfn+HPAGE_PMD_NR). Now change it to match exactly for hugetlbfs page to avoid hiding any potential problems. Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- mm/page_vma_mapped.c | 2 ++ 1 file changed, 2 insertions(+)