diff mbox series

[11/11] mm/thp: another PVMW_SYNC fix in page_vma_mapped_walk()

Message ID 1bdf384c-8137-a149-2a1e-475a4791c3c@google.com (mailing list archive)
State New
Headers show
Series mm: page_vma_mapped_walk() cleanup and THP fixes | expand

Commit Message

Hugh Dickins June 10, 2021, 6:54 a.m. UTC
Aha!  Shouldn't that quick scan over pte_none()s make sure that it holds
ptlock in the PVMW_SYNC case?  That too might have been responsible for
BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though
I've never seen any.

Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
---
 mm/page_vma_mapped.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Kirill A. Shutemov June 10, 2021, 9:43 a.m. UTC | #1
On Wed, Jun 09, 2021 at 11:54:46PM -0700, Hugh Dickins wrote:
> Aha!  Shouldn't that quick scan over pte_none()s make sure that it holds
> ptlock in the PVMW_SYNC case?  That too might have been responsible for
> BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though
> I've never seen any.
> 
> Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: <stable@vger.kernel.org>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Hugh Dickins June 11, 2021, 6:29 p.m. UTC | #2
On Thu, 10 Jun 2021, Kirill A. Shutemov wrote:
> On Wed, Jun 09, 2021 at 11:54:46PM -0700, Hugh Dickins wrote:
> > Aha!  Shouldn't that quick scan over pte_none()s make sure that it holds
> > ptlock in the PVMW_SYNC case?  That too might have been responsible for
> > BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though
> > I've never seen any.
> > 
> > Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
> > Signed-off-by: Hugh Dickins <hughd@google.com>
> > Cc: <stable@vger.kernel.org>
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Thanks Kirill.

And Wang Yugui has now reported the good news, that this afterthought
patch finally fixes the unmap_page() BUGs they were hitting on 5.10.

Andrew, please add a link to
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/
and
Tested-by: Wang Yugui <wangyugui@e16-tech.com>

Thanks,
Hugh
diff mbox series

Patch

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 6eb2f1863506..7ae4a016304b 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -277,6 +277,10 @@  bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 				goto restart;
 			}
 			pvmw->pte++;
+			if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
+				pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+				spin_lock(pvmw->ptl);
+			}
 		} while (pte_none(*pvmw->pte));
 
 		if (!pvmw->ptl) {