| Message ID | 20230801124844.278698-7-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | smaps / mm/gup: fix gup_can_follow_protnone fallout | expand |
On Tue, Aug 01, 2023 at 02:48:42PM +0200, David Hildenbrand wrote: > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 2cd3e5502180..0b709d2c46c6 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1467,7 +1467,6 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, > if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) > return ERR_PTR(-EFAULT); > > - /* Full NUMA hinting faults to serialise migration in fault paths */ > if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) > return NULL; Perhaps squashing into patch 1? Thanks,
On 01.08.23 18:07, Peter Xu wrote: > On Tue, Aug 01, 2023 at 02:48:42PM +0200, David Hildenbrand wrote: >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 2cd3e5502180..0b709d2c46c6 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1467,7 +1467,6 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, >> if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) >> return ERR_PTR(-EFAULT); >> >> - /* Full NUMA hinting faults to serialise migration in fault paths */ >> if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) >> return NULL; > > Perhaps squashing into patch 1? Thanks, I decided against it so I don't have to make patch description of patch #1 even longer with something that's mostly unrelated to the core change.
On Tue, Aug 01, 2023 at 02:48:42PM +0200, David Hildenbrand wrote: > That comment for pmd_protnone() was added in commit 2b4847e73004 > ("mm: numa: serialise parallel get_user_page against THP migration"), which > noted: > > THP does not unmap pages due to a lack of support for migration > entries at a PMD level. This allows races with get_user_pages > > Nowadays, we do have PMD migration entries, so the comment no longer > applies. Let's drop it. > > Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Mel Gorman <mgorman@techsingularity.net>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2cd3e5502180..0b709d2c46c6 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1467,7 +1467,6 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) return ERR_PTR(-EFAULT); - /* Full NUMA hinting faults to serialise migration in fault paths */ if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) return NULL;
That comment for pmd_protnone() was added in commit 2b4847e73004 ("mm: numa: serialise parallel get_user_page against THP migration"), which noted: THP does not unmap pages due to a lack of support for migration entries at a PMD level. This allows races with get_user_pages Nowadays, we do have PMD migration entries, so the comment no longer applies. Let's drop it. Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/huge_memory.c | 1 - 1 file changed, 1 deletion(-)