Messages in this thread | | | Date | Fri, 17 Dec 2021 18:30:28 +0100 | Subject | Re: [PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in __page_mapcount() | From | David Hildenbrand <> |
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On 17.12.21 18:16, Nadav Amit wrote: > >> On Dec 17, 2021, at 3:30 AM, David Hildenbrand <david@redhat.com> wrote: >> >> Let's return early for hugetlb, which really only relies on the compound >> mapcount so far and does not support PageDoubleMap() yet. Use the chance >> to cleanup the file-THP case to make it easier to grasp. While at it, use >> head_compound_mapcount(). >> >> This is a preparation for further changes. > > It would be useful to add “no functional change intended” or something.
Absolutely, same applies to other "simplification" patches.
> >> >> Reviewed-by: Peter Xu <peterx@redhat.com> >> Signed-off-by: David Hildenbrand <david@redhat.com> >> --- >> mm/util.c | 11 +++++++---- >> 1 file changed, 7 insertions(+), 4 deletions(-) >> >> diff --git a/mm/util.c b/mm/util.c >> index 741ba32a43ac..3239e75c148d 100644 >> --- a/mm/util.c >> +++ b/mm/util.c >> @@ -732,15 +732,18 @@ int __page_mapcount(struct page *page) >> { >> int ret; >> >> - ret = atomic_read(&page->_mapcount) + 1; >> + if (PageHuge(page)) >> + return compound_mapcount(page); > > Before you return, perhaps you can add an assertion like: > > VM_BUG_ON(PageDoubleMap(page)); > > This would be make the code clearer and would ease debugging in the > future (if support for double-map is expanded). >
I'd probably have to add this to a couple of places -- and I assume anybody working on that has to grep the kernel for use of PageDoubleMap already.
Thanks!
-- Thanks,
David / dhildenb
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