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!