Re: [PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in __page_mapcount()
From: Nadav Amit <hidden>
Date: 2021-12-17 17:16:05
Also in:
linux-kselftest, linux-mm, lkml
On Dec 17, 2021, at 3:30 AM, David Hildenbrand [off-list ref] 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.
quoted hunk ↗ jump to hunk
Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: David Hildenbrand <redacted> --- 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).