[PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in __page_mapcount()
From: David Hildenbrand <hidden>
Date: 2021-12-17 11:33:46
Also in:
linux-kselftest, linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
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. 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); /* * For file THP page->_mapcount contains total number of mapping * of the page: no need to look into compound_mapcount. */ - if (!PageAnon(page) && !PageHuge(page)) - return ret; + if (!PageAnon(page)) + return atomic_read(&page->_mapcount) + 1; + + ret = atomic_read(&page->_mapcount) + 1; page = compound_head(page); - ret += atomic_read(compound_mapcount_ptr(page)) + 1; + ret += head_compound_mapcount(page); if (PageDoubleMap(page)) ret--; return ret;
--
2.31.1