From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: remove redundant compound_head() calling There is a READ_ONCE() in the macro of compound_head(), which will prevent compiler from optimizing the code when there are more than once calling of it in a function. Remove the redundant calling of compound_head() from page_to_index() and page_add_file_rmap() for better code generation. Link: https://lkml.kernel.org/r/20210811101431.83940-1-songmuchun@xxxxxxxxxxxxx Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: David Howells <dhowells@xxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/pagemap.h | 7 +++---- mm/rmap.c | 6 ++++-- 2 files changed, 7 insertions(+), 6 deletions(-) --- a/include/linux/pagemap.h~mm-remove-redundant-compound_head-calling +++ a/include/linux/pagemap.h @@ -521,18 +521,17 @@ static inline struct page *read_mapping_ */ static inline pgoff_t page_to_index(struct page *page) { - pgoff_t pgoff; + struct page *head; if (likely(!PageTransTail(page))) return page->index; + head = compound_head(page); /* * We don't initialize ->index for tail pages: calculate based on * head page */ - pgoff = compound_head(page)->index; - pgoff += page - compound_head(page); - return pgoff; + return head->index + page - head; } extern pgoff_t hugetlb_basepage_index(struct page *page); --- a/mm/rmap.c~mm-remove-redundant-compound_head-calling +++ a/mm/rmap.c @@ -1230,11 +1230,13 @@ void page_add_file_rmap(struct page *pag nr_pages); } else { if (PageTransCompound(page) && page_mapping(page)) { + struct page *head = compound_head(page); + VM_WARN_ON_ONCE(!PageLocked(page)); - SetPageDoubleMap(compound_head(page)); + SetPageDoubleMap(head); if (PageMlocked(page)) - clear_page_mlock(compound_head(page)); + clear_page_mlock(head); } if (!atomic_inc_and_test(&page->_mapcount)) goto out; _
