Commit fe3df441 authored by Muchun Song's avatar Muchun Song Committed by Linus Torvalds
Browse files

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@bytedance.com


Signed-off-by: default avatarMuchun Song <songmuchun@bytedance.com>
Reviewed-by: default avatarDavid Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5ef5f810

include/linux/pagemap.h

+3 −4
Original line number Diff line number Diff line
@@ -521,18 +521,17 @@ static inline struct page *read_mapping_page(struct address_space *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);

mm/rmap.c

+4 −2
Original line number Diff line number Diff line
@@ -1230,11 +1230,13 @@ void page_add_file_rmap(struct page *page, bool compound) 
						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;