mm/rmap: always inline anon/file rmap duplication of a single PTE

As we grow the code, the compiler might make stupid decisions and
unnecessarily degrade fork() performance.  Let's make sure to always
inline functions that operate on a single PTE so the compiler will always
optimize out the loop and avoid a function call.

This is a preparation for maintining a total mapcount for large folios.

Link: https://lkml.kernel.org/r/20240409192301.907377-3-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/rmap.h

@@ -347,8 +347,12 @@ static inline void folio_dup_file_rmap_ptes(struct folio *folio,
 {
 	__folio_dup_file_rmap(folio, page, nr_pages, RMAP_LEVEL_PTE);
 }
-#define folio_dup_file_rmap_pte(folio, page) \
-	folio_dup_file_rmap_ptes(folio, page, 1)
+
+static __always_inline void folio_dup_file_rmap_pte(struct folio *folio,
+		struct page *page)
+{
+	__folio_dup_file_rmap(folio, page, 1, RMAP_LEVEL_PTE);
+}
 
 /**
  * folio_dup_file_rmap_pmd - duplicate a PMD mapping of a page range of a folio
@@ -448,8 +452,13 @@ static inline int folio_try_dup_anon_rmap_ptes(struct folio *folio,
 	return __folio_try_dup_anon_rmap(folio, page, nr_pages, src_vma,
 					 RMAP_LEVEL_PTE);
 }
-#define folio_try_dup_anon_rmap_pte(folio, page, vma) \
-	folio_try_dup_anon_rmap_ptes(folio, page, 1, vma)
+
+static __always_inline int folio_try_dup_anon_rmap_pte(struct folio *folio,
+		struct page *page, struct vm_area_struct *src_vma)
+{
+	return __folio_try_dup_anon_rmap(folio, page, 1, src_vma,
+					 RMAP_LEVEL_PTE);
+}
 
 /**
  * folio_try_dup_anon_rmap_pmd - try duplicating a PMD mapping of a page range