mm/mapping_dirty_helpers: guard hugepage pud's usage

Mapping dirty helpers have, so far, been only used on X86, but a port of vmwgfx to ARM64 exposed a problem which results in a compilation error on ARM64 systems: mm/mapping_dirty_helpers.c: In function `wp_clean_pud_entry': mm/mapping_dirty_helpers.c:172:32: error: implicit declaration of function `pud_dirty'; did you mean `pmd_dirty'? [-Werror=implicit-function-declaration] This is due to the fact that mapping_dirty_helpers code assumes that pud_dirty is always defined, which is not the case for architectures that don't define CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD. ARM64 arch is a little inconsistent when it comes to PUD hugepage helpers, e.g. it defines pud_young but not pud_dirty but regardless of that the core kernel code shouldn't assume that any of the PUD hugepage helpers are available unless CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD is defined. This prevents compilation errors whenever one of the drivers is ported to new architectures. Link: https://lkml.kernel.org/r/20210409165151.694574-1-zackr@vmware.com Signed-off-by: Zack Rusin <zackr@vmware.com> Reviewed-by: Thomas Hellstrm (Intel) <thomas_os@shipmail.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: zackr

mm/mapping_dirty_helpers.c

@@ -165,10 +165,12 @@ static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
 return 0;
 }
 
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 /* Huge pud */
 walk->action = ACTION_CONTINUE;
 if (pud_trans_huge(pudval) || pud_devmap(pudval))
 WARN_ON(pud_write(pudval) || pud_dirty(pudval));
+#endif
 
 return 0;
 }