From 9449c9cb420b249eb6d7dad3953e4686443d7bd9 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Thu, 25 Jun 2020 20:30:04 -0700 Subject: [PATCH] mm/debug_vm_pgtable: fix build failure with powerpc 8xx Since commit 9e343b467c70 ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses"), READ_ONCE() cannot be used anymore to read complex page table entries. This leads to: CC mm/debug_vm_pgtable.o In file included from ./include/asm-generic/bug.h:5, from ./arch/powerpc/include/asm/bug.h:109, from ./include/linux/bug.h:5, from ./include/linux/mmdebug.h:5, from ./include/linux/gfp.h:5, from mm/debug_vm_pgtable.c:13: In function 'pte_clear_tests', inlined from 'debug_vm_pgtable' at mm/debug_vm_pgtable.c:363:2: ./include/linux/compiler.h:392:38: error: Unsupported access size for {READ,WRITE}_ONCE(). mm/debug_vm_pgtable.c:249:14: note: in expansion of macro 'READ_ONCE' 249 | pte_t pte = READ_ONCE(*ptep); | ^~~~~~~~~ make[2]: *** [mm/debug_vm_pgtable.o] Error 1 Fix it by using the recently added ptep_get() helper. Link: http://lkml.kernel.org/r/6ca8c972e6c920dc4ae0d4affbed9703afa4d010.1592490570.git.christophe.leroy@csgroup.eu Fixes: 9e343b467c70 ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses") Signed-off-by: Christophe Leroy Acked-by: Will Deacon Reviewed-by: Anshuman Khandual Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: "Peter Zijlstra (Intel)" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/debug_vm_pgtable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index e45623016aea..61ab16fb2e36 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -246,13 +246,13 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep, unsigned long vaddr) { - pte_t pte = READ_ONCE(*ptep); + pte_t pte = ptep_get(ptep); pte = __pte(pte_val(pte) | RANDOM_ORVALUE); set_pte_at(mm, vaddr, ptep, pte); barrier(); pte_clear(mm, vaddr, ptep); - pte = READ_ONCE(*ptep); + pte = ptep_get(ptep); WARN_ON(!pte_none(pte)); }