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-rw-r--r--mm/page_vma_mapped.c25
1 files changed, 10 insertions, 15 deletions
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index eb462e7..53afbb9 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -6,17 +6,6 @@
#include "internal.h"
-static inline bool check_pmd(struct page_vma_mapped_walk *pvmw)
-{
- pmd_t pmde;
- /*
- * Make sure we don't re-load pmd between present and !trans_huge check.
- * We need a consistent view.
- */
- pmde = READ_ONCE(*pvmw->pmd);
- return pmd_present(pmde) && !pmd_trans_huge(pmde);
-}
-
static inline bool not_found(struct page_vma_mapped_walk *pvmw)
{
page_vma_mapped_walk_done(pvmw);
@@ -116,6 +105,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
+ pmd_t pmde;
/* The only possible pmd mapping has been handled on last iteration */
if (pvmw->pmd && !pvmw->pte)
@@ -148,7 +138,13 @@ restart:
if (!pud_present(*pud))
return false;
pvmw->pmd = pmd_offset(pud, pvmw->address);
- if (pmd_trans_huge(*pvmw->pmd) || is_pmd_migration_entry(*pvmw->pmd)) {
+ /*
+ * Make sure the pmd value isn't cached in a register by the
+ * compiler and used as a stale value after we've observed a
+ * subsequent update.
+ */
+ pmde = READ_ONCE(*pvmw->pmd);
+ if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
pvmw->ptl = pmd_lock(mm, pvmw->pmd);
if (likely(pmd_trans_huge(*pvmw->pmd))) {
if (pvmw->flags & PVMW_MIGRATION)
@@ -174,9 +170,8 @@ restart:
spin_unlock(pvmw->ptl);
pvmw->ptl = NULL;
}
- } else {
- if (!check_pmd(pvmw))
- return false;
+ } else if (!pmd_present(pmde)) {
+ return false;
}
if (!map_pte(pvmw))
goto next_pte;
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