Le 07/06/2019 à 05:56, Nicholas Piggin a écrit :
The change to pmdp_invalidate to mark the pmd with _PAGE_INVALID broke
the synchronisation against lock free lookups, __find_linux_pte's
pmd_none check no longer returns true for such cases.
Fix this by adding a check for this condition as well.
Fixes: da7ad366b497 ("powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT
bit")
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Suggested-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/mm/pgtable.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index db4a6253df92..533fc6fa6726 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -372,13 +372,25 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
pdshift = PMD_SHIFT;
pmdp = pmd_offset(&pud, ea);
pmd = READ_ONCE(*pmdp);
+
/*
- * A hugepage collapse is captured by pmd_none, because
- * it mark the pmd none and do a hpte invalidate.
+ * A hugepage collapse is captured by this condition, see
+ * pmdp_collapse_flush.
*/
if (pmd_none(pmd))
return NULL;
+#ifdef CONFIG_PPC_BOOK3S_64
+ /*
+ * A hugepage split is captured by this condition, see
+ * pmdp_invalidate.
+ *
+ * Huge page modification can be caught here too.
+ */
+ if (pmd_is_serializing(pmd))
+ return NULL;
+#endif
+
Could get rid of that #ifdef by adding the following in book3s32 and
nohash pgtable.h:
static inline bool pmd_is_serializing() { return false; }
Christophe
if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) {
if (is_thp)
*is_thp = true;
