FAILED: patch "[PATCH] powerpc/64s: __find_linux_pte() synchronization vs" failed to apply to 5.1-stable tree

PATCH [email protected] 1 participant 1 message Jun 17, 2019

Subsystems (2)

Stable branch PowerPC

lore

Share & tools

lore

[email protected]

author maintainer

2019-06-17 12:09 UTC #0 lore raw

The patch below does not apply to the 5.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a00196a272161338d4b1d66ec69e3d57c6b280e0 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <[email protected]>
Date: Fri, 7 Jun 2019 13:56:36 +1000
Subject: [PATCH] powerpc/64s: __find_linux_pte() synchronization vs
pmdp_invalidate()

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 [email protected] # v4.20+

Signed-off-by Nicholas Piggin <[email protected]>

Reviewed-by Aneesh Kumar K.V <[email protected]>

Signed-off-by Michael Ellerman <[email protected]>

arch/powerpc/mm/pgtable.c +14 -2

index db4a6253df92..533fc6fa6726 100644
@@ -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
+
 	if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) {
 		if (is_thp)
 			*is_thp = true;