linux-kernel - [PATCH] mm/uffd: Hide PTE

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Message-Id: <20220419202531.27415-1-peterx@redhat.com>
Date:   Tue, 19 Apr 2022 16:25:31 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Alistair Popple <apopple@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>, peterx@...hat.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] mm/uffd: Hide PTE_MARKER option

The PTE_MARKER option should not need to be exposed to the kernel builder,
keep it internal and remove the prompt so it won't be seen.

Instead, make the PTE_MARKER_UFFD_WP option to explicitly choose PTE_MARKER
when necessary.

While PTE_MARKER_UFFD_WP will still prompt to user, change the wording so
that it'll not mention PTE_MARKER at all but renaming it to "Userfaultfd
write protection support for shmem/hugetlbfs".

Reported-by: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: Peter Xu <peterx@...hat.com>
---

NOTE: IMHO this patch can either be standalone if easier, or be squashed
into patch "mm: Enable PTE markers by default" in -mm.

Please review, thanks.
---
 mm/Kconfig | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 3eca34c864c5..d740e1ff3b2f 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -910,16 +910,16 @@ config ANON_VMA_NAME
 	  difference in their name.
 
 config PTE_MARKER
-	bool "Marker PTEs support"
-	default y
+	bool
 
 	help
 	  Allows to create marker PTEs for file-backed memory.
 
 config PTE_MARKER_UFFD_WP
-	bool "Marker PTEs support for userfaultfd write protection"
+	bool "Userfaultfd write protection support for shmem/hugetlbfs"
 	default y
-	depends on PTE_MARKER && HAVE_ARCH_USERFAULTFD_WP
+	depends on HAVE_ARCH_USERFAULTFD_WP
+	select PTE_MARKER
 
 	help
 	  Allows to create marker PTEs for userfaultfd write protection
-- 
2.32.0