linux-kernel - [PATCH RFC 2/7] s390/vdso: don't clear PG

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Message-Id: <20181205122851.5891-3-david@redhat.com>
Date:   Wed,  5 Dec 2018 13:28:46 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-m68k@...ts.linux-m68k.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        David Hildenbrand <david@...hat.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: [PATCH RFC 2/7] s390/vdso: don't clear PG_reserved

The VDSO is part of the kernel image and therefore the struct pages are
marked as reserved during boot.

As we install a special mapping, the actual struct pages will never be
exposed to MM via the page tables. We can therefore leave the pages
marked as reserved.

Suggested-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Souptick Joarder <jrdr.linux@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...nel.org>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 arch/s390/kernel/vdso.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index ebe748a9f472..9e24d23c26c0 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -292,7 +292,6 @@ static int __init vdso_init(void)
 	BUG_ON(vdso32_pagelist == NULL);
 	for (i = 0; i < vdso32_pages - 1; i++) {
 		struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
-		ClearPageReserved(pg);
 		get_page(pg);
 		vdso32_pagelist[i] = pg;
 	}
@@ -310,7 +309,6 @@ static int __init vdso_init(void)
 	BUG_ON(vdso64_pagelist == NULL);
 	for (i = 0; i < vdso64_pages - 1; i++) {
 		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
-		ClearPageReserved(pg);
 		get_page(pg);
 		vdso64_pagelist[i] = pg;
 	}
-- 
2.17.2