From nobody Fri Nov 29 19:26:07 2024 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 38AD614E2E3; Tue, 17 Sep 2024 07:31:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726558307; cv=none; b=ilgwBmqTV6xA00s9ykv32/36X6zvtsf7DqBKzg/tYwxV0UIyepSZJpTsSmogARsfSng0nprJZEtcvlbQeMFnAqTNk897TLcVKChcsfMXksXgSfVGuGsygTDlj8oSY86zRx8+TUdQpJe1IdUlNcXotC51ptb7tR8G6KMmVJLl03M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726558307; c=relaxed/simple; bh=Wrn9vGLLb36vMNF1zYZDE7W/OZuIZQCQKfm9bxbLjfM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YMp7IH/Ag2rf5woitBlH0GcNw7Wy79NozouIP+QXQP8BJhWtPmrDimCCVXhKrtisu/rDMhz+35IkZoiMleQZSiYReK0plm2ATt06bniqjojMMRpyChcgIFqQunew6v/3zOdkX3spQYGvz/IA1v+Kn6vVKXRFZkYIs9XII/2pD5c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0434D106F; Tue, 17 Sep 2024 00:32:15 -0700 (PDT) Received: from a077893.arm.com (unknown [10.163.61.158]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 11DEC3F64C; Tue, 17 Sep 2024 00:31:40 -0700 (PDT) From: Anshuman Khandual To: linux-mm@kvack.org Cc: Anshuman Khandual , Andrew Morton , David Hildenbrand , Ryan Roberts , "Mike Rapoport (IBM)" , Arnd Bergmann , x86@kernel.org, linux-m68k@lists.linux-m68k.org, linux-fsdevel@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH V2 3/7] mm: Use ptep_get() for accessing PTE entries Date: Tue, 17 Sep 2024 13:01:13 +0530 Message-Id: <20240917073117.1531207-4-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240917073117.1531207-1-anshuman.khandual@arm.com> References: <20240917073117.1531207-1-anshuman.khandual@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Convert PTE accesses via ptep_get() helper that defaults as READ_ONCE() but also provides the platform an opportunity to override when required. This stores read page table entry value in a local variable which can be used in multiple instances there after. This helps in avoiding multiple memory load operations as well possible race conditions. Cc: Andrew Morton Cc: David Hildenbrand Cc: Ryan Roberts Cc: "Mike Rapoport (IBM)" Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual Reviewed-by: Ryan Roberts --- include/linux/pgtable.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 2a6a3cccfc36..547eeae8c43f 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1060,7 +1060,8 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b) */ #define set_pte_safe(ptep, pte) \ ({ \ - WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \ + pte_t __old =3D ptep_get(ptep); \ + WARN_ON_ONCE(pte_present(__old) && !pte_same(__old, pte)); \ set_pte(ptep, pte); \ }) =20 --=20 2.25.1