From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933753AbcHJSSs (ORCPT ); Wed, 10 Aug 2016 14:18:48 -0400 Received: from mga01.intel.com ([192.55.52.88]:38608 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933542AbcHJSSm (ORCPT ); Wed, 10 Aug 2016 14:18:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,501,1464678000"; d="scan'208";a="1023178277" Subject: [PATCH] x86, mm: Fix swap entry comment and macro To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen Date: Wed, 10 Aug 2016 10:23:25 -0700 Message-Id: <20160810172325.E56AD7DA@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen A recent patch changed the format of a swap PTE. The comment explaining the format of the swap PTE is wrong about the bits used for the swap type field. Amusingly, the ASCII art and the patch description are correct, but the comment itself is wrong. As I was looking at this, I also noticed that the SWP_OFFSET_FIRST_BIT has an off-by-one error. This does not really hurt anything. It just wasted a bit of space in the PTE, giving us 2^59 bytes of addressable space in our swapfiles instead of 2^60. But, it doesn't match with the comments, and it wastes a bit of space, so fix it. Fixes: 00839ee3b299 ("x86/mm: Move swap offset/type up in PTE to work around erratum") Signed-off-by: Dave Hansen --- b/arch/x86/include/asm/pgtable_64.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN arch/x86/include/asm/pgtable_64.h~x86-pgtables-fix-comment arch/x86/include/asm/pgtable_64.h --- a/arch/x86/include/asm/pgtable_64.h~x86-pgtables-fix-comment 2016-08-09 16:22:46.631898618 -0700 +++ b/arch/x86/include/asm/pgtable_64.h 2016-08-09 16:26:29.744037506 -0700 @@ -145,7 +145,7 @@ static inline int pgd_large(pgd_t pgd) { * * | ... | 11| 10| 9|8|7|6|5| 4| 3|2|1|0| <- bit number * | ... |SW3|SW2|SW1|G|L|D|A|CD|WT|U|W|P| <- bit names - * | OFFSET (14->63) | TYPE (10-13) |0|X|X|X| X| X|X|X|0| <- swp entry + * | OFFSET (14->63) | TYPE (9-13) |0|X|X|X| X| X|X|X|0| <- swp entry * * G (8) is aliased and used as a PROT_NONE indicator for * !present ptes. We need to start storing swap entries above @@ -156,7 +156,7 @@ static inline int pgd_large(pgd_t pgd) { #define SWP_TYPE_FIRST_BIT (_PAGE_BIT_PROTNONE + 1) #define SWP_TYPE_BITS 5 /* Place the offset above the type: */ -#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS + 1) +#define SWP_OFFSET_FIRST_BIT (SWP_TYPE_FIRST_BIT + SWP_TYPE_BITS) #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS) _