From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751603AbdGZIjw (ORCPT ); Wed, 26 Jul 2017 04:39:52 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57626 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751467AbdGZIjv (ORCPT ); Wed, 26 Jul 2017 04:39:51 -0400 Date: Wed, 26 Jul 2017 09:39:46 +0100 From: Catalin Marinas To: Punit Agrawal Cc: Andrew Morton , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, steve.capper@arm.com, will.deacon@arm.com, kirill.shutemov@linux.intel.com, Michal Hocko , Mike Kravetz Subject: Re: [PATCH 1/1] mm/hugetlb: Make huge_pte_offset() consistent and document behaviour Message-ID: <20170726083945.4ejqwnxomplrqxrf@armageddon.cambridge.arm.com> References: <20170725154114.24131-1-punit.agrawal@arm.com> <20170725154114.24131-2-punit.agrawal@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725154114.24131-2-punit.agrawal@arm.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 25, 2017 at 04:41:14PM +0100, Punit Agrawal wrote: > When walking the page tables to resolve an address that points to > !p*d_present() entry, huge_pte_offset() returns inconsistent values > depending on the level of page table (PUD or PMD). > > It returns NULL in the case of a PUD entry while in the case of a PMD > entry, it returns a pointer to the page table entry. > > A similar inconsitency exists when handling swap entries - returns NULL > for a PUD entry while a pointer to the pte_t is retured for the PMD > entry. > > Update huge_pte_offset() to make the behaviour consistent - return NULL > in the case of p*d_none() and a pointer to the pte_t for hugepage or > swap entries. > > Document the behaviour to clarify the expected behaviour of this > function. This is to set clear semantics for architecture specific > implementations of huge_pte_offset(). > > Signed-off-by: Punit Agrawal Reviewed-by: Catalin Marinas From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id AF8D06B02F4 for ; Wed, 26 Jul 2017 04:39:53 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id u199so111479084pgb.13 for ; Wed, 26 Jul 2017 01:39:53 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id e9si9284577pgn.812.2017.07.26.01.39.52 for ; Wed, 26 Jul 2017 01:39:52 -0700 (PDT) Date: Wed, 26 Jul 2017 09:39:46 +0100 From: Catalin Marinas Subject: Re: [PATCH 1/1] mm/hugetlb: Make huge_pte_offset() consistent and document behaviour Message-ID: <20170726083945.4ejqwnxomplrqxrf@armageddon.cambridge.arm.com> References: <20170725154114.24131-1-punit.agrawal@arm.com> <20170725154114.24131-2-punit.agrawal@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725154114.24131-2-punit.agrawal@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Punit Agrawal Cc: Andrew Morton , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, steve.capper@arm.com, will.deacon@arm.com, kirill.shutemov@linux.intel.com, Michal Hocko , Mike Kravetz On Tue, Jul 25, 2017 at 04:41:14PM +0100, Punit Agrawal wrote: > When walking the page tables to resolve an address that points to > !p*d_present() entry, huge_pte_offset() returns inconsistent values > depending on the level of page table (PUD or PMD). > > It returns NULL in the case of a PUD entry while in the case of a PMD > entry, it returns a pointer to the page table entry. > > A similar inconsitency exists when handling swap entries - returns NULL > for a PUD entry while a pointer to the pte_t is retured for the PMD > entry. > > Update huge_pte_offset() to make the behaviour consistent - return NULL > in the case of p*d_none() and a pointer to the pte_t for hugepage or > swap entries. > > Document the behaviour to clarify the expected behaviour of this > function. This is to set clear semantics for architecture specific > implementations of huge_pte_offset(). > > Signed-off-by: Punit Agrawal Reviewed-by: Catalin Marinas -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org