From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 99C00280310 for ; Tue, 22 Aug 2017 06:11:25 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id o82so68066056pfj.11 for ; Tue, 22 Aug 2017 03:11:25 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id h5si9647733pln.768.2017.08.22.03.11.24 for ; Tue, 22 Aug 2017 03:11:24 -0700 (PDT) Date: Tue, 22 Aug 2017 11:11:18 +0100 From: Catalin Marinas Subject: Re: [PATCH v2] mm/hugetlb.c: make huge_pte_offset() consistent and document behaviour Message-ID: <20170822101117.ilnys32tugytbbjc@armageddon.cambridge.arm.com> References: <20170725154114.24131-2-punit.agrawal@arm.com> <20170818145415.7588-1-punit.agrawal@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170818145415.7588-1-punit.agrawal@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Punit Agrawal Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Naoya Horiguchi , Steve Capper , Will Deacon , "Kirill A . Shutemov" , Michal Hocko , Mike Kravetz On Fri, Aug 18, 2017 at 03:54:15PM +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 a > pointer to the pte_t for hugepage or swap entries. Only return NULL in > instances where we have a p*d_none() entry and the size parameter > doesn't match the hugepage size at this level of the page table. > > 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 > Cc: Catalin Marinas > Cc: Naoya Horiguchi > Cc: Steve Capper > Cc: Will Deacon > Cc: Kirill A. Shutemov > Cc: Michal Hocko > Cc: Mike Kravetz FWIW: Reviewed-by: Catalin Marinas Thanks. -- 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