From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933762Ab2GLL1I (ORCPT ); Thu, 12 Jul 2012 07:27:08 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:59565 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932632Ab2GLL1D (ORCPT ); Thu, 12 Jul 2012 07:27:03 -0400 Date: Thu, 12 Jul 2012 12:26:45 +0100 From: Will Deacon To: Michal Hocko Cc: Hugh Dickins , Andrew Morton , Hillf Danton , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace Message-ID: <20120712112645.GG2816@mudshark.cambridge.arm.com> References: <1341412376-6272-1-git-send-email-will.deacon@arm.com> <20120709122523.GC4627@tiehlicka.suse.cz> <20120709141324.GK7315@mudshark.cambridge.arm.com> <20120710094513.GB9108@mudshark.cambridge.arm.com> <20120710104234.GI9108@mudshark.cambridge.arm.com> <20120711174802.GG13498@mudshark.cambridge.arm.com> <20120712111659.GF21013@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120712111659.GF21013@tiehlicka.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 12, 2012 at 12:16:59PM +0100, Michal Hocko wrote: > On Wed 11-07-12 18:48:02, Will Deacon wrote: > > Just to confirm, the following quick hack at least results in the correct > > flushing for me (on ARM): > > > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index e198831..7a7c9d3 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -1141,6 +1141,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, > > } > > > > set_page_private(page, (unsigned long)spool); > > + clear_bit(PG_arch_1, &page->flags); > > > > vma_commit_reservation(h, vma, addr); > > > > > > > > The question is whether we should tidy that up for the core code or get > > architectures to clear the bit in arch_make_huge_pte (which also seems to > > work). > > This should go into arch specific code IMO. Even the page flag name > suggests this shouldn't be in the base code. Well, the comment in linux/page-flags.h does state that: * PG_arch_1 is an architecture specific page state bit. The generic code * guarantees that this bit is cleared for a page when it first is entered into * the page cache. so it's not completely clear cut that the architecture should be responsible for clearing this bit when allocating pages from the hugepage pool. Will From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace Date: Thu, 12 Jul 2012 12:26:45 +0100 Message-ID: <20120712112645.GG2816@mudshark.cambridge.arm.com> References: <1341412376-6272-1-git-send-email-will.deacon@arm.com> <20120709122523.GC4627@tiehlicka.suse.cz> <20120709141324.GK7315@mudshark.cambridge.arm.com> <20120710094513.GB9108@mudshark.cambridge.arm.com> <20120710104234.GI9108@mudshark.cambridge.arm.com> <20120711174802.GG13498@mudshark.cambridge.arm.com> <20120712111659.GF21013@tiehlicka.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120712111659.GF21013@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org To: Michal Hocko Cc: Hugh Dickins , Andrew Morton , Hillf Danton , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" List-Id: linux-arch.vger.kernel.org On Thu, Jul 12, 2012 at 12:16:59PM +0100, Michal Hocko wrote: > On Wed 11-07-12 18:48:02, Will Deacon wrote: > > Just to confirm, the following quick hack at least results in the correct > > flushing for me (on ARM): > > > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index e198831..7a7c9d3 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -1141,6 +1141,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, > > } > > > > set_page_private(page, (unsigned long)spool); > > + clear_bit(PG_arch_1, &page->flags); > > > > vma_commit_reservation(h, vma, addr); > > > > > > > > The question is whether we should tidy that up for the core code or get > > architectures to clear the bit in arch_make_huge_pte (which also seems to > > work). > > This should go into arch specific code IMO. Even the page flag name > suggests this shouldn't be in the base code. Well, the comment in linux/page-flags.h does state that: * PG_arch_1 is an architecture specific page state bit. The generic code * guarantees that this bit is cleared for a page when it first is entered into * the page cache. so it's not completely clear cut that the architecture should be responsible for clearing this bit when allocating pages from the hugepage pool. Will -- 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