Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760219AbYFWRak (ORCPT ); Mon, 23 Jun 2008 13:30:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755269AbYFWRad (ORCPT ); Mon, 23 Jun 2008 13:30:33 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:37013 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754879AbYFWRac (ORCPT ); Mon, 23 Jun 2008 13:30:32 -0400 Date: Mon, 23 Jun 2008 10:27:03 -0700 (PDT) From: Linus Torvalds To: Jeff Chua cc: Hugh Dickins , Greg KH , linux-kernel@vger.kernel.org, stable@kernel.org, Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov , Nick Piggin , KAMEZAWA Hiroyuki , Ingo Molnar , Roland McGrath Subject: Re: [patch 2/5] Reinstate ZERO_PAGE optimization in get_user_pages() and fix XIP In-Reply-To: Message-ID: References: <20080622185327.348377223@mini.kroah.org> <20080622190140.GD20141@suse.de> <20080622202950.GB20800@suse.de> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2442 Lines: 75 On Tue, 24 Jun 2008, Jeff Chua wrote: > On Tue, Jun 24, 2008 at 12:39 AM, Linus Torvalds > wrote: > > > > Jeff, does this still work with vmware? > > > No, this breaks vmware. Does this trace help? Not really. I have no idea what vmware does, so any traces from vmware are pretty useless. On the other hand, if you add a trace to the "use_zero_page()" function to print out the vm_flags and other details, that probably would help. That said, since the previous patch _did_ work, I bet that one that does both VM_LOCKED and VM_SHARED works too. There was a reason I wanted to do that VM_SHARED test. I think the VM_SHARED test is sane, unlike the VM_LOCKED test (that is a fairly dubious hack for mlock). So here's the final version. I bet it works. Linus --- mm/memory.c | 23 +++++++++++++++++++++-- 1 files changed, 21 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 9aefaae..423e0e7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1045,6 +1045,26 @@ no_page_table: return page; } +/* Can we do the FOLL_ANON optimization? */ +static inline int use_zero_page(struct vm_area_struct *vma) +{ + /* + * We don't want to optimize FOLL_ANON for make_pages_present() + * when it tries to page in a VM_LOCKED region. As to VM_SHARED, + * we want to get the page from the page tables to make sure + * that we serialize and update with any other user of that + * mapping. + */ + if (vma->vm_flags & (VM_LOCKED | VM_SHARED)) + return 0; + /* + * And if we have a fault or a nopfn routine, it's not an + * anonymous region. + */ + return !vma->vm_ops || + (!vma->vm_ops->fault && !vma->vm_ops->nopfn); +} + int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int len, int write, int force, struct page **pages, struct vm_area_struct **vmas) @@ -1119,8 +1139,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, foll_flags = FOLL_TOUCH; if (pages) foll_flags |= FOLL_GET; - if (!write && !(vma->vm_flags & VM_LOCKED) && - (!vma->vm_ops || !vma->vm_ops->fault)) + if (!write && use_zero_page(vma)) foll_flags |= FOLL_ANON; do { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/