From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932622AbWLTAXf (ORCPT ); Tue, 19 Dec 2006 19:23:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932626AbWLTAXf (ORCPT ); Tue, 19 Dec 2006 19:23:35 -0500 Received: from smtp.osdl.org ([65.172.181.25]:48612 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932622AbWLTAXe (ORCPT ); Tue, 19 Dec 2006 19:23:34 -0500 Date: Tue, 19 Dec 2006 16:23:08 -0800 (PST) From: Linus Torvalds To: Peter Zijlstra cc: Andrei Popa , Andrew Morton , Linux Kernel Mailing List , Hugh Dickins , Florian Weimer , Marc Haber , Martin Michlmayr Subject: Re: 2.6.19 file content corruption on ext3 In-Reply-To: <1166571749.10372.178.camel@twins> Message-ID: References: <1166314399.7018.6.camel@localhost> <20061217040620.91dac272.akpm@osdl.org> <1166362772.8593.2.camel@localhost> <20061217154026.219b294f.akpm@osdl.org> <1166460945.10372.84.camel@twins> <1166466272.10372.96.camel@twins> <1166468651.6983.6.camel@localhost> <1166471069.6940.4.camel@localhost> <1166571749.10372.178.camel@twins> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 20 Dec 2006, Peter Zijlstra wrote: > On Mon, 2006-12-18 at 12:14 -0800, Linus Torvalds wrote: > > OR: > > > > - page_mkclean_one() is simply buggy. > > GOLD! Ok. I was looking at that, and I wondered.. However, if that works, then I _think_ the correct sequence is the following.. The rule should be: - we flush the tlb _after_ we have cleared it, but _before_ we insert the new entry. But I dunno. These things are damn subtle. Does this patch fix it for you? I actually suspect we should do this as an arch-specific macro, and totally replace the current "ptep_clear_flush_dirty()" with one that does "ptep_clear_flush_dirty_and_set_wp()". Because what I'd _really_ prefer to do on x86 (and probably on most other sane architectures) is to do - atomically replace the pte with the EXACT SAME ONE, but one that has the writable bit clear. bit_clear(_PAGE_BIT_RW, &(ptep)->pte_low); - flush the TLB, making sure that all CPU's will no longer write to it: flush_tlb_page(vma, address); - finally, just fetch-and-clear the dirty bit (and since it's no longer writable, nobody should be settign it any more) ret = bit_clear(__PAGE_BIT_DIRTY, &(ptep)->pte_low); and now we should be all done. But the "ptep_get_and_clear() + flush_tlb_page()" sequence should hopefully also work. Pls test. Linus ---- diff --git a/mm/rmap.c b/mm/rmap.c index d8a842a..eec8706 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -448,9 +448,10 @@ static int page_mkclean_one(struct page *page, struct vm_area_struct *vma) goto unlock; entry = ptep_get_and_clear(mm, address, pte); + flush_tlb_page(vma, address); entry = pte_mkclean(entry); entry = pte_wrprotect(entry); - ptep_establish(vma, address, pte, entry); + set_pte_at(mm, address, pte, entry); lazy_mmu_prot_update(entry); ret = 1;