From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id C44F26B0587 for ; Tue, 1 Aug 2017 20:58:42 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id c14so34905621pgn.11 for ; Tue, 01 Aug 2017 17:58:42 -0700 (PDT) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id v17si6104711pgb.844.2017.08.01.17.58.41 for ; Tue, 01 Aug 2017 17:58:41 -0700 (PDT) Date: Wed, 2 Aug 2017 09:58:39 +0900 From: Minchan Kim Subject: Re: [PATCH v2 4/4] mm: fix KSM data corruption Message-ID: <20170802005839.GD6388@bbox> References: <1501566977-20293-1-git-send-email-minchan@kernel.org> <1501566977-20293-5-git-send-email-minchan@kernel.org> <20170801193341.GA24406@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170801193341.GA24406@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team , Nadav Amit , Mel Gorman , Hugh Dickins Hi Andrea, On Tue, Aug 01, 2017 at 09:33:41PM +0200, Andrea Arcangeli wrote: > Hello, > > On Tue, Aug 01, 2017 at 02:56:17PM +0900, Minchan Kim wrote: > > CPU0 CPU1 CPU2 CPU3 > > ---- ---- ---- ---- > > Write the same > > value on page > > > > [cache PTE as > > dirty in TLB] > > > > MADV_FREE > > pte_mkclean() > > > > 4 > clear_refs > > pte_wrprotect() > > > > write_protect_page() > > [ success, no flush ] > > > > pages_indentical() > > [ ok ] > > > > Write to page > > different value > > > > [Ok, using stale > > PTE] > > > > replace_page() > > > > Later, CPU1, CPU2 and CPU3 would flush the TLB, but that is too late. CPU0 > > already wrote on the page, but KSM ignored this write, and it got lost. > > " > > > > In above scenario, MADV_FREE is fixed by changing TLB batching API > > including [set|clear]_tlb_flush_pending. Remained thing is soft-dirty part. > > > > This patch changes soft-dirty uses TLB batching API instead of flush_tlb_mm > > and KSM checks pending TLB flush by using mm_tlb_flush_pending so that > > it will flush TLB to avoid data lost if there are other parallel threads > > pending TLB flush. > > > > [1] http://lkml.kernel.org/r/BD3A0EBE-ECF4-41D4-87FA-C755EA9AB6BD@gmail.com > > > > Note: > > I failed to reproduce this problem through Nadav's test program which > > need to tune timing in my system speed so didn't confirm it work. > > Nadav, Could you test this patch on your test machine? > > Reviewed-by: Andrea Arcangeli Thanks for the review! -- 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