From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 367D4C43381 for ; Tue, 26 Feb 2019 12:08:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0937D217F9 for ; Tue, 26 Feb 2019 12:08:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="iY6CeDlh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727095AbfBZMI2 (ORCPT ); Tue, 26 Feb 2019 07:08:28 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:60570 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726553AbfBZMIW (ORCPT ); Tue, 26 Feb 2019 07:08:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=lfUmCPqGS7QS2Sd5zo2Jhz+ziCeUoxTm8lko19+1Ww0=; b=iY6CeDlhaoSGmWvwLX128Ce10 /4YRVf2EuolKpSwQYwH+m1tcUP+Wpoudk+A3w0GrJlmQBgSfTrsuodQ7BxQsKOeUaT9Yxtnufqbz6 MZqAYjX+IMIRnvr6VH6Pgt8qTBwZfQ0WIvkB885CfhdGGPIQMsWg3RRBlybGaU8Dn5ncqmxYGDg9Y OeTll5yS67Vo1b+F67YE7zDDfubiRiSFI8TA1prEcIoFZh4xnom1VNUcauB2yapwTpH5vNwLhFNHh u6IHO5QSV3DpgiLnrjY81eyntuVJkE39uOs2e16q2iHOllS9B9WiEDKs9BQXwPjpIP5iE4HRtOQW9 kGK+YvmFg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gybX3-00026Y-LC; Tue, 26 Feb 2019 12:08:21 +0000 Date: Tue, 26 Feb 2019 04:08:21 -0800 From: Matthew Wilcox To: Dan Williams Cc: linux-nvdimm , linux-fsdevel , Linux Kernel Mailing List , "Balcer, Piotr" Subject: Re: find_get_entries_tag regression bisected Message-ID: <20190226120820.GB11592@bombadil.infradead.org> References: <20190216153511.GM12668@bombadil.infradead.org> <20190216172948.GN12668@bombadil.infradead.org> <20190216211105.GO12668@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Feb 25, 2019 at 09:03:00PM -0800, Dan Williams wrote: > On Sat, Feb 16, 2019 at 1:11 PM Matthew Wilcox wrote: > > > > On Sat, Feb 16, 2019 at 09:29:48AM -0800, Matthew Wilcox wrote: > > > On Sat, Feb 16, 2019 at 07:35:11AM -0800, Matthew Wilcox wrote: > > > > Another way to fix this would be to mask the address in dax_entry_mkclean(), > > > > but I think this is cleaner. > > > > > > That's clearly rubbish, dax_entry_mkclean() can't possibly mask the > > > address. It might be mis-aligned in another process. But ... if it's > > > misaligned in another process, dax_entry_mkclean() will only clean the first > > > PTE associated with the PMD; it won't clean the whole thing. I think we need > > > something like this: > > > > Nope, this isn't enough. It's _necessary_ to find the processes that > > have part of this PMD page mapped, but not the start of it. But it's > > not _sufficient_ because it'll still only mkclean the first PTE. So we > > need a loop. I'm feeling a bit over my head here. I may have a go at > > a fuller fix, but if someone else wants to have a go at it, be my guest! > > Nothing comes to mind outside of pseudo-reverting this conversion by > introducing a way to get back to the old semantics. If you don't see a > path forward, us mere Xarray-mortals stand no chance. This is a pre-existing bug. Fixing the regression is easy.