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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 49B4CC4321A for ; Fri, 28 Jun 2019 16:54:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 208BF208C4 for ; Fri, 28 Jun 2019 16:54:24 +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="Z8w/Lg4I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726835AbfF1QyT (ORCPT ); Fri, 28 Jun 2019 12:54:19 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:38532 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726605AbfF1QyT (ORCPT ); Fri, 28 Jun 2019 12:54:19 -0400 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=4aCzK6AWV7v8l05GIE3EDguMtt1Ba9XnxuuiQ3Rlk3Q=; b=Z8w/Lg4IyFUwGyPbT6LlhpKWU wUw/qfThpPpDK1EVkDTJ1UJiw38r1aWCtwbytMCtGAED4QvCWUMKs5Oh/6QO0Wybph75WFSCNiE4z SSCY5E2KKmjqFf4YfC/RXkZbftMs0PDsnBkPp83MsdPmHC1whEcp4+szoDy/HcGbBBak06He3xVFX Dv2t+nDoKM8qsnEYpPu09UUtlaDwdS+RkH8iyE0U10HWCA+u5ZYlH/WcMlbenvCowHplBHyZKDmM9 2YOpnvA7s/rZiLu/O8vCEzzqGKQwJz/jt4166JDneHDGirGpfGEMfS4Uo/xcZIJl7ErIdb9zvCDZq /5Yxuz+9w==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hgu8f-0002TR-BH; Fri, 28 Jun 2019 16:54:17 +0000 Date: Fri, 28 Jun 2019 09:54:17 -0700 From: Matthew Wilcox To: Dan Williams Cc: linux-nvdimm , Jan Kara , stable , Robert Barror , Seema Pandit , linux-fsdevel , Linux Kernel Mailing List Subject: Re: [PATCH] filesystem-dax: Disable PMD support Message-ID: <20190628165417.GD4286@bombadil.infradead.org> References: <156159454541.2964018.7466991316059381921.stgit@dwillia2-desk3.amr.corp.intel.com> <20190627123415.GA4286@bombadil.infradead.org> <20190627195948.GB4286@bombadil.infradead.org> <20190628163721.GC4286@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Jun 28, 2019 at 09:39:01AM -0700, Dan Williams wrote: > On Fri, Jun 28, 2019 at 9:37 AM Matthew Wilcox wrote: > > That was the conclusion I came to; that one thread holding the mmap sem > > for read isn't being woken up when it should be. Just need to find it ... > > obviously it's something to do with the PMD entries. > > Can you explain to me one more time, yes I'm slow on the uptake on > this, the difference between xas_load() and xas_find_conflict() and > why it's ok for dax_lock_page() to use xas_load() while > grab_mapping_entry() uses xas_find_conflict()? When used with a non-zero 'order', xas_find_conflict() will return an entry whereas xas_load() might return a pointer to a node. dax_lock_page() always uses a zero order, so they would always do the same thing (xas_find_conflict() would be less efficient).