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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DDF2C77B73 for ; Tue, 2 May 2023 03:23:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233333AbjEBDXR (ORCPT ); Mon, 1 May 2023 23:23:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230202AbjEBDXP (ORCPT ); Mon, 1 May 2023 23:23:15 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 656DA30FB; Mon, 1 May 2023 20:23:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=nXmf0Oq3hf/xcZYM/3kRmIN8D01IMk38tYjoW66T3NY=; b=GzRXVt0QN1kSn5nmjZq6AFgAAJ Pui33jCvlrbmp7hG351ObI6AbFlVgohdWAIeNp7x7F4CTECjTisr78jIPJGGLx6nUJfg4wbde/3eh kQET8VP233fNOd5CZMpq/WDxzrH0Y/CErIvzC5gQCflnseANAiBWyDI1YLtycN7Qdlb68o13+ionH hfw1GqRsSjt84fb7crwkNpLcAoIREVB/GSIWISdvddcQYptG2xHdjCr0m+YEBC8bG/NEkykmXlKuG yIVMNL5kULJoFDRQ6g/xohHCQG5HkjZRFhQbR6VT6xJ/hUUQL/0IK9xkkCWdWorsEeRGq+foXdeTN aSHi96ZQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1ptgb2-007wdp-Md; Tue, 02 May 2023 03:22:32 +0000 Date: Tue, 2 May 2023 04:22:32 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/3] mm: handle swap page faults under VMA lock if page is uncontended Message-ID: References: <20230501175025.36233-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, May 01, 2023 at 07:30:13PM -0700, Suren Baghdasaryan wrote: > On Mon, May 1, 2023 at 7:02 PM Matthew Wilcox wrote: > > > > On Mon, May 01, 2023 at 10:50:23AM -0700, Suren Baghdasaryan wrote: > > > +++ b/mm/memory.c > > > @@ -3711,11 +3711,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > > if (!pte_unmap_same(vmf)) > > > goto out; > > > > > > - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { > > > - ret = VM_FAULT_RETRY; > > > - goto out; > > > - } > > > - > > > entry = pte_to_swp_entry(vmf->orig_pte); > > > if (unlikely(non_swap_entry(entry))) { > > > if (is_migration_entry(entry)) { > > > > You're missing the necessary fallback in the (!folio) case. > > swap_readpage() is synchronous and will sleep. > > True, but is it unsafe to do that under VMA lock and has to be done > under mmap_lock? ... you were the one arguing that we didn't want to wait for I/O with the VMA lock held?