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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CC77DC2B9F4 for ; Tue, 22 Jun 2021 18:13:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5E68761002 for ; Tue, 22 Jun 2021 18:13:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5E68761002 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 585436B006E; Tue, 22 Jun 2021 14:13:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 535406B0070; Tue, 22 Jun 2021 14:13:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3B0B66B0071; Tue, 22 Jun 2021 14:13:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0189.hostedemail.com [216.40.44.189]) by kanga.kvack.org (Postfix) with ESMTP id 005906B006E for ; Tue, 22 Jun 2021 14:13:08 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3D7AA181370A2 for ; Tue, 22 Jun 2021 18:13:09 +0000 (UTC) X-FDA: 78282156498.01.3179197 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf28.hostedemail.com (Postfix) with ESMTP id DBEA420015E3 for ; Tue, 22 Jun 2021 18:13:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624385588; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=miPd5CYvzE+oNS2YKPohgJHcAhxiPdT10XDw8a3tjh8=; b=Og/BgatMQ9BKn5JX5dFbZlln51EgaRnLu/eusRWeeyz2m6pTQ53DsBA54KBFz/8f9/HOiO diygGdxMvflZgnPZ1mWJc5nr2kdtHVfPBqrgPgwgYdZlr6RcSU4ePleU36lFFBU86PX9Vz MFjb4d47abJOi9/K0+kE1WyipI49ilQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-518-Zn3GIKvjNVeF1SIxtLQnQA-1; Tue, 22 Jun 2021 14:13:06 -0400 X-MC-Unique: Zn3GIKvjNVeF1SIxtLQnQA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 35BBC1084F4C; Tue, 22 Jun 2021 18:13:05 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-118-65.rdu2.redhat.com [10.10.118.65]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0688D6091B; Tue, 22 Jun 2021 18:13:02 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <3221175.1624375240@warthog.procyon.org.uk> <3231150.1624384533@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, Linus Torvalds , Al Viro , Ted Ts'o , Dave Hansen , Andrew Morton , Linux-MM , Ext4 Developers List , linux-fsdevel , Linux Kernel Mailing List Subject: Re: Do we need to unrevert "fs: do not prefault sys_write() user buffer pages"? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3232237.1624385582.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Tue, 22 Jun 2021 19:13:02 +0100 Message-ID: <3232238.1624385582@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="Og/BgatM"; spf=none (imf28.hostedemail.com: domain of dhowells@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=dhowells@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: jxnfcb59whypra77duu4yzhg1zdw5tjs X-Rspamd-Queue-Id: DBEA420015E3 X-Rspamd-Server: rspam06 X-HE-Tag: 1624385588-514028 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Matthew Wilcox wrote: > > It may also cause the read in to happen in the background whilst write= _begin > > is being done. > = > Huh? Last I checked, the fault_in_readable actually read a byte from > the page. It has to wait for the read to complete before that can > happen. Ah, good point. David