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 02D47C04FDF for ; Wed, 16 Aug 2023 13:02:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245286AbjHPNBy (ORCPT ); Wed, 16 Aug 2023 09:01:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245317AbjHPNBi (ORCPT ); Wed, 16 Aug 2023 09:01:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 235342117 for ; Wed, 16 Aug 2023 06:00:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692190856; 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: in-reply-to:in-reply-to:references:references; bh=JL9XHCcHn9+lzn3csLfA/07hiNGl99qLxrzUXZlZiMU=; b=CMYD8dFjSI7u01vLA2WbsRQ8g22bq/SAEriyUdMTLBVRXXzsfhnWF63Sabd09o+DYcm9N8 yv2iq3jwWHPKkhfNKprmpAWYiaLPpVEuBzTZ/0SJptfmwZvxhC6Sbtwc5tEroGrREHq4FK OpvVdJfAFgyug0jL0GDUxkdktEtsUHw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-669-Zdu0GcBbNlWDvx1senW_nQ-1; Wed, 16 Aug 2023 09:00:51 -0400 X-MC-Unique: Zdu0GcBbNlWDvx1senW_nQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 09950185A7A3; Wed, 16 Aug 2023 13:00:50 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.13]) by smtp.corp.redhat.com (Postfix) with ESMTP id 491CA492C14; Wed, 16 Aug 2023 13:00:48 +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: <03730b50cebb4a349ad8667373bb8127@AcuMS.aculab.com> References: <03730b50cebb4a349ad8667373bb8127@AcuMS.aculab.com> <20230816120741.534415-1-dhowells@redhat.com> <20230816120741.534415-3-dhowells@redhat.com> To: David Laight Cc: dhowells@redhat.com, Al Viro , Linus Torvalds , Jens Axboe , Christoph Hellwig , "Christian Brauner" , Matthew Wilcox , "Jeff Layton" , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc() MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <608852.1692190847.1@warthog.procyon.org.uk> Date: Wed, 16 Aug 2023 14:00:47 +0100 Message-ID: <608853.1692190847@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Laight wrote: > > Couldn't the relevant code directly call __copy_from_iter_mc() ? > Or a version then checked iov_is_copy_mc() and then fell > back to the standard function. No, because the marked iterator is handed by the coredump code to __kernel_write_iter() and thence on to who-knows-what driver - which will call copy_from_iter() or some such. $DRIVER shouldn't need to know about ->copy_mc. One thing I do wonder about, though, is what should happen if they call, say, csum_and_copy_from_iter()? That doesn't have an _mc variant. Or what if they extract the pages and operate directly on those? David