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[2620:137:e000::1:20]) by mx.google.com with ESMTP id v16-20020a17090a899000b0024968f6f8e1si5702676pjn.24.2023.04.20.18.37.07; Thu, 20 Apr 2023 18:37:19 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linux.org.uk header.s=zeniv-20220401 header.b=CPHwR0ig; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=zeniv.linux.org.uk Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229471AbjDUBMJ (ORCPT + 99 others); Thu, 20 Apr 2023 21:12:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231590AbjDUBMH (ORCPT ); Thu, 20 Apr 2023 21:12:07 -0400 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [IPv6:2a03:a000:7:0:5054:ff:fe1c:15ff]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C52D2108; Thu, 20 Apr 2023 18:12:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=dnj+MwCbtv8NOzvIf0pmIsPDMO0RM2xq9qIHLD7iX50=; b=CPHwR0igmjjSKRMhIU5CVABr3L RHq9WCCAqi4m5UCt2vC7XJSeG8JnOkQet7uVZUngpAaKWXFx+5pFKYKJBSfhCYo3yAQNXNHw5rgLG FWZA/tfrftfflE9xd3redguLME3UR69V2eBvI55VD9KpYcxqcxoNOGDdDse5lMvIZnbw06FpNsMkT PwrmaLqmPHRIKfGi/j2ol1hbGra+C3hUFICY9D7elfvypvHe9KF2TrNn8RQqmGcm4QgViKj6jNG38 gyHy7f8m1WiCKigzm2GfHG24I6DKi/g8IhlvoNIk/YyQlr1NclnTDFE7jg+tNPVFIPm0ypj3jj54l mD42JdcQ==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1ppfJR-00B1x8-0S; Fri, 21 Apr 2023 01:11:45 +0000 Date: Fri, 21 Apr 2023 02:11:45 +0100 From: Al Viro To: David Howells Cc: Jens Axboe , Christoph Hellwig , Matthew Wilcox , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , Christian Brauner , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Hellwig , John Hubbard Subject: Re: [PATCH v18 09/15] iov_iter: Kill ITER_PIPE Message-ID: <20230421011145.GW3390869@ZenIV> References: <20230314220757.3827941-1-dhowells@redhat.com> <20230314220757.3827941-10-dhowells@redhat.com> <20230420222231.GT3390869@ZenIV> <20230420223657.GV3390869@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230420223657.GV3390869@ZenIV> Sender: Al Viro X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 20, 2023 at 11:36:57PM +0100, Al Viro wrote: > Don't get me wrong - I'd love to kill ITER_PIPE off; it's just that tons > of ->splice_read() duplicating the corresponding ->read_iter() up to the > point where it would call generic_file_read_iter(), modulo ignoring > O_DIRECT case and then calling filemap_splice_read() instead... Painful > and asking for trouble down the road. FWIW, broken in this series: * a bunch of 9p variants (those could probably switch to direct) * afs * ceph (very likely) * ecryptfs (atime propagation) * dax on various filesystems (probably) * f2fs * gfs2 * nfs * ocfs2 * orangefs * xfs * zonefs (probably) * splice from UDP sockets, unless I'm misreading something. Your sock_splice_read() still falls back to generic_file_splice_read(), rather than to direct_splice_read() and sockets don't have O_DIRECT in flags. Neither do they have associated page cache ;-) Sure, we could provide a bunch of ->splice_read(), but then we'd have to make sure that all subsequent changes to matching ->read_iter() get duplicated - unless they are on O_DIRECT-only paths, that is...