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=0.1 required=3.0 tests=BAYES_50, 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 5D011C433ED for ; Sun, 25 Apr 2021 01:28:36 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 81D6A6148E for ; Sun, 25 Apr 2021 01:28:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81D6A6148E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 52AAF100EBBB3; Sat, 24 Apr 2021 18:28:34 -0700 (PDT) Received-SPF: None (mailfrom) identity=mailfrom; client-ip=2607:5300:60:148a::1; helo=zeniv-ca.linux.org.uk; envelope-from=viro@ftp.linux.org.uk; receiver= Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 24801100EC1D9 for ; Sat, 24 Apr 2021 18:28:30 -0700 (PDT) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1laTZP-0082ev-3T; Sun, 25 Apr 2021 01:28:23 +0000 Date: Sun, 25 Apr 2021 01:28:23 +0000 From: Al Viro To: Dan Williams Subject: [RFC] inconsistent semantics of _copy_mc_to_iter() Message-ID: MIME-Version: 1.0 Content-Disposition: inline Sender: Al Viro Message-ID-Hash: P5TCXBDXRLHWDRHDLJG36LNRALQAM23U X-Message-ID-Hash: P5TCXBDXRLHWDRHDLJG36LNRALQAM23U X-MailFrom: viro@ftp.linux.org.uk X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: linux-nvdimm@lists.01.org X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit In case of failure halfway through the operation we get very different results depending upon the iov_iter flavour: iovec, pipe - advances by the amount actually copied, kvec, bvec - does *NOT* advance at all Which semantics is desired? AFAICS, the calls can be repeated - e.g. the loop in dax_iomap_actor() will call dax_copy_to_iter() again on the short read and with iovec-backed iter it will try to copy from the place of failure (presumably returning 0 that time around and terminating the loop), while with bvec or kvec it will go and paste the copies of the same chunk again until it runs out of destination. _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org