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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8DA25C71153 for ; Mon, 28 Aug 2023 12:40:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693226419; h=from:from:sender:sender: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:list-id:list-help:list-unsubscribe: list-subscribe:list-post; bh=TLnvMQnkyoR7wwCry5GRCKzwjL5P4BV+bNSPRJ9AdUw=; b=O86O7TFapER+jvp2LAj4jUWIohXWXtsKU57Ff2SPHzIPCxvO3k30Z0BpiWdGewVuY6shml udSFrLdn5a/NLEPu37yOniwcU5SZ4djvJVkFfmIxWD8js5lFsDQDK/xT+snOqIvPF69U8T kha+3WN8jM51J4Q0bottndwJ8PbUvo8= 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-329-RxkP91JcNuOgs8_E8EVrmw-1; Mon, 28 Aug 2023 08:40:15 -0400 X-MC-Unique: RxkP91JcNuOgs8_E8EVrmw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 07371858EED; Mon, 28 Aug 2023 12:40:15 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id CD2B72026D4B; Mon, 28 Aug 2023 12:40:14 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 5F2171946588; Mon, 28 Aug 2023 12:40:14 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 0AC301946587 for ; Mon, 28 Aug 2023 12:40:12 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id A2AB02026D68; Mon, 28 Aug 2023 12:40:12 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast10.extmail.prod.ext.rdu2.redhat.com [10.11.55.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9BADA2026D4B for ; Mon, 28 Aug 2023 12:40:12 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-inbound-delivery-1.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7B6841C0896A for ; Mon, 28 Aug 2023 12:40:12 +0000 (UTC) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-161-1ijWz2k3NgqWVCBEWszHLg-1; Mon, 28 Aug 2023 08:40:10 -0400 X-MC-Unique: 1ijWz2k3NgqWVCBEWszHLg-1 Received: by verein.lst.de (Postfix, from userid 2407) id 981DA68D05; Mon, 28 Aug 2023 14:30:25 +0200 (CEST) Date: Mon, 28 Aug 2023 14:30:23 +0200 From: Christoph Hellwig To: Al Viro Message-ID: <20230828123023.GA11084@lst.de> References: <20230601145904.1385409-1-hch@lst.de> <20230601145904.1385409-4-hch@lst.de> <20230827194122.GA325446@ZenIV> MIME-Version: 1.0 In-Reply-To: <20230827194122.GA325446@ZenIV> User-Agent: Mutt/1.5.17 (2007-11-01) X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Subject: Re: [Cluster-devel] [PATCH 03/12] filemap: update ki_pos in generic_perform_write X-BeenThere: cluster-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: "\[Cluster devel\]" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Darrick J. Wong" , linux-mm@kvack.org, Christoph Hellwig , Miklos Szeredi , Matthew Wilcox , cluster-devel@redhat.com, Ilya Dryomov , linux-ext4@vger.kernel.org, Chao Yu , linux-nfs@vger.kernel.org, linux-block@vger.kernel.org, Damien Le Moal , Hannes Reinecke , Jaegeuk Kim , ceph-devel@vger.kernel.org, Xiubo Li , Trond Myklebust , Jens Axboe , Christian Brauner , Theodore Ts'o , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Anna Schumaker , linux-fsdevel@vger.kernel.org, Andrew Morton Errors-To: cluster-devel-bounces@redhat.com Sender: "Cluster-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: lst.de Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sun, Aug 27, 2023 at 08:41:22PM +0100, Al Viro wrote: > That part is somewhat fishy - there's a case where you return a positive value > and advance ->ki_pos by more than that amount. I really wonder if all callers > of ->write_iter() are OK with that. Consider e.g. this: This should not exist in the latest version merged by Jens. Can you check if you still see issues in the version in the block tree or linux-next. > Suppose ->write_iter() ends up doing returning a positive value smaller than > the increment of kiocb.ki_pos. What do we get? ret is positive, so > kiocb.ki_pos gets copied into *ppos, which is ksys_write's pos and there > we copy it into file->f_pos. > > Is it really OK to have write() return 4096 and advance the file position > by 16K? AFAICS, userland wouldn't get any indication of something > odd going on - just a short write to a regular file, with followup write > of remaining 12K getting quietly written in the range 16K..28K. > > I don't remember what POSIX says about that, but it would qualify as > nasty surprise for any userland program - sure, one can check fsync() > results before closing the sucker and see if everything looks fine, > but the way it's usually discussed could easily lead to assumption that > (synchronous) O_DIRECT writes would not be affected by anything of that > sort. ki_pos should always be updated by the write return value. Everything else is a bug.