From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <w.bumiller@proxmox.com> Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 6E3CE6C81C for <pbs-devel@lists.proxmox.com>; Tue, 30 Mar 2021 08:57:06 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 601D31BAD0 for <pbs-devel@lists.proxmox.com>; Tue, 30 Mar 2021 08:57:06 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [212.186.127.180]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id 38F041BAC0 for <pbs-devel@lists.proxmox.com>; Tue, 30 Mar 2021 08:57:05 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 0386B42970 for <pbs-devel@lists.proxmox.com>; Tue, 30 Mar 2021 08:57:05 +0200 (CEST) Date: Tue, 30 Mar 2021 08:57:02 +0200 (CEST) From: Wolfgang Bumiller <w.bumiller@proxmox.com> To: Dietmar Maurer <dietmar@proxmox.com>, Proxmox Backup Server development discussion <pbs-devel@lists.proxmox.com>, Dominik Csapak <d.csapak@proxmox.com> Message-ID: <1291429125.1461.1617087422468@webmail.proxmox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Priority: 3 Importance: Normal X-Mailer: Open-Xchange Mailer v7.10.5-Rev5 X-Originating-Client: open-xchange-appsuite X-SPAM-LEVEL: Spam detection results: 0 AWL 0.028 Adjusted score from AWL reputation of From: address KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_DNSWL_MED -2.3 Sender listed at https://www.dnswl.org/, medium trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [pbs-devel] [PATCH pxar] encoder: flush after writing last entry X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion <pbs-devel.lists.proxmox.com> List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=unsubscribe> List-Archive: <http://lists.proxmox.com/pipermail/pbs-devel/> List-Post: <mailto:pbs-devel@lists.proxmox.com> List-Help: <mailto:pbs-devel-request@lists.proxmox.com?subject=help> List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=subscribe> X-List-Received-Date: Tue, 30 Mar 2021 06:57:06 -0000 > On 03/29/2021 6:25 PM Dietmar Maurer <dietmar@proxmox.com> wrote: > > > > > + flush(self.output.as_mut()).await?; > > > > According to the patch comment this hasn't broken anywhere at the time, > > but was there any test-code that did need this? > > > > I'd like to make this at least conditional on the writer being > > `EncoderOutput::Owned` to not cause additional flushes for every single > > level of directory nesting. > > Oh, I was not aware that this calls flush for every directory. I guess > nobody really wants that. > > > That said, I'm not even convinced an `Owned` writer would really need > > this? You don't need to explicitly call `flush()` on a `std::fs::File` > > or even a `std::io::BufWriter` explicitly (`BufWriter` explicitly > > flushes in its `Drop` handler), unless you *explicitly* want to handle > > its error, but then you should keep ownership of the writer you pass to > > the encoder anyway and flush manually, not leave that up to the pxar > > code. > > I am ok with reverting this patch. After an off-list talk with Dominik we concluded that keeping it for `Owned` writers is the safer approach for the simple reason that in *async* code (eg. tokio's async BufWriter equivalent) you *do* need to flush buffered writers. This is probably because there's no `AsyncDrop` and there's no guarantee that the future's `Drop` handler is called in a place where it is safe to call tokio's `block_in_place` (after all it panics when it is outside a tokio RT thread, *including* being inside a `runtime.block_on()` called from outside a tokio RT thread). So yeah, let's not revert this, but limit it to `EncoderOutput::Owned`.