From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 3CA879E50D for ; Mon, 27 Nov 2023 14:22:55 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 186627DB4 for ; Mon, 27 Nov 2023 14:22:25 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for ; Mon, 27 Nov 2023 14:22:24 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 3B1AA44B4F for ; Mon, 27 Nov 2023 14:22:24 +0100 (CET) Date: Mon, 27 Nov 2023 14:22:15 +0100 From: Wolfgang Bumiller To: Fabian =?utf-8?Q?Gr=C3=BCnbichler?= Cc: pbs-devel@lists.proxmox.com Message-ID: References: <20230629103213.1041236-1-f.gruenbichler@proxmox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230629103213.1041236-1-f.gruenbichler@proxmox.com> X-SPAM-LEVEL: Spam detection results: 0 AWL 0.098 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: Re: [pbs-devel] [PATCH proxmox-backup] mapped loop device: use read loop instead of read_exact X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Nov 2023 13:22:55 -0000 On Thu, Jun 29, 2023 at 12:32:13PM +0200, Fabian Grünbichler wrote: > since read_exact does not support short reads, which can easily happen if the > mapped image's EOF is not aligned with the request size. > > Signed-off-by: Fabian Grünbichler > --- > > Notes: > reported on the forum: > > https://forum.proxmox.com/threads/problem-backing-up-using-backup-client.129347 > > did a quick test reading from a mapped image full of random data, observed > no performance difference.. Do you get one if we just drop the loop logic and *actually* just `read()` once? IMO this is more in line with what a read syscall *should* be doing. Further, we use a `CachedChunkReader` under it which actually does a read loop anyway, so AFAICT this *can't* make a difference. > > pbs-fuse-loop/src/fuse_loop.rs | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) > > diff --git a/pbs-fuse-loop/src/fuse_loop.rs b/pbs-fuse-loop/src/fuse_loop.rs > index 3d0ef123..7e780799 100644 > --- a/pbs-fuse-loop/src/fuse_loop.rs > +++ b/pbs-fuse-loop/src/fuse_loop.rs > @@ -188,13 +188,20 @@ impl FuseLoopSession { > match self.reader.seek(SeekFrom::Start(req.offset)).await { > Ok(_) => { > let mut buf = vec![0u8; req.size]; > - match self.reader.read_exact(&mut buf).await { > - Ok(_) => { > - req.reply(&buf) > - }, > - Err(e) => { > - req.io_fail(e) > + let mut read = 0; > + let mut res = Ok(()); > + while read < req.size && res.is_ok() { > + match self.reader.read(&mut buf).await { > + Ok(0) => { break; }, > + Ok(n) => { read += n; }, > + Err(e) => { res = Err(e); }, > } > + }; > + if let Err(e) = res { > + req.io_fail(e) > + } else { > + buf.truncate(read); > + req.reply(&buf) > } > }, > Err(e) => { > -- > 2.39.2