From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.3xo.fr (mail.3xo.fr [212.129.21.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 919491F1927; Thu, 24 Apr 2025 07:40:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.129.21.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745480426; cv=none; b=JA5yENP9+RZrMYgEOrCBJXODRkolFQkelRoVo/IMqh/TdbWsE7+H4/j+TLZu4qID2beblU0ih0TiEBdsJZVHD6aZN1Dkl6l7LkKcAA+DYhG2MrR56FZBBC5JVye6kZe77Nq/A16zE0iAQ12m3tYPudeXUa2QWi6EBIz86/4oWM0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745480426; c=relaxed/simple; bh=wJzBuNv3LpnWTInF73DPDdf568PiX49EKsvdzlN+VNM=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=hTQwLLKCBthzbjAq4tcso/6l3WzfYrz2tyaiDMnarx8ZxlOOEqgBBp87G8BfTw6kMVkhIc4Xl28Qzo9UYM0YgsUY6m+1qAJIhu9fQg5+c1E0iQDP3rZKKD3SK1KLQ8tVAu2UY0T/T2Pr7+Tlpj32n5ux0un/qtNpzeE9WjPGF6M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=3xo.fr; spf=pass smtp.mailfrom=3xo.fr; dkim=pass (2048-bit key) header.d=3xo.fr header.i=@3xo.fr header.b=o88nyfQg; arc=none smtp.client-ip=212.129.21.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=3xo.fr Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=3xo.fr Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=3xo.fr header.i=@3xo.fr header.b="o88nyfQg" Received: from localhost (mail.3xo.fr [212.129.21.66]) by mail.3xo.fr (Postfix) with ESMTP id 4616ECB; Thu, 24 Apr 2025 09:40:21 +0200 (CEST) X-Virus-Scanned: Debian amavis at nxo2.3xo.fr Received: from mail.3xo.fr ([212.129.21.66]) by localhost (mail.3xo.fr [212.129.21.66]) (amavis, port 10024) with ESMTP id H1RaQ-c1-sZu; Thu, 24 Apr 2025 09:40:18 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 mail.3xo.fr B33EA8D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=3xo.fr; s=3xo; t=1745480418; bh=tkMxtFneChkyh6FH2tvBrsB//VGTblVVYgMkNJr9ZRg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=o88nyfQgvhZspqftbeutotYHg7ag/f98EgtlBX4u5ywFKamoDhhB2xAe8/pOJC40Y ghJpjAiFBUQkHUtiILfM/4WQc16ky+ePbgr/s0VSRbkGbKGyRa6YrdCgU3t33brc+Y 4v0B95j6b44kNRBTBtvddbUK9vFLLwgTwJ6QjhU3HnrzAe7vj2dOoyd9G0LTD8qNC3 dh+e8aGQ95LP0eGCZ4FMdOEBx58CvTwfDObEsRmEWnIgTCsodkw2cWGrD61P5/q1NJ kGVS8Vg9YRtIzyWeXT2ymX2dtPmZqRa+9KdJTfat6CCgETkKPNVMc9B2wrS8v6olY+ 0+VdMLzZblIeg== Received: from mail.3xo.fr (mail.3xo.fr [212.129.21.66]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by mail.3xo.fr (Postfix) with ESMTPSA id B33EA8D; Thu, 24 Apr 2025 09:40:18 +0200 (CEST) Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 24 Apr 2025 09:40:18 +0200 From: Nicolas Baranger To: Paulo Alcantara Cc: Christoph Hellwig , hch@lst.de, David Howells , netfs@lists.linux.dev, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Steve French , Jeff Layton , Christian Brauner Subject: Re: [netfs/cifs - Linux 6.14] loop on file cat + file copy when files are on CIFS share In-Reply-To: References: <10bec2430ed4df68bde10ed95295d093@3xo.fr> <35940e6c0ed86fd94468e175061faeac@3xo.fr> <48685a06c2608b182df3b7a767520c1d@3xo.fr> <5087f9cb3dc1487423de34725352f57c@3xo.fr> <53697288e2891aea51061c54a2e42595@manguebit.com> Message-ID: X-Sender: nicolas.baranger@3xo.fr Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Paolo Thanks again for help. I'm sorry, I made a mistake in my answer yesterday: > After a lot of testing, the mounts buffers values: rsize=65536, > wsize=65536, bsize=16777216,... The actual values in /etc/fstab are: rsize=4194304,wsize=4194304,bsize=16777216 But negociated values in /proc/mounts are: rsize=65536,wsize=65536,bsize=16777216 And don't know if it's related but I have: grep -i maxbuf /proc/fs/cifs/DebugData CIFSMaxBufSize: 16384 I've just force a manual 'mount -o remount' and now I have in /proc/mounts the good values (SMB version is 3.1.1). Where does this behavior comes from ? After some search, it appears that when the CIFS share is mounted by systemd option x-systemd.automount (for example doing 'ls' in the mount point directory), negociated values are: rsize=65536,wsize=65536,bsize=16777216 If I umount / remount manually, the negociated values are those defined in /etc/fstab ! Don't know if it's a normal behavior but it is a source of errors / mistake and makes troubleshooting performance issues harder Kind regards Nicolas Le 2025-04-23 18:28, Nicolas Baranger a écrit : > Hi Paolo > > Thanks for answer, all explanations and help > > I'm happy you found those 2 bugs and starting to patch them. > Reading your answer, I want to remember that I already found a bug in > cifs DIO starting from Linux 6.10 (when cifs statring to use netfs to > do its IO) and it was fixed by David and Christoph > full story here: > https://lore.kernel.org/all/14271ed82a5be7fcc5ceea5f68a10bbd@manguebit.com/T/ > >> I've noticed that you disabled caching with 'cache=none', is there any >> particular reason for that? > > Yes, it's related with the precedent use case describes in the other > bug: > For backuping servers, I've got some KSMBD cifs share on which there > are some 4TB+ sparses files (back-files) which are LUKS + BTRFS > formatted. > The cifs share is mounted on servers and each server mount its own > back-file as a block device and make its backup inside this crypted > disk file > Due to performance issues, it is required that the disk files are using > 4KB block and are mounted in servers using losetup DIO option (+ 4K > block size options) > When I use something else than 'cache=none', sometimes the BTRFS > filesystem on the back file get corrupted and I also need to mount the > BTRFS filesystem with 'space_cache=v2' to avoid filesystem corruption > >> Have you also set rsize, wsize and bsize mount options? If so, why? > > After a lot of testing, the mounts buffers values: rsize=65536, > wsize=65536, bsize=16777216, are the one which provide the best > performances with no corruptions on the back-file filesystem and with > these options a ~2TB backup is possible in few hours during timeframe > ~1 -> ~5 AM each night > > For me it's important that kernel async DIO on netfs continue to work > as it's used by all my production backup system (transfer speed ratio > compared with and without DIO is between 10 to 25) > > I will try the patch "[PATCH] netfs: Fix setting of transferred bytes > with short DIO reads", thanks > > Let me know if you need further explanations, > > Kind regards > Nicolas Baranger > > Le 2025-04-22 01:45, Paulo Alcantara a écrit : > > Nicolas Baranger writes: > > If you need more traces or details on (both?) issues : > > - 1) infinite loop issue during 'cat' or 'copy' since Linux 6.14.0 > > - 2) (don't know if it's related) the very high number of several bytes > TCP packets transmitted in SMB transaction (more than a hundred) for a > 5 > bytes file transfert under Linux 6.13.8 > According to your mount options and network traces, cat(1) is > attempting > to read 16M from 'toto' file, in which case netfslib will create 256 > subrequests to handle 64K (rsize=65536) reads from 'toto' file. > > The first 64K read at offset 0 succeeds and server returns 5 bytes, the > client then sets NETFS_SREQ_HIT_EOF to indicate that this subrequest > hit > the EOF. The next subrequests will still be processed by netfslib and > sent to the server, but they all fail with STATUS_END_OF_FILE. > > So, the problem is with short DIO reads in netfslib that are not being > handled correctly. It is returning a fixed number of bytes read to > every read(2) call in your cat command, 16711680 bytes which is the > offset of last subrequest. This will make cat(1) retry forever as > netfslib is failing to return the correct number of bytes read, > including EOF. > > While testing a potential fix, I also found other problems with DIO in > cifs.ko, so I'm working with Dave to get the proper fixes for both > netfslib and cifs.ko. > > I've noticed that you disabled caching with 'cache=none', is there any > particular reason for that? > > Have you also set rsize, wsize and bsize mount options? If so, why? > > If you want to keep 'cache=none', then a possible workaround for you > would be making rsize and wsize always greater than bsize. The default > values (rsize=4194304,wsize=4194304,bsize=1048576) would do it.