From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1F4C851993E; Tue, 8 Sep 2026 09:49:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788860950; cv=none; b=F+C47nBHHi+ur7cu2ZjNeJ73wj5nrIxoLuc3IuHLhfhfHtxIvWJXtp+97dGmlEe7L50QhyYwVIoB+p5Q1BLLRz5U7BMzXti5uuEfPQg2fRmRQ2S8JkYlugSyxJsTYV/vjtXIxBWCVvDm1Kt0l6iHDeUX+iEuY9bJ0TPfVb8Nrnc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788860950; c=relaxed/simple; bh=DeONDPrlwaO0nZcfKM6QnKtDw9x47qDXSFM8M1+Kqsg=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=gt78pvXDeAfFlhsmPRmZPMLcee9WT46Grr1NEqxlbb8suMUziIiHw0z2MOcVSFoezeFB2k5vF1spjsIiu/H735UW1MHpzzwqM82LeZjmAO8PEXw62lNloJ3dmi2WgOXnLgCgA+8X/Zpq/llmpTB2ucvTw7UkqYMjJT+eeRC337E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 055911F00A3D; Tue, 8 Sep 2026 09:49:07 +0000 (UTC) Message-ID: <4a4a2c6522a0574af0bd0925aad9bd75987e933a.camel@kernel.org> Subject: Re: [REGRESSION] reads and writes hang if NFS server has v3 disabled From: Jeff Layton To: Benji Wiebe , Chuck Lever Cc: Linux kernel regressions list , linux-nfs@vger.kernel.org, stable@vger.kernel.org Date: Tue, 08 Sep 2026 05:49:06 -0400 In-Reply-To: References: <52ddb3307fcc0893cc20ed63c4dc924f6bcaa8fd.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-09-07 at 13:57 -0500, Benji Wiebe wrote: > On 9/4/26 8:45 AM, Jeff Layton wrote: > > On Fri, 2026-09-04 at 09:09 -0400, Chuck Lever wrote: > > > [ Adding correct addresses from MAINTAINERS ] > > >=20 > > > On Fri, Sep 4, 2026, at 9:05 AM, Chuck Lever wrote: > > > > I'm using a minimal Fedora 45 VM (kvm) for testing.=E2=80=8A=C2=A0 = I export a > > > > directory with rw and mount it from my personal computer running Fe= dora > > > > 45 as well. If /etc/nfs.=E2=80=8Aconf has vers3=3Dn, then reads and= writes hang in > > > > D+ state, and there's a continuous > > > >=20 > > > >=20 > > > > I'm using a minimal Fedora 45 VM (kvm) for testing.=C2=A0 I export = a > > > > directory with rw and mount it from my personal computer running Fe= dora > > > > 45 as well. > > > > If /etc/nfs.conf has vers3=3Dn, then reads and writes hang in D+ st= ate, > > > > and there's a continuous loop of V3 NULL calls, with the server rep= lying > > > > that it only supports v4. > > > > If nfs.conf has vers3=3Dy, then the reads and writes succeed. > > > > Introduced in 70b7e3526c53d9dd, still present in the latest > > > > mainline/master (841e384b841a). > > > >=20 > > > > The hung state can be rescued by changing the setting and restartin= g > > > > nfs-server, at which point the read/write will complete. > > > >=20 > > > > I can do more testing / get more information as needed. > > > >=20 > > > > Here's links to pcap files with it working/bugged: > > > > http://grepper.net/lkml-files/nfs-working.pcap > > > > http://grepper.net/lkml-files/nfs-bugged.pcap > > > > http://grepper.net/lkml-files/nfs-bug-kernel.config > > > >=20 > > > > #regzbot introduced:=C2=A0 70b7e3526c53d9dd7caccdbeff5b0485640d8cf1 > > >=20 > > > It's not immediately obvious to me why 70b7e3526c53d9dd should > > > cause this kind of behavior regression. > > >=20 > > > Jeff, it's a netlink change. Can you triage? > > >=20 > >=20 > > Sure. > >=20 > > Looking at the captures, it looks like the server is handing out a > > flexfiles v3 pNFS layout for the trivial server, and that's (of course) > > failing in this situation. > >=20 > > So we have at least one server bug there -- it shouldn't advertise a > > flexfiles v3 layout when it's not serving v3! I'll plan to fix that > > soon. > >=20 > > That doesn't seem to have anything to do with commit 70b7e3526c53d9dd > > though. I'm not sure why a bisect would have landed there. > I checked and rechecked several times (and again now!) and=20 > 70b7e3526c53d9dd always had the bug present and 565ee23ea2374 did not=20 > have the bug present.> The bug is in 565ee23ea2374, but until 70b7e3526c53d9dd is applied, the code it's in is not used, so that explains why you're seeing it there. =20 > > What does the /etc/exports entry for this export look like? Disabling > > pnfs should work around this for now too if you have it explicitly > > enabled here. >=20 > The /etc/exports entry I'm using: > /home/export *(rw,no_root_squash) >=20 > I'm new to the kernel development process; is there a patch I can apply= =20 > now to see if it fixes the bug? You want commit f76017a7663c4ce5e379f8a8d39f032bdb1fd865 from Chuck's nfsd-fixes branch. Basically, what's happening is that pnfs is being enabled even though you haven't requested it: https://lore.kernel.org/linux-nfs/20260414-pnfs-exp-fix-v1-1-9face14c16c2@k= ernel.org/ --=20 Jeff Layton