From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C478820764E; Tue, 18 Mar 2025 11:30:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742297416; cv=none; b=MHSl4GaNd2SSnM2bELZ7lw7VGIdJJDzW1QC69lap7zqupyl/H2z6YAgCvYIYuuctkXMU7pPbN3ufm3ez/VtLcw1Syy+WlcwhiDhxd7c7RZORTm+lZZRKFxf9dDb39B54FcfWqwqkWptUKGKAysjm6nY3+c++oAZB6TGJnIgSQos= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742297416; c=relaxed/simple; bh=hDZqpee3ghUYrFgRwUEn3lMKVn4rh6MX4hf18mA9WgA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ZJsMH58PjUg6dJ3793fm/eyYSRcT7k+QTCKX3KNHYPd/ecWJa7Hjq4Xw4+jrpSlyT/t41Vc/S8eQTp0il+UXsZ7e0+Qg71hDVvVJj7zKBbNMN5skG+QkfRVZ/iXoZQu9sXqZaj95azJaQVe2cbYh7+flpGdOrI0ao0KdVq6crZI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QdF9WdmV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QdF9WdmV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09663C4CEE3; Tue, 18 Mar 2025 11:30:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742297416; bh=hDZqpee3ghUYrFgRwUEn3lMKVn4rh6MX4hf18mA9WgA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=QdF9WdmVgPVeKnWlEORKj2j3IvX0AFn+jMsn/8jU6r3ZmB6TU471YOfBXxfYAuGdd wHdTPIFDREnCE3vswhwY0nGtkcMGN32CApK8XypVL7o7iQ7WT3DEzasLvu1XL3f3tV ZwXv8mVc3i9+Bn8KbU+QWDY39ZlMy5xo2lGechyJtyxeS4OfuqQ2mv87czR3X8l3by 6K09r6hP6x8gyXF6A/BycNg0fDiOqLqJrPL1KnsapRE6IliIIZYj02D+CkPrLUE32y EZdKXDqv4VWKGFfeaBp/fQJAjpQpUYyAvnzbNs5t7QN0OUMEuOj/qUMaPisXOLWN4Y j31rZIrw9nehw== Message-ID: Subject: Re: [PATCH RFC 0/9] nfs/sunrpc: stop holding netns references in client-side NFS and RPC objects From: Jeff Layton To: Trond Myklebust , "davem@davemloft.net" , "chuck.lever@oracle.com" , "pabeni@redhat.com" , "okorniev@redhat.com" , "tom@talpey.com" , "anna@kernel.org" , "horms@kernel.org" , "kuba@kernel.org" , "Dai.Ngo@oracle.com" , "edumazet@google.com" , "neilb@suse.de" Cc: "josef@toxicpanda.com" , "linux-nfs@vger.kernel.org" , "bcodding@redhat.com" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" Date: Tue, 18 Mar 2025 07:30:13 -0400 In-Reply-To: <8e781348f00184205c38e96e9e8af046d4d2f500.camel@hammerspace.com> References: <20250317-rpc-shutdown-v1-0-85ba8e20b75d@kernel.org> <05463008488b1fea6fb47a2d1a525096fecda861.camel@kernel.org> <8e781348f00184205c38e96e9e8af046d4d2f500.camel@hammerspace.com> 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text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-03-17 at 22:11 +0000, Trond Myklebust wrote: > On Mon, 2025-03-17 at 17:57 -0400, Jeff Layton wrote: > > On Mon, 2025-03-17 at 21:35 +0000, Trond Myklebust wrote: > > > On Mon, 2025-03-17 at 16:59 -0400, Jeff Layton wrote: > > > > We have a long-standing problem with containers that have NFS > > > > mounts > > > > in > > > > them. Best practice is to unmount gracefully, of course, but > > > > sometimes > > > > containers just spontaneously die (e.g. SIGSEGV in the init task > > > > in > > > > the > > > > container). When that happens the orchestrator will see that all > > > > of > > > > the > > > > tasks are dead, and will detach the mount namespace and kill off > > > > the > > > > network connection. > > > >=20 > > > > If there are RPCs in flight at the time, the rpc_clnt will try to > > > > retransmit them indefinitely, but there is no hope of them ever > > > > contacting the server since nothing in userland can reach the > > > > netns > > > > at that point to fix anything. > > > >=20 > > > > This patchset takes the approach of changing various nfs client > > > > and > > > > sunrpc objects to not hold a netns reference. Instead, when a > > > > nfs_net > > > > or > > > > sunrpc_net is exiting, all nfs_server, nfs_client and rpc_clnt > > > > objects > > > > associated with it are shut down, and the pre_exit functions > > > > block > > > > until they are gone. > > > >=20 > > > > With this approach, when the last userland task in the container > > > > exits, > > > > the NFS and RPC clients get cleaned up automatically. As a bonus, > > > > this > > > > fixes another bug with the gssproxy RPC client that causes net > > > > namespace > > > > leaks in any container where it runs (details in the patch > > > > descriptions). > > > >=20 > > >=20 > > > So with this approach, what happens if the NFS mount was created in > > > a > > > container, but got bind mounted somewhere else? > > >=20 > >=20 > > The lifetime of these objects are tied to the net namespace. If it > > gets > > bind-mounted into a different mount namespace, while the tasks are > > setns()'ed into the correct net namespace, then I expect the mount > > would end up shut down at that point and be unusable, just like if > > you > > echo 1 into the shutdown file in sysfs. > >=20 > > Hopefully no one is doing anything that silly. You wouldn't be able > > to > > upcall, for one thing, since there wouldn't be any more userland > > processes attached to the netns. > >=20 > > I'll test that scenario and get back to you though. I do want to make > > sure that that's not going to lead to a crash or anything. >=20 > I agree with you that it's not a sane scenario, and that there is no > need to try to make it work. However the user space tools are there to > allow it to happen, so we need to ensure that the kernel won't panic or > cause any new exotic hangs. Unfortunately, this does create a hang. Bind-mounting it will cause the superblock's refcount to increase, which keeps the nfs_server struct active. That holds a reference to the nfs_client, which prevents everything from coming down properly in pre_exit. I'll have to think about how we can solve that. Let me know if you have ideas. --=20 Jeff Layton