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Thu, 1 May 2025 04:27:27 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v6 08/10] net: add symlinks to ref_tracker_dir for netns Date: Wed, 30 Apr 2025 21:26:47 -0700 Message-ID: <20250501042719.81002-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <0c4e532ed8b58f8253a14f8ed59d93523a096f16.camel@kernel.org> References: <0c4e532ed8b58f8253a14f8ed59d93523a096f16.camel@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D046UWB001.ant.amazon.com (10.13.139.187) To EX19D004ANA001.ant.amazon.com (10.37.240.138) From: Jeff Layton Date: Wed, 30 Apr 2025 21:07:20 -0700 > On Wed, 2025-04-30 at 20:50 -0700, Kuniyuki Iwashima wrote: > > From: Jeff Layton > > Date: Wed, 30 Apr 2025 20:42:40 -0700 > > > On Wed, 2025-04-30 at 20:07 -0700, Kuniyuki Iwashima wrote: > > > > From: Jeff Layton > > > > Date: Wed, 30 Apr 2025 19:59:23 -0700 > > > > > On Wed, 2025-04-30 at 14:29 -0700, Kuniyuki Iwashima wrote: > > > > > > From: Jeff Layton > > > > > > Date: Wed, 30 Apr 2025 08:06:54 -0700 > > > > > > > After assigning the inode number to the namespace, use it to create a > > > > > > > unique name for each netns refcount tracker with the ns.inum value in > > > > > > > it, and register a symlink to the debugfs file for it. > > > > > > > > > > > > > > init_net is registered before the ref_tracker dir is created, so add a > > > > > > > late_initcall() to register its files and symlinks. > > > > > > > > > > > > > > Signed-off-by: Jeff Layton > > > > > > > --- > > > > > > > net/core/net_namespace.c | 28 +++++++++++++++++++++++++++- > > > > > > > 1 file changed, 27 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c > > > > > > > index 008de9675ea98fa8c18628b2f1c3aee7f3ebc9c6..6cbc8eabb8e56c847fc34fa8ec9994e8b275b0af 100644 > > > > > > > --- a/net/core/net_namespace.c > > > > > > > +++ b/net/core/net_namespace.c > > > > > > > @@ -763,12 +763,38 @@ struct net *get_net_ns_by_pid(pid_t pid) > > > > > > > } > > > > > > > EXPORT_SYMBOL_GPL(get_net_ns_by_pid); > > > > > > > > > > > > > > +#ifdef CONFIG_NET_NS_REFCNT_TRACKER > > > > > > > +static void net_ns_net_debugfs(struct net *net) > > > > > > > +{ > > > > > > > + ref_tracker_dir_symlink(&net->refcnt_tracker, "netns-%u-refcnt", net->ns.inum); > > > > > > > + ref_tracker_dir_symlink(&net->notrefcnt_tracker, "netns-%u-notrefcnt", net->ns.inum); > > > > > > > > > > > > Could you use net->net_cookie ? > > > > > > > > > > > > net->ns.inum is always 1 when CONFIG_PROC_FS=n. > > > > > > > > > > My main use-case for this is to be able to match the inode number in > > > > > the /proc//ns/net symlink with the correct ref_tracker debugfs > > > > > file. Is there a way to use the net_cookie to make that association? > > > > > > > > It's roundabout, but net_cookie can be retrieved by creating a > > > > random socket in the netns and calling setsockopt(SO_NETNS_COOKIE). > > > > > > > > Ido proposed a handy ip-netns subcommand here, and I guess it will > > > > be implemented soon(?) > > > > https://lore.kernel.org/netdev/1d99d7ccfc3a7a18840948ab6ba1c0b5fad90901.camel@fejes.dev/ > > > > > > For the cases where I was looking at netns leaks, there were no more > > > processes in the container, so there was no way to enter the container > > > and spawn a socket at that point. > > > > Then how do you get net->ns.inum ? > > > > In my case, I was looking at /sys/kernel/debug/sunrpc/rpc_xprt/*/info. > That also displays net->ns.inum in the same format. When I was > originally working on this, the problem I was chasing was due to stuck > RPC transports (rpc_xprt). Thanks for the info. Prefarably the debugfs should also display netns_cookie instaed of inum, and the change is acceptable as the debugfs is not uAPI. Then we don't need to expose possibly non-unique value just for historical reason. > > > > > > > > > > The point of the symlinks is to have a way to easily identify what > > > you're tracking. NAME_MAX is 255. We could do something like this > > > instead: > > > > > > snprintf(..., "netns-%u-%llx-refcnt", net->ns.inum, net->net_cookie); > > > > > > Obviously the inums would all be 1 when PROC_FS=n, but the cookies > > > would be unique. Would that work? > > > > This works, but depending on the question above, there's no point in > > using inum ? > > Having the inum is definitely useful to me, particularly since the > net_cookie would be pretty useless for the problems I've been chasing. > > I'll plan to respin this to include the net_cookie though, since that > would disambiguate the names when PROC_FS=n. It might also turn out to > be useful for someone, once there is a way to fetch the net_cookie from > userland. > --