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 3B52C25A2AB; Mon, 14 Apr 2025 12:21:02 +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=1744633263; cv=none; b=kmuyg1qyx//NETOzWJRyk+cYmQVADbQsGDqZU+/l7a/T9O2BqXIVSXvltCadKYOAD4YOGh7t77h/LP3Ft4Ug9yNUvDTMcYYW3dEXDWhwSrp5XzOWdx1lKhw5jIzzI7yTzLLi3/m+eAyb7XGp0X0tWkAy8eWtg2hRNAXpvISWq2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744633263; c=relaxed/simple; bh=L4Ewx2ih54zQ98R+2DDZwrjQOY6wrybXnZcgST+v2SI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=gOIN3DcSpqfwYv0bVfkgqcas1mh4PzH4/rxuvW4qvyVPmFcSUExCpOGU6A3DH8NWCP6g/Zqb0fB3iR1cmyExMMdymVZjSbfmkujT43lv3RxYX6oc/VyZWEaxougi64xBgfe+1R45N5BRP6A6gzOThJuiNkJleW/yDO34zDOsgUY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sahMxwrL; 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="sahMxwrL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E33A6C4CEE2; Mon, 14 Apr 2025 12:21:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744633262; bh=L4Ewx2ih54zQ98R+2DDZwrjQOY6wrybXnZcgST+v2SI=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=sahMxwrLe/JGLj3NXKbw2gPKJsar1F9tYMuGRzdvTK6pepdmkc2x7Y7Aelxa1JoCl g8PqVkcfCf9PyiqsnmxKDQM1H4Z/axFG3DwjvrJTTX5aMEaBHoXObZxs6sclUZhTMc Elss6JEFPJT7SDGOga2ayho7tS9K553yBdwf3iZdqMENzzCJkv8dAYpNgzmlvfKnTR py1U89XCVu+OGk/HFDZPnQOr+sN4H0avZS3EHvqb4FFkQk5s0hQFmCBbm/Gs+fdjRN GYLSTt8PMUjbyaT7I6HtpfCpwypi7keD9I9u4J61GmlaohRK3gQKpddhRdRO05XNB2 rEaSeH3ZWq8KQ== Message-ID: Subject: Re: [PATCH v2 2/2] net: add debugfs files for showing netns refcount tracking info From: Jeff Layton To: Andrew Lunn Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Andrew Morton , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 14 Apr 2025 08:20:59 -0400 In-Reply-To: <71adf369-a803-4d06-906c-97b5bf48bcf8@lunn.ch> References: <20250408-netns-debugfs-v2-0-ca267f51461e@kernel.org> <20250408-netns-debugfs-v2-2-ca267f51461e@kernel.org> <1e717326-8551-419e-b185-5cfb20573b4f@lunn.ch> <91d6d3c60ef5d4ed90418f8a06228767be8a5b1b.camel@kernel.org> <23f93f84e000ebee28614bf85a4013648fa66a00.camel@kernel.org> <71adf369-a803-4d06-906c-97b5bf48bcf8@lunn.ch> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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07:40:59AM -0400, Jeff Layton wrote: > > On Thu, 2025-04-10 at 16:12 +0200, Andrew Lunn wrote: > > > > Oh, ok. I guess you mean these names? > > > >=20 > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0ref_tracker_dir_ini= t(&net->refcnt_tracker, 128, "net refcnt"); > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0ref_tracker_dir_ini= t(&net->notrefcnt_tracker, 128, "net notrefcnt"); > > > >=20 > > > > Two problems there: > > > >=20 > > > > 1/ they have an embedded space in the name which is just painful. M= aybe we can replace those with underscores? > > > > 2/ they aren't named in a per-net namespace way > > >=20 > > > So the first question is, are the names ABI? Are they exposed to > > > userspace anywhere? Can we change them? > > >=20 > > > If we can change them, space to _ is a simple change. Another option > > > is what hwmon does, hwmon_sanitize_name() which turns a name into > > > something which is legal in a filesystem. If all of this code can be > > > pushed into the core tracker, so all trackers appear in debugfs, such > > > a sanitiser is the way i would go. > > >=20 > > > And if we can change the name, putting the netns into the name would > > > also work. There is then no need for the directory, if they have > > > unique names. > > >=20 > > > Looking at other users of ref_tracker_dir_init(): > > >=20 > > > ~/linux$ grep -r ref_tracker_dir_init > > > lib/test_ref_tracker.c: ref_tracker_dir_init(&ref_dir, 100, "selftest= "); > > >=20 > > > Can only be loaded once, so is unique. > > >=20 > > > drivers/gpu/drm/i915/intel_wakeref.c: ref_tracker_dir_init(&wf->debug= , INTEL_REFTRACK_DEAD_COUNT, name); > > >=20 > > > Looks like it is unique for one GPU, but if you have multiple GPUs > > > they are not unique. > > >=20 > >=20 > > We'll need some input from the i915 folks then. >=20 > That is why i think it would be better to add a warning, give the i915 > folks a heads up, and leave them to fix it how they want. We want the > warning anyway to cover new refcount instances being added. >=20 There will definitely be a pr_warn() if creation fails. I was hoping to send a suggested change alongside the patchset, but I may have to just leave it up to them. I threw together a draft patchset that auto-registers a debugfs file for every call to ref_tracker_dir_init(). The problem I've hit now though is that at least in the networking cases, the kernel calls ref_tracker_dir_init() very early in the process of creating a new objects, so we're not getting good names here: The "name" in alloc_netdev_mqs is actually a format string, so we end up with a name like "eth%d" here: net/core/dev.c: ref_tracker_dir_init(&dev->refcnt_tracker, 128, name); At the point that we call these (preinit), net->ns.inum hasn't been assigned yet, so we can't incorporate it properly into the dentry name: net/core/net_namespace.c: ref_tracker_dir_init(&net->refcnt_tracker, = 128, "net refcnt"); net/core/net_namespace.c: ref_tracker_dir_init(&net->notrefcnt_tracke= r, 128, "net notrefcnt"); We could do the ref_tracker_dir_init() calls later, but we may end up missing some references that way (or end up crashing because the "dir" isn't initialized. My current thinking is to add a new ref_tracker_dir_finalize() function that we could use to=C2=A0finalize the name and register the debugfs files after we have the requisite info. It's an extra manual step, but I like that better than moving around the ref_tracker_dir_init() calls. Thoughts? -- Jeff Layton