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 B40CB1DFE8; Sun, 13 Apr 2025 11:41:01 +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=1744544461; cv=none; b=VjmMXIz5uHrnp8DEJySXWVn7boEiNttK+zbG9WH7CwjNHxt6jni7pzz9i29V/9LcqGAp9kxtrnPLXkmZh9TwR6cx+hxjDscfvgwnBx0DzkD16C77VzQ8X7ZHujWEzGKREEmd91l1gMxyyXhqa0Uu/X2b6Fm6Bl94FspW5INp2TQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744544461; c=relaxed/simple; bh=ffvqt8L01qWYtXJDqwSfuXvM+gZQInj456g8b/wy6CY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=HJ/eZvUguLB/cJAuauMBs15bljOcYkNEAgZsnR9MiQotz1bm+uBOnB+xUo47+MHjL/R1ljU76OPVKr7jyyHJvQUYV2M1aP4jZTCTJIVs8FKtUQ8CG7vUyiY7lm5OMYHN8kg4MLYYdqOQstXNI4i2P6P418IjY5MMo6E/hT6jfUA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=p0S29jIJ; 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="p0S29jIJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E161C4CEDD; Sun, 13 Apr 2025 11:41:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744544461; bh=ffvqt8L01qWYtXJDqwSfuXvM+gZQInj456g8b/wy6CY=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=p0S29jIJh00W66s/Fkm4AVC4rhG67CtKcdbeRtkbqDfqrEoEr7rW5W5gMs1MKVqVs hdiJl2UYR+1mqkTNPap5B7g0lLeh4FLjnMw4e4py/foHsF1n9w6mxluEwka2p+F+S7 4u7evALw0XCMe8wgWWRSg1nJzTKnO6l9Yn8zustcrPlApbfFZ2S+IeFjEWaX5WIBaf C2A+3ggPG+pPzGvrKx8kXqOIBAVbbEWrI6Lq8nFGlY3HSWHs7lSuaZBpQumCNCNfIM co4ZqrBjKMRWrRbYnTuGZEIPIWosRKabtQ5521PKzFeyL36nPmMueKGu6bSe114fXi zsOkmKktNUuUw== Message-ID: <23f93f84e000ebee28614bf85a4013648fa66a00.camel@kernel.org> 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: Sun, 13 Apr 2025 07:40:59 -0400 In-Reply-To: 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> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn 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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_init(&n= et->refcnt_tracker, 128, "net refcnt"); > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0ref_tracker_dir_init(&n= et->notrefcnt_tracker, 128, "net notrefcnt"); > >=20 > > Two problems there: > >=20 > > 1/ they have an embedded space in the name which is just painful. Maybe= 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. > > drivers/gpu/drm/i915/intel_wakeref.c: ref_tracker_dir_init(&wf->debug, IN= TEL_REFTRACK_DEAD_COUNT, name); >=20 > Looks like it is unique for one GPU, but if you have multiple GPUs > they are not unique. >=20 We'll need some input from the i915 folks then. > drivers/gpu/drm/i915/intel_runtime_pm.c: ref_tracker_dir_init(&rpm->debug= , INTEL_REFTRACK_DEAD_COUNT, dev_name(rpm->kdev)); >=20 > At a guess kdev is unique. >=20 Yeah, looks like it. > drivers/gpu/drm/display/drm_dp_tunnel.c: ref_tracker_dir_init(&mgr->ref_t= racker, 16, "dptun"); >=20 > Probably not unique. >=20 Looking more here, perhaps we can incorporate mgr->dev->unique into the name? I don't know much about dp drivers. Can multiple mgrs point to the same device? > 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_tracker, 1= 28, "net notrefcnt"); >=20 > Not unique across name spaces, but ... That's easily fixable. net->ns.inum is unique. >=20 > So could the tracker core check if the debugfs file already exists, > emit a warning if it does, and keep going? I think debugfs_lookup() > will tell you if a file already exists, or debugfs_create_file() will > return -EEXIST, which is probably safer, no race condition. >=20 Yeah, that should be possible. I think too that we can eliminate the buffer management in this codepath by allowing pr_ostream() to output directly to a seq_file. I'll look into that as well. Thanks for the input! --=20 Jeff Layton