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 E917330B538 for ; Mon, 2 Feb 2026 19:43:39 +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=1770061420; cv=none; b=bjcRgSPYktIDd02dcY0woAjD7WqIL0hCXZ2tkJl+5lTIhnvK6Xn/2qNB80lTUYvjd4U283IOPN/dk9mkSzjh1wRMQHtXTB4HUfsKWd7sP9+MHqLH5+ZQuXU+XXNhdL2Sbapzfgo4NEfShJjSf73ks6zNZJopFcYiHvJM2X6C8RQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770061420; c=relaxed/simple; bh=hq/wkgdPnsy/n7unUoWg2bNDVpMpHe1tPcwYEi7v2Ho=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cYYuzhPhRe805pn6cs1LoeNGKgj+4b3DT1pI2oR/r6xfu0LXKB55E9OnSLe5ZHoLf+v29gminDHVwTUBzG80dQoRkg/utonjFU08MSI3nqfwreeXSi6AARyP8rczKiQC8bWCC4HkWs3vqf08SSk+DS55VKWt4qAvG4CJiNCbCNQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=utBPvsVE; 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="utBPvsVE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72ECAC19425; Mon, 2 Feb 2026 19:43:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770061419; bh=hq/wkgdPnsy/n7unUoWg2bNDVpMpHe1tPcwYEi7v2Ho=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=utBPvsVEODaRCMfLB7ORx2MPLqLsfljOjbRy6a8CbKkOvkPoWWGDlgbsJ1t9BOUN7 SXTnFqw1B8ZBbKyDZ6wZvrzIu+XtWPEC6YX8pkEPoHKlMchwqt7aFWmw4sQ68wmAcf y7IUpHuie9G+JZq7NEzh5Z5OuZTp4pNA5Vzh2Lgl4qjmB/OQ6ETbUjb/8gTB29z/uK cmlsSGKcF9eoFb0UEqGVh+kZNqL7Q73+ElJdDQ1L4JOMBHPfwUFwfbEuGlJZHhk6ks DHE1mvbixEuVLnBXhwN+k5RdKVkRLZgEYJblZeLD7tsGt+j86guUkZSZ1Q4Zhxx80C 5Xy+yRY9IXG0A== Received: from phl-compute-03.internal (phl-compute-03.internal [10.202.2.43]) by mailfauth.phl.internal (Postfix) with ESMTP id 6D9F5F40068; Mon, 2 Feb 2026 14:43:38 -0500 (EST) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-03.internal (MEProxy); Mon, 02 Feb 2026 14:43:38 -0500 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefgedrtddtgddujeekheduucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfurfetoffkrfgpnffqhgenuceu rghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujf gurhepfffhvfevuffkfhggtggujgesthdtredttddtvdenucfhrhhomhepmfhirhihlhcu ufhhuhhtshgvmhgruhcuoehkrghssehkvghrnhgvlhdrohhrgheqnecuggftrfgrthhtvg hrnhepueeijeeiffekheeffffftdekleefleehhfefhfduheejhedvffeluedvudefgfek necuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepkhhirh hilhhlodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhithihqdduieduudeivdeiheeh qddvkeeggeegjedvkedqkhgrsheppehkvghrnhgvlhdrohhrghesshhhuhhtvghmohhvrd hnrghmvgdpnhgspghrtghpthhtohepudeipdhmohguvgepshhmthhpohhuthdprhgtphht thhopehvihhrohesiigvnhhivhdrlhhinhhugidrohhrghdruhhkpdhrtghpthhtohepsg hrrghunhgvrheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepjhgrtghksehsuhhsvgdr tgiipdhrtghpthhtohephhhughhhugesghhoohhglhgvrdgtohhmpdhrtghpthhtohepsg grohhlihhnrdifrghngheslhhinhhugidrrghlihgsrggsrgdrtghomhdprhgtphhtthho pehlihhnuhigqdhmmheskhhvrggtkhdrohhrghdprhgtphhtthhopehlihhnuhigqdhfsh guvghvvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidq khgvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhg X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 2 Feb 2026 14:43:37 -0500 (EST) Date: Mon, 2 Feb 2026 19:43:36 +0000 From: Kiryl Shutsemau To: Al Viro Cc: Christian Brauner , Jan Kara , Hugh Dickins , Baolin Wang , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Orphan filesystems after mount namespace destruction and tmpfs "leak" Message-ID: References: <20260202184356.GD3183987@ZenIV> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260202184356.GD3183987@ZenIV> On Mon, Feb 02, 2026 at 06:43:56PM +0000, Al Viro wrote: > > I am not sure what a possible solution would be here. I can only think > > of blocking exit(2) for the last process in the namespace until all > > filesystems are cleanly unmounted, but that is not very informative > > either. > > That's insane - if nothing else, the process that holds the sucker > opened may very well be waiting for the one you've blocked. Good point. I obviously don't underhand lifecycle here. > You are getting exactly what you asked for - same as you would on > lazy umount, for that matter. > > Filesystem may be active without being attached to any namespace; > it's an intentional behaviour. What's more, it _is_ visible to > ustat(2), as well as lsof(1) and similar userland tools in case > of opened file keeping it busy. I can only see the opened file, not the rest of filesystem, right? Do you see the USB stick scenario problematic? It is weird to me that umount would fail with -EBUSY here, but kill full namespace is fine. -- Kiryl Shutsemau / Kirill A. Shutemov