linux-kernel - Re: [PATCH 2/4] fs/namespace: add umounted mounts to umount_mnt

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Message-ID: <20251002163427.GN39973@ZenIV>
Date: Thu, 2 Oct 2025 17:34:27 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Bhavik Sachdev <b.sachdev1904@...il.com>
Cc: Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Aleksa Sarai <cyphar@...har.com>,
	Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
	Jan Kara <jack@...e.cz>, John Garry <john.g.garry@...cle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	Andrei Vagin <avagin@...il.com>,
	Alexander Mikhalitsyn <alexander@...alicyn.com>
Subject: Re: [PATCH 2/4] fs/namespace: add umounted mounts to umount_mnt_ns

On Thu, Oct 02, 2025 at 06:18:38PM +0530, Bhavik Sachdev wrote:

> @@ -1438,6 +1440,18 @@ static void mntput_no_expire(struct mount *mnt)
>  	mnt->mnt.mnt_flags |= MNT_DOOMED;
>  	rcu_read_unlock();
>  
> +	if (mnt_ns_attached(mnt)) {
> +		struct mnt_namespace *ns;
> +
> +		move_from_ns(mnt);
> +		ns = mnt->mnt_ns;
> +		if (ns) {
> +			ns->nr_mounts--;
> +			__touch_mnt_namespace(ns);
> +		}
> +		mnt->mnt_ns = NULL;
> +	}

Sorry, no.  You are introducing very special locking for one namespace's rbtree.
Not gonna fly.

NAKed-by: Al Viro <viro@...iv.linux.org.uk>