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Date: Fri, 2 Feb 2024 07:36:21 -0800
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Alice Ryhl <aliceryhl@google.com>
Cc: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>,
	Wedson Almeida Filho <wedsonaf@gmail.com>,
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andreas Hindborg <a.hindborg@samsung.com>,
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	linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v4 7/9] rust: file: add `Kuid` wrapper
Message-ID: <2024020214-concierge-rework-2ac5@gregkh>
References: <20240202-alice-file-v4-0-fc9c2080663b@google.com>
 <20240202-alice-file-v4-7-fc9c2080663b@google.com>
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In-Reply-To: <20240202-alice-file-v4-7-fc9c2080663b@google.com>

On Fri, Feb 02, 2024 at 10:55:41AM +0000, Alice Ryhl wrote:
> +    /// Returns the given task's pid in the current pid namespace.
> +    pub fn pid_in_current_ns(&self) -> Pid {
> +        let current = Task::current_raw();
> +        // SAFETY: Calling `task_active_pid_ns` with the current task is always safe.
> +        let namespace = unsafe { bindings::task_active_pid_ns(current) };
> +        // SAFETY: We know that `self.0.get()` is valid by the type invariant, and the namespace
> +        // pointer is not dangling since it points at this task's namespace.
> +        unsafe { bindings::task_tgid_nr_ns(self.0.get(), namespace) }
> +    }

pids are reference counted in the kernel, how does this deal with that?
Are they just ignored somehow?  Where is the reference count given back?

thanks,

greg k-h