linux-kernel - Re: [PATCH RFC] fhandle: expose u64 mount id to name_to_handle

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Date: Sun, 26 May 2024 01:55:48 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Aleksa Sarai <cyphar@...har.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Chuck Lever <chuck.lever@...cle.com>,
	Jeff Layton <jlayton@...nel.org>,
	Amir Goldstein <amir73il@...il.com>,
	Alexander Aring <alex.aring@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] fhandle: expose u64 mount id to name_to_handle_at(2)

On Mon, May 20, 2024 at 05:35:49PM -0400, Aleksa Sarai wrote:
> Now that we have stabilised the unique 64-bit mount ID interface in
> statx, we can now provide a race-free way for name_to_handle_at(2) to
> provide a file handle and corresponding mount without needing to worry
> about racing with /proc/mountinfo parsing.

What are the guarantees for the mount ID?  Is it stable across reboots?
If not mixing it with file handles is a very bad idea.