linux-kernel - TmpFs Incorporation Of FsCrypt?

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Message-ID: <CALaQ_hqfXkfU0TwcXReRPuc_gCo=5OGF1dtV2To0mPFP3a49CQ@mail.gmail.com>
Date: Wed, 14 Jan 2026 01:25:39 -0600
From: Nathan Royce <nroycea+kernel@...il.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Hugh Dickins <hughd@...gle.com>
Subject: TmpFs Incorporation Of FsCrypt?

I recently saw the PRs for BTRFS relating to FSCRYPT, and thought I'd
explore the fscrypt package.

I started with `status` before moving to `setup` on the `/tmp` path
which is tmpfs.
As expected I'm sure, I got: `[ERROR] fscrypt setup: filesystem type
tmpfs is not supported for fscrypt setup`

Looking in https://github.com/google/fscrypt, I saw:
https://github.com/google/fscrypt/blob/ea916da7fa9844cc3da608e75510f478c7b09f7d/cli-tests/t_not_supported.sh
which coincides with my presumably expected error.

But I also saw: `The source files are located on an in-memory
filesystem such as tmpfs.` in the main README, which makes me wonder
if there is intent/plan to bring fscrypt to tmpfs.

I'm kind of thinking a use case of having keys and/or a password
manager database on external/encrypted storage, that gets transferred
to some random path in `/run/user/<#>` (tmpfs) on login where it is
encrypted as well (then the storage is unmounted/locked/removed), and
the respective program that uses the file(s) would point to a freshly
generated config that points to the random location.