fs: notice when init abandons fs sharing

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PID 1 may choose to stop sharing fs_struct state with us. Either via
unshare(CLONE_FS) or unshare(CLONE_NEWNS). Of course, PID 1 could have
chosen to create arbitrary process trees that all share fs_struct state
via CLONE_FS. This is a strong statement: We only care about PID 1 aka
the thread-group leader so subthread's fs_struct state doesn't matter.

PID 1 unsharing fs_struct state is a bug. PID 1 relies on various
kthreads to be able to perform work based on its fs_struct state.
Breaking that contract sucks for both sides. So just don't bother with
extra work for this. No sane init system should ever do this.

Link: https://patch.msgid.link/20260601-work-kthread-nullfs-v4-2-77ee053060e0@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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Christian Brauner 2026-06-01 15:56:35 +02:00

parent 21bcea3ef2

commit d114eb8577

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fs/fs_struct.c

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