linux-kernel - Re: [PATCH v3 11/70] ns: add active reference count

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Message-ID: <20251029070201.2327405-1-safinaskar@gmail.com>
Date: Wed, 29 Oct 2025 10:02:01 +0300
From: Askar Safin <safinaskar@...il.com>
To: brauner@...nel.org
Cc: amir73il@...il.com,
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Subject: Re: [PATCH v3 11/70] ns: add active reference count

Christian Brauner <brauner@...nel.org>:
> Currently namespace file handles allow much broader access to namespaces
> than what is currently possible via (1)-(4). The reason is that

There is no any (4) here.


> On current kernels a namespace is visible to userspace in the
> following cases:
[...]
> (3) The namespace is a hierarchical namespace type and is the parent of
>     a single or multiple child namespaces.
[...]
> To handle this nicely we introduce an active reference count which
> tracks (1)-(3). This is easy to do as all of these things are already
[...]
> + * Inactive -> Active:
> + *   When walking a hierarchical namespace tree upwards and reopening
> + *   parent namespaces via NS_GET_PARENT that only exist because they
> + *   are a parent of an actively used namespace it is possible to
> + *   necrobump an inactive namespace back to the active state.

These quoted parts contradict to each other. You say "we introduce an
active reference count which tracks (1)-(3)", and (3) says "The namespace
is a hierarchical namespace type and is the parent of a single or multiple
child namespaces". I. e. active reference will count such parents. But then
in code you say:

> + * Inactive -> Active:
> + *   When walking a hierarchical namespace tree upwards and reopening
> + *   parent namespaces via NS_GET_PARENT that only exist because they
> + *   are a parent of an actively used namespace it is possible to
> + *   necrobump an inactive namespace back to the active state.

I. e. now you say that such parents are inactive and can become active.




-- 
Askar Safin