netdev - Re: [PATCH net 3/5] netdevsim: avoid debugfs warning message when module is remove

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Message-ID: <20200112064110.43245268@cakuba>
Date:   Sun, 12 Jan 2020 06:45:25 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net 3/5] netdevsim: avoid debugfs warning message when
 module is remove

On Sat, 11 Jan 2020 16:37:23 +0000, Taehee Yoo wrote:
> When module is being removed, it couldn't be held by try_module_get().
> debugfs's open function internally tries to hold file_operation->owner
> if .owner is set.
> If holding owner operation is failed, it prints a warning message.

> [  412.227709][ T1720] debugfs file owner did not clean up at exit: ipsec

> In order to avoid the warning message, this patch makes netdevsim module
> does not set .owner. Unsetting .owner is safe because these are protected
> by inode_lock().

So inode_lock will protect from the code getting unloaded/disappearing?
At a quick glance at debugs code it doesn't seem that inode_lock would
do that. Could you explain a little more to a non-fs developer like
myself? :)

Alternatively should we perhaps hold a module reference for each device
created and force user space to clean up the devices? That may require
some fixes to the test which use netdevsim.

> Fixes: 7699353da875 ("netdevsim: add ipsec offload testing")
> Fixes: 31d3ad832948 ("netdevsim: add bpf offload support")
> Signed-off-by: Taehee Yoo <ap420073@...il.com>