linux-kernel - Re: udev kset_create_and_add() with own struct kobj

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Message-ID: <3353d6c1-54ce-46c0-8b65-a0383c8da324@163.com>
Date: Tue, 16 Jul 2024 20:07:16 +0800
From: Lk Sii <lk_sii@....com>
To: Alexander Aring <aahringo@...hat.com>,
 Greg KH <gregkh@...uxfoundation.org>
Cc: rafael@...nel.org,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 gfs2 <gfs2@...ts.linux.dev>, David Teigland <teigland@...hat.com>
Subject: Re: udev kset_create_and_add() with own struct kobj_type?

On 2024/7/15 23:27, Alexander Aring wrote:
> Hi,
> 
> I am currently implementing namespace support into the fs/dlm
> subsystem. The DLM subsystem uses kset_create_and_add("dlm",
> &dlm_uevent_ops, kernel_kobj); to create the "dlm" sysfs directory.
> Underneath it creates for each lockspace a subdirectory using
> kobject_init_and_add() with a non-static name and being known during
> runtime.
> 
> Now I want to add namespace support and need to change the "default"
> kset->kobj.ktype = &kset_ktype; that is set by
> kset_create_and_add()->kset_create() to my own kobj_type because I
> need to implement a different ".child_ns_type" callback before
> kset_register() is called.
> 
you maybe use kset_register() instead of kset_create_and_add().
you maybe find example codes from below kernel files:
fs/nfs/sysfs.c
fs/f2fs/sysfs.c
fs/ubifs/sysfs.c

not sure if this info is helpful for your requirements.

> So kset_create_and_add() does not allow me to add my own
> ".child_ns_type" callback for the kset that is required for me to have
> my sysfs "kernel/dlm" directory separated by each net-namespace
> without breaking any backwards compatibility.
> 
> My current solution is that I mostly copy&pasted the code of
> kset_create_and_add()/kset_create() to have a way to tell my own
> struct kobj_type that contains the implemented my own ".child_ns_type"
> callback.
> 
> I am writing this mail to get some advice on what I can do here
> without doing the copy&pasted code?
> Add a parameter to kset_create_and_add() that allows me to set an
> "struct kobj_type"?
> Introducing a new function that does allow me to set the new parameter
> (I probably like that because then I don't need to update all other
> users)?
> 
> Thanks in advance for any advice.
> 
> - Alex
> 
>