linux-kernel - Re: [RFC V2 PATCH] kernfs: create raw version kernfs_path_len and kernfs

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Date:	Mon, 29 Feb 2016 10:00:53 -0800
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Li Zefan <lizefan@...wei.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-rt-users@...r.kernel.org,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	hch@...radead.org
Subject: Re: [RFC V2 PATCH] kernfs: create raw version kernfs_path_len and
 kernfs_path

On 2/27/2016 3:51 AM, Tejun Heo wrote:
> Hello,
>
> On Sat, Feb 27, 2016 at 6:45 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>>> It can be, but we can print out the ino and userland can match that up
>>> with path if necessary.
>>
>> Wouldn't be cgroup id the better choice?
>
> AFAIK we aren't exposing cgroup id to userland anywhere right now.
> Eventually, I think the right thing to do is using the same number for
> both.

Thanks for all the comments.

Since the current tracepoints print the path length too by 
__trace_wb_cgroup_size and __trace_wbc_cgroup_size, but we can't get the 
path length if we switch to group ino. So, I'm supposed I have to drop 
all the *_size stuff.

And, when CONFIG_CGROUP_WRITEBACK is not enabled, 
__trace_wb_assign_cgroup and __trace_wbc_assign_cgroup return 
"strcpy(buf, "/")", so to get aligned with this, I need print out the 
ino of "/", right? But, the ROOT_INO may vary from different filesystems.

All of them will be addressed in V4, but it may experience some delay 
since I have to travel this week.

Regards,
Yang

>
> Thanks.
>