linux-ext4 - Re: [RFC v4+ hot_track 13/19] debugfs: introduce one function

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Message-ID: <CAEH94Lj2baN-EzjTvxURc5ECyfjh9Z+w6NZbNUok3osOLF55ag@mail.gmail.com>
Date:	Tue, 30 Oct 2012 06:45:19 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	david@...morbit.com, tytso@....edu, cmm@...ibm.com,
	wuzhy@...ux.vnet.ibm.com, wenqing.lz@...bao.com
Subject: Re: [RFC v4+ hot_track 13/19] debugfs: introduce one function

On Tue, Oct 30, 2012 at 6:34 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Tue, Oct 30, 2012 at 06:25:50AM +0800, Zhi Yong Wu wrote:
>> On Tue, Oct 30, 2012 at 2:11 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> > On Mon, Oct 29, 2012 at 12:30:55PM +0800, zwu.kernel@...il.com wrote:
>> >> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>> >>
>> >>   The debugfs function is used to get expected dentry.
>> >
>> > Huh?  Why do you need this?  Why haven't you added documentation for the
>> It is used to determine if one sysfs directory has been created. OK, i
>> will add some doc, thanks for your suggestion.
>
> You didn't answer the "why" part here.  How come you think you need
ah, Let me say its scenario at first. If we do two mount ops as below:
1.) mount -o loop,hot_track image1 /data1
2.) mount -o loop,hot_track image2 /data2

The mount -o hot_track operation will automatically create one sysfs
directory /sys/kernel/debug/hot_track. To prevent this dir being
created again when 2.) is done, we need to know if it has existed at
first. In my patch, i at first get its dentry by this new function,
then determine if its d_inode field is NULL, if no, it means that this
sysfs dir has existed.
This is the reason that i want to add one new function.

> this?  Can't you just save off the dentry you created somewhere so you
> don't need to look it up again?
Because i can't find one appropriate place to save it.
>
> greg k-h



-- 
Regards,

Zhi Yong Wu
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