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

[Zhi Yong Wu]

On Tue, Oct 30, 2012 at 6:54 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Oct 30, 2012 at 06:45:19AM +0800, Zhi Yong Wu wrote:
>> On Tue, Oct 30, 2012 at 6:34 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> wrote:
>> >> > On Mon, Oct 29, 2012 at 12:30:55PM +0800, zwu.kernel@xxxxxxxxx wrote:
>> >> >> From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
>> >> >>
>> >> >>   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.
>
> Why not do like the rest of the kernel does and just have a:
>         static dentry *hot_track_root;
> and use that as your root debugfs directory dentry:
ah, i'm one newbie, don't get familar with other kernel part, but this
is one good point, i will apply it, thanks.
>
>         if (!hot_track_root) {
>                 /* Create root directory */
>                 hot_track_root = debugfs_create(...);
>         }
>
> No need to look anything up :)
>
> thanks,
>
> greg k-h



-- 
Regards,

Zhi Yong Wu
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/