[ltt-dev] [PATCH] LTTng: Make mark-control work in debugfs

[Mathieu Desnoyers]

* Gui Jianfeng (guijianfeng at cn.fujitsu.com) wrote:
> KOSAKI Motohiro wrote:
> >>   Hi Mathieu,
> >>
> >>   I guess it's not easy to implement the *mkdir* for marker control.
> >>   But I have an alternative solution that we can add a control file
> >>   *new_channel* at the same level of channel directories, and add a 
> >>   control file *new_marker* in each channel directory.
> >>   Making use of the following, we can create a marker even if it 
> >>   doesn't exist by now.
> >>
> >>   cd /mnt/ltt/markers
> >>   echo "channel_name" > new_channel
> >>   echo "marker_name" > channel_name/new_marker
> > 
> > No.
> > good user interface is important than easy implementation.
> > 
> > this UI is really ugly.
> 
>   Hi Kosaki-san,
> 
>   Thank you for your kind comments.
>   I say *not easy* becasue debugfs itself doesn't support *mkdir* completely.
>   If we are going to implement mkdir in marker control, we have to modify debugfs
>   itself. IMHO, it's not reasonable and i guess most of the debugfs subsystems don't 
>   like to see this change.
>   On the other hand, it's very natual to use a control file to do something in debugfs.
>   So, I choose this solution. I hope that what I say will clarify the situation.:)
>   Mathieu, What do you say?
> 

Hi Gui,

I would recommend adding mkdir support in our own directories. That
means we have to override debugfs use of "simple" libfs basic
operations. We want to use the same operations, but also define a mkdir
callback. See

fs/debugfs/inode.c:
debugfs_get_inode :
it sets inode->i_op = &simple_dir_inode_operations;

We will need to override this with our own. See
fs/libfs.c: simple_dir_inode_operations

I fully agree with Kosaki : the quality of the user interface is what
matters and is much more important than implementation difficulty.

Thanks,

Mathieu

> 
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> 
> -- 
> Regards
> Gui Jianfeng
> 
> 
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-- 
Mathieu Desnoyers
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