Re: file system writes

[Jan Hudec <bulb@ucw.cz>]

[-- Attachment #1: Type: text/plain, Size: 1494 bytes --]

On Thu, Jan 13, 2005 at 10:35:44 -0800, jenn wrote:
> Hello,
> 
> I had a question I hoped someone could answer.
> 
> I am modifying reiserfs code. I have added code to the fs that writes
> kernel data to a file on the same system. On mount, I make a file by
> creating a dentry, and then calling i_op->create. I then release the
> dentry. Everything appears to work fine I can see the file on the system
> and open it etc... 
> 
> I try to write data to this file after creating it like this: 
> 
> I make a file pointer
> I call filp_open with the name of the file
> I call set_fs (to tell it it is a kernel address)
> I call fp->f_op->write 
> I call filp_close
> 
> The write operation returns successfully but no data appears in the
> file. I open it and it is empty. It does work if I try to write to a
> file on another system though... like I can write to etc/ or /opt.
> 
> Brahhhh...
> 
> If anyone has some ideas thanks!

Is the whole world gone mad? Why is everybody trying to write files from
kernel?? I was said many times here, that it's forbidden to write to
files in kernel. What are you actualy trying to do??

That being said, it's doable and you are on the right track. Some stupid
mistake like forgetting to call fput perhaps?

But of course, I can't repeat it enough: FILES MUST NOT BE READ NOR
WRITTEN BY KERNEL!

-------------------------------------------------------------------------------
						 Jan 'Bulb' Hudec <bulb@ucw.cz>

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 189 bytes --]