Hello,
There is an articel in LinuxJournal from this April issue by Greg KH which
explains
how to read and how to write a file from kernel module.
He reads the file using set_fs(KERNEL_DS) and write to the file using
fget(fd)
and vfs_write().
It is clearly not recommended to do such a thing , as he admitted in this
article.
Moreover, the article itself is titled "Driving Me Nuts - Things You Never
Should Do in the Kernel".
see:
http://www.linuxjournal.com/article/8110
Regards,
Rami Rosen
From: Gilboa Davara <[EMAIL PROTECTED]>
To: IL List <[email protected]>
Subject: Re: File I/O within kernel threads?
Date: Thu, 28 Jul 2005 17:24:41 +0300
Gilad,
First, thanks for the answer.
On Thu, 2005-07-28 at 16:44 +0300, Gilad Ben-Yossef wrote:
> A kernel thread is indeed proccess context, but since you brought it
up
> already and assuming we're talking 2.6, the "correct" way to do is
use
> work queues (and hence schedule_work) instead of schedule_task. This
> will give you the option to start your own work queue (and hence your
> own kernel thread) thus not having to worry about starving other
tasks.
>
> And while we're on the subject, you might want to take a look into
using
> a work queue instead of a kernel thread all together - it's a very
nice
> interface to do these sort of things.
>
> To learn more about Work queues see here (page 23):
>
> http://lwn.net/images/pdf/LDD3/ch07.pdf
Funny... I forgot all about work queues.
Thanks! It'll save me the need to create way-too-many-kernel-threads.
>
>
> On another different and related note, if you're consider doing IO
from
> kernel sapce (which is a terribly bad as you've pointed out already
but
> I wonder if you know just *how* difficult to debug and racy it is)
The rest of the kernel code is already there.
Let me put this way. The reset button is my new best friend :-/
I assume that I must guard all the file->ops->read/write file operation
myself to prevent ugly race conditions, right?
> for
> fear of perfomance, a saner approach that may or may not fit your
bill
> is using RelayFS:
>
> http://sourcefrog.net/weblog/software/linux-kernel/relayfs.html
Interesting... I remember reading about this in KernelTrap.
I doubt that i'll help me. I need concurrent R/W from within the kernel
space.
>
>
> Hope this helps,
> Gilad
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