> explains how you can do I/O from within kernel space.
At a glance I looked specifically for DIRECT IO in the article, I think it just explains cached IO from kernel buffer, which is very trivial and easy to do. Also I am reiterating here again, I have implemented one solution using do_mmap from inside the kernel and that works fine for DIRECT IO too. Please refer to my original mail
But I am looking for a solution where I dont have to inject any kernel data into user space virtual address space.
> Of particular note are the calls to set_fs/get_fs. These calls modify
> the address space in such a way that copy_to/from_user will now work
> on kernel buffers.
You are right about set_gs/get_fs, I have done it sevaral times for doing cached IO. Problem area is get_user_pages function which tries to pin pages in memory and fails for kernel buffers.
Thanks,
Rajat
On Tue, Oct 19, 2010 at 2:01 AM, Dave Hylands <dhylands@xxxxxxxxx> wrote:
Hi Rajat,
Not sure if it's relevant, but this article:
On Mon, Oct 18, 2010 at 1:14 PM, Rajat Sharma <fs.rajat@xxxxxxxxx> wrote:
> Greg,
>
> okay I give you an example, currently ecryptfs does not support DIRECT IO
> operation, if it wants to encrypt data in kernel buffers and since file was
> opened in DIRECT IO mode, the lower filesystem should not complain about
> kernel buffers
<http://www.linuxjournal.com/article/8110>
explains how you can do I/O from within kernel space.
Of particular note are the calls to set_fs/get_fs. These calls modify
the address space in such a way that copy_to/from_user will now work
on kernel buffers.
I'm pretty sure that this is NOT a recoemmended practice, but I
figured I'd throw it out there.
--
Dave Hylands
Shuswap, BC, Canada
http://www.DaveHylands.com/
