On Tue, Dec 14, 2021 at 06:03:11PM +0800, Tiezhu Yang wrote:

On 12/13/2021 10:43 PM, Matthew Wilcox wrote:

quoted

On Mon, Dec 13, 2021 at 08:30:33AM +0000, David Laight wrote:

quoted

From: Matthew Wilcox

quoted

Sent: 12 December 2021 11:48

On Sat, Dec 11, 2021 at 05:53:46PM +0000, David Laight wrote:

quoted

From: Tiezhu Yang

quoted

Sent: 11 December 2021 03:33

v2:
  -- add copy_to_user_or_kernel() in lib/usercopy.c
  -- define userbuf as bool type

Instead of having a flag to indicate whether the buffer is user or kernel,
would it be better to have two separate buffer pointers.
One for a user space buffer, the other for a kernel space buffer.
Exactly one of the buffers should always be NULL.

No.  You should be using an iov_iter instead.  See
https://lore.kernel.org/all/Ya4bdB0UBJCZhUSo@casper.infradead.org/ (local)
for a start on this.

iov_iter gets horribly expensive...

Oh, right.  Reading the kcore is a high-performance path, my mistake.

Hi,

Thank you for your discussions.

The intention of this patchset is to simplify the related code with no
functional changes and no side effects.

At this moment, if you are OK, I will send v3 used with inline function
copy_to_user_or_kernel() to keep it simple, maybe other more changes can
be done in the future if no any side effect.

That would be pointless.  I already sent a series to remove this,
which you were cc'd on.