On 3/12/20 9:04 PM, Jarkko Sakkinen wrote:

On Sun, Mar 08, 2020 at 01:04:09PM -0400, Waiman Long wrote:

quoted

+		/*
+		 * Read methods will just return the required length
+		 * without any copying if the provided length isn't big
+		 * enough.
+		 */
+		if ((ret > 0) && (ret <= buflen) && buffer &&
+		    copy_to_user(buffer, tmpbuf, ret))
+			ret = -EFAULT;

Please, reorg and remove redundant parentheses:

/*
 * Read methods will just return the required length
 * without any copying if the provided length isn't big
 * enough.
 */
if (ret > 0 && ret <= buflen) {
	if (buffer && copy_to_user(buffer, tmpbuf, ret))
		ret = -EFAULT;
}

Now the comment is attached to the exact right thing. The previous
organization is a pain to look at when backtracking commits for
whatever reason in the future.

Yes, I can reorganize the code.

I'm also wondering, would it be possible to rework the code in a way
that you don't have check whether buffer is valid on a constant basis?

One way to do that is to extract the down_read/up_read block into a
helper function and then have 2 separate paths - one for length
retrieval and another one for reading the key. I think that will make
the code a bit easier easier to read.

Thanks,
Longman