Patch to improve readability of sock_rcvlowat() - comments wanted...

[Jesper Juhl]

Hi all,

Some time ago I posted about a question about some cleanup of what I 
thought looked like some strange code in the kernel - specifically about 
the sock_rcvlowat() function in linux/include/net/sock.h

static inline int sock_rcvlowat(struct sock *sk, int waitall, int len)
{
         return (waitall ? len : min(sk->rcvlowat, len)) ? : 1;
}

The empty second expression puzzled me. Mark Hahn (amongst many other 
people) pointed out to me that it was a valid gcc extention (thank you), 
but I still found it hard to read and exchanged several emails with Mark 
about how to improve the function. Mark came up with a much more 
readable version that achieves the exact same result and generates just 
as good (if not better) code than the original one-line function - the 
function below:

static inline int sock_rcvlowat(struct sock *sk, int waitall, int len)
{
         int r = len;
         if (!waitall)
                 r = min(sk->rcvlowat, len);
         return max(1,r);
}

I have included a patch below (against 2.4.5pre1) that makes the change 
to the more readable version and would like people on the list to 
consider it as a replacement.
Credit for the code should go 100% to Mark as he wrote it, I'm just 
submitting it to the list since I found it so nice :-)

--- linux-2.4.5pre1/include/net/sock.h  Tue May  8 00:12:14 2001
+++ linux/include/net/sock.h    Tue May  8 00:46:43 2001
@@ -1265,7 +1265,10 @@

  static inline int sock_rcvlowat(struct sock *sk, int waitall, int len)
  {
-       return (waitall ? len : min(sk->rcvlowat, len)) ? : 1;
+       int r = len;
+       if (!waitall)
+               r = min(sk->rcvlowat, len);
+       return max(1,r);
  }

  /* Alas, with timeout socket operations are not restartable.

Best regards,
Jesper Juhl - [e-mail]
- struggeling to understand this magnificent kernel beast ;) -