[Fwd: [PATCH] [TIPC]: Enhancements to msg_set_bits() routine]

[Fwd: [PATCH] [TIPC]: Enhancements to msg_set_bits() routine]

[Jon Paul Maloy]

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This patch makes two enhancements to msg_set_bits():

1) It now ignores any bits of the new field value that are not
   covered by the mask being used.  (Previously, if the new value
   exceeded the size of the mask the extra bits could corrupt
   other fields in the message header word being updated.)

2) The code has been optimized to minimize the number of run-time
   endianness conversion operations by leveraging the fact that the
   mask (and, in some cases, the value as well) is constant and the
   necessary conversion can be performed by the compiler.

Apply the attached patch, or pull from:

 git://tipc.cslab.ericsson.net/pub/git/tipc.git

 (rebased on linux/kernel/git/davem/net-2.6.git)

Summary:

 net/tipc/msg.h |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)


///Jon




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>From 1c3c79c4c79aa8a665ddf41c08b4363cbb946950 Mon Sep 17 00:00:00 2001
From: Jon Paul Maloy <jon.maloy@ericsson.com>
Date: Mon, 23 Apr 2007 11:49:07 -0400
Subject: [PATCH 1/1] [TIPC]: Enhancements to msg_set_bits() routine

This patch makes two enhancements to msg_set_bits():

1) It now ignores any bits of the new field value that are not
   covered by the mask being used.  (Previously, if the new value
   exceeded the size of the mask the extra bits could corrupt
   other fields in the message header word being updated.)

2) The code has been optimized to minimize the number of run-time
   endianness conversion operations by leveraging the fact that the
   mask (and, in some cases, the value as well) is constant and the
   necessary conversion can be performed by the compiler.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Jon Paul Maloy <jon.maloy@ericsson.com>
---
 net/tipc/msg.h |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 62d5490..5c64e55 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -1,8 +1,8 @@
 /*
  * net/tipc/msg.h: Include file for TIPC message header routines
  *
- * Copyright (c) 2000-2006, Ericsson AB
- * Copyright (c) 2005, Wind River Systems
+ * Copyright (c) 2000-2007, Ericsson AB
+ * Copyright (c) 2005-2007, Wind River Systems
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -71,8 +71,11 @@ static inline void msg_set_word(struct tipc_msg *m, u32 w, u32 val)
 static inline void msg_set_bits(struct tipc_msg *m, u32 w,
 				u32 pos, u32 mask, u32 val)
 {
-	u32 word = msg_word(m,w) & ~(mask << pos);
-	msg_set_word(m, w, (word |= (val << pos)));
+	val = (val & mask) << pos;
+	val = htonl(val);
+	mask = htonl(mask << pos);
+	m->hdr[w] &= ~mask;
+	m->hdr[w] |= val;
 }
 
 /*
-- 
1.5.0.5

Re: [Fwd: [PATCH] [TIPC]: Enhancements to msg_set_bits() routine]

[Ingo Oeser]

Hi Jon,

Jon Paul Maloy schrieb:
> 2) The code has been optimized to minimize the number of run-time
>    endianness conversion operations by leveraging the fact that the
>    mask (and, in some cases, the value as well) is constant and the
>    necessary conversion can be performed by the compiler.

3) It can be checked by sparse, if you use proper types.
 
> diff --git a/net/tipc/msg.h b/net/tipc/msg.h
> index 62d5490..5c64e55 100644
> --- a/net/tipc/msg.h
> +++ b/net/tipc/msg.h
> @@ -71,8 +71,11 @@ static inline void msg_set_word(struct tipc_msg *m, u32
> w, u32 val) static inline void msg_set_bits(struct tipc_msg *m, u32 w,
>  				u32 pos, u32 mask, u32 val)

static inlinevoid msg_set_bits(struct tipc_msg *m, u32 w,
  				u32 pos, __be32 mask, __be32 val)


Care to resubmit?


Best Regards

Ingo Oeser

Re: [Fwd: [PATCH] [TIPC]: Enhancements to msg_set_bits() routine]

[Ingo Oeser]

Hi Jon,

Jon Paul Maloy schrieb:
> Ingo Oeser wrote:
> > static inlinevoid msg_set_bits(struct tipc_msg *m, u32 w,
> >   				u32 pos, __be32 mask, __be32 val)
> >
> >
> > Care to resubmit?

> I don't mind at all, but I would first like to understand better
> what this means. 
> If I understand it correctly __be32 literally means "big-endian
> 32-bit integer", but the way it is used doesn't seem to imply this,
> since both input and output to htonl() often is of that type.

Yes, you are right! I mixed up htonl and ntohl :-)
Sorry for the confusion!

Best Regards

Ingo Oeser