[PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'

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* [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
@ 2013-05-30  6:03 Chen Gang
  2013-05-30  9:55 ` Chen Gang
                   ` (2 more replies)
  0 siblings, 3 replies; 19+ messages in thread
From: Chen Gang @ 2013-05-30  6:03 UTC (permalink / raw)
  To: edumazet, Pravin Shelar, mgorman
  Cc: David Miller, Andrew Morton, linux-kernel, netdev


Both 'transport_header' and 'mac_header' are u16, which are never equal
to '~0U'.

So need use '0xffff' instead of '~0U'.

The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
  include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
  ...


Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 include/linux/skbuff.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2e0ced1..03ba058 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
 }
 static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
 {
-	return skb->transport_header != ~0U;
+	return skb->transport_header != 0xffff;
 }
 
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
@@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
 
 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
 {
-	return skb->mac_header != ~0U;
+	return skb->mac_header != 0xffff;
 }
 
 static inline void skb_reset_mac_header(struct sk_buff *skb)
-- 
1.7.7.6

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-05-30  6:03 [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U' Chen Gang
@ 2013-05-30  9:55 ` Chen Gang
  2013-05-30 15:30 ` Ben Hutchings
  2013-05-31 21:05 ` Andy Shevchenko
  2 siblings, 0 replies; 19+ messages in thread
From: Chen Gang @ 2013-05-30  9:55 UTC (permalink / raw)
  To: edumazet, Pravin Shelar, mgorman
  Cc: David Miller, Andrew Morton, linux-kernel, netdev


It seems a good idea to "fgrep -rn '~0U'" all source code, and check
each one by one.

:-)


On 05/30/2013 02:03 PM, Chen Gang wrote:
> 
> Both 'transport_header' and 'mac_header' are u16, which are never equal
> to '~0U'.
> 
> So need use '0xffff' instead of '~0U'.
> 
> The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>   ...
> 
> 
> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> ---
>  include/linux/skbuff.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2e0ced1..03ba058 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
>  }
>  static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->transport_header != ~0U;
> +	return skb->transport_header != 0xffff;
>  }
>  
>  static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
> @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
>  
>  static inline int skb_mac_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->mac_header != ~0U;
> +	return skb->mac_header != 0xffff;
>  }
>  
>  static inline void skb_reset_mac_header(struct sk_buff *skb)
> 


-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-05-30  6:03 [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U' Chen Gang
  2013-05-30  9:55 ` Chen Gang
@ 2013-05-30 15:30 ` Ben Hutchings
  2013-06-03  8:52   ` Chen Gang
  2013-05-31 21:05 ` Andy Shevchenko
  2 siblings, 1 reply; 19+ messages in thread
From: Ben Hutchings @ 2013-05-30 15:30 UTC (permalink / raw)
  To: Chen Gang
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev

On Thu, 2013-05-30 at 14:03 +0800, Chen Gang wrote:
> Both 'transport_header' and 'mac_header' are u16, which are never equal
> to '~0U'.
> 
> So need use '0xffff' instead of '~0U'.

...and give this magic number a name?

Ben.

> The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>   ...
> 
> 
> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> ---
>  include/linux/skbuff.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2e0ced1..03ba058 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
>  }
>  static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->transport_header != ~0U;
> +	return skb->transport_header != 0xffff;
>  }
>  
>  static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
> @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
>  
>  static inline int skb_mac_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->mac_header != ~0U;
> +	return skb->mac_header != 0xffff;
>  }
>  
>  static inline void skb_reset_mac_header(struct sk_buff *skb)

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.


^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-05-30 15:30 ` Ben Hutchings
@ 2013-06-03  8:52   ` Chen Gang
  0 siblings, 0 replies; 19+ messages in thread
From: Chen Gang @ 2013-06-03  8:52 UTC (permalink / raw)
  To: Ben Hutchings
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev

On 05/30/2013 11:30 PM, Ben Hutchings wrote:
> On Thu, 2013-05-30 at 14:03 +0800, Chen Gang wrote:
>> > Both 'transport_header' and 'mac_header' are u16, which are never equal
>> > to '~0U'.
>> > 
>> > So need use '0xffff' instead of '~0U'.
> ..and give this magic number a name?

It sounds a good idea. I will check which name is suitable for it, then
send patch v2, and please help to check it, too.


Thanks.
-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-05-30  6:03 [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U' Chen Gang
  2013-05-30  9:55 ` Chen Gang
  2013-05-30 15:30 ` Ben Hutchings
@ 2013-05-31 21:05 ` Andy Shevchenko
  2013-06-03  9:23   ` Chen Gang
  2 siblings, 1 reply; 19+ messages in thread
From: Andy Shevchenko @ 2013-05-31 21:05 UTC (permalink / raw)
  To: Chen Gang
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev

On Thu, May 30, 2013 at 9:03 AM, Chen Gang <gang.chen@asianux.com> wrote:
>
> Both 'transport_header' and 'mac_header' are u16, which are never equal
> to '~0U'.
>
> So need use '0xffff' instead of '~0U'.

Why not "(u16)~0" ?
Or even better "!= USHORT_MAX"?

Or mac_header + 1 == 0, though it less clear.

--
With Best Regards,
Andy Shevchenko

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-05-31 21:05 ` Andy Shevchenko
@ 2013-06-03  9:23   ` Chen Gang
  2013-06-03 10:14     ` Andy Shevchenko
  0 siblings, 1 reply; 19+ messages in thread
From: Chen Gang @ 2013-06-03  9:23 UTC (permalink / raw)
  To: Andy Shevchenko
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

On 06/01/2013 05:05 AM, Andy Shevchenko wrote:
> On Thu, May 30, 2013 at 9:03 AM, Chen Gang <gang.chen@asianux.com> wrote:
>> >
>> > Both 'transport_header' and 'mac_header' are u16, which are never equal
>> > to '~0U'.
>> >
>> > So need use '0xffff' instead of '~0U'.
> Why not "(u16)~0" ?
> Or even better "!= USHORT_MAX"?
> 
> Or mac_header + 1 == 0, though it less clear.

It seems they are just the same as '0xffff' (are all 'magic' number).

We'd better to give a meaningful name to it just like Ben said.


Thanks.
-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-06-03  9:23   ` Chen Gang
@ 2013-06-03 10:14     ` Andy Shevchenko
  2013-06-03 10:51       ` Chen Gang
  0 siblings, 1 reply; 19+ messages in thread
From: Andy Shevchenko @ 2013-06-03 10:14 UTC (permalink / raw)
  To: Chen Gang
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

On Mon, Jun 3, 2013 at 12:23 PM, Chen Gang <gang.chen@asianux.com> wrote:
> On 06/01/2013 05:05 AM, Andy Shevchenko wrote:

>> Why not "(u16)~0" ?
> We'd better to give a meaningful name to it just like Ben said.

Yeah, you could give a name, though I don't see this needs for
constants like (u16)~0. It's a usual way to mark some values
uninitialized.
Just an example from kernel:

        /* This is limited by 16 bit "slot" numbers,
         * and by available on-disk context storage.
         *
         * Also (u16)~0 is special (denotes a "free" extent).

--
With Best Regards,
Andy Shevchenko

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'
  2013-06-03 10:14     ` Andy Shevchenko
@ 2013-06-03 10:51       ` Chen Gang
  2013-06-03 11:24         ` [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' " Chen Gang
  0 siblings, 1 reply; 19+ messages in thread
From: Chen Gang @ 2013-06-03 10:51 UTC (permalink / raw)
  To: Andy Shevchenko
  Cc: edumazet, Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

On 06/03/2013 06:14 PM, Andy Shevchenko wrote:
> On Mon, Jun 3, 2013 at 12:23 PM, Chen Gang <gang.chen@asianux.com> wrote:
>> On 06/01/2013 05:05 AM, Andy Shevchenko wrote:
> 
>>> Why not "(u16)~0" ?
>> We'd better to give a meaningful name to it just like Ben said.
> 
> Yeah, you could give a name, though I don't see this needs for
> constants like (u16)~0. It's a usual way to mark some values
> uninitialized.
> Just an example from kernel:
> 
>         /* This is limited by 16 bit "slot" numbers,
>          * and by available on-disk context storage.
>          *
>          * Also (u16)~0 is special (denotes a "free" extent).
> 

After "fgrep -rn 'u16' * | fgrep '~0'", it seems better to define a
meaningful macro for it (e.g. "#define SKB_HEADER_WAS_UNSET    0xffff").


Thanks.
-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 10:51       ` Chen Gang
@ 2013-06-03 11:24         ` Chen Gang
  2013-06-03 11:34           ` Andy Shevchenko
  2013-06-03 12:26             ` David Laight
  0 siblings, 2 replies; 19+ messages in thread
From: Chen Gang @ 2013-06-03 11:24 UTC (permalink / raw)
  To: Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings


Both 'transport_header' and 'mac_header' are u16, which are never equal
to '~0U'.

So need use '(u16) ~0U' instead of '~0U'.

The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
  include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
  ...

Use meaningful macro instead of hard code number, and better to
initialize 'skb->transport_header' in __alloc_skb_head(), too.


Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 include/linux/skbuff.h |    6 ++++--
 net/core/skbuff.c      |   11 ++++++-----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5f93119..59493f8 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -40,6 +40,8 @@
 #define CHECKSUM_COMPLETE 2
 #define CHECKSUM_PARTIAL 3
 
+#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
+
 #define SKB_DATA_ALIGN(X)	(((X) + (SMP_CACHE_BYTES - 1)) & \
 				 ~(SMP_CACHE_BYTES - 1))
 #define SKB_WITH_OVERHEAD(X)	\
@@ -1593,7 +1595,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
 }
 static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
 {
-	return skb->transport_header != ~0U;
+	return skb->transport_header != SKB_HEADER_UNSET_16;
 }
 
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
@@ -1636,7 +1638,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
 
 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
 {
-	return skb->mac_header != ~0U;
+	return skb->mac_header != SKB_HEADER_UNSET_16;
 }
 
 static inline void skb_reset_mac_header(struct sk_buff *skb)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f45de07..18c6974 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -200,7 +200,8 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
 	atomic_set(&skb->users, 1);
 
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_UNSET_16;
+	skb->transport_header = SKB_HEADER_UNSET_16;
 #endif
 out:
 	return skb;
@@ -276,8 +277,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
-	skb->transport_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_UNSET_16;
+	skb->transport_header = SKB_HEADER_UNSET_16;
 #endif
 
 	/* make sure we initialize shinfo sequentially */
@@ -345,8 +346,8 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
-	skb->transport_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_UNSET_16;
+	skb->transport_header = SKB_HEADER_UNSET_16;
 #endif
 
 	/* make sure we initialize shinfo sequentially */
-- 
1.7.7.6

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* Re: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 11:24         ` [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' " Chen Gang
@ 2013-06-03 11:34           ` Andy Shevchenko
  2013-06-03 11:46             ` Chen Gang
  2013-06-03 12:26             ` David Laight
  1 sibling, 1 reply; 19+ messages in thread
From: Andy Shevchenko @ 2013-06-03 11:34 UTC (permalink / raw)
  To: Chen Gang
  Cc: edumazet, Pravin Shelar, Mel Gorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

On Mon, Jun 3, 2013 at 2:24 PM, Chen Gang <gang.chen@asianux.com> wrote:
>
> Both 'transport_header' and 'mac_header' are u16, which are never equal
> to '~0U'.
>
> So need use '(u16) ~0U' instead of '~0U'.
>
> The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>   ...
>
> Use meaningful macro instead of hard code number, and better to
> initialize 'skb->transport_header' in __alloc_skb_head(), too.

Looks okay. Couple of questions below.

> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -40,6 +40,8 @@
>  #define CHECKSUM_COMPLETE 2
>  #define CHECKSUM_PARTIAL 3
>
> +#define SKB_HEADER_UNSET_16    ((unsigned short) ~0U)

Isn't better to use the same type as used in the structure description?

> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -200,7 +200,8 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
>         atomic_set(&skb->users, 1);
>
>  #ifdef NET_SKBUFF_DATA_USES_OFFSET
> -       skb->mac_header = (__u16) ~0U;
> +       skb->mac_header = SKB_HEADER_UNSET_16;
> +       skb->transport_header = SKB_HEADER_UNSET_16;

Is it correct to assign transport_header here as well?

--
With Best Regards,
Andy Shevchenko

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 11:34           ` Andy Shevchenko
@ 2013-06-03 11:46             ` Chen Gang
  0 siblings, 0 replies; 19+ messages in thread
From: Chen Gang @ 2013-06-03 11:46 UTC (permalink / raw)
  To: Andy Shevchenko
  Cc: edumazet, Pravin Shelar, Mel Gorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

On 06/03/2013 07:34 PM, Andy Shevchenko wrote:
>> --- a/include/linux/skbuff.h
>> > +++ b/include/linux/skbuff.h
>> > @@ -40,6 +40,8 @@
>> >  #define CHECKSUM_COMPLETE 2
>> >  #define CHECKSUM_PARTIAL 3
>> >
>> > +#define SKB_HEADER_UNSET_16    ((unsigned short) ~0U)
> Isn't better to use the same type as used in the structure description?
> 

It sounds reasonable, I will wait 1 days, if no additional suggestions
or completions, I will send patch v3.


>> > --- a/net/core/skbuff.c
>> > +++ b/net/core/skbuff.c
>> > @@ -200,7 +200,8 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
>> >         atomic_set(&skb->users, 1);
>> >
>> >  #ifdef NET_SKBUFF_DATA_USES_OFFSET
>> > -       skb->mac_header = (__u16) ~0U;
>> > +       skb->mac_header = SKB_HEADER_UNSET_16;
>> > +       skb->transport_header = SKB_HEADER_UNSET_16;
> Is it correct to assign transport_header here as well?

At least, it is correct: they are in the same structure, and almost a
neighbor with each other.

Hmm... I guess that may be useless currently which will waste one
instruction.

But I still suggest to add it, it can avoid the new mistakes in the future.

Welcome another members to provide their suggestions for it.


Thanks.
-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* RE: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 11:24         ` [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' " Chen Gang
@ 2013-06-03 12:26             ` David Laight
  2013-06-03 12:26             ` David Laight
  1 sibling, 0 replies; 19+ messages in thread
From: David Laight @ 2013-06-03 12:26 UTC (permalink / raw)
  To: Chen Gang, Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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> +#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
> +

The _16 part isn't really correct, the type could be changed
and then it would be wrong.

I think I might have used SKB_HEADER_OFFSET.

	David

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^ permalink raw reply	[flat|nested] 19+ messages in thread

* RE: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
@ 2013-06-03 12:26             ` David Laight
  0 siblings, 0 replies; 19+ messages in thread
From: David Laight @ 2013-06-03 12:26 UTC (permalink / raw)
  To: Chen Gang, Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

> +#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
> +

The _16 part isn't really correct, the type could be changed
and then it would be wrong.

I think I might have used SKB_HEADER_OFFSET.

	David


^ permalink raw reply	[flat|nested] 19+ messages in thread

* RE: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 12:26             ` David Laight
@ 2013-06-03 12:47               ` David Laight
  -1 siblings, 0 replies; 19+ messages in thread
From: David Laight @ 2013-06-03 12:47 UTC (permalink / raw)
  To: David Laight, Chen Gang, Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 518 bytes --]

> > +#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
> > +
> 
> The _16 part isn't really correct, the type could be changed
> and then it would be wrong.
> 
> I think I might have used SKB_HEADER_OFFSET.

I meant SKB_HEADER_UNSET_OFFSET or SKB_HEADER_OFFSET_UNSET

> NrybXÇ§v^)Þº{.n+z^)w*jg\x1eÝ¢j/zÞ–2Þ™&)ß¡a\x7f\x1eGh\x0fj:+vwÙ¥

I've NFI what adds this!

	David

ÿôèº{.nÇ+‰·Ÿ®‰†+%ŠËÿ±éÝ¶\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dÊ‡Ú™ë,j\a¢f£¢·hšïêÿ‘êçz_è®\x03(éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨èÚ&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

^ permalink raw reply	[flat|nested] 19+ messages in thread

* RE: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
@ 2013-06-03 12:47               ` David Laight
  0 siblings, 0 replies; 19+ messages in thread
From: David Laight @ 2013-06-03 12:47 UTC (permalink / raw)
  To: David Laight, Chen Gang, Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings

> > +#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
> > +
> 
> The _16 part isn't really correct, the type could be changed
> and then it would be wrong.
> 
> I think I might have used SKB_HEADER_OFFSET.

I meant SKB_HEADER_UNSET_OFFSET or SKB_HEADER_OFFSET_UNSET

> NrybXǧv^)޺{.n+z^)w*jg\x1eݢj/zޖ2ޙ&)ߡa\x7f\x1eGh\x0fj:+vw٥

I've NFI what adds this!

	David


^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' instead of '~0U'
  2013-06-03 12:47               ` David Laight
  (?)
@ 2013-06-05  0:44               ` Chen Gang
  2013-06-05  0:54                 ` [PATCH v3] include/linux/skbuff.h: using '(__u16) " Chen Gang
  -1 siblings, 1 reply; 19+ messages in thread
From: Chen Gang @ 2013-06-05  0:44 UTC (permalink / raw)
  To: David Laight
  Cc: Andy Shevchenko, edumazet, Pravin Shelar, mgorman, David Miller,
	Andrew Morton, linux-kernel, netdev, Ben Hutchings

On 06/03/2013 08:47 PM, David Laight wrote:
>>> +#define SKB_HEADER_UNSET_16	((unsigned short) ~0U)
>>> > > +
>> > 
>> > The _16 part isn't really correct, the type could be changed
>> > and then it would be wrong.
>> > 
>> > I think I might have used SKB_HEADER_OFFSET.
> I meant SKB_HEADER_UNSET_OFFSET or SKB_HEADER_OFFSET_UNSET
> 

It sound good, I choose the 2nd: 'SKB_HEADER_OFFSET_UNSET', for it may
be a 'noun', not a 'sentence'.

I will send patch v3 (also use '__u16' instead of 'unsigned short')


Thanks.
-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v3] include/linux/skbuff.h: using '(__u16) ~0U' instead of '~0U'
  2013-06-05  0:44               ` Chen Gang
@ 2013-06-05  0:54                 ` Chen Gang
  2013-06-05  8:36                   ` David Miller
  0 siblings, 1 reply; 19+ messages in thread
From: Chen Gang @ 2013-06-05  0:54 UTC (permalink / raw)
  To: David Laight, Andy Shevchenko, edumazet
  Cc: Pravin Shelar, mgorman, David Miller, Andrew Morton,
	linux-kernel, netdev, Ben Hutchings


Both 'transport_header' and 'mac_header' are __u16, which are
never equal to '~0U'.

So need use '(__u16) ~0U' instead of '~0U'.

The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
  include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
  ...

Use meaningful macro instead of hard code number, and better to
initialize 'skb->transport_header' in __alloc_skb_head(), too.



Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 include/linux/skbuff.h |    6 ++++--
 net/core/skbuff.c      |   11 ++++++-----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5f93119..3314911 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -40,6 +40,8 @@
 #define CHECKSUM_COMPLETE 2
 #define CHECKSUM_PARTIAL 3
 
+#define SKB_HEADER_OFFSET_UNSET	((__u16) ~0U)
+
 #define SKB_DATA_ALIGN(X)	(((X) + (SMP_CACHE_BYTES - 1)) & \
 				 ~(SMP_CACHE_BYTES - 1))
 #define SKB_WITH_OVERHEAD(X)	\
@@ -1593,7 +1595,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
 }
 static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
 {
-	return skb->transport_header != ~0U;
+	return skb->transport_header != SKB_HEADER_OFFSET_UNSET;
 }
 
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
@@ -1636,7 +1638,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
 
 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
 {
-	return skb->mac_header != ~0U;
+	return skb->mac_header != SKB_HEADER_OFFSET_UNSET;
 }
 
 static inline void skb_reset_mac_header(struct sk_buff *skb)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f45de07..6808433 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -200,7 +200,8 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
 	atomic_set(&skb->users, 1);
 
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+	skb->transport_header = SKB_HEADER_OFFSET_UNSET;
 #endif
 out:
 	return skb;
@@ -276,8 +277,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
-	skb->transport_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+	skb->transport_header = SKB_HEADER_OFFSET_UNSET;
 #endif
 
 	/* make sure we initialize shinfo sequentially */
@@ -345,8 +346,8 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
 	skb_reset_tail_pointer(skb);
 	skb->end = skb->tail + size;
 #ifdef NET_SKBUFF_DATA_USES_OFFSET
-	skb->mac_header = (__u16) ~0U;
-	skb->transport_header = (__u16) ~0U;
+	skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+	skb->transport_header = SKB_HEADER_OFFSET_UNSET;
 #endif
 
 	/* make sure we initialize shinfo sequentially */
-- 
1.7.7.6

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* Re: [PATCH v3] include/linux/skbuff.h: using '(__u16) ~0U' instead of '~0U'
  2013-06-05  0:54                 ` [PATCH v3] include/linux/skbuff.h: using '(__u16) " Chen Gang
@ 2013-06-05  8:36                   ` David Miller
  2013-06-05 11:15                     ` Chen Gang
  0 siblings, 1 reply; 19+ messages in thread
From: David Miller @ 2013-06-05  8:36 UTC (permalink / raw)
  To: gang.chen
  Cc: David.Laight, andy.shevchenko, edumazet, pshelar, mgorman, akpm,
	linux-kernel, netdev, bhutchings

From: Chen Gang <gang.chen@asianux.com>
Date: Wed, 05 Jun 2013 08:54:22 +0800

> 
> Both 'transport_header' and 'mac_header' are __u16, which are
> never equal to '~0U'.
> 
> So need use '(__u16) ~0U' instead of '~0U'.
> 
> The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>   ...
> 
> Use meaningful macro instead of hard code number, and better to
> initialize 'skb->transport_header' in __alloc_skb_head(), too.
> 
> 
> 
> Signed-off-by: Chen Gang <gang.chen@asianux.com>

Your patch doesn't apply to the tree because this has been fixed already
for several days by using "typeof(x) ~0U"

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v3] include/linux/skbuff.h: using '(__u16) ~0U' instead of '~0U'
  2013-06-05  8:36                   ` David Miller
@ 2013-06-05 11:15                     ` Chen Gang
  0 siblings, 0 replies; 19+ messages in thread
From: Chen Gang @ 2013-06-05 11:15 UTC (permalink / raw)
  To: David Miller
  Cc: David.Laight, andy.shevchenko, edumazet, pshelar, mgorman, akpm,
	linux-kernel, netdev, bhutchings

On 06/05/2013 04:36 PM, David Miller wrote:
> From: Chen Gang <gang.chen@asianux.com>
> Date: Wed, 05 Jun 2013 08:54:22 +0800
> 
>> > 
>> > Both 'transport_header' and 'mac_header' are __u16, which are
>> > never equal to '~0U'.
>> > 
>> > So need use '(__u16) ~0U' instead of '~0U'.
>> > 
>> > The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>> >   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>> >   ...
>> > 
>> > Use meaningful macro instead of hard code number, and better to
>> > initialize 'skb->transport_header' in __alloc_skb_head(), too.
>> > 
>> > 
>> > 
>> > Signed-off-by: Chen Gang <gang.chen@asianux.com>
> Your patch doesn't apply to the tree because this has been fixed already
> for several days by using "typeof(x) ~0U"
> 
> 

OK, thanks.

-- 
Chen Gang

Asianux Corporation

^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2013-06-05 11:16 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-05-30  6:03 [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U' Chen Gang
2013-05-30  9:55 ` Chen Gang
2013-05-30 15:30 ` Ben Hutchings
2013-06-03  8:52   ` Chen Gang
2013-05-31 21:05 ` Andy Shevchenko
2013-06-03  9:23   ` Chen Gang
2013-06-03 10:14     ` Andy Shevchenko
2013-06-03 10:51       ` Chen Gang
2013-06-03 11:24         ` [PATCH v2] include/linux/skbuff.h: using '(u16) ~0U' " Chen Gang
2013-06-03 11:34           ` Andy Shevchenko
2013-06-03 11:46             ` Chen Gang
2013-06-03 12:26           ` David Laight
2013-06-03 12:26             ` David Laight
2013-06-03 12:47             ` David Laight
2013-06-03 12:47               ` David Laight
2013-06-05  0:44               ` Chen Gang
2013-06-05  0:54                 ` [PATCH v3] include/linux/skbuff.h: using '(__u16) " Chen Gang
2013-06-05  8:36                   ` David Miller
2013-06-05 11:15                     ` Chen Gang

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