Hi all,
I noticed recently that, in skb_checksum(), "offset" and "start" are
essentially the same thing and have the same value throughout the
function, despite being computed differently. Using a single variable
allows some cleanups and makes the skb_checksum() function smaller,
more readable, and presumably marginally faster.
We appear to have many other "sk_buff walker" functions built on the
exact same model, so the cleanup applies to them, too. Here is a list
of the functions I found to be affected:
net/appletalk/ddp.c:atalk_sum_skb()
net/core/datagram.c:skb_copy_datagram_iovec()
net/core/datagram.c:skb_copy_and_csum_datagram()
net/core/skbuff.c:skb_copy_bits()
net/core/skbuff.c:skb_store_bits()
net/core/skbuff.c:skb_checksum()
net/core/skbuff.c:skb_copy_and_csum_bit()
net/core/user_dma.c:dma_skb_copy_datagram_iovec()
net/xfrm/xfrm_algo.c:skb_icv_walk()
net/xfrm/xfrm_algo.c:skb_to_sgvec()
OTOH, I admit I'm a bit surprised, the cleanup is rather obvious so I'm
really wondering if I am missing something. Can anyone please comment
on this?
Signed-off-by: Jean Delvare <[EMAIL PROTECTED]>
---
net/appletalk/ddp.c | 25 +++++--------
net/core/datagram.c | 50 ++++++++----------------
net/core/skbuff.c | 100 +++++++++++++++++--------------------------------
net/core/user_dma.c | 25 +++++--------
net/xfrm/xfrm_algo.c | 44 ++++++++--------------
5 files changed, 86 insertions(+), 158 deletions(-)
--- linux-2.6.21-rc4.orig/net/core/skbuff.c 2007-03-19 09:23:49.000000000
+0100
+++ linux-2.6.21-rc4/net/core/skbuff.c 2007-03-20 07:12:45.000000000 +0100
@@ -1081,13 +1081,13 @@ pull_pages:
int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
{
int i, copy;
- int start = skb_headlen(skb);
+ int end = skb_headlen(skb);
if (offset > (int)skb->len - len)
goto fault;
/* Copy header. */
- if ((copy = start - offset) > 0) {
+ if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
memcpy(to, skb->data + offset, copy);
@@ -1098,11 +1098,9 @@ int skb_copy_bits(const struct sk_buff *
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
u8 *vaddr;
@@ -1111,8 +1109,8 @@ int skb_copy_bits(const struct sk_buff *
vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);
memcpy(to,
- vaddr + skb_shinfo(skb)->frags[i].page_offset+
- offset - start, copy);
+ vaddr + skb_shinfo(skb)->frags[i].page_offset,
+ copy);
kunmap_skb_frag(vaddr);
if ((len -= copy) == 0)
@@ -1120,30 +1118,25 @@ int skb_copy_bits(const struct sk_buff *
offset += copy;
to += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- if (skb_copy_bits(list, offset - start,
- to, copy))
+ if (skb_copy_bits(list, 0, to, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
to += copy;
}
- start = end;
}
}
if (!len)
@@ -1168,12 +1161,12 @@ fault:
int skb_store_bits(const struct sk_buff *skb, int offset, void *from, int len)
{
int i, copy;
- int start = skb_headlen(skb);
+ int end = skb_headlen(skb);
if (offset > (int)skb->len - len)
goto fault;
- if ((copy = start - offset) > 0) {
+ if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
memcpy(skb->data + offset, from, copy);
@@ -1185,11 +1178,9 @@ int skb_store_bits(const struct sk_buff
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + frag->size;
+ end = offset + frag->size;
if ((copy = end - offset) > 0) {
u8 *vaddr;
@@ -1197,8 +1188,7 @@ int skb_store_bits(const struct sk_buff
copy = len;
vaddr = kmap_skb_frag(frag);
- memcpy(vaddr + frag->page_offset + offset - start,
- from, copy);
+ memcpy(vaddr + frag->page_offset, from, copy);
kunmap_skb_frag(vaddr);
if ((len -= copy) == 0)
@@ -1206,30 +1196,25 @@ int skb_store_bits(const struct sk_buff
offset += copy;
from += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- if (skb_store_bits(list, offset - start,
- from, copy))
+ if (skb_store_bits(list, 0, from, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
from += copy;
}
- start = end;
}
}
if (!len)
@@ -1246,8 +1231,8 @@ EXPORT_SYMBOL(skb_store_bits);
__wsum skb_checksum(const struct sk_buff *skb, int offset,
int len, __wsum csum)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
int pos = 0;
/* Checksum header. */
@@ -1262,11 +1247,9 @@ __wsum skb_checksum(const struct sk_buff
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
__wsum csum2;
u8 *vaddr;
@@ -1275,8 +1258,8 @@ __wsum skb_checksum(const struct sk_buff
if (copy > len)
copy = len;
vaddr = kmap_skb_frag(frag);
- csum2 = csum_partial(vaddr + frag->page_offset +
- offset - start, copy, 0);
+ csum2 = csum_partial(vaddr + frag->page_offset,
+ copy, 0);
kunmap_skb_frag(vaddr);
csum = csum_block_add(csum, csum2, pos);
if (!(len -= copy))
@@ -1284,31 +1267,26 @@ __wsum skb_checksum(const struct sk_buff
offset += copy;
pos += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
__wsum csum2;
if (copy > len)
copy = len;
- csum2 = skb_checksum(list, offset - start,
- copy, 0);
+ csum2 = skb_checksum(list, 0, copy, 0);
csum = csum_block_add(csum, csum2, pos);
if ((len -= copy) == 0)
return csum;
offset += copy;
pos += copy;
}
- start = end;
}
}
BUG_ON(len);
@@ -1321,8 +1299,8 @@ __wsum skb_checksum(const struct sk_buff
__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
u8 *to, int len, __wsum csum)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
int pos = 0;
/* Copy header. */
@@ -1339,11 +1317,9 @@ __wsum skb_copy_and_csum_bits(const stru
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
__wsum csum2;
u8 *vaddr;
@@ -1353,9 +1329,8 @@ __wsum skb_copy_and_csum_bits(const stru
copy = len;
vaddr = kmap_skb_frag(frag);
csum2 = csum_partial_copy_nocheck(vaddr +
- frag->page_offset +
- offset - start, to,
- copy, 0);
+ frag->page_offset,
+ to, copy, 0);
kunmap_skb_frag(vaddr);
csum = csum_block_add(csum, csum2, pos);
if (!(len -= copy))
@@ -1364,7 +1339,6 @@ __wsum skb_copy_and_csum_bits(const stru
to += copy;
pos += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
@@ -1372,16 +1346,13 @@ __wsum skb_copy_and_csum_bits(const stru
for (; list; list = list->next) {
__wsum csum2;
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- csum2 = skb_copy_and_csum_bits(list,
- offset - start,
+ csum2 = skb_copy_and_csum_bits(list, 0,
to, copy, 0);
csum = csum_block_add(csum, csum2, pos);
if ((len -= copy) == 0)
@@ -1390,7 +1361,6 @@ __wsum skb_copy_and_csum_bits(const stru
to += copy;
pos += copy;
}
- start = end;
}
}
BUG_ON(len);
--- linux-2.6.21-rc4.orig/net/core/datagram.c 2007-02-21 08:36:31.000000000
+0100
+++ linux-2.6.21-rc4/net/core/datagram.c 2007-03-19 21:13:04.000000000
+0100
@@ -247,8 +247,8 @@ EXPORT_SYMBOL(skb_kill_datagram);
int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
struct iovec *to, int len)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
/* Copy header. */
if (copy > 0) {
@@ -263,11 +263,9 @@ int skb_copy_datagram_iovec(const struct
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
int err;
u8 *vaddr;
@@ -277,8 +275,8 @@ int skb_copy_datagram_iovec(const struct
if (copy > len)
copy = len;
vaddr = kmap(page);
- err = memcpy_toiovec(to, vaddr + frag->page_offset +
- offset - start, copy);
+ err = memcpy_toiovec(to, vaddr + frag->page_offset,
+ copy);
kunmap(page);
if (err)
goto fault;
@@ -286,30 +284,24 @@ int skb_copy_datagram_iovec(const struct
return 0;
offset += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- if (skb_copy_datagram_iovec(list,
- offset - start,
- to, copy))
+ if (skb_copy_datagram_iovec(list, 0, to, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
}
- start = end;
}
}
if (!len)
@@ -323,9 +315,9 @@ static int skb_copy_and_csum_datagram(co
u8 __user *to, int len,
__wsum *csump)
{
- int start = skb_headlen(skb);
+ int end = skb_headlen(skb);
int pos = 0;
- int i, copy = start - offset;
+ int i, copy = end - offset;
/* Copy header. */
if (copy > 0) {
@@ -344,11 +336,9 @@ static int skb_copy_and_csum_datagram(co
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
__wsum csum2;
int err = 0;
@@ -360,8 +350,7 @@ static int skb_copy_and_csum_datagram(co
copy = len;
vaddr = kmap(page);
csum2 = csum_and_copy_to_user(vaddr +
- frag->page_offset +
- offset - start,
+ frag->page_offset,
to, copy, 0, &err);
kunmap(page);
if (err)
@@ -373,24 +362,20 @@ static int skb_copy_and_csum_datagram(co
to += copy;
pos += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list=list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
__wsum csum2 = 0;
if (copy > len)
copy = len;
- if (skb_copy_and_csum_datagram(list,
- offset - start,
+ if (skb_copy_and_csum_datagram(list, 0,
to, copy,
&csum2))
goto fault;
@@ -401,7 +386,6 @@ static int skb_copy_and_csum_datagram(co
to += copy;
pos += copy;
}
- start = end;
}
}
if (!len)
--- linux-2.6.21-rc4.orig/net/core/user_dma.c 2007-02-21 08:36:31.000000000
+0100
+++ linux-2.6.21-rc4/net/core/user_dma.c 2007-03-20 07:16:27.000000000
+0100
@@ -49,8 +49,8 @@ int dma_skb_copy_datagram_iovec(struct d
struct sk_buff *skb, int offset, struct iovec *to,
size_t len, struct dma_pinned_list *pinned_list)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
dma_cookie_t cookie = 0;
/* Copy header. */
@@ -69,11 +69,9 @@ int dma_skb_copy_datagram_iovec(struct d
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
copy = end - offset;
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -82,8 +80,8 @@ int dma_skb_copy_datagram_iovec(struct d
if (copy > len)
copy = len;
- cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
page,
- frag->page_offset + offset - start,
copy);
+ cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
+ page, frag->page_offset, copy);
if (cookie < 0)
goto fault;
len -= copy;
@@ -91,25 +89,21 @@ int dma_skb_copy_datagram_iovec(struct d
goto end;
offset += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
copy = end - offset;
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_skb_copy_datagram_iovec(chan, list,
- offset - start, to, copy,
- pinned_list);
+ 0, to, copy, pinned_list);
if (cookie < 0)
goto fault;
len -= copy;
@@ -117,7 +111,6 @@ int dma_skb_copy_datagram_iovec(struct d
goto end;
offset += copy;
}
- start = end;
}
}
--- linux-2.6.21-rc4.orig/net/xfrm/xfrm_algo.c 2007-03-19 21:34:08.000000000
+0100
+++ linux-2.6.21-rc4/net/xfrm/xfrm_algo.c 2007-03-19 21:41:59.000000000
+0100
@@ -532,8 +532,8 @@ EXPORT_SYMBOL_GPL(xfrm_count_enc_support
int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc,
int offset, int len, icv_update_fn_t icv_update)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
int err;
struct scatterlist sg;
@@ -556,11 +556,9 @@ int skb_icv_walk(const struct sk_buff *s
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -568,7 +566,7 @@ int skb_icv_walk(const struct sk_buff *s
copy = len;
sg.page = frag->page;
- sg.offset = frag->page_offset + offset-start;
+ sg.offset = frag->page_offset;
sg.length = copy;
err = icv_update(desc, &sg, copy);
@@ -579,22 +577,19 @@ int skb_icv_walk(const struct sk_buff *s
return 0;
offset += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- err = skb_icv_walk(list, desc, offset-start,
+ err = skb_icv_walk(list, desc, 0,
copy, icv_update);
if (unlikely(err))
return err;
@@ -602,7 +597,6 @@ int skb_icv_walk(const struct sk_buff *s
return 0;
offset += copy;
}
- start = end;
}
}
BUG_ON(len);
@@ -617,8 +611,8 @@ EXPORT_SYMBOL_GPL(skb_icv_walk);
int
skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
{
- int start = skb_headlen(skb);
- int i, copy = start - offset;
+ int end = skb_headlen(skb);
+ int i, copy = end - offset;
int elt = 0;
if (copy > 0) {
@@ -634,45 +628,39 @@ skb_to_sgvec(struct sk_buff *skb, struct
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
if (copy > len)
copy = len;
sg[elt].page = frag->page;
- sg[elt].offset = frag->page_offset+offset-start;
+ sg[elt].offset = frag->page_offset;
sg[elt].length = copy;
elt++;
if (!(len -= copy))
return elt;
offset += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- elt += skb_to_sgvec(list, sg+elt, offset -
start, copy);
+ elt += skb_to_sgvec(list, sg+elt, 0, copy);
if ((len -= copy) == 0)
return elt;
offset += copy;
}
- start = end;
}
}
BUG_ON(len);
--- linux-2.6.21-rc4.orig/net/appletalk/ddp.c 2007-02-21 08:36:30.000000000
+0100
+++ linux-2.6.21-rc4/net/appletalk/ddp.c 2007-03-19 21:40:07.000000000
+0100
@@ -937,11 +937,11 @@ static unsigned long atalk_sum_partial(c
static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset,
int len, unsigned long sum)
{
- int start = skb_headlen(skb);
+ int end = skb_headlen(skb);
int i, copy;
/* checksum stuff in header space */
- if ( (copy = start - offset) > 0) {
+ if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
sum = atalk_sum_partial(skb->data + offset, copy, sum);
@@ -953,11 +953,9 @@ static unsigned long atalk_sum_skb(const
/* checksum stuff in frags */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- int end;
+ BUG_TRAP(len >= 0);
- BUG_TRAP(start <= offset + len);
-
- end = start + skb_shinfo(skb)->frags[i].size;
+ end = offset + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
u8 *vaddr;
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -965,36 +963,31 @@ static unsigned long atalk_sum_skb(const
if (copy > len)
copy = len;
vaddr = kmap_skb_frag(frag);
- sum = atalk_sum_partial(vaddr + frag->page_offset +
- offset - start, copy, sum);
+ sum = atalk_sum_partial(vaddr + frag->page_offset,
+ copy, sum);
kunmap_skb_frag(vaddr);
if (!(len -= copy))
return sum;
offset += copy;
}
- start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- int end;
-
- BUG_TRAP(start <= offset + len);
+ BUG_TRAP(len >= 0);
- end = start + list->len;
+ end = offset + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
- sum = atalk_sum_skb(list, offset - start,
- copy, sum);
+ sum = atalk_sum_skb(list, 0, copy, sum);
if ((len -= copy) == 0)
return sum;
offset += copy;
}
- start = end;
}
}
--
Jean Delvare
Suse L3
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