net: add skb_frag_foreach_page and use with kmap_atomic
Skb frags may contain compound pages. Various operations map frags
temporarily using kmap_atomic, but this function works on single
pages, not whole compound pages. The distinction is only relevant
for high mem pages that require temporary mappings.
Introduce a looping mechanism that for compound highmem pages maps
one page at a time, does not change behavior on other pages.
Use the loop in the kmap_atomic callers in net/core/skbuff.c.
Verified by triggering skb_copy_bits with
tcpdump -n -c 100 -i ${DEV} -w /dev/null &
netperf -t TCP_STREAM -H ${HOST}
and by triggering __skb_checksum with
ethtool -K ${DEV} tx off
repeated the tests with looping on a non-highmem platform
(x86_64) by making skb_frag_must_loop always return true.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9c0e015..0f0933b 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -938,8 +938,10 @@
struct ubuf_info *uarg = skb_shinfo(skb)->destructor_arg;
for (i = 0; i < num_frags; i++) {
- u8 *vaddr;
skb_frag_t *f = &skb_shinfo(skb)->frags[i];
+ u32 p_off, p_len, copied;
+ struct page *p;
+ u8 *vaddr;
page = alloc_page(gfp_mask);
if (!page) {
@@ -950,10 +952,15 @@
}
return -ENOMEM;
}
- vaddr = kmap_atomic(skb_frag_page(f));
- memcpy(page_address(page),
- vaddr + f->page_offset, skb_frag_size(f));
- kunmap_atomic(vaddr);
+
+ skb_frag_foreach_page(f, f->page_offset, skb_frag_size(f),
+ p, p_off, p_len, copied) {
+ vaddr = kmap_atomic(p);
+ memcpy(page_address(page) + copied, vaddr + p_off,
+ p_len);
+ kunmap_atomic(vaddr);
+ }
+
set_page_private(page, (unsigned long)head);
head = page;
}
@@ -1753,16 +1760,20 @@
end = start + skb_frag_size(f);
if ((copy = end - offset) > 0) {
+ u32 p_off, p_len, copied;
+ struct page *p;
u8 *vaddr;
if (copy > len)
copy = len;
- vaddr = kmap_atomic(skb_frag_page(f));
- memcpy(to,
- vaddr + f->page_offset + offset - start,
- copy);
- kunmap_atomic(vaddr);
+ skb_frag_foreach_page(f,
+ f->page_offset + offset - start,
+ copy, p, p_off, p_len, copied) {
+ vaddr = kmap_atomic(p);
+ memcpy(to + copied, vaddr + p_off, p_len);
+ kunmap_atomic(vaddr);
+ }
if ((len -= copy) == 0)
return 0;
@@ -2122,15 +2133,20 @@
end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
+ u32 p_off, p_len, copied;
+ struct page *p;
u8 *vaddr;
if (copy > len)
copy = len;
- vaddr = kmap_atomic(skb_frag_page(frag));
- memcpy(vaddr + frag->page_offset + offset - start,
- from, copy);
- kunmap_atomic(vaddr);
+ skb_frag_foreach_page(frag,
+ frag->page_offset + offset - start,
+ copy, p, p_off, p_len, copied) {
+ vaddr = kmap_atomic(p);
+ memcpy(vaddr + p_off, from + copied, p_len);
+ kunmap_atomic(vaddr);
+ }
if ((len -= copy) == 0)
return 0;
@@ -2195,20 +2211,27 @@
end = start + skb_frag_size(frag);
if ((copy = end - offset) > 0) {
+ u32 p_off, p_len, copied;
+ struct page *p;
__wsum csum2;
u8 *vaddr;
if (copy > len)
copy = len;
- vaddr = kmap_atomic(skb_frag_page(frag));
- csum2 = ops->update(vaddr + frag->page_offset +
- offset - start, copy, 0);
- kunmap_atomic(vaddr);
- csum = ops->combine(csum, csum2, pos, copy);
+
+ skb_frag_foreach_page(frag,
+ frag->page_offset + offset - start,
+ copy, p, p_off, p_len, copied) {
+ vaddr = kmap_atomic(p);
+ csum2 = ops->update(vaddr + p_off, p_len, 0);
+ kunmap_atomic(vaddr);
+ csum = ops->combine(csum, csum2, pos, p_len);
+ pos += p_len;
+ }
+
if (!(len -= copy))
return csum;
offset += copy;
- pos += copy;
}
start = end;
}
@@ -2281,24 +2304,31 @@
end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
if ((copy = end - offset) > 0) {
+ skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ u32 p_off, p_len, copied;
+ struct page *p;
__wsum csum2;
u8 *vaddr;
- skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
if (copy > len)
copy = len;
- vaddr = kmap_atomic(skb_frag_page(frag));
- csum2 = csum_partial_copy_nocheck(vaddr +
- frag->page_offset +
- offset - start, to,
- copy, 0);
- kunmap_atomic(vaddr);
- csum = csum_block_add(csum, csum2, pos);
+
+ skb_frag_foreach_page(frag,
+ frag->page_offset + offset - start,
+ copy, p, p_off, p_len, copied) {
+ vaddr = kmap_atomic(p);
+ csum2 = csum_partial_copy_nocheck(vaddr + p_off,
+ to + copied,
+ p_len, 0);
+ kunmap_atomic(vaddr);
+ csum = csum_block_add(csum, csum2, pos);
+ pos += p_len;
+ }
+
if (!(len -= copy))
return csum;
offset += copy;
to += copy;
- pos += copy;
}
start = end;
}