From c613c209c3f351d47158f728271d0c73b6dd24c6 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Mon, 31 Jul 2017 08:15:47 -0400 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 36 +++++++++++++++++ net/core/skbuff.c | 88 ++++++++++++++++++++++++++++-------------- 2 files changed, 95 insertions(+), 29 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 18e76bf9574e..6f9f1b2715ec 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -345,6 +345,42 @@ static inline void skb_frag_size_sub(skb_frag_t *frag, int delta) frag->size -= delta; } +static inline bool skb_frag_must_loop(struct page *p) +{ +#if defined(CONFIG_HIGHMEM) + if (PageHighMem(p)) + return true; +#endif + return false; +} + +/** + * skb_frag_foreach_page - loop over pages in a fragment + * + * @f: skb frag to operate on + * @f_off: offset from start of f->page.p + * @f_len: length from f_off to loop over + * @p: (temp var) current page + * @p_off: (temp var) offset from start of current page, + * non-zero only on first page. + * @p_len: (temp var) length in current page, + * < PAGE_SIZE only on first and last page. + * @copied: (temp var) length so far, excluding current p_len. + * + * A fragment can hold a compound page, in which case per-page + * operations, notably kmap_atomic, must be called for each + * regular page. + */ +#define skb_frag_foreach_page(f, f_off, f_len, p, p_off, p_len, copied) \ + for (p = skb_frag_page(f) + ((f_off) >> PAGE_SHIFT), \ + p_off = (f_off) & (PAGE_SIZE - 1), \ + p_len = skb_frag_must_loop(p) ? \ + min_t(u32, f_len, PAGE_SIZE - p_off) : f_len, \ + copied = 0; \ + copied < f_len; \ + copied += p_len, p++, p_off = 0, \ + p_len = min_t(u32, f_len - copied, PAGE_SIZE)) \ + #define HAVE_HW_TIME_STAMP /** diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 9c0e015ff3fe..0f0933b338d7 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -938,8 +938,10 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) 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 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) } 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 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) 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 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len) 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 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len, 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 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 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; } -- 2.20.1