net: refactor tcp splice receive path to improve readability
- move all of the details on offsets, lengths and buffers into a single function instead of doing these operation from multiple places - use a bottom up approach: try to avoid details in the high level functions, introduce them gradually as we go deeper in the function call stack With helpful feedback from Jarek Poplawski. Signed-off-by: Octavian Purdila <opurdila@ixiacom.com> Acked-by: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Octavian Purdila
David S. Miller
parent
b9e4085768
commit
2870c43d17
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@ -1282,114 +1282,83 @@ static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,
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return 0;
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}
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/*
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* Map linear and fragment data from the skb to spd. Returns number of
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* pages mapped.
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*/
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static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
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unsigned int *total_len,
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struct splice_pipe_desc *spd)
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static inline void __segment_seek(struct page **page, unsigned int *poff,
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unsigned int *plen, unsigned int off)
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{
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unsigned int nr_pages = spd->nr_pages;
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unsigned int poff, plen, len, toff, tlen;
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int headlen, seg, error = 0;
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*poff += off;
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*page += *poff / PAGE_SIZE;
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*poff = *poff % PAGE_SIZE;
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*plen -= off;
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}
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toff = *offset;
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tlen = *total_len;
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if (!tlen) {
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error = 1;
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goto err;
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static inline int __splice_segment(struct page *page, unsigned int poff,
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unsigned int plen, unsigned int *off,
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unsigned int *len, struct sk_buff *skb,
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struct splice_pipe_desc *spd)
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{
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if (!*len)
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return 1;
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/* skip this segment if already processed */
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if (*off >= plen) {
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*off -= plen;
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return 0;
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}
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/* ignore any bits we already processed */
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if (*off) {
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__segment_seek(&page, &poff, &plen, *off);
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*off = 0;
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}
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do {
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unsigned int flen = min(*len, plen);
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/* the linear region may spread across several pages */
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flen = min_t(unsigned int, flen, PAGE_SIZE - poff);
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if (spd_fill_page(spd, page, flen, poff, skb))
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return 1;
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__segment_seek(&page, &poff, &plen, flen);
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*len -= flen;
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} while (*len && plen);
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return 0;
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}
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/*
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* Map linear and fragment data from the skb to spd. It reports failure if the
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* pipe is full or if we already spliced the requested length.
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*/
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int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
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unsigned int *len,
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struct splice_pipe_desc *spd)
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{
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int seg;
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/*
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* if the offset is greater than the linear part, go directly to
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* the fragments.
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* map the linear part
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*/
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headlen = skb_headlen(skb);
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if (toff >= headlen) {
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toff -= headlen;
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goto map_frag;
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}
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/*
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* first map the linear region into the pages/partial map, skipping
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* any potential initial offset.
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*/
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len = 0;
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while (len < headlen) {
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void *p = skb->data + len;
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poff = (unsigned long) p & (PAGE_SIZE - 1);
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plen = min_t(unsigned int, headlen - len, PAGE_SIZE - poff);
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len += plen;
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if (toff) {
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if (plen <= toff) {
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toff -= plen;
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continue;
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}
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plen -= toff;
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poff += toff;
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toff = 0;
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}
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plen = min(plen, tlen);
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if (!plen)
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break;
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/*
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* just jump directly to update and return, no point
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* in going over fragments when the output is full.
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*/
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error = spd_fill_page(spd, virt_to_page(p), plen, poff, skb);
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if (error)
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goto done;
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tlen -= plen;
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}
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if (__splice_segment(virt_to_page(skb->data),
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(unsigned long) skb->data & (PAGE_SIZE - 1),
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skb_headlen(skb),
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offset, len, skb, spd))
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return 1;
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/*
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* then map the fragments
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*/
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map_frag:
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for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
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const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
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plen = f->size;
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poff = f->page_offset;
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if (toff) {
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if (plen <= toff) {
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toff -= plen;
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continue;
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}
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plen -= toff;
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poff += toff;
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toff = 0;
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}
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plen = min(plen, tlen);
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if (!plen)
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break;
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error = spd_fill_page(spd, f->page, plen, poff, skb);
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if (error)
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break;
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tlen -= plen;
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if (__splice_segment(f->page, f->page_offset, f->size,
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offset, len, skb, spd))
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return 1;
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}
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done:
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if (spd->nr_pages - nr_pages) {
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*offset = 0;
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*total_len = tlen;
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return 0;
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}
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err:
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/* update the offset to reflect the linear part skip, if any */
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if (!error)
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*offset = toff;
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return error;
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return 0;
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}
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/*
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