From 2870c43d1795bcb40b12bad6456f07ad8e64b3de Mon Sep 17 00:00:00 2001 From: Octavian Purdila Date: Tue, 15 Jul 2008 00:49:11 -0700 Subject: [PATCH] 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 Acked-by: Jarek Poplawski Signed-off-by: David S. Miller --- net/core/skbuff.c | 153 ++++++++++++++++++---------------------------- 1 file changed, 61 insertions(+), 92 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 50a853f7cd8e..48a43727d12f 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1282,114 +1282,83 @@ static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page, return 0; } -/* - * Map linear and fragment data from the skb to spd. Returns number of - * pages mapped. - */ -static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset, - unsigned int *total_len, - struct splice_pipe_desc *spd) -{ - unsigned int nr_pages = spd->nr_pages; - unsigned int poff, plen, len, toff, tlen; - int headlen, seg, error = 0; - - toff = *offset; - tlen = *total_len; - if (!tlen) { - error = 1; - goto err; +static inline void __segment_seek(struct page **page, unsigned int *poff, + unsigned int *plen, unsigned int off) +{ + *poff += off; + *page += *poff / PAGE_SIZE; + *poff = *poff % PAGE_SIZE; + *plen -= off; +} + +static inline int __splice_segment(struct page *page, unsigned int poff, + unsigned int plen, unsigned int *off, + unsigned int *len, struct sk_buff *skb, + struct splice_pipe_desc *spd) +{ + if (!*len) + return 1; + + /* skip this segment if already processed */ + if (*off >= plen) { + *off -= plen; + return 0; } - /* - * if the offset is greater than the linear part, go directly to - * the fragments. - */ - headlen = skb_headlen(skb); - if (toff >= headlen) { - toff -= headlen; - goto map_frag; + /* ignore any bits we already processed */ + if (*off) { + __segment_seek(&page, &poff, &plen, *off); + *off = 0; } - /* - * first map the linear region into the pages/partial map, skipping - * any potential initial offset. - */ - len = 0; - while (len < headlen) { - void *p = skb->data + len; - - poff = (unsigned long) p & (PAGE_SIZE - 1); - plen = min_t(unsigned int, headlen - len, PAGE_SIZE - poff); - len += plen; - - if (toff) { - if (plen <= toff) { - toff -= plen; - continue; - } - plen -= toff; - poff += toff; - toff = 0; - } + do { + unsigned int flen = min(*len, plen); - plen = min(plen, tlen); - if (!plen) - break; + /* the linear region may spread across several pages */ + flen = min_t(unsigned int, flen, PAGE_SIZE - poff); - /* - * just jump directly to update and return, no point - * in going over fragments when the output is full. - */ - error = spd_fill_page(spd, virt_to_page(p), plen, poff, skb); - if (error) - goto done; + if (spd_fill_page(spd, page, flen, poff, skb)) + return 1; - tlen -= plen; - } + __segment_seek(&page, &poff, &plen, flen); + *len -= flen; + + } while (*len && plen); + + return 0; +} + +/* + * Map linear and fragment data from the skb to spd. It reports failure if the + * pipe is full or if we already spliced the requested length. + */ +int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset, + unsigned int *len, + struct splice_pipe_desc *spd) +{ + int seg; + + /* + * map the linear part + */ + if (__splice_segment(virt_to_page(skb->data), + (unsigned long) skb->data & (PAGE_SIZE - 1), + skb_headlen(skb), + offset, len, skb, spd)) + return 1; /* * then map the fragments */ -map_frag: for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) { const skb_frag_t *f = &skb_shinfo(skb)->frags[seg]; - plen = f->size; - poff = f->page_offset; - - if (toff) { - if (plen <= toff) { - toff -= plen; - continue; - } - plen -= toff; - poff += toff; - toff = 0; - } - - plen = min(plen, tlen); - if (!plen) - break; - - error = spd_fill_page(spd, f->page, plen, poff, skb); - if (error) - break; - - tlen -= plen; + if (__splice_segment(f->page, f->page_offset, f->size, + offset, len, skb, spd)) + return 1; } -done: - if (spd->nr_pages - nr_pages) { - *offset = 0; - *total_len = tlen; - return 0; - } -err: - /* update the offset to reflect the linear part skip, if any */ - if (!error) - *offset = toff; - return error; + return 0; } /* -- 2.20.1