net: splice: avoid high order page splitting

splice() can handle pages of any order, but network code tries hard to
split them in PAGE_SIZE units. Not quite successfully anyway, as
__splice_segment() assumed poff < PAGE_SIZE. This is true for
the skb->data part, not necessarily for the fragments.

This patch removes this logic to give the pages as they are in the skb.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bc96100..b03fc0c 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1707,20 +1707,6 @@ static bool spd_fill_page(struct splice_pipe_desc *spd,
        return false;
 }
 
-static inline void __segment_seek(struct page **page, unsigned int *poff,
-                                 unsigned int *plen, unsigned int off)
-{
-       unsigned long n;
-
-       *poff += off;
-       n = *poff / PAGE_SIZE;
-       if (n)
-               *page = nth_page(*page, n);
-
-       *poff = *poff % PAGE_SIZE;
-       *plen -= off;
-}
-
 static bool __splice_segment(struct page *page, unsigned int poff,
                             unsigned int plen, unsigned int *off,
                             unsigned int *len, struct sk_buff *skb,
@@ -1728,6 +1714,8 @@ static bool __splice_segment(struct page *page, unsigned int poff,
                             struct sock *sk,
                             struct pipe_inode_info *pipe)
 {
+       unsigned int flen;
+
        if (!*len)
                return true;
 
@@ -1738,24 +1726,16 @@ static bool __splice_segment(struct page *page, unsigned int poff,
        }
 
        /* ignore any bits we already processed */
-       if (*off) {
-               __segment_seek(&page, &poff, &plen, *off);
-               *off = 0;
-       }
-
-       do {
-               unsigned int flen = min(*len, plen);
+       poff += *off;
+       plen -= *off;
+       *off = 0;
 
-               /* the linear region may spread across several pages  */
-               flen = min_t(unsigned int, flen, PAGE_SIZE - poff);
+       flen = min(*len, plen);
 
-               if (spd_fill_page(spd, pipe, page, &flen, poff, skb, linear, sk))
-                       return true;
-
-               __segment_seek(&page, &poff, &plen, flen);
-               *len -= flen;
+       if (spd_fill_page(spd, pipe, page, &flen, poff, skb, linear, sk))
+               return true;
 
-       } while (*len && plen);
+       *len -= flen;
 
        return false;
 }