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>

1 files changed, 9 insertions, 29 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3ab989b0de42..f5dfdf7727c4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1706,20 +1706,6 @@ 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,
@@ -1727,6 +1713,8 @@ 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;
 
@@ -1737,24 +1725,16 @@ 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;
 }