[PATCH] [NET]: Unmap fragment page once iterator is done

From: Wedson Almeida Filho
Date: Fri Jun 14 2013 - 20:55:42 EST

Callers of skb_seq_read() are currently forced to call skb_abort_seq_read()
even when consuming all the data because the last call to skb_seq_read (the
one that returns 0 to indicate the end) fails to unmap the last fragment page.

With this patch callers will be allowed to traverse the SKB data by calling
skb_prepare_seq_read() once and repeatedly calling skb_seq_read() as originally
intended (and documented in the original commit 677e90eda), that is, only call
skb_abort_seq_read() if the sequential read is actually aborted.

Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx>
net/core/skbuff.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index cfd777b..26ea1cf 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2554,8 +2554,13 @@ unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
unsigned int block_limit, abs_offset = consumed + st->lower_offset;
skb_frag_t *frag;

- if (unlikely(abs_offset >= st->upper_offset))
+ if (unlikely(abs_offset >= st->upper_offset)) {
+ if (st->frag_data) {
+ kunmap_atomic(st->frag_data);
+ st->frag_data = NULL;
+ }
return 0;
+ }

block_limit = skb_headlen(st->cur_skb) + st->stepped_offset;

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