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Date: Tue, 28 Aug 2018 16:33:57 -0700
From: Doron Roberts-Kedes <doronrk@...com>
To: "David S . Miller" <davem@...emloft.net>
CC: Aviad Yehezkel <aviadye@...lanox.com>,
Vakul Garg <vakul.garg@....com>,
Dave Watson <davejwatson@...com>,
Boris Pismenny <borisp@...lanox.com>, <netdev@...r.kernel.org>,
Doron Roberts-Kedes <doronrk@...com>
Subject: [PATCH net-next,v5] net/tls: Calculate nsg for zerocopy path without skb_cow_data.
decrypt_skb fails if the number of sg elements required to map it
is greater than MAX_SKB_FRAGS. nsg must always be calculated, but
skb_cow_data adds unnecessary memcpy's for the zerocopy case.
The new function skb_nsg calculates the number of scatterlist elements
required to map the skb without the extra overhead of skb_cow_data.
This patch reduces memcpy by 50% on my encrypted NBD benchmarks.
Reported-by: Vakul Garg <Vakul.garg@....com>
Reviewed-by: Vakul Garg <Vakul.garg@....com>
Tested-by: Vakul Garg <Vakul.garg@....com>
Signed-off-by: Doron Roberts-Kedes <doronrk@...com>
---
net/tls/tls_sw.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 79 insertions(+), 1 deletion(-)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 52fbe727d7c1..4ba62cd00a94 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -43,6 +43,82 @@
#define MAX_IV_SIZE TLS_CIPHER_AES_GCM_128_IV_SIZE
+static int __skb_nsg(struct sk_buff *skb, int offset, int len,
+ unsigned int recursion_level)
+{
+ int start = skb_headlen(skb);
+ int i, chunk = start - offset;
+ struct sk_buff *frag_iter;
+ int elt = 0;
+
+ if (unlikely(recursion_level >= 24))
+ return -EMSGSIZE;
+
+ if (chunk > 0) {
+ if (chunk > len)
+ chunk = len;
+ elt++;
+ len -= chunk;
+ if (len == 0)
+ return elt;
+ offset += chunk;
+ }
+
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ int end;
+
+ WARN_ON(start > offset + len);
+
+ end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
+ chunk = end - offset;
+ if (chunk > 0) {
+ if (chunk > len)
+ chunk = len;
+ elt++;
+ len -= chunk;
+ if (len == 0)
+ return elt;
+ offset += chunk;
+ }
+ start = end;
+ }
+
+ if (unlikely(skb_has_frag_list(skb))) {
+ skb_walk_frags(skb, frag_iter) {
+ int end, ret;
+
+ WARN_ON(start > offset + len);
+
+ end = start + frag_iter->len;
+ chunk = end - offset;
+ if (chunk > 0) {
+ if (chunk > len)
+ chunk = len;
+ ret = __skb_nsg(frag_iter, offset - start, chunk,
+ recursion_level + 1);
+ if (unlikely(ret < 0))
+ return ret;
+ elt += ret;
+ len -= chunk;
+ if (len == 0)
+ return elt;
+ offset += chunk;
+ }
+ start = end;
+ }
+ }
+ BUG_ON(len);
+ return elt;
+}
+
+/* Return the number of scatterlist elements required to completely map the
+ * skb, or -EMSGSIZE if the recursion depth is exceeded.
+ */
+static int skb_nsg(struct sk_buff *skb, int offset, int len)
+{
+ return __skb_nsg(skb, offset, len, 0);
+}
+
static int tls_do_decryption(struct sock *sk,
struct scatterlist *sgin,
struct scatterlist *sgout,
@@ -678,12 +754,14 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
n_sgout = iov_iter_npages(out_iov, INT_MAX) + 1;
else
n_sgout = sg_nents(out_sg);
+ n_sgin = skb_nsg(skb, rxm->offset + tls_ctx->rx.prepend_size,
+ rxm->full_len - tls_ctx->rx.prepend_size);
} else {
n_sgout = 0;
*zc = false;
+ n_sgin = skb_cow_data(skb, 0, &unused);
}
- n_sgin = skb_cow_data(skb, 0, &unused);
if (n_sgin < 1)
return -EBADMSG;
--
2.17.1
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