[bpf-next PATCH 04/16] net: generalize sk_alloc_sg to work with scatterlist rings

John Fastabend
2018-03-05T19:51:21Z

The current implementation of sk_alloc_sg expects scatterlist to always
start at entry 0 and complete at entry MAX_SKB_FRAGS.

Future patches will want to support starting at arbitrary offset into
scatterlist so add an additional sg_start parameters and then default
to the current values in TLS code paths.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
include/net/sock.h | 2 +-
net/core/sock.c | 27 ++++++++++++++++-----------
net/tls/tls_sw.c | 4 ++--
3 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 447150c..b7c75e0 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2142,7 +2142,7 @@ static inline struct page_frag *sk_page_frag(struct sock *sk)
bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);

int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
- int *sg_num_elem, unsigned int *sg_size,
+ int sg_start, int *sg_curr, unsigned int *sg_size,
int first_coalesce);

/*
diff --git a/net/core/sock.c b/net/core/sock.c
index 4bda3e9..d14f64b 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2239,19 +2239,20 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
EXPORT_SYMBOL(sk_page_frag_refill);

int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
- int *sg_num_elem, unsigned int *sg_size,
+ int sg_start, int *sg_curr_index, unsigned int *sg_curr_size,
int first_coalesce)
{
+ int sg_curr = *sg_curr_index, use = 0, rc = 0;
+ unsigned int size = *sg_curr_size;
struct page_frag *pfrag;
- unsigned int size = *sg_size;
- int num_elem = *sg_num_elem, use = 0, rc = 0;
struct scatterlist *sge;
- unsigned int orig_offset;

len -= size;
pfrag = sk_page_frag(sk);

while (len > 0) {
+ unsigned int orig_offset;
+
if (!sk_page_frag_refill(sk, pfrag)) {
rc = -ENOMEM;
goto out;
@@ -2269,17 +2270,21 @@ int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
orig_offset = pfrag->offset;
pfrag->offset += use;

- sge = sg + num_elem - 1;
- if (num_elem > first_coalesce && sg_page(sg) == pfrag->page &&
+ sge = sg + sg_curr - 1;
+ if (sg_curr > first_coalesce && sg_page(sg) == pfrag->page &&
sg->offset + sg->length == orig_offset) {
sg->length += use;
} else {
- sge++;
+ sge = sg + sg_curr;
sg_unmark_end(sge);
sg_set_page(sge, pfrag->page, use, orig_offset);
get_page(pfrag->page);
- ++num_elem;
- if (num_elem == MAX_SKB_FRAGS) {
+ sg_curr++;
+
+ if (sg_curr == MAX_SKB_FRAGS)
+ sg_curr = 0;
+
+ if (sg_curr == sg_start) {
rc = -ENOSPC;
break;
}
@@ -2288,8 +2293,8 @@ int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
len -= use;
}
out:
- *sg_size = size;
- *sg_num_elem = num_elem;
+ *sg_curr_size = size;
+ *sg_curr_index = sg_curr;
return rc;
}
EXPORT_SYMBOL(sk_alloc_sg);
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 0fc8a24..057a558 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -94,7 +94,7 @@ static int alloc_encrypted_sg(struct sock *sk, int len)
int rc = 0;

rc = sk_alloc_sg(sk, len,
- ctx->sg_encrypted_data,
+ ctx->sg_encrypted_data, 0,
&ctx->sg_encrypted_num_elem,
&ctx->sg_encrypted_size, 0);

@@ -107,7 +107,7 @@ static int alloc_plaintext_sg(struct sock *sk, int len)
struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx);
int rc = 0;

- rc = sk_alloc_sg(sk, len, ctx->sg_plaintext_data,
+ rc = sk_alloc_sg(sk, len, ctx->sg_plaintext_data, 0,
&ctx->sg_plaintext_num_elem, &ctx->sg_plaintext_size,
tls_ctx->pending_open_record_frags);