netdev - [PATCH net-next 1/6] net: sockmap: use bitmap for copy info

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Date:   Sun,  6 Oct 2019 21:09:27 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        davejwatson@...com, borisp@...lanox.com, aviadye@...lanox.com,
        john.fastabend@...il.com, daniel@...earbox.net,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>
Subject: [PATCH net-next 1/6] net: sockmap: use bitmap for copy info

Don't use bool array in struct sk_msg_sg, save 12 bytes.

Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@...ronome.com>
---
 include/linux/skmsg.h | 12 ++++++++----
 net/core/filter.c     |  4 ++--
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index e4b3fb4bb77c..fe80d537945d 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -28,13 +28,14 @@ struct sk_msg_sg {
 	u32				end;
 	u32				size;
 	u32				copybreak;
-	bool				copy[MAX_MSG_FRAGS];
+	unsigned long			copy;
 	/* The extra element is used for chaining the front and sections when
 	 * the list becomes partitioned (e.g. end < start). The crypto APIs
 	 * require the chaining.
 	 */
 	struct scatterlist		data[MAX_MSG_FRAGS + 1];
 };
+static_assert(BITS_PER_LONG >= MAX_MSG_FRAGS);
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
 struct sk_msg {
@@ -227,7 +228,7 @@ static inline void sk_msg_compute_data_pointers(struct sk_msg *msg)
 {
 	struct scatterlist *sge = sk_msg_elem(msg, msg->sg.start);
 
-	if (msg->sg.copy[msg->sg.start]) {
+	if (test_bit(msg->sg.start, &msg->sg.copy)) {
 		msg->data = NULL;
 		msg->data_end = NULL;
 	} else {
@@ -246,7 +247,7 @@ static inline void sk_msg_page_add(struct sk_msg *msg, struct page *page,
 	sg_set_page(sge, page, len, offset);
 	sg_unmark_end(sge);
 
-	msg->sg.copy[msg->sg.end] = true;
+	__set_bit(msg->sg.end, &msg->sg.copy);
 	msg->sg.size += len;
 	sk_msg_iter_next(msg, end);
 }
@@ -254,7 +255,10 @@ static inline void sk_msg_page_add(struct sk_msg *msg, struct page *page,
 static inline void sk_msg_sg_copy(struct sk_msg *msg, u32 i, bool copy_state)
 {
 	do {
-		msg->sg.copy[i] = copy_state;
+		if (copy_state)
+			__set_bit(i, &msg->sg.copy);
+		else
+			__clear_bit(i, &msg->sg.copy);
 		sk_msg_iter_var_next(i);
 		if (i == msg->sg.end)
 			break;
diff --git a/net/core/filter.c b/net/core/filter.c
index ed6563622ce3..46196e212413 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2245,7 +2245,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 	 * account for the headroom.
 	 */
 	bytes_sg_total = start - offset + bytes;
-	if (!msg->sg.copy[i] && bytes_sg_total <= len)
+	if (!test_bit(i, &msg->sg.copy) && bytes_sg_total <= len)
 		goto out;
 
 	/* At this point we need to linearize multiple scatterlist
@@ -2450,7 +2450,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 	/* Place newly allocated data buffer */
 	sk_mem_charge(msg->sk, len);
 	msg->sg.size += len;
-	msg->sg.copy[new] = false;
+	__clear_bit(new, &msg->sg.copy);
 	sg_set_page(&msg->sg.data[new], page, len + copy, 0);
 	if (rsge.length) {
 		get_page(sg_page(&rsge));
-- 
2.21.0