1 files changed, 47 insertions, 6 deletions

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 5709bad28329..cd7a6cfcab03 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -555,6 +555,47 @@ u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
         return rds_ib_get_ack(ic);
 }
 
+static struct rds_header *rds_ib_get_header(struct rds_connection *conn,
+                                            struct rds_ib_recv_work *recv,
+                                            u32 data_len)
+{
+        struct rds_ib_connection *ic = conn->c_transport_data;
+        void *hdr_buff = &ic->i_recv_hdrs[recv - ic->i_recvs];
+        void *addr;
+        u32 misplaced_hdr_bytes;
+
+        /*
+         * Support header at the front (RDS 3.1+) as well as header-at-end.
+         *
+         * Cases:
+         * 1) header all in header buff (great!)
+         * 2) header all in data page (copy all to header buff)
+         * 3) header split across hdr buf + data page
+         *    (move bit in hdr buff to end before copying other bit from data page)
+         */
+        if (conn->c_version > RDS_PROTOCOL_3_0 || data_len == RDS_FRAG_SIZE)
+                return hdr_buff;
+
+        if (data_len <= (RDS_FRAG_SIZE - sizeof(struct rds_header))) {
+                addr = kmap_atomic(recv->r_frag->f_page, KM_SOFTIRQ0);
+                memcpy(hdr_buff,
+                       addr + recv->r_frag->f_offset + data_len,
+                       sizeof(struct rds_header));
+                kunmap_atomic(addr, KM_SOFTIRQ0);
+                return hdr_buff;
+        }
+
+        misplaced_hdr_bytes = (sizeof(struct rds_header) - (RDS_FRAG_SIZE - data_len));
+
+        memmove(hdr_buff + misplaced_hdr_bytes, hdr_buff, misplaced_hdr_bytes);
+
+        addr = kmap_atomic(recv->r_frag->f_page, KM_SOFTIRQ0);
+        memcpy(hdr_buff, addr + recv->r_frag->f_offset + data_len,
+               sizeof(struct rds_header) - misplaced_hdr_bytes);
+        kunmap_atomic(addr, KM_SOFTIRQ0);
+        return hdr_buff;
+}
+
 /*
  * It's kind of lame that we're copying from the posted receive pages into
  * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
@@ -645,7 +686,7 @@ struct rds_ib_ack_state {
 };
 
 static void rds_ib_process_recv(struct rds_connection *conn,
-                                struct rds_ib_recv_work *recv, u32 byte_len,
+                                struct rds_ib_recv_work *recv, u32 data_len,
                                 struct rds_ib_ack_state *state)
 {
         struct rds_ib_connection *ic = conn->c_transport_data;
@@ -655,9 +696,9 @@ static void rds_ib_process_recv(struct rds_connection *conn,
         /* XXX shut down the connection if port 0,0 are seen? */
 
         rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
-                 byte_len);
+                 data_len);
 
-        if (byte_len < sizeof(struct rds_header)) {
+        if (data_len < sizeof(struct rds_header)) {
                 rds_ib_conn_error(conn, "incoming message "
                        "from %pI4 didn't inclue a "
                        "header, disconnecting and "
@@ -665,9 +706,9 @@ static void rds_ib_process_recv(struct rds_connection *conn,
                        &conn->c_faddr);
                 return;
         }
-        byte_len -= sizeof(struct rds_header);
+        data_len -= sizeof(struct rds_header);
 
-        ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
+        ihdr = rds_ib_get_header(conn, recv, data_len);
 
         /* Validate the checksum. */
         if (!rds_message_verify_checksum(ihdr)) {
@@ -687,7 +728,7 @@ static void rds_ib_process_recv(struct rds_connection *conn,
         if (ihdr->h_credit)
                 rds_ib_send_add_credits(conn, ihdr->h_credit);
 
-        if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && byte_len == 0) {
+        if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
                 /* This is an ACK-only packet. The fact that it gets
                  * special treatment here is that historically, ACKs
                  * were rather special beasts.