1 files changed, 42 insertions, 1 deletions

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 5709bad28329..28bdcdcdbfe9 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
@@ -667,7 +708,7 @@ static void rds_ib_process_recv(struct rds_connection *conn,
         }
         byte_len -= sizeof(struct rds_header);
 
-        ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
+        ihdr = rds_ib_get_header(conn, recv, byte_len);
 
         /* Validate the checksum. */
         if (!rds_message_verify_checksum(ihdr)) {