v4.19.13 snapshot.
diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
new file mode 100644
index 0000000..f3396c6
--- /dev/null
+++ b/fs/dlm/midcomms.c
@@ -0,0 +1,137 @@
+/******************************************************************************
+*******************************************************************************
+**
+** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
+** Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
+**
+** This copyrighted material is made available to anyone wishing to use,
+** modify, copy, or redistribute it subject to the terms and conditions
+** of the GNU General Public License v.2.
+**
+*******************************************************************************
+******************************************************************************/
+
+/*
+ * midcomms.c
+ *
+ * This is the appallingly named "mid-level" comms layer.
+ *
+ * Its purpose is to take packets from the "real" comms layer,
+ * split them up into packets and pass them to the interested
+ * part of the locking mechanism.
+ *
+ * It also takes messages from the locking layer, formats them
+ * into packets and sends them to the comms layer.
+ */
+
+#include "dlm_internal.h"
+#include "lowcomms.h"
+#include "config.h"
+#include "lock.h"
+#include "midcomms.h"
+
+
+static void copy_from_cb(void *dst, const void *base, unsigned offset,
+ unsigned len, unsigned limit)
+{
+ unsigned copy = len;
+
+ if ((copy + offset) > limit)
+ copy = limit - offset;
+ memcpy(dst, base + offset, copy);
+ len -= copy;
+ if (len)
+ memcpy(dst + copy, base, len);
+}
+
+/*
+ * Called from the low-level comms layer to process a buffer of
+ * commands.
+ *
+ * Only complete messages are processed here, any "spare" bytes from
+ * the end of a buffer are saved and tacked onto the front of the next
+ * message that comes in. I doubt this will happen very often but we
+ * need to be able to cope with it and I don't want the task to be waiting
+ * for packets to come in when there is useful work to be done.
+ */
+
+int dlm_process_incoming_buffer(int nodeid, const void *base,
+ unsigned offset, unsigned len, unsigned limit)
+{
+ union {
+ unsigned char __buf[DLM_INBUF_LEN];
+ /* this is to force proper alignment on some arches */
+ union dlm_packet p;
+ } __tmp;
+ union dlm_packet *p = &__tmp.p;
+ int ret = 0;
+ int err = 0;
+ uint16_t msglen;
+ uint32_t lockspace;
+
+ while (len > sizeof(struct dlm_header)) {
+
+ /* Copy just the header to check the total length. The
+ message may wrap around the end of the buffer back to the
+ start, so we need to use a temp buffer and copy_from_cb. */
+
+ copy_from_cb(p, base, offset, sizeof(struct dlm_header),
+ limit);
+
+ msglen = le16_to_cpu(p->header.h_length);
+ lockspace = p->header.h_lockspace;
+
+ err = -EINVAL;
+ if (msglen < sizeof(struct dlm_header))
+ break;
+ if (p->header.h_cmd == DLM_MSG) {
+ if (msglen < sizeof(struct dlm_message))
+ break;
+ } else {
+ if (msglen < sizeof(struct dlm_rcom))
+ break;
+ }
+ err = -E2BIG;
+ if (msglen > dlm_config.ci_buffer_size) {
+ log_print("message size %d from %d too big, buf len %d",
+ msglen, nodeid, len);
+ break;
+ }
+ err = 0;
+
+ /* If only part of the full message is contained in this
+ buffer, then do nothing and wait for lowcomms to call
+ us again later with more data. We return 0 meaning
+ we've consumed none of the input buffer. */
+
+ if (msglen > len)
+ break;
+
+ /* Allocate a larger temp buffer if the full message won't fit
+ in the buffer on the stack (which should work for most
+ ordinary messages). */
+
+ if (msglen > sizeof(__tmp) && p == &__tmp.p) {
+ p = kmalloc(dlm_config.ci_buffer_size, GFP_NOFS);
+ if (p == NULL)
+ return ret;
+ }
+
+ copy_from_cb(p, base, offset, msglen, limit);
+
+ BUG_ON(lockspace != p->header.h_lockspace);
+
+ ret += msglen;
+ offset += msglen;
+ offset &= (limit - 1);
+ len -= msglen;
+
+ dlm_receive_buffer(p, nodeid);
+ }
+
+ if (p != &__tmp.p)
+ kfree(p);
+
+ return err ? err : ret;
+}
+