[DLM] The core of the DLM for GFS2/CLVM
This is the core of the distributed lock manager which is required
to use GFS2 as a cluster filesystem. It is also used by CLVM and
can be used as a standalone lock manager independantly of either
of these two projects.
It implements VAX-style locking modes.
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steve Whitehouse <swhiteho@redhat.com>
diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
new file mode 100644
index 0000000..d96f9bb
--- /dev/null
+++ b/fs/dlm/midcomms.c
@@ -0,0 +1,140 @@
+/******************************************************************************
+*******************************************************************************
+**
+** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
+** Copyright (C) 2004-2005 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 "rcom.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)
+{
+ unsigned char __tmp[DLM_INBUF_LEN];
+ struct dlm_header *msg = (struct dlm_header *) __tmp;
+ 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(msg, base, offset, sizeof(struct dlm_header),
+ limit);
+
+ msglen = le16_to_cpu(msg->h_length);
+ lockspace = msg->h_lockspace;
+
+ err = -EINVAL;
+ if (msglen < sizeof(struct dlm_header))
+ break;
+ err = -E2BIG;
+ if (msglen > dlm_config.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) &&
+ msg == (struct dlm_header *) __tmp) {
+ msg = kmalloc(dlm_config.buffer_size, GFP_KERNEL);
+ if (msg == NULL)
+ return ret;
+ }
+
+ copy_from_cb(msg, base, offset, msglen, limit);
+
+ BUG_ON(lockspace != msg->h_lockspace);
+
+ ret += msglen;
+ offset += msglen;
+ offset &= (limit - 1);
+ len -= msglen;
+
+ switch (msg->h_cmd) {
+ case DLM_MSG:
+ dlm_receive_message(msg, nodeid, FALSE);
+ break;
+
+ case DLM_RCOM:
+ dlm_receive_rcom(msg, nodeid);
+ break;
+
+ default:
+ log_print("unknown msg type %x from %u: %u %u %u %u",
+ msg->h_cmd, nodeid, msglen, len, offset, ret);
+ }
+ }
+
+ if (msg != (struct dlm_header *) __tmp)
+ kfree(msg);
+
+ return err ? err : ret;
+}
+