[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>

1 files changed, 140 insertions, 0 deletions

diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
new file mode 100644
index 000000000000..d96f9bbb407c
--- /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;
+}
+