Merge tag 'dlm-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm

Pull dlm updates from David Teigland:
 "This set continues the ongoing rework of the low level communication
  layer in the dlm.

  The focus here is on improvements to connection handling, and
  reworking the receiving of messages"

* tag 'dlm-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm:
  fs: dlm: fix race in nodeid2con
  fs: dlm: rework receive handling
  fs: dlm: disallow buffer size below default
  fs: dlm: handle range check as callback
  fs: dlm: fix mark per nodeid setting
  fs: dlm: remove lock dependency warning
  fs: dlm: use free_con to free connection
  fs: dlm: handle possible othercon writequeues
  fs: dlm: move free writequeue into con free
  fs: dlm: fix configfs memory leak
  fs: dlm: fix dlm_local_addr memory leak
  fs: dlm: make connection hash lockless
  fs: dlm: synchronize dlm before shutdown

6 files changed, 260 insertions, 279 deletions

diff --git a/fs/dlm/Kconfig b/fs/dlm/Kconfig
index f82a4952769da5..ee92634196a8e7 100644
--- a/fs/dlm/Kconfig
+++ b/fs/dlm/Kconfig
@@ -4,6 +4,7 @@ menuconfig DLM
 	depends on INET
 	depends on SYSFS && CONFIGFS_FS && (IPV6 || IPV6=n)
 	select IP_SCTP
+	select SRCU
 	help
 	A general purpose distributed lock manager for kernel or userspace
 	applications.
diff --git a/fs/dlm/config.c b/fs/dlm/config.c
index 47f0b98b707f89..49c5f9407098ee 100644
--- a/fs/dlm/config.c
+++ b/fs/dlm/config.c
@@ -125,7 +125,7 @@ static ssize_t cluster_cluster_name_store(struct config_item *item,
 CONFIGFS_ATTR(cluster_, cluster_name);
 
 static ssize_t cluster_set(struct dlm_cluster *cl, unsigned int *cl_field,
-			   int *info_field, int check_zero,
+			   int *info_field, bool (*check_cb)(unsigned int x),
 			   const char *buf, size_t len)
 {
 	unsigned int x;
@@ -137,7 +137,7 @@ static ssize_t cluster_set(struct dlm_cluster *cl, unsigned int *cl_field,
 	if (rc)
 		return rc;
 
-	if (check_zero && !x)
+	if (check_cb && check_cb(x))
 		return -EINVAL;
 
 	*cl_field = x;
@@ -146,13 +146,13 @@ static ssize_t cluster_set(struct dlm_cluster *cl, unsigned int *cl_field,
 	return len;
 }
 
-#define CLUSTER_ATTR(name, check_zero)                                        \
+#define CLUSTER_ATTR(name, check_cb)                                          \
 static ssize_t cluster_##name##_store(struct config_item *item, \
 		const char *buf, size_t len) \
 {                                                                             \
 	struct dlm_cluster *cl = config_item_to_cluster(item);		      \
 	return cluster_set(cl, &cl->cl_##name, &dlm_config.ci_##name,         \
-			   check_zero, buf, len);                             \
+			   check_cb, buf, len);                               \
 }                                                                             \
 static ssize_t cluster_##name##_show(struct config_item *item, char *buf)     \
 {                                                                             \
@@ -161,20 +161,30 @@ static ssize_t cluster_##name##_show(struct config_item *item, char *buf)     \
 }                                                                             \
 CONFIGFS_ATTR(cluster_, name);
 
-CLUSTER_ATTR(tcp_port, 1);
-CLUSTER_ATTR(buffer_size, 1);
-CLUSTER_ATTR(rsbtbl_size, 1);
-CLUSTER_ATTR(recover_timer, 1);
-CLUSTER_ATTR(toss_secs, 1);
-CLUSTER_ATTR(scan_secs, 1);
-CLUSTER_ATTR(log_debug, 0);
-CLUSTER_ATTR(log_info, 0);
-CLUSTER_ATTR(protocol, 0);
-CLUSTER_ATTR(mark, 0);
-CLUSTER_ATTR(timewarn_cs, 1);
-CLUSTER_ATTR(waitwarn_us, 0);
-CLUSTER_ATTR(new_rsb_count, 0);
-CLUSTER_ATTR(recover_callbacks, 0);
+static bool dlm_check_zero(unsigned int x)
+{
+	return !x;
+}
+
+static bool dlm_check_buffer_size(unsigned int x)
+{
+	return (x < DEFAULT_BUFFER_SIZE);
+}
+
+CLUSTER_ATTR(tcp_port, dlm_check_zero);
+CLUSTER_ATTR(buffer_size, dlm_check_buffer_size);
+CLUSTER_ATTR(rsbtbl_size, dlm_check_zero);
+CLUSTER_ATTR(recover_timer, dlm_check_zero);
+CLUSTER_ATTR(toss_secs, dlm_check_zero);
+CLUSTER_ATTR(scan_secs, dlm_check_zero);
+CLUSTER_ATTR(log_debug, NULL);
+CLUSTER_ATTR(log_info, NULL);
+CLUSTER_ATTR(protocol, NULL);
+CLUSTER_ATTR(mark, NULL);
+CLUSTER_ATTR(timewarn_cs, dlm_check_zero);
+CLUSTER_ATTR(waitwarn_us, NULL);
+CLUSTER_ATTR(new_rsb_count, NULL);
+CLUSTER_ATTR(recover_callbacks, NULL);
 
 static struct configfs_attribute *cluster_attrs[] = {
 	[CLUSTER_ATTR_TCP_PORT] = &cluster_attr_tcp_port,
@@ -221,6 +231,7 @@ struct dlm_space {
 	struct list_head members;
 	struct mutex members_lock;
 	int members_count;
+	struct dlm_nodes *nds;
 };
 
 struct dlm_comms {
@@ -430,6 +441,7 @@ static struct config_group *make_space(struct config_group *g, const char *name)
 	INIT_LIST_HEAD(&sp->members);
 	mutex_init(&sp->members_lock);
 	sp->members_count = 0;
+	sp->nds = nds;
 	return &sp->group;
 
  fail:
@@ -451,6 +463,7 @@ static void drop_space(struct config_group *g, struct config_item *i)
 static void release_space(struct config_item *i)
 {
 	struct dlm_space *sp = config_item_to_space(i);
+	kfree(sp->nds);
 	kfree(sp);
 }
 
@@ -857,18 +870,22 @@ int dlm_comm_seq(int nodeid, uint32_t *seq)
 	return 0;
 }
 
-int dlm_comm_mark(int nodeid, unsigned int *mark)
+void dlm_comm_mark(int nodeid, unsigned int *mark)
 {
 	struct dlm_comm *cm;
 
 	cm = get_comm(nodeid);
-	if (!cm)
-		return -ENOENT;
+	if (!cm) {
+		*mark = dlm_config.ci_mark;
+		return;
+	}
 
-	*mark = cm->mark;
-	put_comm(cm);
+	if (cm->mark)
+		*mark = cm->mark;
+	else
+		*mark = dlm_config.ci_mark;
 
-	return 0;
+	put_comm(cm);
 }
 
 int dlm_our_nodeid(void)
@@ -889,7 +906,6 @@ int dlm_our_addr(struct sockaddr_storage *addr, int num)
 
 /* Config file defaults */
 #define DEFAULT_TCP_PORT       21064
-#define DEFAULT_BUFFER_SIZE     4096
 #define DEFAULT_RSBTBL_SIZE     1024
 #define DEFAULT_RECOVER_TIMER      5
 #define DEFAULT_TOSS_SECS         10
diff --git a/fs/dlm/config.h b/fs/dlm/config.h
index f62996cad5616e..c210250a258182 100644
--- a/fs/dlm/config.h
+++ b/fs/dlm/config.h
@@ -12,6 +12,8 @@
 #ifndef __CONFIG_DOT_H__
 #define __CONFIG_DOT_H__
 
+#define DEFAULT_BUFFER_SIZE     4096
+
 struct dlm_config_node {
 	int nodeid;
 	int weight;
@@ -46,7 +48,7 @@ void dlm_config_exit(void);
 int dlm_config_nodes(char *lsname, struct dlm_config_node **nodes_out,
 		     int *count_out);
 int dlm_comm_seq(int nodeid, uint32_t *seq);
-int dlm_comm_mark(int nodeid, unsigned int *mark);
+void dlm_comm_mark(int nodeid, unsigned int *mark);
 int dlm_our_nodeid(void);
 int dlm_our_addr(struct sockaddr_storage *addr, int num);
 
diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 5050fe05769b4d..79f56f16bc2cec 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -65,40 +65,6 @@
 #define MAX_SEND_MSG_COUNT 25
 #define DLM_SHUTDOWN_WAIT_TIMEOUT msecs_to_jiffies(10000)
 
-struct cbuf {
-	unsigned int base;
-	unsigned int len;
-	unsigned int mask;
-};
-
-static void cbuf_add(struct cbuf *cb, int n)
-{
-	cb->len += n;
-}
-
-static int cbuf_data(struct cbuf *cb)
-{
-	return ((cb->base + cb->len) & cb->mask);
-}
-
-static void cbuf_init(struct cbuf *cb, int size)
-{
-	cb->base = cb->len = 0;
-	cb->mask = size-1;
-}
-
-static void cbuf_eat(struct cbuf *cb, int n)
-{
-	cb->len  -= n;
-	cb->base += n;
-	cb->base &= cb->mask;
-}
-
-static bool cbuf_empty(struct cbuf *cb)
-{
-	return cb->len == 0;
-}
-
 struct connection {
 	struct socket *sock;	/* NULL if not connected */
 	uint32_t nodeid;	/* So we know who we are in the list */
@@ -117,8 +83,6 @@ struct connection {
 	int (*rx_action) (struct connection *);	/* What to do when active */
 	void (*connect_action) (struct connection *);	/* What to do to connect */
 	void (*shutdown_action)(struct connection *con); /* What to do to shutdown */
-	struct page *rx_page;
-	struct cbuf cb;
 	int retries;
 #define MAX_CONNECT_RETRIES 3
 	struct hlist_node list;
@@ -126,6 +90,10 @@ struct connection {
 	struct work_struct rwork; /* Receive workqueue */
 	struct work_struct swork; /* Send workqueue */
 	wait_queue_head_t shutdown_wait; /* wait for graceful shutdown */
+	unsigned char *rx_buf;
+	int rx_buflen;
+	int rx_leftover;
+	struct rcu_head rcu;
 };
 #define sock2con(x) ((struct connection *)(x)->sk_user_data)
 
@@ -167,8 +135,8 @@ static struct workqueue_struct *recv_workqueue;
 static struct workqueue_struct *send_workqueue;
 
 static struct hlist_head connection_hash[CONN_HASH_SIZE];
-static DEFINE_MUTEX(connections_lock);
-static struct kmem_cache *con_cache;
+static DEFINE_SPINLOCK(connections_lock);
+DEFINE_STATIC_SRCU(connections_srcu);
 
 static void process_recv_sockets(struct work_struct *work);
 static void process_send_sockets(struct work_struct *work);
@@ -184,15 +152,20 @@ static inline int nodeid_hash(int nodeid)
 
 static struct connection *__find_con(int nodeid)
 {
-	int r;
+	int r, idx;
 	struct connection *con;
 
 	r = nodeid_hash(nodeid);
 
-	hlist_for_each_entry(con, &connection_hash[r], list) {
-		if (con->nodeid == nodeid)
+	idx = srcu_read_lock(&connections_srcu);
+	hlist_for_each_entry_rcu(con, &connection_hash[r], list) {
+		if (con->nodeid == nodeid) {
+			srcu_read_unlock(&connections_srcu, idx);
 			return con;
+		}
 	}
+	srcu_read_unlock(&connections_srcu, idx);
+
 	return NULL;
 }
 
@@ -200,21 +173,25 @@ static struct connection *__find_con(int nodeid)
  * If 'allocation' is zero then we don't attempt to create a new
  * connection structure for this node.
  */
-static struct connection *__nodeid2con(int nodeid, gfp_t alloc)
+static struct connection *nodeid2con(int nodeid, gfp_t alloc)
 {
-	struct connection *con = NULL;
+	struct connection *con, *tmp;
 	int r;
 
 	con = __find_con(nodeid);
 	if (con || !alloc)
 		return con;
 
-	con = kmem_cache_zalloc(con_cache, alloc);
+	con = kzalloc(sizeof(*con), alloc);
 	if (!con)
 		return NULL;
 
-	r = nodeid_hash(nodeid);
-	hlist_add_head(&con->list, &connection_hash[r]);
+	con->rx_buflen = dlm_config.ci_buffer_size;
+	con->rx_buf = kmalloc(con->rx_buflen, GFP_NOFS);
+	if (!con->rx_buf) {
+		kfree(con);
+		return NULL;
+	}
 
 	con->nodeid = nodeid;
 	mutex_init(&con->sock_mutex);
@@ -233,31 +210,41 @@ static struct connection *__nodeid2con(int nodeid, gfp_t alloc)
 			con->rx_action = zerocon->rx_action;
 	}
 
+	r = nodeid_hash(nodeid);
+
+	spin_lock(&connections_lock);
+	/* Because multiple workqueues/threads calls this function it can
+	 * race on multiple cpu's. Instead of locking hot path __find_con()
+	 * we just check in rare cases of recently added nodes again
+	 * under protection of connections_lock. If this is the case we
+	 * abort our connection creation and return the existing connection.
+	 */
+	tmp = __find_con(nodeid);
+	if (tmp) {
+		spin_unlock(&connections_lock);
+		kfree(con->rx_buf);
+		kfree(con);
+		return tmp;
+	}
+
+	hlist_add_head_rcu(&con->list, &connection_hash[r]);
+	spin_unlock(&connections_lock);
+
 	return con;
 }
 
 /* Loop round all connections */
 static void foreach_conn(void (*conn_func)(struct connection *c))
 {
-	int i;
-	struct hlist_node *n;
+	int i, idx;
 	struct connection *con;
 
+	idx = srcu_read_lock(&connections_srcu);
 	for (i = 0; i < CONN_HASH_SIZE; i++) {
-		hlist_for_each_entry_safe(con, n, &connection_hash[i], list)
+		hlist_for_each_entry_rcu(con, &connection_hash[i], list)
 			conn_func(con);
 	}
-}
-
-static struct connection *nodeid2con(int nodeid, gfp_t allocation)
-{
-	struct connection *con;
-
-	mutex_lock(&connections_lock);
-	con = __nodeid2con(nodeid, allocation);
-	mutex_unlock(&connections_lock);
-
-	return con;
+	srcu_read_unlock(&connections_srcu, idx);
 }
 
 static struct dlm_node_addr *find_node_addr(int nodeid)
@@ -614,11 +601,8 @@ static void close_connection(struct connection *con, bool and_other,
 		/* Will only re-enter once. */
 		close_connection(con->othercon, false, true, true);
 	}
-	if (con->rx_page) {
-		__free_page(con->rx_page);
-		con->rx_page = NULL;
-	}
 
+	con->rx_leftover = 0;
 	con->retries = 0;
 	mutex_unlock(&con->sock_mutex);
 	clear_bit(CF_CLOSING, &con->flags);
@@ -672,16 +656,33 @@ static void dlm_tcp_shutdown(struct connection *con)
 	shutdown_connection(con);
 }
 
+static int con_realloc_receive_buf(struct connection *con, int newlen)
+{
+	unsigned char *newbuf;
+
+	newbuf = kmalloc(newlen, GFP_NOFS);
+	if (!newbuf)
+		return -ENOMEM;
+
+	/* copy any leftover from last receive */
+	if (con->rx_leftover)
+		memmove(newbuf, con->rx_buf, con->rx_leftover);
+
+	/* swap to new buffer space */
+	kfree(con->rx_buf);
+	con->rx_buflen = newlen;
+	con->rx_buf = newbuf;
+
+	return 0;
+}
+
 /* Data received from remote end */
 static int receive_from_sock(struct connection *con)
 {
-	int ret = 0;
-	struct msghdr msg = {};
-	struct kvec iov[2];
-	unsigned len;
-	int r;
 	int call_again_soon = 0;
-	int nvec;
+	struct msghdr msg;
+	struct kvec iov;
+	int ret, buflen;
 
 	mutex_lock(&con->sock_mutex);
 
@@ -689,71 +690,55 @@ static int receive_from_sock(struct connection *con)
 		ret = -EAGAIN;
 		goto out_close;
 	}
+
 	if (con->nodeid == 0) {
 		ret = -EINVAL;
 		goto out_close;
 	}
 
-	if (con->rx_page == NULL) {
-		/*
-		 * This doesn't need to be atomic, but I think it should
-		 * improve performance if it is.
-		 */
-		con->rx_page = alloc_page(GFP_ATOMIC);
-		if (con->rx_page == NULL)
+	/* realloc if we get new buffer size to read out */
+	buflen = dlm_config.ci_buffer_size;
+	if (con->rx_buflen != buflen && con->rx_leftover <= buflen) {
+		ret = con_realloc_receive_buf(con, buflen);
+		if (ret < 0)
 			goto out_resched;
-		cbuf_init(&con->cb, PAGE_SIZE);
 	}
 
-	/*
-	 * iov[0] is the bit of the circular buffer between the current end
-	 * point (cb.base + cb.len) and the end of the buffer.
-	 */
-	iov[0].iov_len = con->cb.base - cbuf_data(&con->cb);
-	iov[0].iov_base = page_address(con->rx_page) + cbuf_data(&con->cb);
-	iov[1].iov_len = 0;
-	nvec = 1;
-
-	/*
-	 * iov[1] is the bit of the circular buffer between the start of the
-	 * buffer and the start of the currently used section (cb.base)
+	/* calculate new buffer parameter regarding last receive and
+	 * possible leftover bytes
 	 */
-	if (cbuf_data(&con->cb) >= con->cb.base) {
-		iov[0].iov_len = PAGE_SIZE - cbuf_data(&con->cb);
-		iov[1].iov_len = con->cb.base;
-		iov[1].iov_base = page_address(con->rx_page);
-		nvec = 2;
-	}
-	len = iov[0].iov_len + iov[1].iov_len;
-	iov_iter_kvec(&msg.msg_iter, READ, iov, nvec, len);
+	iov.iov_base = con->rx_buf + con->rx_leftover;
+	iov.iov_len = con->rx_buflen - con->rx_leftover;
 
-	r = ret = sock_recvmsg(con->sock, &msg, MSG_DONTWAIT | MSG_NOSIGNAL);
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
+	ret = kernel_recvmsg(con->sock, &msg, &iov, 1, iov.iov_len,
+			     msg.msg_flags);
 	if (ret <= 0)
 		goto out_close;
-	else if (ret == len)
+	else if (ret == iov.iov_len)
 		call_again_soon = 1;
 
-	cbuf_add(&con->cb, ret);
-	ret = dlm_process_incoming_buffer(con->nodeid,
-					  page_address(con->rx_page),
-					  con->cb.base, con->cb.len,
-					  PAGE_SIZE);
-	if (ret < 0) {
-		log_print("lowcomms err %d: addr=%p, base=%u, len=%u, read=%d",
-			  ret, page_address(con->rx_page), con->cb.base,
-			  con->cb.len, r);
-		cbuf_eat(&con->cb, r);
-	} else {
-		cbuf_eat(&con->cb, ret);
-	}
+	/* new buflen according readed bytes and leftover from last receive */
+	buflen = ret + con->rx_leftover;
+	ret = dlm_process_incoming_buffer(con->nodeid, con->rx_buf, buflen);
+	if (ret < 0)
+		goto out_close;
 
-	if (cbuf_empty(&con->cb) && !call_again_soon) {
-		__free_page(con->rx_page);
-		con->rx_page = NULL;
+	/* calculate leftover bytes from process and put it into begin of
+	 * the receive buffer, so next receive we have the full message
+	 * at the start address of the receive buffer.
+	 */
+	con->rx_leftover = buflen - ret;
+	if (con->rx_leftover) {
+		memmove(con->rx_buf, con->rx_buf + ret,
+			con->rx_leftover);
+		call_again_soon = true;
 	}
 
 	if (call_again_soon)
 		goto out_resched;
+
 	mutex_unlock(&con->sock_mutex);
 	return 0;
 
@@ -791,13 +776,11 @@ static int accept_from_sock(struct connection *con)
 	int nodeid;
 	struct connection *newcon;
 	struct connection *addcon;
+	unsigned int mark;
 
-	mutex_lock(&connections_lock);
 	if (!dlm_allow_conn) {
-		mutex_unlock(&connections_lock);
 		return -1;
 	}
-	mutex_unlock(&connections_lock);
 
 	mutex_lock_nested(&con->sock_mutex, 0);
 
@@ -830,6 +813,9 @@ static int accept_from_sock(struct connection *con)
 		return -1;
 	}
 
+	dlm_comm_mark(nodeid, &mark);
+	sock_set_mark(newsock->sk, mark);
+
 	log_print("got connection from %d", nodeid);
 
 	/*  Check to see if we already have a connection to this node. This
@@ -847,13 +833,24 @@ static int accept_from_sock(struct connection *con)
 		struct connection *othercon = newcon->othercon;
 
 		if (!othercon) {
-			othercon = kmem_cache_zalloc(con_cache, GFP_NOFS);
+			othercon = kzalloc(sizeof(*othercon), GFP_NOFS);
 			if (!othercon) {
 				log_print("failed to allocate incoming socket");
 				mutex_unlock(&newcon->sock_mutex);
 				result = -ENOMEM;
 				goto accept_err;
 			}
+
+			othercon->rx_buflen = dlm_config.ci_buffer_size;
+			othercon->rx_buf = kmalloc(othercon->rx_buflen, GFP_NOFS);
+			if (!othercon->rx_buf) {
+				mutex_unlock(&newcon->sock_mutex);
+				kfree(othercon);
+				log_print("failed to allocate incoming socket receive buffer");
+				result = -ENOMEM;
+				goto accept_err;
+			}
+
 			othercon->nodeid = nodeid;
 			othercon->rx_action = receive_from_sock;
 			mutex_init(&othercon->sock_mutex);
@@ -975,6 +972,8 @@ static void sctp_connect_to_sock(struct connection *con)
 		return;
 	}
 
+	dlm_comm_mark(con->nodeid, &mark);
+
 	mutex_lock(&con->sock_mutex);
 
 	/* Some odd races can cause double-connects, ignore them */
@@ -999,11 +998,6 @@ static void sctp_connect_to_sock(struct connection *con)
 	if (result < 0)
 		goto socket_err;
 
-	/* set skb mark */
-	result = dlm_comm_mark(con->nodeid, &mark);
-	if (result < 0)
-		goto bind_err;
-
 	sock_set_mark(sock->sk, mark);
 
 	con->rx_action = receive_from_sock;
@@ -1076,6 +1070,8 @@ static void tcp_connect_to_sock(struct connection *con)
 		return;
 	}
 
+	dlm_comm_mark(con->nodeid, &mark);
+
 	mutex_lock(&con->sock_mutex);
 	if (con->retries++ > MAX_CONNECT_RETRIES)
 		goto out;
@@ -1090,11 +1086,6 @@ static void tcp_connect_to_sock(struct connection *con)
 	if (result < 0)
 		goto out_err;
 
-	/* set skb mark */
-	result = dlm_comm_mark(con->nodeid, &mark);
-	if (result < 0)
-		goto out_err;
-
 	sock_set_mark(sock->sk, mark);
 
 	memset(&saddr, 0, sizeof(saddr));
@@ -1238,6 +1229,14 @@ static void init_local(void)
 	}
 }
 
+static void deinit_local(void)
+{
+	int i;
+
+	for (i = 0; i < dlm_local_count; i++)
+		kfree(dlm_local_addr[i]);
+}
+
 /* Initialise SCTP socket and bind to all interfaces */
 static int sctp_listen_for_all(void)
 {
@@ -1546,13 +1545,6 @@ static void process_send_sockets(struct work_struct *work)
 		send_to_sock(con);
 }
 
-
-/* Discard all entries on the write queues */
-static void clean_writequeues(void)
-{
-	foreach_conn(clean_one_writequeue);
-}
-
 static void work_stop(void)
 {
 	if (recv_workqueue)
@@ -1608,26 +1600,34 @@ static void shutdown_conn(struct connection *con)
 		con->shutdown_action(con);
 }
 
+static void connection_release(struct rcu_head *rcu)
+{
+	struct connection *con = container_of(rcu, struct connection, rcu);
+
+	kfree(con->rx_buf);
+	kfree(con);
+}
+
 static void free_conn(struct connection *con)
 {
 	close_connection(con, true, true, true);
-	if (con->othercon)
-		kmem_cache_free(con_cache, con->othercon);
-	hlist_del(&con->list);
-	kmem_cache_free(con_cache, con);
+	spin_lock(&connections_lock);
+	hlist_del_rcu(&con->list);
+	spin_unlock(&connections_lock);
+	if (con->othercon) {
+		clean_one_writequeue(con->othercon);
+		call_rcu(&con->othercon->rcu, connection_release);
+	}
+	clean_one_writequeue(con);
+	call_rcu(&con->rcu, connection_release);
 }
 
 static void work_flush(void)
 {
-	int ok;
+	int ok, idx;
 	int i;
-	struct hlist_node *n;
 	struct connection *con;
 
-	if (recv_workqueue)
-		flush_workqueue(recv_workqueue);
-	if (send_workqueue)
-		flush_workqueue(send_workqueue);
 	do {
 		ok = 1;
 		foreach_conn(stop_conn);
@@ -1635,9 +1635,10 @@ static void work_flush(void)
 			flush_workqueue(recv_workqueue);
 		if (send_workqueue)
 			flush_workqueue(send_workqueue);
+		idx = srcu_read_lock(&connections_srcu);
 		for (i = 0; i < CONN_HASH_SIZE && ok; i++) {
-			hlist_for_each_entry_safe(con, n,
-						  &connection_hash[i], list) {
+			hlist_for_each_entry_rcu(con, &connection_hash[i],
+						 list) {
 				ok &= test_bit(CF_READ_PENDING, &con->flags);
 				ok &= test_bit(CF_WRITE_PENDING, &con->flags);
 				if (con->othercon) {
@@ -1648,6 +1649,7 @@ static void work_flush(void)
 				}
 			}
 		}
+		srcu_read_unlock(&connections_srcu, idx);
 	} while (!ok);
 }
 
@@ -1656,16 +1658,18 @@ void dlm_lowcomms_stop(void)
 	/* Set all the flags to prevent any
 	   socket activity.
 	*/
-	mutex_lock(&connections_lock);
 	dlm_allow_conn = 0;
-	mutex_unlock(&connections_lock);
+
+	if (recv_workqueue)
+		flush_workqueue(recv_workqueue);
+	if (send_workqueue)
+		flush_workqueue(send_workqueue);
+
 	foreach_conn(shutdown_conn);
 	work_flush();
-	clean_writequeues();
 	foreach_conn(free_conn);
 	work_stop();
-
-	kmem_cache_destroy(con_cache);
+	deinit_local();
 }
 
 int dlm_lowcomms_start(void)
@@ -1684,16 +1688,9 @@ int dlm_lowcomms_start(void)
 		goto fail;
 	}
 
-	error = -ENOMEM;
-	con_cache = kmem_cache_create("dlm_conn", sizeof(struct connection),
-				      __alignof__(struct connection), 0,
-				      NULL);
-	if (!con_cache)
-		goto fail;
-
 	error = work_start();
 	if (error)
-		goto fail_destroy;
+		goto fail;
 
 	dlm_allow_conn = 1;
 
@@ -1710,12 +1707,8 @@ int dlm_lowcomms_start(void)
 fail_unlisten:
 	dlm_allow_conn = 0;
 	con = nodeid2con(0,0);
-	if (con) {
-		close_connection(con, false, true, true);
-		kmem_cache_free(con_cache, con);
-	}
-fail_destroy:
-	kmem_cache_destroy(con_cache);
+	if (con)
+		free_conn(con);
 fail:
 	return error;
 }
diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
index 921322d133e3d9..fde3a6afe4beaf 100644
--- a/fs/dlm/midcomms.c
+++ b/fs/dlm/midcomms.c
@@ -22,114 +22,84 @@
  * into packets and sends them to the comms layer.
  */
 
+#include <asm/unaligned.h>
+
 #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)
+int dlm_process_incoming_buffer(int nodeid, unsigned char *buf, int len)
 {
-	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;
+	const unsigned char *ptr = buf;
+	const struct dlm_header *hd;
 	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;
+	int ret = 0;
 
-		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;
+	while (len >= sizeof(struct dlm_header)) {
+		hd = (struct dlm_header *)ptr;
+
+		/* no message should be more than this otherwise we
+		 * cannot deliver this message to upper layers
+		 */
+		msglen = get_unaligned_le16(&hd->h_length);
+		if (msglen > DEFAULT_BUFFER_SIZE) {
+			log_print("received invalid length header: %u, will abort message parsing",
+				  msglen);
+			return -EBADMSG;
 		}
-		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. */
 
+		/* caller will take care that leftover
+		 * will be parsed next call with more data
+		 */
 		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;
-		}
+		switch (hd->h_cmd) {
+		case DLM_MSG:
+			if (msglen < sizeof(struct dlm_message)) {
+				log_print("dlm msg too small: %u, will skip this message",
+					  msglen);
+				goto skip;
+			}
 
-		copy_from_cb(p, base, offset, msglen, limit);
+			break;
+		case DLM_RCOM:
+			if (msglen < sizeof(struct dlm_rcom)) {
+				log_print("dlm rcom msg too small: %u, will skip this message",
+					  msglen);
+				goto skip;
+			}
 
-		BUG_ON(lockspace != p->header.h_lockspace);
+			break;
+		default:
+			log_print("unsupported h_cmd received: %u, will skip this message",
+				  hd->h_cmd);
+			goto skip;
+		}
 
+		/* for aligned memory access, we just copy current message
+		 * to begin of the buffer which contains already parsed buffer
+		 * data and should provide align access for upper layers
+		 * because the start address of the buffer has a aligned
+		 * address. This memmove can be removed when the upperlayer
+		 * is capable of unaligned memory access.
+		 */
+		memmove(buf, ptr, msglen);
+		dlm_receive_buffer((union dlm_packet *)buf, nodeid);
+
+skip:
 		ret += msglen;
-		offset += msglen;
-		offset &= (limit - 1);
 		len -= msglen;
-
-		dlm_receive_buffer(p, nodeid);
+		ptr += msglen;
 	}
 
-	if (p != &__tmp.p)
-		kfree(p);
-
-	return err ? err : ret;
+	return ret;
 }
 
diff --git a/fs/dlm/midcomms.h b/fs/dlm/midcomms.h
index 2e122e81c8d0d9..61e90a92184938 100644
--- a/fs/dlm/midcomms.h
+++ b/fs/dlm/midcomms.h
@@ -12,8 +12,7 @@
 #ifndef __MIDCOMMS_DOT_H__
 #define __MIDCOMMS_DOT_H__
 
-int dlm_process_incoming_buffer(int nodeid, const void *base, unsigned offset,
-				unsigned len, unsigned limit);
+int dlm_process_incoming_buffer(int nodeid, unsigned char *buf, int buflen);
 
 #endif				/* __MIDCOMMS_DOT_H__ */