[DLM] Use workqueues for dlm lowcomms

This patch converts the DLM TCP lowcomms to use workqueues rather than using its
own daemon functions. Simultaneously removing a lot of code and making it more
scalable on multi-processor machines.

Signed-Off-By: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

2 files changed, 115 insertions, 284 deletions

diff --git a/fs/dlm/lowcomms-sctp.c b/fs/dlm/lowcomms-sctp.c
index 5aeadadd8afd..dc83a9d979b5 100644
--- a/fs/dlm/lowcomms-sctp.c
+++ b/fs/dlm/lowcomms-sctp.c
@@ -72,6 +72,8 @@ struct nodeinfo {
         struct list_head        writequeue; /* outgoing writequeue_entries */
         spinlock_t              writequeue_lock;
         int                     nodeid;
+        struct work_struct      swork; /* Send workqueue */
+        struct work_struct      lwork; /* Locking workqueue */
 };
 
 static DEFINE_IDR(nodeinfo_idr);
@@ -96,6 +98,7 @@ struct connection {
         atomic_t                waiting_requests;
         struct cbuf             cb;
         int                     eagain_flag;
+        struct work_struct      work; /* Send workqueue */
 };
 
 /* An entry waiting to be sent */
@@ -137,19 +140,23 @@ static void cbuf_eat(struct cbuf *cb, int n)
 static LIST_HEAD(write_nodes);
 static DEFINE_SPINLOCK(write_nodes_lock);
 
+
 /* Maximum number of incoming messages to process before
  * doing a schedule()
  */
 #define MAX_RX_MSG_COUNT 25
 
-/* Manage daemons */
-static struct task_struct *recv_task;
-static struct task_struct *send_task;
-static DECLARE_WAIT_QUEUE_HEAD(lowcomms_recv_wait);
+/* Work queues */
+static struct workqueue_struct *recv_workqueue;
+static struct workqueue_struct *send_workqueue;
+static struct workqueue_struct *lock_workqueue;
 
 /* The SCTP connection */
 static struct connection sctp_con;
 
+static void process_send_sockets(struct work_struct *work);
+static void process_recv_sockets(struct work_struct *work);
+static void process_lock_request(struct work_struct *work);
 
 static int nodeid_to_addr(int nodeid, struct sockaddr *retaddr)
 {
@@ -222,6 +229,8 @@ static struct nodeinfo *nodeid2nodeinfo(int nodeid, gfp_t alloc)
         spin_lock_init(&ni->lock);
         INIT_LIST_HEAD(&ni->writequeue);
         spin_lock_init(&ni->writequeue_lock);
+        INIT_WORK(&ni->lwork, process_lock_request);
+        INIT_WORK(&ni->swork, process_send_sockets);
         ni->nodeid = nodeid;
 
         if (nodeid > max_nodeid)
@@ -249,11 +258,8 @@ static struct nodeinfo *assoc2nodeinfo(sctp_assoc_t assoc)
 /* Data or notification available on socket */
 static void lowcomms_data_ready(struct sock *sk, int count_unused)
 {
-        atomic_inc(&sctp_con.waiting_requests);
         if (test_and_set_bit(CF_READ_PENDING, &sctp_con.flags))
-                return;
-
-        wake_up_interruptible(&lowcomms_recv_wait);
+                queue_work(recv_workqueue, &sctp_con.work);
 }
 
 
@@ -361,10 +367,10 @@ static void init_failed(void)
                                 spin_lock_bh(&write_nodes_lock);
                                 list_add_tail(&ni->write_list, &write_nodes);
                                 spin_unlock_bh(&write_nodes_lock);
+                                queue_work(send_workqueue, &ni->swork);
                         }
                 }
         }
-        wake_up_process(send_task);
 }
 
 /* Something happened to an association */
@@ -446,8 +452,8 @@ static void process_sctp_notification(struct msghdr *msg, char *buf)
                                 spin_lock_bh(&write_nodes_lock);
                                 list_add_tail(&ni->write_list, &write_nodes);
                                 spin_unlock_bh(&write_nodes_lock);
+                                queue_work(send_workqueue, &ni->swork);
                         }
-                        wake_up_process(send_task);
                 }
                 break;
 
@@ -580,8 +586,8 @@ static int receive_from_sock(void)
                                 spin_lock_bh(&write_nodes_lock);
                                 list_add_tail(&ni->write_list, &write_nodes);
                                 spin_unlock_bh(&write_nodes_lock);
+                                queue_work(send_workqueue, &ni->swork);
                         }
-                        wake_up_process(send_task);
                 }
         }
 
@@ -590,6 +596,7 @@ static int receive_from_sock(void)
                 return 0;
 
         cbuf_add(&sctp_con.cb, ret);
+        // PJC: TODO: Add to node's workqueue....can we ??
         ret = dlm_process_incoming_buffer(cpu_to_le32(sinfo->sinfo_ppid),
                                           page_address(sctp_con.rx_page),
                                           sctp_con.cb.base, sctp_con.cb.len,
@@ -820,7 +827,8 @@ void dlm_lowcomms_commit_buffer(void *arg)
                 spin_lock_bh(&write_nodes_lock);
                 list_add_tail(&ni->write_list, &write_nodes);
                 spin_unlock_bh(&write_nodes_lock);
-                wake_up_process(send_task);
+
+                queue_work(send_workqueue, &ni->swork);
         }
         return;
 
@@ -1088,101 +1096,75 @@ int dlm_lowcomms_close(int nodeid)
         return 0;
 }
 
-static int write_list_empty(void)
+// PJC: The work queue function for receiving.
+static void process_recv_sockets(struct work_struct *work)
 {
-        int status;
+        if (test_and_clear_bit(CF_READ_PENDING, &sctp_con.flags)) {
+                int ret;
+                int count = 0;
 
-        spin_lock_bh(&write_nodes_lock);
-        status = list_empty(&write_nodes);
-        spin_unlock_bh(&write_nodes_lock);
+                do {
+                        ret = receive_from_sock();
 
-        return status;
+                        /* Don't starve out everyone else */
+                        if (++count >= MAX_RX_MSG_COUNT) {
+                                cond_resched();
+                                count = 0;
+                        }
+                } while (!kthread_should_stop() && ret >=0);
+        }
+        cond_resched();
 }
 
-static int dlm_recvd(void *data)
+// PJC: the work queue function for sending
+static void process_send_sockets(struct work_struct *work)
 {
-        DECLARE_WAITQUEUE(wait, current);
-
-        while (!kthread_should_stop()) {
-                int count = 0;
-
-                set_current_state(TASK_INTERRUPTIBLE);
-                add_wait_queue(&lowcomms_recv_wait, &wait);
-                if (!test_bit(CF_READ_PENDING, &sctp_con.flags))
-                        schedule();
-                remove_wait_queue(&lowcomms_recv_wait, &wait);
-                set_current_state(TASK_RUNNING);
-
-                if (test_and_clear_bit(CF_READ_PENDING, &sctp_con.flags)) {
-                        int ret;
-
-                        do {
-                                ret = receive_from_sock();
-
-                                /* Don't starve out everyone else */
-                                if (++count >= MAX_RX_MSG_COUNT) {
-                                        cond_resched();
-                                        count = 0;
-                                }
-                        } while (!kthread_should_stop() && ret >=0);
-                }
-                cond_resched();
+        if (sctp_con.eagain_flag) {
+                sctp_con.eagain_flag = 0;
+                refill_write_queue();
         }
-
-        return 0;
+        process_output_queue();
 }
 
-static int dlm_sendd(void *data)
+// PJC: Process lock requests from a particular node.
+// TODO: can we optimise this out on UP ??
+static void process_lock_request(struct work_struct *work)
 {
-        DECLARE_WAITQUEUE(wait, current);
-
-        add_wait_queue(sctp_con.sock->sk->sk_sleep, &wait);
-
-        while (!kthread_should_stop()) {
-                set_current_state(TASK_INTERRUPTIBLE);
-                if (write_list_empty())
-                        schedule();
-                set_current_state(TASK_RUNNING);
-
-                if (sctp_con.eagain_flag) {
-                        sctp_con.eagain_flag = 0;
-                        refill_write_queue();
-                }
-                process_output_queue();
-        }
-
-        remove_wait_queue(sctp_con.sock->sk->sk_sleep, &wait);
-
-        return 0;
 }
 
 static void daemons_stop(void)
 {
-        kthread_stop(recv_task);
-        kthread_stop(send_task);
+        destroy_workqueue(recv_workqueue);
+        destroy_workqueue(send_workqueue);
+        destroy_workqueue(lock_workqueue);
 }
 
 static int daemons_start(void)
 {
-        struct task_struct *p;
         int error;
+        recv_workqueue = create_workqueue("dlm_recv");
+        error = IS_ERR(recv_workqueue);
+        if (error) {
+                log_print("can't start dlm_recv %d", error);
+                return error;
+        }
 
-        p = kthread_run(dlm_recvd, NULL, "dlm_recvd");
-        error = IS_ERR(p);
+        send_workqueue = create_singlethread_workqueue("dlm_send");
+        error = IS_ERR(send_workqueue);
         if (error) {
-                log_print("can't start dlm_recvd %d", error);
+                log_print("can't start dlm_send %d", error);
+                destroy_workqueue(recv_workqueue);
                 return error;
         }
-        recv_task = p;
 
-        p = kthread_run(dlm_sendd, NULL, "dlm_sendd");
-        error = IS_ERR(p);
+        lock_workqueue = create_workqueue("dlm_rlock");
+        error = IS_ERR(lock_workqueue);
         if (error) {
-                log_print("can't start dlm_sendd %d", error);
-                kthread_stop(recv_task);
+                log_print("can't start dlm_rlock %d", error);
+                destroy_workqueue(send_workqueue);
+                destroy_workqueue(recv_workqueue);
                 return error;
         }
-        send_task = p;
 
         return 0;
 }
@@ -1194,6 +1176,8 @@ int dlm_lowcomms_start(void)
 {
         int error;
 
+        INIT_WORK(&sctp_con.work, process_recv_sockets);
+
         error = init_sock();
         if (error)
                 goto fail_sock;
@@ -1224,4 +1208,3 @@ void dlm_lowcomms_stop(void)
         for (i = 0; i < dlm_local_count; i++)
                 kfree(dlm_local_addr[i]);
 }
-
diff --git a/fs/dlm/lowcomms-tcp.c b/fs/dlm/lowcomms-tcp.c
index b4fb5783ef8a..86e5f81da7cb 100644
--- a/fs/dlm/lowcomms-tcp.c
+++ b/fs/dlm/lowcomms-tcp.c
@@ -115,6 +115,8 @@ struct connection {
         atomic_t waiting_requests;
 #define MAX_CONNECT_RETRIES 3
         struct connection *othercon;
+        struct work_struct rwork; /* Receive workqueue */
+        struct work_struct swork; /* Send workqueue */
 };
 #define sock2con(x) ((struct connection *)(x)->sk_user_data)
 
@@ -131,14 +133,9 @@ struct writequeue_entry {
 
 static struct sockaddr_storage dlm_local_addr;
 
-/* Manage daemons */
-static struct task_struct *recv_task;
-static struct task_struct *send_task;
-
-static wait_queue_t lowcomms_send_waitq_head;
-static DECLARE_WAIT_QUEUE_HEAD(lowcomms_send_waitq);
-static wait_queue_t lowcomms_recv_waitq_head;
-static DECLARE_WAIT_QUEUE_HEAD(lowcomms_recv_waitq);
+/* Work queues */
+static struct workqueue_struct *recv_workqueue;
+static struct workqueue_struct *send_workqueue;
 
 /* An array of pointers to connections, indexed by NODEID */
 static struct connection **connections;
@@ -146,17 +143,8 @@ static DECLARE_MUTEX(connections_lock);
 static struct kmem_cache *con_cache;
 static int conn_array_size;
 
-/* List of sockets that have reads pending */
-static LIST_HEAD(read_sockets);
-static DEFINE_SPINLOCK(read_sockets_lock);
-
-/* List of sockets which have writes pending */
-static LIST_HEAD(write_sockets);
-static DEFINE_SPINLOCK(write_sockets_lock);
-
-/* List of sockets which have connects pending */
-static LIST_HEAD(state_sockets);
-static DEFINE_SPINLOCK(state_sockets_lock);
+static void process_recv_sockets(struct work_struct *work);
+static void process_send_sockets(struct work_struct *work);
 
 static struct connection *nodeid2con(int nodeid, gfp_t allocation)
 {
@@ -189,6 +177,8 @@ static struct connection *nodeid2con(int nodeid, gfp_t allocation)
                 init_rwsem(&con->sock_sem);
                 INIT_LIST_HEAD(&con->writequeue);
                 spin_lock_init(&con->writequeue_lock);
+                INIT_WORK(&con->swork, process_send_sockets);
+                INIT_WORK(&con->rwork, process_recv_sockets);
 
                 connections[nodeid] = con;
         }
@@ -203,41 +193,22 @@ static void lowcomms_data_ready(struct sock *sk, int count_unused)
 {
         struct connection *con = sock2con(sk);
 
-        atomic_inc(&con->waiting_requests);
-        if (test_and_set_bit(CF_READ_PENDING, &con->flags))
-                return;
-
-        spin_lock_bh(&read_sockets_lock);
-        list_add_tail(&con->read_list, &read_sockets);
-        spin_unlock_bh(&read_sockets_lock);
-
-        wake_up_interruptible(&lowcomms_recv_waitq);
+        if (!test_and_set_bit(CF_READ_PENDING, &con->flags))
+                queue_work(recv_workqueue, &con->rwork);
 }
 
 static void lowcomms_write_space(struct sock *sk)
 {
         struct connection *con = sock2con(sk);
 
-        if (test_and_set_bit(CF_WRITE_PENDING, &con->flags))
-                return;
-
-        spin_lock_bh(&write_sockets_lock);
-        list_add_tail(&con->write_list, &write_sockets);
-        spin_unlock_bh(&write_sockets_lock);
-
-        wake_up_interruptible(&lowcomms_send_waitq);
+        if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags))
+                queue_work(send_workqueue, &con->swork);
 }
 
 static inline void lowcomms_connect_sock(struct connection *con)
 {
-        if (test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
-                return;
-
-        spin_lock_bh(&state_sockets_lock);
-        list_add_tail(&con->state_list, &state_sockets);
-        spin_unlock_bh(&state_sockets_lock);
-
-        wake_up_interruptible(&lowcomms_send_waitq);
+        if (!test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
+                queue_work(send_workqueue, &con->swork);
 }
 
 static void lowcomms_state_change(struct sock *sk)
@@ -388,7 +359,8 @@ out:
         return 0;
 
 out_resched:
-        lowcomms_data_ready(con->sock->sk, 0);
+        if (!test_and_set_bit(CF_READ_PENDING, &con->flags))
+                queue_work(recv_workqueue, &con->rwork);
         up_read(&con->sock_sem);
         cond_resched();
         return 0;
@@ -477,6 +449,8 @@ static int accept_from_sock(struct connection *con)
                         othercon->nodeid = nodeid;
                         othercon->rx_action = receive_from_sock;
                         init_rwsem(&othercon->sock_sem);
+                        INIT_WORK(&othercon->swork, process_send_sockets);
+                        INIT_WORK(&othercon->rwork, process_recv_sockets);
                         set_bit(CF_IS_OTHERCON, &othercon->flags);
                         newcon->othercon = othercon;
                 }
@@ -498,7 +472,8 @@ static int accept_from_sock(struct connection *con)
          * beween processing the accept adding the socket
          * to the read_sockets list
          */
-        lowcomms_data_ready(newsock->sk, 0);
+        if (!test_and_set_bit(CF_READ_PENDING, &newcon->flags))
+                queue_work(recv_workqueue, &newcon->rwork);
         up_read(&con->sock_sem);
 
         return 0;
@@ -757,12 +732,8 @@ void dlm_lowcomms_commit_buffer(void *mh)
         kunmap(e->page);
         spin_unlock(&con->writequeue_lock);
 
-        if (test_and_set_bit(CF_WRITE_PENDING, &con->flags) == 0) {
-                spin_lock_bh(&write_sockets_lock);
-                list_add_tail(&con->write_list, &write_sockets);
-                spin_unlock_bh(&write_sockets_lock);
-
-                wake_up_interruptible(&lowcomms_send_waitq);
+        if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags)) {
+                queue_work(send_workqueue, &con->swork);
         }
         return;
 
@@ -803,6 +774,7 @@ static void send_to_sock(struct connection *con)
                 offset = e->offset;
                 BUG_ON(len == 0 && e->users == 0);
                 spin_unlock(&con->writequeue_lock);
+                kmap(e->page);
 
                 ret = 0;
                 if (len) {
@@ -884,85 +856,29 @@ out:
 }
 
 /* Look for activity on active sockets */
-static void process_sockets(void)
+static void process_recv_sockets(struct work_struct *work)
 {
-        struct list_head *list;
-        struct list_head *temp;
-        int count = 0;
-
-        spin_lock_bh(&read_sockets_lock);
-        list_for_each_safe(list, temp, &read_sockets) {
-
-                struct connection *con =
-                        list_entry(list, struct connection, read_list);
-                list_del(&con->read_list);
-                clear_bit(CF_READ_PENDING, &con->flags);
-
-                spin_unlock_bh(&read_sockets_lock);
+        struct connection *con = container_of(work, struct connection, rwork);
+        int err;
 
-                /* This can reach zero if we are processing requests
-                 * as they come in.
-                 */
-                if (atomic_read(&con->waiting_requests) == 0) {
-                        spin_lock_bh(&read_sockets_lock);
-                        continue;
-                }
-
-                do {
-                        con->rx_action(con);
-
-                        /* Don't starve out everyone else */
-                        if (++count >= MAX_RX_MSG_COUNT) {
-                                cond_resched();
-                                count = 0;
-                        }
-
-                } while (!atomic_dec_and_test(&con->waiting_requests) &&
-                         !kthread_should_stop());
-
-                spin_lock_bh(&read_sockets_lock);
-        }
-        spin_unlock_bh(&read_sockets_lock);
+        clear_bit(CF_READ_PENDING, &con->flags);
+        do {
+                err = con->rx_action(con);
+        } while (!err);
 }
 
-/* Try to send any messages that are pending
- */
-static void process_output_queue(void)
-{
-        struct list_head *list;
-        struct list_head *temp;
-
-        spin_lock_bh(&write_sockets_lock);
-        list_for_each_safe(list, temp, &write_sockets) {
-                struct connection *con =
-                        list_entry(list, struct connection, write_list);
-                clear_bit(CF_WRITE_PENDING, &con->flags);
-                list_del(&con->write_list);
-
-                spin_unlock_bh(&write_sockets_lock);
-                send_to_sock(con);
-                spin_lock_bh(&write_sockets_lock);
-        }
-        spin_unlock_bh(&write_sockets_lock);
-}
 
-static void process_state_queue(void)
+static void process_send_sockets(struct work_struct *work)
 {
-        struct list_head *list;
-        struct list_head *temp;
-
-        spin_lock_bh(&state_sockets_lock);
-        list_for_each_safe(list, temp, &state_sockets) {
-                struct connection *con =
-                        list_entry(list, struct connection, state_list);
-                list_del(&con->state_list);
-                clear_bit(CF_CONNECT_PENDING, &con->flags);
-                spin_unlock_bh(&state_sockets_lock);
+        struct connection *con = container_of(work, struct connection, swork);
 
+        if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
                 connect_to_sock(con);
-                spin_lock_bh(&state_sockets_lock);
         }
-        spin_unlock_bh(&state_sockets_lock);
+
+        if (test_and_clear_bit(CF_WRITE_PENDING, &con->flags)) {
+                send_to_sock(con);
+        }
 }
 
 
@@ -979,97 +895,29 @@ static void clean_writequeues(void)
         }
 }
 
-static int read_list_empty(void)
-{
-        int status;
-
-        spin_lock_bh(&read_sockets_lock);
-        status = list_empty(&read_sockets);
-        spin_unlock_bh(&read_sockets_lock);
-
-        return status;
-}
-
-/* DLM Transport comms receive daemon */
-static int dlm_recvd(void *data)
+static void work_stop(void)
 {
-        init_waitqueue_entry(&lowcomms_recv_waitq_head, current);
-        add_wait_queue(&lowcomms_recv_waitq, &lowcomms_recv_waitq_head);
-
-        while (!kthread_should_stop()) {
-                set_current_state(TASK_INTERRUPTIBLE);
-                if (read_list_empty())
-                        schedule();
-                set_current_state(TASK_RUNNING);
-
-                process_sockets();
-        }
-
-        return 0;
+        destroy_workqueue(recv_workqueue);
+        destroy_workqueue(send_workqueue);
 }
 
-static int write_and_state_lists_empty(void)
+static int work_start(void)
 {
-        int status;
-
-        spin_lock_bh(&write_sockets_lock);
-        status = list_empty(&write_sockets);
-        spin_unlock_bh(&write_sockets_lock);
-
-        spin_lock_bh(&state_sockets_lock);
-        if (list_empty(&state_sockets) == 0)
-                status = 0;
-        spin_unlock_bh(&state_sockets_lock);
-
-        return status;
-}
-
-/* DLM Transport send daemon */
-static int dlm_sendd(void *data)
-{
-        init_waitqueue_entry(&lowcomms_send_waitq_head, current);
-        add_wait_queue(&lowcomms_send_waitq, &lowcomms_send_waitq_head);
-
-        while (!kthread_should_stop()) {
-                set_current_state(TASK_INTERRUPTIBLE);
-                if (write_and_state_lists_empty())
-                        schedule();
-                set_current_state(TASK_RUNNING);
-
-                process_state_queue();
-                process_output_queue();
-        }
-
-        return 0;
-}
-
-static void daemons_stop(void)
-{
-        kthread_stop(recv_task);
-        kthread_stop(send_task);
-}
-
-static int daemons_start(void)
-{
-        struct task_struct *p;
         int error;
-
-        p = kthread_run(dlm_recvd, NULL, "dlm_recvd");
-        error = IS_ERR(p);
+        recv_workqueue = create_workqueue("dlm_recv");
+        error = IS_ERR(recv_workqueue);
         if (error) {
-                log_print("can't start dlm_recvd %d", error);
+                log_print("can't start dlm_recv %d", error);
                 return error;
         }
-        recv_task = p;
 
-        p = kthread_run(dlm_sendd, NULL, "dlm_sendd");
-        error = IS_ERR(p);
+        send_workqueue = create_singlethread_workqueue("dlm_send");
+        error = IS_ERR(send_workqueue);
         if (error) {
-                log_print("can't start dlm_sendd %d", error);
-                kthread_stop(recv_task);
+                log_print("can't start dlm_send %d", error);
+                destroy_workqueue(recv_workqueue);
                 return error;
         }
-        send_task = p;
 
         return 0;
 }
@@ -1086,7 +934,7 @@ void dlm_lowcomms_stop(void)
                         connections[i]->flags |= 0xFF;
         }
 
-        daemons_stop();
+        work_stop();
         clean_writequeues();
 
         for (i = 0; i < conn_array_size; i++) {
@@ -1138,7 +986,7 @@ int dlm_lowcomms_start(void)
         if (error)
                 goto fail_unlisten;
 
-        error = daemons_start();
+        error = work_start();
         if (error)
                 goto fail_unlisten;