[Cluster-devel] [RFC PATCH dlm/next 08/16] fs: dlm: make buffer handling per msg

[Alexander Aring <aahringo@redhat.com>]

This patch makes the void pointer handle for lowcomms functionality per
message and not per page allocation entry. A refcount handling for the
handle was added to keep the message alive until the user doesn't need
it anymore.

There exists now a per message callback which will be called when
allocating a new buffer. This callback will be guaranted to be called
according the order of the sending buffer, which can be used that the
caller increments a sequence number.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/lowcomms.c | 100 +++++++++++++++++++++++++++++++++++++++++-----
 fs/dlm/lowcomms.h |   5 ++-
 fs/dlm/midcomms.c |   8 +++-
 3 files changed, 101 insertions(+), 12 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 2fc1198105ac..3e1ddcb3f69b 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -114,6 +114,17 @@ struct writequeue_entry {
 	int end;
 	int users;
 	struct connection *con;
+	struct list_head msgs;
+	struct kref ref;
+};
+
+struct dlm_msg {
+	struct writequeue_entry *entry;
+	void *ppc;
+	int len;
+
+	struct list_head list;
+	struct kref ref;
 };
 
 struct dlm_node_addr {
@@ -954,12 +965,36 @@ static int accept_from_sock(struct listen_connection *con)
 	return result;
 }
 
-static void free_entry(struct writequeue_entry *e)
+static void dlm_page_release(struct kref *kref)
 {
+	struct writequeue_entry *e = container_of(kref, struct writequeue_entry,
+						  ref);
+
 	__free_page(e->page);
 	kfree(e);
 }
 
+static void dlm_msg_release(struct kref *kref)
+{
+	struct dlm_msg *msg = container_of(kref, struct dlm_msg, ref);
+
+	kref_put(&msg->entry->ref, dlm_page_release);
+	kfree(msg);
+}
+
+static void free_entry(struct writequeue_entry *e)
+{
+	struct dlm_msg *msg, *tmp;
+
+	list_for_each_entry_safe(msg, tmp, &e->msgs, list) {
+		list_del(&msg->list);
+		kref_put(&msg->ref, dlm_msg_release);
+	}
+
+	list_del(&e->list);
+	kref_put(&e->ref, dlm_page_release);
+}
+
 /*
  * writequeue_entry_complete - try to delete and free write queue entry
  * @e: write queue entry to try to delete
@@ -972,10 +1007,8 @@ static void writequeue_entry_complete(struct writequeue_entry *e, int completed)
 	e->offset += completed;
 	e->len -= completed;
 
-	if (e->len == 0 && e->users == 0) {
-		list_del(&e->list);
+	if (e->len == 0 && e->users == 0)
 		free_entry(e);
-	}
 }
 
 /*
@@ -1345,12 +1378,16 @@ static struct writequeue_entry *new_writequeue_entry(struct connection *con,
 
 	entry->con = con;
 	entry->users = 1;
+	kref_init(&entry->ref);
+	INIT_LIST_HEAD(&entry->msgs);
 
 	return entry;
 }
 
 static struct writequeue_entry *new_wq_entry(struct connection *con, int len,
-					     gfp_t allocation, char **ppc)
+					     gfp_t allocation, char **ppc,
+					     void (*cb)(void *buf, void *priv),
+					     void *priv)
 {
 	struct writequeue_entry *e;
 
@@ -1358,7 +1395,12 @@ static struct writequeue_entry *new_wq_entry(struct connection *con, int len,
 	if (!list_empty(&con->writequeue)) {
 		e = list_last_entry(&con->writequeue, struct writequeue_entry, list);
 		if (DLM_WQ_REMAIN_BYTES(e) >= len) {
+			kref_get(&e->ref);
+
 			*ppc = page_address(e->page) + e->end;
+			if (cb)
+				cb(*ppc, priv);
+
 			e->end += len;
 			e->users++;
 			spin_unlock(&con->writequeue_lock);
@@ -1372,19 +1414,26 @@ static struct writequeue_entry *new_wq_entry(struct connection *con, int len,
 	if (!e)
 		return NULL;
 
+	kref_get(&e->ref);
 	*ppc = page_address(e->page);
 	e->end += len;
 
 	spin_lock(&con->writequeue_lock);
+	if (cb)
+		cb(*ppc, priv);
+
 	list_add_tail(&e->list, &con->writequeue);
 	spin_unlock(&con->writequeue_lock);
 
 	return e;
 };
 
-void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
+void *dlm_lowcomms_new_buffer(int nodeid, int len, gfp_t allocation, char **ppc,
+			      void (*cb)(void *buf, void *priv), void *priv)
 {
+	struct writequeue_entry *e;
 	struct connection *con;
+	struct dlm_msg *msg;
 
 	if (len > LOWCOMMS_MAX_TX_BUFFER_LEN ||
 	    len < sizeof(struct dlm_header)) {
@@ -1397,16 +1446,36 @@ void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
 	if (!con)
 		return NULL;
 
-	return new_wq_entry(con, len, allocation, ppc);
+	msg = kzalloc(sizeof(*msg), allocation);
+	if (!msg)
+		return NULL;
+
+	kref_init(&msg->ref);
+
+	e = new_wq_entry(con, len, allocation, ppc, cb, priv);
+	if (!e) {
+		kfree(msg);
+		return NULL;
+	}
+
+	msg->ppc = *ppc;
+	msg->len = len;
+	msg->entry = e;
+
+	return msg;
 }
 
 void dlm_lowcomms_commit_buffer(void *mh)
 {
-	struct writequeue_entry *e = (struct writequeue_entry *)mh;
+	struct dlm_msg *msg = mh;
+	struct writequeue_entry *e = msg->entry;
 	struct connection *con = e->con;
 	int users;
 
 	spin_lock(&con->writequeue_lock);
+	list_add(&msg->list, &e->msgs);
+	kref_get(&msg->ref);
+
 	users = --e->users;
 	if (users)
 		goto out;
@@ -1422,6 +1491,20 @@ void dlm_lowcomms_commit_buffer(void *mh)
 	return;
 }
 
+void dlm_lowcomms_put_buffer(void *mh)
+{
+	struct dlm_msg *msg = mh;
+
+	kref_put(&msg->ref, dlm_msg_release);
+}
+
+void dlm_lowcomms_get_buffer(void *mh)
+{
+	struct dlm_msg *msg = mh;
+
+	kref_get(&msg->ref);
+}
+
 /* Send a message */
 static void send_to_sock(struct connection *con)
 {
@@ -1500,7 +1583,6 @@ static void clean_one_writequeue(struct connection *con)
 
 	spin_lock(&con->writequeue_lock);
 	list_for_each_entry_safe(e, safe, &con->writequeue, list) {
-		list_del(&e->list);
 		free_entry(e);
 	}
 	spin_unlock(&con->writequeue_lock);
diff --git a/fs/dlm/lowcomms.h b/fs/dlm/lowcomms.h
index f74888ed43b4..6417c5fca215 100644
--- a/fs/dlm/lowcomms.h
+++ b/fs/dlm/lowcomms.h
@@ -21,10 +21,13 @@ int dlm_lowcomms_start(void);
 void dlm_lowcomms_stop(void);
 void dlm_lowcomms_exit(void);
 int dlm_lowcomms_close(int nodeid);
-void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc);
+void *dlm_lowcomms_new_buffer(int nodeid, int len, gfp_t allocation, char **ppc,
+			      void (*cb)(void *buf, void *priv), void *priv);
 void dlm_lowcomms_commit_buffer(void *mh);
 int dlm_lowcomms_connect_node(int nodeid);
 int dlm_lowcomms_addr(int nodeid, struct sockaddr_storage *addr, int len);
+void dlm_lowcomms_put_buffer(void *mh);
+void dlm_lowcomms_get_buffer(void *mh);
 
 #endif				/* __LOWCOMMS_DOT_H__ */
 
diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
index 717a3ed34f6a..e058e017c77d 100644
--- a/fs/dlm/midcomms.c
+++ b/fs/dlm/midcomms.c
@@ -32,23 +32,27 @@
 
 void *dlm_midcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
 {
-	return dlm_lowcomms_get_buffer(nodeid, len, allocation, ppc);
+	return dlm_lowcomms_new_buffer(nodeid, len, allocation, ppc, NULL,
+				       NULL);
 }
 
 void dlm_midcomms_commit_buffer(void *mh)
 {
 	dlm_lowcomms_commit_buffer(mh);
+	dlm_lowcomms_put_buffer(mh);
 }
 
 void *dlm_midcomms_stateless_get_buffer(int nodeid, int len, gfp_t allocation,
 					char **ppc)
 {
-	return dlm_lowcomms_get_buffer(nodeid, len, allocation, ppc);
+	return dlm_lowcomms_new_buffer(nodeid, len, allocation, ppc, NULL,
+				       NULL);
 }
 
 void dlm_midcomms_stateless_commit_buffer(void *mh)
 {
 	dlm_lowcomms_commit_buffer(mh);
+	dlm_lowcomms_put_buffer(mh);
 }
 
 void midcomms_add_member(int nodeid)
-- 
2.26.2