[PATCH -v2 09/16] fanotify: add group priorities

[Eric Paris <eparis@redhat.com>]

In preperation for blocking fanotify calls group priorities must be added.
async events will be sent as quickly as possible without waiting for a
response.

Signed-off-by: Eric Paris <eparis@redhat.com>
---

 fs/notify/group.c          |   30 ++++++++++++++++++++++++------
 include/linux/fanotify.h   |    5 ++++-
 net/fanotify/af_fanotify.c |    2 +-
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/notify/group.c b/fs/notify/group.c
index 21037cc..37b8630 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -42,15 +42,16 @@ void fanotify_get_group(struct fanotify_group *group)
 	atomic_inc(&group->refcnt);
 }
 
-struct fanotify_group *fanotify_find_group(unsigned int group_num, unsigned int mask)
+struct fanotify_group *fanotify_find_group(unsigned int priority, unsigned int group_num, unsigned int mask)
 {
 	struct fanotify_group *group_iter;
 	struct fanotify_group *group = NULL;
 
 	mutex_lock(&fanotify_grp_mutex);
 	list_for_each_entry_rcu(group_iter, &fanotify_groups, group_list) {
-		if (group_iter->group_num == group_num) {
-			if (group_iter->mask == mask) {
+		if (group_iter->priority == priority) {
+			if ((group_iter->mask == mask) &&
+			    (group_iter->group_num == group_num)) {
 				fanotify_get_group(group_iter);
 				group = group_iter;
 			} else
@@ -69,6 +70,7 @@ struct fanotify_group *fanotify_find_group(unsigned int group_num, unsigned int
 
 	group->group_num = group_num;
 	group->mask = mask;
+	group->priority = priority;
 
 	mutex_init(&group->notification_mutex);
 	INIT_LIST_HEAD(&group->notification_list);
@@ -77,9 +79,26 @@ struct fanotify_group *fanotify_find_group(unsigned int group_num, unsigned int
 	mutex_init(&group->fastpath_mutex);
 	INIT_LIST_HEAD(&group->fastpath_entries);
 
-	/* add it */
-	list_add_rcu(&group->group_list, &fanotify_groups);
+	/* Do we need to be the first entry? */
+	if (list_empty(&fanotify_groups)) {
+		list_add_rcu(&group->group_list, &fanotify_groups);
+		goto out;
+	}
+
+	list_for_each_entry(group_iter, &fanotify_groups, group_list) {
+		/* insert in front of this one? */
+		if (priority < group_iter->priority) {
+			/* I used list_add_tail() to insert in front of group_iter...  */
+			list_add_tail_rcu(&group->group_list, &group_iter->group_list);
+			break;
+		}
 
+		/* are we at the end?  if so insert at end */
+		if (list_is_last(&group_iter->group_list, &fanotify_groups)) {
+			list_add_tail_rcu(&group->group_list, &fanotify_groups);
+			break;
+		}
+	}
 out:
 	mutex_unlock(&fanotify_grp_mutex);
 	return group;
@@ -100,7 +119,6 @@ void fanotify_put_group(struct fanotify_group *group)
 {
 	mutex_lock(&fanotify_grp_mutex);
 	if (atomic_dec_and_test(&group->refcnt)) {
-
 		list_del_rcu(&group->group_list);
 		mutex_unlock(&fanotify_grp_mutex);
 
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index a1ea7e0..22496b2 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -42,6 +42,7 @@
 #endif
 
 struct fanotify_addr {
+	uint32_t priority;
         uint32_t group_num;
         uint32_t mask;
         uint32_t timeout;
@@ -89,6 +90,8 @@ struct fanotify_group {
 	/* stores all fastapth entries assoc with this group so they can be cleaned on unregister */
 	struct mutex fastpath_mutex;	/* protect fastpath_entries list */
 	struct list_head fastpath_entries; /* all fastpath entries for this group */
+
+	unsigned int priority;		/* order this group should receive msgs.  low first */
 };
 
 #ifdef CONFIG_FANOTIFY
@@ -97,7 +100,7 @@ extern void fanotify(struct file *file, unsigned int mask);
 extern void fanotify_inode_delete(struct inode *inode);
 
 extern void fanotify_get_group(struct fanotify_group *group);
-extern struct fanotify_group *fanotify_find_group(unsigned int group_num, unsigned int mask);
+extern struct fanotify_group *fanotify_find_group(unsigned int priority, unsigned int group_num, unsigned int mask);
 extern void fanotify_put_group(struct fanotify_group *group);
 
 /* things called from the socket */
diff --git a/net/fanotify/af_fanotify.c b/net/fanotify/af_fanotify.c
index f63ee7a..a7d3b96 100644
--- a/net/fanotify/af_fanotify.c
+++ b/net/fanotify/af_fanotify.c
@@ -143,7 +143,7 @@ static int fan_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 		return -EINVAL;
 
 	fan_sock = fan_sk(sock->sk);
-	fan_sock->group = fanotify_find_group(fan_addr->group_num, fan_addr->mask);
+	fan_sock->group = fanotify_find_group(fan_addr->priority, fan_addr->group_num, fan_addr->mask);
 
 	if (IS_ERR(fan_sock->group))
 		return PTR_ERR(fan_sock->group);