3 files changed, 97 insertions, 7 deletions

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 43a606f15370..50b3abc06215 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -149,12 +149,15 @@ static bool fanotify_should_merge(struct fanotify_event *old,
 }
 
 /* and the list better be locked by something too! */
-static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
+static int fanotify_merge(struct fsnotify_group *group,
+			  struct fsnotify_event *event)
 {
-	struct fsnotify_event *test_event;
 	struct fanotify_event *old, *new = FANOTIFY_E(event);
+	unsigned int bucket = fanotify_event_hash_bucket(group, new);
+	struct hlist_head *hlist = &group->fanotify_data.merge_hash[bucket];
 
-	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
+	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
+		 group, event, bucket);
 
 	/*
 	 * Don't merge a permission event with any other event so that we know
@@ -164,8 +167,7 @@ static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
 	if (fanotify_is_perm_event(new->mask))
 		return 0;
 
-	list_for_each_entry_reverse(test_event, list, list) {
-		old = FANOTIFY_E(test_event);
+	hlist_for_each_entry(old, hlist, merge_list) {
 		if (fanotify_should_merge(old, new)) {
 			old->mask |= new->mask;
 			return 1;
@@ -203,8 +205,11 @@ static int fanotify_get_response(struct fsnotify_group *group,
 			return ret;
 		}
 		/* Event not yet reported? Just remove it. */
-		if (event->state == FAN_EVENT_INIT)
+		if (event->state == FAN_EVENT_INIT) {
 			fsnotify_remove_queued_event(group, &event->fae.fse);
+			/* Permission events are not supposed to be hashed */
+			WARN_ON_ONCE(!hlist_unhashed(&event->fae.merge_list));
+		}
 		/*
 		 * Event may be also answered in case signal delivery raced
 		 * with wakeup. In that case we have nothing to do besides
@@ -679,6 +684,24 @@ static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
 	return fsid;
 }
 
+/*
+ * Add an event to hash table for faster merge.
+ */
+static void fanotify_insert_event(struct fsnotify_group *group,
+				  struct fsnotify_event *fsn_event)
+{
+	struct fanotify_event *event = FANOTIFY_E(fsn_event);
+	unsigned int bucket = fanotify_event_hash_bucket(group, event);
+	struct hlist_head *hlist = &group->fanotify_data.merge_hash[bucket];
+
+	assert_spin_locked(&group->notification_lock);
+
+	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
+		 group, event, bucket);
+
+	hlist_add_head(&event->merge_list, hlist);
+}
+
 static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 				 const void *data, int data_type,
 				 struct inode *dir,
@@ -749,7 +772,9 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 	}
 
 	fsn_event = &event->fse;
-	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
+	ret = fsnotify_add_event(group, fsn_event, fanotify_merge,
+				 fanotify_is_hashed_event(mask) ?
+				 fanotify_insert_event : NULL);
 	if (ret) {
 		/* Permission events shouldn't be merged */
 		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
@@ -772,6 +797,7 @@ static void fanotify_free_group_priv(struct fsnotify_group *group)
 {
 	struct user_struct *user;
 
+	kfree(group->fanotify_data.merge_hash);
 	user = group->fanotify_data.user;
 	atomic_dec(&user->fanotify_listeners);
 	free_uid(user);
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 9871f76cd9c2..4a5e555dc3d2 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -3,6 +3,7 @@
 #include <linux/path.h>
 #include <linux/slab.h>
 #include <linux/exportfs.h>
+#include <linux/hashtable.h>
 
 extern struct kmem_cache *fanotify_mark_cache;
 extern struct kmem_cache *fanotify_fid_event_cachep;
@@ -150,6 +151,7 @@ enum fanotify_event_type {
 
 struct fanotify_event {
 	struct fsnotify_event fse;
+	struct hlist_node merge_list;	/* List for hashed merge */
 	u32 mask;
 	struct {
 		unsigned int type : FANOTIFY_EVENT_TYPE_BITS;
@@ -162,6 +164,7 @@ static inline void fanotify_init_event(struct fanotify_event *event,
 				       unsigned int hash, u32 mask)
 {
 	fsnotify_init_event(&event->fse);
+	INIT_HLIST_NODE(&event->merge_list);
 	event->hash = hash;
 	event->mask = mask;
 	event->pid = NULL;
@@ -299,3 +302,25 @@ static inline struct path *fanotify_event_path(struct fanotify_event *event)
 	else
 		return NULL;
 }
+
+/*
+ * Use 128 size hash table to speed up events merge.
+ */
+#define FANOTIFY_HTABLE_BITS	(7)
+#define FANOTIFY_HTABLE_SIZE	(1 << FANOTIFY_HTABLE_BITS)
+#define FANOTIFY_HTABLE_MASK	(FANOTIFY_HTABLE_SIZE - 1)
+
+/*
+ * Permission events and overflow event do not get merged - don't hash them.
+ */
+static inline bool fanotify_is_hashed_event(u32 mask)
+{
+	return !fanotify_is_perm_event(mask) && !(mask & FS_Q_OVERFLOW);
+}
+
+static inline unsigned int fanotify_event_hash_bucket(
+						struct fsnotify_group *group,
+						struct fanotify_event *event)
+{
+	return event->hash & FANOTIFY_HTABLE_MASK;
+}
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 16162207e886..b89f332248bd 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -90,6 +90,23 @@ static int fanotify_event_info_len(unsigned int fid_mode,
 }
 
 /*
+ * Remove an hashed event from merge hash table.
+ */
+static void fanotify_unhash_event(struct fsnotify_group *group,
+				  struct fanotify_event *event)
+{
+	assert_spin_locked(&group->notification_lock);
+
+	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
+		 group, event, fanotify_event_hash_bucket(group, event));
+
+	if (WARN_ON_ONCE(hlist_unhashed(&event->merge_list)))
+		return;
+
+	hlist_del_init(&event->merge_list);
+}
+
+/*
  * Get an fanotify notification event if one exists and is small
  * enough to fit in "count". Return an error pointer if the count
  * is not large enough. When permission event is dequeued, its state is
@@ -126,6 +143,8 @@ static struct fanotify_event *get_one_event(struct fsnotify_group *group,
 	fsnotify_remove_first_event(group);
 	if (fanotify_is_perm_event(event->mask))
 		FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
+	if (fanotify_is_hashed_event(event->mask))
+		fanotify_unhash_event(group, event);
 out:
 	spin_unlock(&group->notification_lock);
 	return event;
@@ -925,6 +944,20 @@ static struct fsnotify_event *fanotify_alloc_overflow_event(void)
 	return &oevent->fse;
 }
 
+static struct hlist_head *fanotify_alloc_merge_hash(void)
+{
+	struct hlist_head *hash;
+
+	hash = kmalloc(sizeof(struct hlist_head) << FANOTIFY_HTABLE_BITS,
+		       GFP_KERNEL_ACCOUNT);
+	if (!hash)
+		return NULL;
+
+	__hash_init(hash, FANOTIFY_HTABLE_SIZE);
+
+	return hash;
+}
+
 /* fanotify syscalls */
 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 {
@@ -993,6 +1026,12 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	atomic_inc(&user->fanotify_listeners);
 	group->memcg = get_mem_cgroup_from_mm(current->mm);
 
+	group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
+	if (!group->fanotify_data.merge_hash) {
+		fd = -ENOMEM;
+		goto out_destroy_group;
+	}
+
 	group->overflow_event = fanotify_alloc_overflow_event();
 	if (unlikely(!group->overflow_event)) {
 		fd = -ENOMEM;