On 64bit arch, use the available 32bit in event for next_bucket field,
that is used to chain all events by order of insertion.
The group has a cursor for the bucket containing the first event and
every event stores the bucket of the next event to read.
On 32bit arch, hashed notification queue is disabled.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/notify/notification.c | 49 ++++++++++++++++++++++++--------
include/linux/fsnotify_backend.h | 42 +++++++++++++++++++++++++++
2 files changed, 79 insertions(+), 12 deletions(-)
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 58c8f6c1be1b..d98f4c8bfb0e 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -84,8 +84,8 @@ static void fsnotify_queue_check(struct fsnotify_group *group)
if (fsnotify_notify_queue_is_empty(group))
return;
- first_empty = list_empty(&group->notification_list[group->first_bucket]);
- last_empty = list_empty(&group->notification_list[group->last_bucket]);
+ first_empty = WARN_ON_ONCE(list_empty(&group->notification_list[group->first_bucket]));
+ last_empty = WARN_ON_ONCE(list_empty(&group->notification_list[group->last_bucket]));
list = &group->notification_list[0];
for (i = 0; i <= group->max_bucket; i++, list++) {
@@ -121,12 +121,23 @@ static void fsnotify_queue_event(struct fsnotify_group *group,
pr_debug("%s: group=%p event=%p bucket=%u\n", __func__, group, event, b);
- /*
- * TODO: set next_bucket of last event.
- */
- group->last_bucket = b;
- if (!group->num_events)
- group->first_bucket = b;
+ if (fsnotify_notify_queue_is_hashed(group)) {
+ /*
+ * On first insert, set this event's list as the list to read first event.
+ * Otherwise, point from last event to this event's list.
+ */
+ struct list_head *last_l = &group->notification_list[group->last_bucket];
+
+ if (!group->num_events) {
+ group->first_bucket = b;
+ } else if (!WARN_ON_ONCE(list_empty(last_l))) {
+ struct fsnotify_event *last_e;
+
+ last_e = list_last_entry(last_l, struct fsnotify_event, list);
+ fsnotify_event_set_next_bucket(last_e, b);
+ }
+ group->last_bucket = b;
+ }
group->num_events++;
list_add_tail(&event->list, list);
}
@@ -186,8 +197,8 @@ int fsnotify_add_event(struct fsnotify_group *group,
return ret;
}
-void fsnotify_remove_queued_event(struct fsnotify_group *group,
- struct fsnotify_event *event)
+static void __fsnotify_remove_queued_event(struct fsnotify_group *group,
+ struct fsnotify_event *event)
{
assert_spin_locked(&group->notification_lock);
/*
@@ -198,6 +209,17 @@ void fsnotify_remove_queued_event(struct fsnotify_group *group,
group->num_events--;
}
+void fsnotify_remove_queued_event(struct fsnotify_group *group,
+ struct fsnotify_event *event)
+{
+ /*
+ * if called for removal of event in the middle of a hashed queue,
+ * events may be read not in insertion order.
+ */
+ WARN_ON_ONCE(fsnotify_notify_queue_is_hashed(group));
+ __fsnotify_remove_queued_event(group, event);
+}
+
/* Return the notification list of the first event */
struct list_head *fsnotify_first_notification_list(struct fsnotify_group *group)
{
@@ -213,6 +235,7 @@ struct list_head *fsnotify_first_notification_list(struct fsnotify_group *group)
return list;
/*
+ * Oops... first bucket is not supposed to be empty.
* Look for any non-empty bucket.
*/
fsnotify_queue_check(group);
@@ -239,10 +262,12 @@ struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)
pr_debug("%s: group=%p bucket=%u\n", __func__, group, group->first_bucket);
event = list_first_entry(list, struct fsnotify_event, list);
- fsnotify_remove_queued_event(group, event);
+ __fsnotify_remove_queued_event(group, event);
/*
- * TODO: update group->first_bucket to next_bucket in first event.
+ * Removed event points to the next list to read from.
*/
+ group->first_bucket = fsnotify_event_next_bucket(event);
+
return event;
}
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index b2a80bc00108..3fc3c9e4d21c 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -161,9 +161,12 @@ struct fsnotify_ops {
};
#ifdef CONFIG_FANOTIFY
+#if BITS_PER_LONG == 64
+/* Use available 32bit of event for hashed queue support */
#define FSNOTIFY_HASHED_QUEUE
#define FSNOTIFY_HASHED_QUEUE_MAX_BITS 8
#endif
+#endif
/*
* all of the information about the original object we want to now send to
@@ -173,6 +176,9 @@ struct fsnotify_ops {
struct fsnotify_event {
struct list_head list;
unsigned int key; /* Key for hashed queue add/merge */
+#ifdef FSNOTIFY_HASHED_QUEUE
+ unsigned int next_bucket; /* Bucket to read next event from */
+#endif
};
/*
@@ -277,6 +283,41 @@ static inline struct list_head *fsnotify_event_notification_list(
return &group->notification_list[fsnotify_event_bucket(group, event)];
}
+#ifdef FSNOTIFY_HASHED_QUEUE
+static inline bool fsnotify_notify_queue_is_hashed(struct fsnotify_group *group)
+{
+ return group->max_bucket > 0;
+}
+
+static inline unsigned int fsnotify_event_next_bucket(struct fsnotify_event *event)
+{
+ return event->next_bucket;
+}
+
+static inline void fsnotify_event_set_next_bucket(struct fsnotify_event *event,
+ unsigned int b)
+{
+ event->next_bucket = b;
+}
+
+#else
+static inline bool fsnotify_notify_queue_is_hashed(struct fsnotify_group *group)
+{
+ return false;
+}
+
+static inline unsigned int fsnotify_event_next_bucket(struct fsnotify_event *event)
+{
+ return 0;
+}
+
+static inline void fsnotify_event_set_next_bucket(struct fsnotify_event *event,
+ unsigned int b)
+{
+}
+
+#endif
+
/* When calling fsnotify tell it if the data is a path or inode */
enum fsnotify_data_type {
FSNOTIFY_EVENT_NONE,
@@ -620,6 +661,7 @@ static inline void fsnotify_init_event(struct fsnotify_event *event,
{
INIT_LIST_HEAD(&event->list);
event->key = key;
+ fsnotify_event_set_next_bucket(event, 0);
}
#else
--
2.25.1
