@@ -148,6 +148,9 @@ static bool fanotify_should_merge(struct fanotify_event *old,
return false;
}
+/* Limit event merges to limit CPU overhead per event */
+#define FANOTIFY_MAX_MERGE_EVENTS 128
+
/* and the list better be locked by something too! */
static int fanotify_merge(struct fsnotify_group *group,
struct fsnotify_event *event)
@@ -155,6 +158,7 @@ static int fanotify_merge(struct fsnotify_group *group,
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];
+ int i = 0;
pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
group, event, bucket);
@@ -168,6 +172,8 @@ static int fanotify_merge(struct fsnotify_group *group,
return 0;
hlist_for_each_entry(old, hlist, merge_list) {
+ if (++i > FANOTIFY_MAX_MERGE_EVENTS)
+ break;
if (fanotify_should_merge(old, new)) {
old->mask |= new->mask;
return 1;
Event merges are expensive when event queue size is large, so limit the linear search to 128 merge tests. In combination with 128 size hash table, there is a potential to merge with up to 16K events in the hashed queue. Signed-off-by: Amir Goldstein <amir73il@gmail.com> --- fs/notify/fanotify/fanotify.c | 6 ++++++ 1 file changed, 6 insertions(+)