From: Amir Goldstein amir73il@gmail.com
[ Upstream commit f367a62a7cad2447d835a9f14fc63997a9137246 ]
With inotify, when a watch is set on a directory and on its child, an event on the child is reported twice, once with wd of the parent watch and once with wd of the child watch without the filename.
With fanotify, when a watch is set on a directory and on its child, an event on the child is reported twice, but it has the exact same information - either an open file descriptor of the child or an encoded fid of the child.
The reason that the two identical events are not merged is because the object id used for merging events in the queue is the child inode in one event and parent inode in the other.
For events with path or dentry data, use the victim inode instead of the watched inode as the object id for event merging, so that the event reported on parent will be merged with the event reported on the child.
Link: https://lore.kernel.org/r/20200319151022.31456-9-amir73il@gmail.com Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Sasha Levin sashal@kernel.org --- fs/notify/fanotify/fanotify.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 14d0ac4664595..f5d30573f4a99 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -314,7 +314,12 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group, if (!event) goto out; init: __maybe_unused - fsnotify_init_event(&event->fse, (unsigned long)inode); + /* + * Use the victim inode instead of the watching inode as the id for + * event queue, so event reported on parent is merged with event + * reported on child when both directory and child watches exist. + */ + fsnotify_init_event(&event->fse, (unsigned long)id); event->mask = mask; if (FAN_GROUP_FLAG(group, FAN_REPORT_TID)) event->pid = get_pid(task_pid(current));