From: Jan Kara <jack@xxxxxxx> Subject: fsnotify: add a way to stop queueing events on group shutdown Implement a function that can be called when a group is being shutdown to stop queueing new events to the group. Fanotify will use this. Fixes: 5838d4442bd5971687b72221736222637e03140d Link: http://lkml.kernel.org/r/1473797711-14111-2-git-send-email-jack@xxxxxxx Signed-off-by: Jan Kara <jack@xxxxxxx> Reviewed-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/notify/group.c | 19 +++++++++++++++++++ fs/notify/notification.c | 8 +++++++- include/linux/fsnotify_backend.h | 3 +++ 3 files changed, 29 insertions(+), 1 deletion(-) diff -puN fs/notify/group.c~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown fs/notify/group.c --- a/fs/notify/group.c~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown +++ a/fs/notify/group.c @@ -40,6 +40,17 @@ static void fsnotify_final_destroy_group } /* + * Stop queueing new events for this group. Once this function returns + * fsnotify_add_event() will not add any new events to the group's queue. + */ +void fsnotify_group_stop_queueing(struct fsnotify_group *group) +{ + mutex_lock(&group->notification_mutex); + group->shutdown = true; + mutex_unlock(&group->notification_mutex); +} + +/* * Trying to get rid of a group. Remove all marks, flush all events and release * the group reference. * Note that another thread calling fsnotify_clear_marks_by_group() may still @@ -47,6 +58,14 @@ static void fsnotify_final_destroy_group */ void fsnotify_destroy_group(struct fsnotify_group *group) { + /* + * Stop queueing new events. The code below is careful enough to not + * require this but fanotify needs to stop queuing events even before + * fsnotify_destroy_group() is called and this makes the other callers + * of fsnotify_destroy_group() to see the same behavior. + */ + fsnotify_group_stop_queueing(group); + /* clear all inode marks for this group, attach them to destroy_list */ fsnotify_detach_group_marks(group); diff -puN fs/notify/notification.c~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown fs/notify/notification.c --- a/fs/notify/notification.c~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown +++ a/fs/notify/notification.c @@ -82,7 +82,8 @@ void fsnotify_destroy_event(struct fsnot * Add an event to the group notification queue. The group can later pull this * event off the queue to deal with. The function returns 0 if the event was * added to the queue, 1 if the event was merged with some other queued event, - * 2 if the queue of events has overflown. + * 2 if the event was not queued - either the queue of events has overflown + * or the group is shutting down. */ int fsnotify_add_event(struct fsnotify_group *group, struct fsnotify_event *event, @@ -96,6 +97,11 @@ int fsnotify_add_event(struct fsnotify_g mutex_lock(&group->notification_mutex); + if (group->shutdown) { + mutex_unlock(&group->notification_mutex); + return 2; + } + if (group->q_len >= group->max_events) { ret = 2; /* Queue overflow event only if it isn't already queued */ diff -puN include/linux/fsnotify_backend.h~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown include/linux/fsnotify_backend.h --- a/include/linux/fsnotify_backend.h~fsnotify-add-a-way-to-stop-queueing-events-on-group-shutdown +++ a/include/linux/fsnotify_backend.h @@ -148,6 +148,7 @@ struct fsnotify_group { #define FS_PRIO_1 1 /* fanotify content based access control */ #define FS_PRIO_2 2 /* fanotify pre-content access */ unsigned int priority; + bool shutdown; /* group is being shut down, don't queue more events */ /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */ struct mutex mark_mutex; /* protect marks_list */ @@ -292,6 +293,8 @@ extern struct fsnotify_group *fsnotify_a extern void fsnotify_get_group(struct fsnotify_group *group); /* drop reference on a group from fsnotify_alloc_group */ extern void fsnotify_put_group(struct fsnotify_group *group); +/* group destruction begins, stop queuing new events */ +extern void fsnotify_group_stop_queueing(struct fsnotify_group *group); /* destroy group */ extern void fsnotify_destroy_group(struct fsnotify_group *group); /* fasync handler function */ _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
