From: Jan Kara <jack@xxxxxxx> Subject: fsnotify: convert notification_mutex to a spinlock notification_mutex is used to protect the list of pending events. As such there's no reason to use a sleeping lock for it. Convert it to a spinlock. [jack@xxxxxxx: fixed version] Link: http://lkml.kernel.org/r/1474031567-1831-1-git-send-email-jack@xxxxxxx Link: http://lkml.kernel.org/r/1473797711-14111-5-git-send-email-jack@xxxxxxx Signed-off-by: Jan Kara <jack@xxxxxxx> Reviewed-by: Lino Sanfilippo <LinoSanfilippo@xxxxxx> Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> Cc: Miklos Szeredi <mszeredi@xxxxxxxxxx> Cc: Eric Paris <eparis@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/notify/fanotify/fanotify_user.c | 27 ++++++++++++++------------- fs/notify/group.c | 6 +++--- fs/notify/inotify/inotify_user.c | 16 ++++++++-------- fs/notify/notification.c | 27 +++++++++++++++------------ include/linux/fsnotify_backend.h | 2 +- 5 files changed, 41 insertions(+), 37 deletions(-) diff -puN fs/notify/fanotify/fanotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock fs/notify/fanotify/fanotify_user.c --- a/fs/notify/fanotify/fanotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock +++ a/fs/notify/fanotify/fanotify_user.c @@ -49,12 +49,13 @@ struct kmem_cache *fanotify_perm_event_c * enough to fit in "count". Return an error pointer if the count * is not large enough. * - * Called with the group->notification_mutex held. + * Called with the group->notification_lock held. */ static struct fsnotify_event *get_one_event(struct fsnotify_group *group, size_t count) { - BUG_ON(!mutex_is_locked(&group->notification_mutex)); + BUG_ON(IS_ENABLED(CONFIG_SMP) && + !spin_is_locked(&group->notification_lock)); pr_debug("%s: group=%p count=%zd\n", __func__, group, count); @@ -64,7 +65,7 @@ static struct fsnotify_event *get_one_ev if (FAN_EVENT_METADATA_LEN > count) return ERR_PTR(-EINVAL); - /* held the notification_mutex the whole time, so this is the + /* held the notification_lock the whole time, so this is the * same event we peeked above */ return fsnotify_remove_first_event(group); } @@ -244,10 +245,10 @@ static unsigned int fanotify_poll(struct int ret = 0; poll_wait(file, &group->notification_waitq, wait); - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); if (!fsnotify_notify_queue_is_empty(group)) ret = POLLIN | POLLRDNORM; - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); return ret; } @@ -268,9 +269,9 @@ static ssize_t fanotify_read(struct file add_wait_queue(&group->notification_waitq, &wait); while (1) { - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); kevent = get_one_event(group, count); - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); if (IS_ERR(kevent)) { ret = PTR_ERR(kevent); @@ -387,17 +388,17 @@ static int fanotify_release(struct inode * dequeue them and set the response. They will be freed once the * response is consumed and fanotify_get_response() returns. */ - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); while (!fsnotify_notify_queue_is_empty(group)) { fsn_event = fsnotify_remove_first_event(group); if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) { - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); fsnotify_destroy_event(group, fsn_event); - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); } else FANOTIFY_PE(fsn_event)->response = FAN_ALLOW; } - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); /* Response for all permission events it set, wakeup waiters */ wake_up(&group->fanotify_data.access_waitq); @@ -423,10 +424,10 @@ static long fanotify_ioctl(struct file * switch (cmd) { case FIONREAD: - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); list_for_each_entry(fsn_event, &group->notification_list, list) send_len += FAN_EVENT_METADATA_LEN; - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); ret = put_user(send_len, (int __user *) p); break; } diff -puN fs/notify/group.c~fsnotify-convert-notification_mutex-to-a-spinlock fs/notify/group.c --- a/fs/notify/group.c~fsnotify-convert-notification_mutex-to-a-spinlock +++ a/fs/notify/group.c @@ -45,9 +45,9 @@ static void fsnotify_final_destroy_group */ void fsnotify_group_stop_queueing(struct fsnotify_group *group) { - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); group->shutdown = true; - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); } /* @@ -125,7 +125,7 @@ struct fsnotify_group *fsnotify_alloc_gr atomic_set(&group->refcnt, 1); atomic_set(&group->num_marks, 0); - mutex_init(&group->notification_mutex); + spin_lock_init(&group->notification_lock); INIT_LIST_HEAD(&group->notification_list); init_waitqueue_head(&group->notification_waitq); group->max_events = UINT_MAX; diff -puN fs/notify/inotify/inotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock fs/notify/inotify/inotify_user.c --- a/fs/notify/inotify/inotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock +++ a/fs/notify/inotify/inotify_user.c @@ -115,10 +115,10 @@ static unsigned int inotify_poll(struct int ret = 0; poll_wait(file, &group->notification_waitq, wait); - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); if (!fsnotify_notify_queue_is_empty(group)) ret = POLLIN | POLLRDNORM; - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); return ret; } @@ -138,7 +138,7 @@ static int round_event_name_len(struct f * enough to fit in "count". Return an error pointer if * not large enough. * - * Called with the group->notification_mutex held. + * Called with the group->notification_lock held. */ static struct fsnotify_event *get_one_event(struct fsnotify_group *group, size_t count) @@ -157,7 +157,7 @@ static struct fsnotify_event *get_one_ev if (event_size > count) return ERR_PTR(-EINVAL); - /* held the notification_mutex the whole time, so this is the + /* held the notification_lock the whole time, so this is the * same event we peeked above */ fsnotify_remove_first_event(group); @@ -234,9 +234,9 @@ static ssize_t inotify_read(struct file add_wait_queue(&group->notification_waitq, &wait); while (1) { - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); kevent = get_one_event(group, count); - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); pr_debug("%s: group=%p kevent=%p\n", __func__, group, kevent); @@ -300,13 +300,13 @@ static long inotify_ioctl(struct file *f switch (cmd) { case FIONREAD: - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); list_for_each_entry(fsn_event, &group->notification_list, list) { send_len += sizeof(struct inotify_event); send_len += round_event_name_len(fsn_event); } - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); ret = put_user(send_len, (int __user *) p); break; } diff -puN fs/notify/notification.c~fsnotify-convert-notification_mutex-to-a-spinlock fs/notify/notification.c --- a/fs/notify/notification.c~fsnotify-convert-notification_mutex-to-a-spinlock +++ a/fs/notify/notification.c @@ -63,7 +63,8 @@ EXPORT_SYMBOL_GPL(fsnotify_get_cookie); /* return true if the notify queue is empty, false otherwise */ bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group) { - BUG_ON(!mutex_is_locked(&group->notification_mutex)); + BUG_ON(IS_ENABLED(CONFIG_SMP) && + !spin_is_locked(&group->notification_lock)); return list_empty(&group->notification_list) ? true : false; } @@ -95,10 +96,10 @@ int fsnotify_add_event(struct fsnotify_g pr_debug("%s: group=%p event=%p\n", __func__, group, event); - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); if (group->shutdown) { - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); return 2; } @@ -106,7 +107,7 @@ int fsnotify_add_event(struct fsnotify_g ret = 2; /* Queue overflow event only if it isn't already queued */ if (!list_empty(&group->overflow_event->list)) { - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); return ret; } event = group->overflow_event; @@ -116,7 +117,7 @@ int fsnotify_add_event(struct fsnotify_g if (!list_empty(list) && merge) { ret = merge(list, event); if (ret) { - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); return ret; } } @@ -124,7 +125,7 @@ int fsnotify_add_event(struct fsnotify_g queue: group->q_len++; list_add_tail(&event->list, list); - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); wake_up(&group->notification_waitq); kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); @@ -139,7 +140,8 @@ struct fsnotify_event *fsnotify_remove_f { struct fsnotify_event *event; - BUG_ON(!mutex_is_locked(&group->notification_mutex)); + BUG_ON(IS_ENABLED(CONFIG_SMP) && + !spin_is_locked(&group->notification_lock)); pr_debug("%s: group=%p\n", __func__, group); @@ -161,7 +163,8 @@ struct fsnotify_event *fsnotify_remove_f */ struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) { - BUG_ON(!mutex_is_locked(&group->notification_mutex)); + BUG_ON(IS_ENABLED(CONFIG_SMP) && + !spin_is_locked(&group->notification_lock)); return list_first_entry(&group->notification_list, struct fsnotify_event, list); @@ -175,14 +178,14 @@ void fsnotify_flush_notify(struct fsnoti { struct fsnotify_event *event; - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); while (!fsnotify_notify_queue_is_empty(group)) { event = fsnotify_remove_first_event(group); - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); fsnotify_destroy_event(group, event); - mutex_lock(&group->notification_mutex); + spin_lock(&group->notification_lock); } - mutex_unlock(&group->notification_mutex); + spin_unlock(&group->notification_lock); } /* diff -puN include/linux/fsnotify_backend.h~fsnotify-convert-notification_mutex-to-a-spinlock include/linux/fsnotify_backend.h --- a/include/linux/fsnotify_backend.h~fsnotify-convert-notification_mutex-to-a-spinlock +++ a/include/linux/fsnotify_backend.h @@ -135,7 +135,7 @@ struct fsnotify_group { const struct fsnotify_ops *ops; /* how this group handles things */ /* needed to send notification to userspace */ - struct mutex notification_mutex; /* protect the notification_list */ + spinlock_t notification_lock; /* protect the notification_list */ struct list_head notification_list; /* list of event_holder this group needs to send to userspace */ wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */ unsigned int q_len; /* events on the queue */ _ -- 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
