Commit 6f73171e authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fsnotify: allow fsnotify_{peek,remove}_first_event with empty queue 

Current code has an assumtion that fsnotify_notify_queue_is_empty() is
called to verify that queue is not empty before trying to peek or remove
an event from queue.

Remove this assumption by moving the fsnotify_notify_queue_is_empty()
into the functions, allow them to return NULL value and check return
value by all callers.

This is a prep patch for multi event queues.

Link: https://lore.kernel.org/r/20210304104826.3993892-2-amir73il@gmail.com


Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 1e28eed1

fs/notify/fanotify/fanotify_user.c

+16 −10
Original line number Diff line number Diff line
@@ -100,24 +100,30 @@ static struct fanotify_event *get_one_event(struct fsnotify_group *group, 
{

	size_t event_size = FAN_EVENT_METADATA_LEN;

	struct fanotify_event *event = NULL;

	struct fsnotify_event *fsn_event;

	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);



	pr_debug("%s: group=%p count=%zd\n", __func__, group, count);



	spin_lock(&group->notification_lock);

	if (fsnotify_notify_queue_is_empty(group))

	fsn_event = fsnotify_peek_first_event(group);

	if (!fsn_event)

		goto out;



	if (fid_mode) {

		event_size += fanotify_event_info_len(fid_mode,

			FANOTIFY_E(fsnotify_peek_first_event(group)));

	}

	event = FANOTIFY_E(fsn_event);

	if (fid_mode)

		event_size += fanotify_event_info_len(fid_mode, event);



	if (event_size > count) {

		event = ERR_PTR(-EINVAL);

		goto out;

	}

	event = FANOTIFY_E(fsnotify_remove_first_event(group));



	/*

	 * Held the notification_lock the whole time, so this is the

	 * same event we peeked above.

	 */

	fsnotify_remove_first_event(group);

	if (fanotify_is_perm_event(event->mask))

		FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;

out:
@@ -573,6 +579,7 @@ static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t 
static int fanotify_release(struct inode *ignored, struct file *file)

{

	struct fsnotify_group *group = file->private_data;

	struct fsnotify_event *fsn_event;



	/*

	 * Stop new events from arriving in the notification queue. since
@@ -601,13 +608,12 @@ static int fanotify_release(struct inode *ignored, struct file *file) 
	 * dequeue them and set the response. They will be freed once the

	 * response is consumed and fanotify_get_response() returns.

	 */

	while (!fsnotify_notify_queue_is_empty(group)) {

		struct fanotify_event *event;

	while ((fsn_event = fsnotify_remove_first_event(group))) {

		struct fanotify_event *event = FANOTIFY_E(fsn_event);



		event = FANOTIFY_E(fsnotify_remove_first_event(group));

		if (!(event->mask & FANOTIFY_PERM_EVENTS)) {

			spin_unlock(&group->notification_lock);

			fsnotify_destroy_event(group, &event->fse);

			fsnotify_destroy_event(group, fsn_event);

		} else {

			finish_permission_event(group, FANOTIFY_PERM(event),

						FAN_ALLOW);

fs/notify/inotify/inotify_user.c

+2 −3
Original line number Diff line number Diff line
@@ -146,10 +146,9 @@ static struct fsnotify_event *get_one_event(struct fsnotify_group *group, 
	size_t event_size = sizeof(struct inotify_event);

	struct fsnotify_event *event;



	if (fsnotify_notify_queue_is_empty(group))

		return NULL;



	event = fsnotify_peek_first_event(group);

	if (!event)

		return NULL;



	pr_debug("%s: group=%p event=%p\n", __func__, group, event);

fs/notify/notification.c

+19 −23
Original line number Diff line number Diff line
@@ -47,13 +47,6 @@ u32 fsnotify_get_cookie(void) 
}

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)

{

	assert_spin_locked(&group->notification_lock);

	return list_empty(&group->notification_list) ? true : false;

}



void fsnotify_destroy_event(struct fsnotify_group *group,

			    struct fsnotify_event *event)

{
@@ -141,33 +134,36 @@ void fsnotify_remove_queued_event(struct fsnotify_group *group, 
}



/*

 * Remove and return the first event from the notification list.  It is the

 * responsibility of the caller to destroy the obtained event

 * Return the first event on the notification list without removing it.

 * Returns NULL if the list is empty.

 */

struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)

struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group)

{

	struct fsnotify_event *event;



	assert_spin_locked(&group->notification_lock);



	pr_debug("%s: group=%p\n", __func__, group);

	if (fsnotify_notify_queue_is_empty(group))

		return NULL;



	event = list_first_entry(&group->notification_list,

	return list_first_entry(&group->notification_list,

				struct fsnotify_event, list);

	fsnotify_remove_queued_event(group, event);

	return event;

}



/*

 * This will not remove the event, that must be done with

 * fsnotify_remove_first_event()

 * Remove and return the first event from the notification list.  It is the

 * responsibility of the caller to destroy the obtained event

 */

struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group)

struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)

{

	assert_spin_locked(&group->notification_lock);

	struct fsnotify_event *event = fsnotify_peek_first_event(group);



	return list_first_entry(&group->notification_list,

				struct fsnotify_event, list);

	if (!event)

		return NULL;



	pr_debug("%s: group=%p event=%p\n", __func__, group, event);



	fsnotify_remove_queued_event(group, event);



	return event;

}



/*

include/linux/fsnotify_backend.h

+7 −1
Original line number Diff line number Diff line
@@ -495,7 +495,13 @@ static inline void fsnotify_queue_overflow(struct fsnotify_group *group) 
	fsnotify_add_event(group, group->overflow_event, NULL);

}



/* true if the group notification queue is empty */

static inline bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)

{

	assert_spin_locked(&group->notification_lock);



	return list_empty(&group->notification_list);

}



extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);

/* return, but do not dequeue the first event on the notification queue */

extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);