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fsnotify: Let userspace know about lost events due to ENOMEM

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Currently if notification event is lost due to event allocation failing
we ENOMEM, we just silently continue (except for fanotify permission
events where we deny the access). This is undesirable as userspace has
no way of knowing whether the notifications it got are complete or not.
Treat lost events due to ENOMEM the same way as lost events due to queue
overflow so that userspace knows something bad happened and it likely
needs to rescan the filesystem.

Reviewed-by: Amir Goldstein <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
This commit is contained in:
Jan Kara 2018-02-21 15:07:52 +01:00
commit 7b1f641776
4 changed files with 23 additions and 3 deletions
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9
fs/notify/fanotify/fanotify.c
View file

@ -221,8 +221,15 @@ static int fanotify_handle_event(struct fsnotify_group *group,
event = fanotify_alloc_event(group, inode, mask, data);
ret = -ENOMEM;
if (unlikely(!event))
if (unlikely(!event)) {
/*
* We don't queue overflow events for permission events as
* there the access is denied and so no event is in fact lost.
*/
if (!fanotify_is_perm_event(mask))
fsnotify_queue_overflow(group);
goto finish;
}
fsn_event = &event->fse;
ret = fsnotify_add_event(group, fsn_event, fanotify_merge);

8
fs/notify/inotify/inotify_fsnotify.c
View file

@ -99,8 +99,14 @@ int inotify_handle_event(struct fsnotify_group *group,
fsn_mark);
event = kmalloc(alloc_len, GFP_KERNEL);
if (unlikely(!event))
if (unlikely(!event)) {
/*
* Treat lost event due to ENOMEM the same way as queue
* overflow to let userspace know event was lost.
*/
fsnotify_queue_overflow(group);
return -ENOMEM;
}
fsn_event = &event->fse;
fsnotify_init_event(fsn_event, inode, mask);

3
fs/notify/notification.c
View file

@ -111,7 +111,8 @@ int fsnotify_add_event(struct fsnotify_group *group,
return 2;
}
if (group->q_len >= group->max_events) {
if (event == group->overflow_event ||
group->q_len >= group->max_events) {
ret = 2;
/* Queue overflow event only if it isn't already queued */
if (!list_empty(&group->overflow_event->list)) {