fanotify: allow freeze when waiting response for permission events

This is a long-standing issue that uninterruptible sleep in fanotify
could make system hibernation fail if the usperspace server gets frozen
before the process waiting for the response (as reported e.g. [1][2]).

A few years ago, there was an attempt to switch to interruptible sleep
while waiting [3], but that would lead to EINTR returns from open(2)
and break userspace [4], so it's been changed to only killable [5].

And the core freezer logic had been rewritten [6][7] in v6.1, allowing
freezing in uninterrupted sleep, so we can solve this problem now.

[1] https://lore.kernel.org/lkml/1518774280-38090-1-git-send-email-t.vivek@samsung.com/
[2] https://lore.kernel.org/lkml/c1bb16b7-9eee-9cea-2c96-a512d8b3b9c7@nwra.com/
[3] https://lore.kernel.org/linux-fsdevel/20190213145443.26836-1-jack@suse.cz/
[4] https://lore.kernel.org/linux-fsdevel/d0031e3a-f050-0832-fa59-928a80ffd44b@nwra.com/
[5] https://lore.kernel.org/linux-fsdevel/20190221105558.GA20921@quack2.suse.cz/
[6] https://lore.kernel.org/lkml/20220822114649.055452969@infradead.org/
[7] https://lore.kernel.org/lkml/20230908-avoid-spurious-freezer-wakeups-v4-0-6155aa3dafae@quicinc.com/

Signed-off-by: Winston Wen <wentao@uniontech.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <BD33543C483B89AB+20240305061804.1186796-1-wentao@uniontech.com>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 1e4def21811e4a49ad15561fe26ad1c387d76362..224bccaab4cc3fc6c54107975363a35894d4e917 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -228,8 +228,10 @@ static int fanotify_get_response(struct fsnotify_group *group,
 
        pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 
-       ret = wait_event_killable(group->fanotify_data.access_waitq,
-                                 event->state == FAN_EVENT_ANSWERED);
+       ret = wait_event_state(group->fanotify_data.access_waitq,
+                                 event->state == FAN_EVENT_ANSWERED,
+                                 (TASK_KILLABLE|TASK_FREEZABLE));
+
        /* Signal pending? */
        if (ret < 0) {
                spin_lock(&group->notification_lock);