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/[email protected]/
[2] https://lore.kernel.org/lkml/[email protected]/
[3] https://lore.kernel.org/linux-fsdevel/[email protected]/
[4] https://lore.kernel.org/linux-fsdevel/[email protected]/
[5] https://lore.kernel.org/linux-fsdevel/[email protected]/
[6] https://lore.kernel.org/lkml/[email protected]/
[7] https://lore.kernel.org/lkml/20230908-avoid-spurious-freezer-wakeups-v4-0-6155aa3dafae@quicinc.com/

Signed-off-by: Winston Wen <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Message-Id: <[email protected]>

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