<s>
Pass-to-Userspace	O
Framework	O
File	B-Application
System	I-Application
(	O
puffs	B-Application
)	O
is	O
a	O
NetBSD	B-Device
kernel	I-Device
subsystem	O
developed	O
for	O
running	O
filesystems	B-Application
in	O
userspace	O
.	O
</s>
<s>
It	O
was	O
added	O
to	O
NetBSD	B-Device
in	O
the	O
5.0	O
release	O
,	O
and	O
was	O
ported	O
to	O
DragonFly	B-Application
BSD	I-Application
in	O
the	O
3.2	O
release	O
.	O
</s>
<s>
In	O
NetBSD	B-Device
5.0	O
,	O
puffs	B-Application
includes	O
refuse	O
,	O
a	O
reimplementation	O
of	O
the	O
libfuse	O
high-level	O
interface	O
.	O
</s>
<s>
Some	O
filesystems	B-Application
use	O
the	O
low-level	O
libfuse	O
interface	O
or	O
the	O
kernel	B-Operating_System
FUSE	B-Application
interface	O
and	O
they	O
cannot	O
be	O
supported	O
through	O
refuse	O
.	O
</s>
<s>
NetBSD	B-Device
6.0	O
addresses	O
that	O
limitation	O
through	O
perfuse	O
,	O
a	O
new	O
compatibility	O
layer	O
that	O
emulates	O
the	O
FUSE	B-Application
kernel	B-Operating_System
interface	O
.	O
</s>
