Re: Should FUSE set IO_FLUSHER for the userspace process?

[Antonio SJ Musumeci <trapexit@spawn.link>]

On 9/19/22 05:20, Miklos Szeredi wrote:
> On Sun, 18 Sept 2022 at 13:03, Nikolaus Rath <Nikolaus@rath.org> wrote:
>> Hi,
>>
>> Should the FUSE kernel driver perhaps set PR_SET_IO_FLUSHER for the FUSE
>> userspace process daemon when a connection is opened?
>>
>> If I understand correctly, this is necessary to avoid a deadlocks if the
>> kernel needs to reclaim memory that has to be written back through FUSE.
> The fuse kernel driver is careful to avoid such deadlocks.  When
> memory reclaim happens, it copies data to temporary buffers and
> immediately finishes the reclaim from the memory management
> subsystem's point of view.   The temp buffers are then sent to
> userspace and written back without having to worry about deadlocks.
> There are lots of details missing from the above description, but this
> is the essence of the writeback deadlock avoidance.
>
> Thanks,
> Miklos

Miklos, does this mean that FUSE servers shouldn't bother setting 
PR_SET_IO_FLUSHER? Are there any benefits to setting it explicitly or 
detriments to not setting it?