On Thu, Aug 28, 2025 at 04:08:19PM +0200, Miklos Szeredi wrote: > On Wed, 27 Aug 2025 at 21:12, Darrick J. Wong <djwong@xxxxxxxxxx> wrote: > > > Well sync() will poke all the fuse filesystems, right? > > Only those with writeback_cache enabled. But yeah, apparently this > was overlooked when dealing with "don't allow DoS-ing sync(2)". > > Can't see a good way out of this. I wonder, is it possible to shift a fuse_simple_request to behave like a fuse_simple_background request? For certain DOS-happy requests, one could use wait_event_interruptible_timeout(&req->waitq...) with a really high timeout. If the wait times out, we shift the completion to asynchronous and return -ETIMEDOUT to the (blocked) caller. That would allow the system to make progress though you'd probably have to take some drastic action if the fuse server sends back a failure (e.g. setting FUSE_I_BAD). (The problem with timeouts is that I tried setting a 60s timeout on fuse2fs and discovered that certain horrid fstests actually create monster files that take 45min to FUSE_RELEASE and so I don't know what a reasonable timeout is...) --D > Thanks, > Miklos
