On 11/28/24 04:54, Sergey Senozhatsky wrote: > Hello Miklos, > > A question: does fuse define any semantics for stalled requests handling? > > We are currently looking at a number of hung_task watchdog crashes with > tasks waiting forever in d_wait_lookup() for dentries to lose PAR_LOOKUP > state, and we suspect that those dentries are from fuse mount point > (we also sometimes see hung_tasks in fuse_lookup()->fuse_simple_request()). > Supposedly (a theory) some tasks are in request_wait_answer() under > PAR_LOOKUP, and the rest of tasks are waiting for them to finish and clear > PAR_LOOKUP bit. > > request_wait_answer() waits indefinitely, however, the interesting > thing is that it uses wait_event_interruptible() (when we wait for > !fc->no_interrupt request to be processed). What is the idea behind > interruptible wait? Is this, may be, for stall requests handling? > Does fuse expect user-space to watchdog or monitor its processes/threads > that issue syscalls on fuse mount points and, e.g., SIGKILL stalled ones? > > To make things even more complex, in our particular case fuse mount > point mounts a remote google driver, so it become a network fs in > some sense, which adds a whole new dimension of possibilities for > stalled/failed requests. How those are expected to be handled? Should > fuse still wait indefinitely or would it make sense to add a timeout > to request_wait_answer() and FR_INTERRUPTED timeout-ed requests? > Please see here https://lore.kernel.org/all/20241114191332.669127-1-joannelkoong@xxxxxxxxx/ Thanks, Bernd
