Re: [PATCH v7 1/6] fuse: decouple fuse_ring creation from ent registration

On 8/19/26 13:34, Miklos Szeredi wrote:
> On Fri, 14 Aug 2026 at 21:00, Joanne Koong <[email protected]> wrote:
>>
>> Currently, the connection's fuse_ring is created lazily on the first
>> FUSE_IO_URING_CMD_REGISTER command. A server registers entries from one
>> thread per queue (one per CPU) and those threads issue their first
>> REGISTER command concurrently. They then race to create the single
>> per-connection fuse_ring, which required open-coded handling in
>> fuse_uring_create() to detect and protect against concurrent creations.
>>
>> Decouple fuse_ring creation from ent registration and move it to
>> FUSE_INIT reply processing after a server has negotiated and set
>> FUSE_OVER_IO_URING. The ring is published before the connection is
>> marked initialized. fuse_uring_register() no longer creates the ring and
>> it instead uses the ring set up at init time.
> 
> I tested this with loraw (a "raw" loopback tester that doesn't use
> libfuse) and it fails with
> 
> root@kvm:~# ./loraw -u  /mnt/fuse
> loraw: loraw.c:1010: lo_start_uring: Assertion `!cqe->res' failed.
> 
> cqe->res is -22 (EINVAL).
> 
> Attaching the reproducer.  To compile:
> 
> cp $(KERNEL_TREE)/include/uapi/linux/fuse.h fuse_kernel.h
> gcc loraw.c -oloraw -luring


Unless Joannes replies earlier, I will take a look in about 5 to 7 hours
- reply expected in the night.


Thanks,
Bernd