Re: [PATCH RFC v7 11/16] fuse: {uring} Allow to queue fg requests through io-uring

[Pavel Begunkov <asml.silence@gmail.com>]

On 11/27/24 13:40, Bernd Schubert wrote:
> This prepares queueing and sending foreground requests through
> io-uring.
> 
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> ---
>   fs/fuse/dev.c         |   5 +-
>   fs/fuse/dev_uring.c   | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   fs/fuse/dev_uring_i.h |   8 +++
>   fs/fuse/fuse_dev_i.h  |   5 ++
>   4 files changed, 175 insertions(+), 2 deletions(-)
> 
...
> +
> +/*
> + * This prepares and sends the ring request in fuse-uring task context.
> + * User buffers are not mapped yet - the application does not have permission
> + * to write to it - this has to be executed in ring task context.
> + */
> +static void
> +fuse_uring_send_req_in_task(struct io_uring_cmd *cmd,
> +			    unsigned int issue_flags)
> +{
> +	struct fuse_uring_cmd_pdu *pdu = (struct fuse_uring_cmd_pdu *)cmd->pdu;
> +	struct fuse_ring_ent *ring_ent = pdu->ring_ent;
> +	struct fuse_ring_queue *queue = ring_ent->queue;
> +	int err;
> +
> +	BUILD_BUG_ON(sizeof(pdu) > sizeof(cmd->pdu));
> +
> +	err = fuse_uring_prepare_send(ring_ent);
> +	if (err)
> +		goto err;
> +
> +	io_uring_cmd_done(cmd, 0, 0, issue_flags);
> +
> +	spin_lock(&queue->lock);
> +	ring_ent->state = FRRS_USERSPACE;

I haven't followed the cancellation/teardown path well, but don't
you need to set FRRS_USERSPACE before io_uring_cmd_done()?

E.g. while we're just before the spin_lock above here, can
fuse_uring_stop_list_entries() find the request, see that the state
is not FRRS_USERSPACE

bool need_cmd_done = ent->state != FRRS_USERSPACE;

and call io_uring_cmd_done a second time?


-- 
Pavel Begunkov