[RFC 02/13] nvme: wire-up support for async-passthru on

[Clay Mayers]

Message-ID: <20211220141734.12206-3-joshi.k at samsung.com>

On 12/20/21 19:47:23 +0530, Kanchan Joshi wrote:
> Introduce handlers for fops->async_cmd(), implementing async passthru on
> char device (including the multipath one).
> The handlers supports NVME_IOCTL_IO64_CMD.
>
I commented on these two issues below in more detail at
https://github.com/joshkan/nvme-uring-pt/issues

> +static void nvme_setup_uring_cmd_data(struct request *rq,
> +		struct io_uring_cmd *ioucmd, void *meta,
> +		void __user *meta_buffer, u32 meta_len, bool write) {
> +	struct nvme_uring_cmd *cmd = nvme_uring_cmd(ioucmd);
> +
> +	/* to free bio on completion, as req->bio will be null at that time */
> +	cmd->bio = rq->bio;
> +	/* meta update is required only for read requests */
> +	if (meta && !write) {
> +		cmd->meta = meta;
> +		cmd->meta_buffer = meta_buffer;
> +		cmd->meta_len = meta_len;
> +	} else {
> +		cmd->meta = NULL;
I believe that not saving meta in cmd->meta will leak it when it's a write. 
But nvme_pt_task_cb also needs to change to copy to user when
cmd->meta_buffer is set instead of cmd->meta.

> +
> +int nvme_ns_chr_async_cmd(struct io_uring_cmd *ioucmd,
> +		enum io_uring_cmd_flags flags)
> +{
> +	struct nvme_ns *ns = container_of(file_inode(ioucmd->file)->i_cdev,
> +			struct nvme_ns, cdev);
> +
> +	return nvme_ns_async_ioctl(ns, ioucmd); }
> +
The uring cmd flags are not being passed to nvme_ns_async_ioctl - what if
IO_URING_F_NONBLOCK Is set?  When it is, I think the nvme_alloc_request()
call in nvme_submit_user_cmd() needs to pass in BLK_MQ_REQ_NOWAIT as
the flags parameter or move to another thread.  Our proto-type does the former
requiring user mode to retry on -EWOULDBLOCK and -EBUSY.

--
Clay Mayers