Re: [PATCH RFC] io_uring: support ioctl

[Hao Xu <haoxu@linux.alibaba.com>]

在 2020/11/2 下午7:07, Pavel Begunkov 写道:
> On 02/11/2020 07:44, Hao Xu wrote:
>> Async ioctl is necessary for some scenarios like nonblocking
>> single-threaded model
> 
> Once I fell for it myself, see Jann explained why that's a bad idea.
Thanks, Pavel. The information is helpful and make sense to me.
It seems I have to rethink it. Btw, your version is more robust.
> https://lore.kernel.org/io-uring/CAG48ez0N_b+kjbddhHe+BUvSnOSvpm1vdfQ9cv+cgTLuCMXqug@mail.gmail.com/
> 
>>
>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
>> ---
>> I've written corresponding liburing tests for this feature. Currently
>> just a simple test for BLKGETSIZE operation. I'll release it later soon
>> when it gets better.
>>
>>   fs/io_uring.c                 | 56 +++++++++++++++++++++++++++++++++++++++++++
>>   fs/ioctl.c                    |  4 ++--
>>   include/linux/fs.h            |  3 ++-
>>   include/uapi/linux/io_uring.h |  1 +
>>   4 files changed, 61 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index b42dfa0243bf..c8ab6b6d2d70 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -539,6 +539,13 @@ struct io_statx {
>>   	struct statx __user		*buffer;
>>   };
>>   
>> +struct io_ioctl {
>> +	struct file			*file;
>> +	unsigned int                    fd;
>> +	unsigned int                    cmd;
>> +	unsigned long                   arg;
>> +};
>> +
>>   struct io_completion {
>>   	struct file			*file;
>>   	struct list_head		list;
>> @@ -665,6 +672,7 @@ struct io_kiocb {
>>   		struct io_splice	splice;
>>   		struct io_provide_buf	pbuf;
>>   		struct io_statx		statx;
>> +		struct io_ioctl         ioctl;
>>   		/* use only after cleaning per-op data, see io_clean_op() */
>>   		struct io_completion	compl;
>>   	};
>> @@ -932,6 +940,10 @@ struct io_op_def {
>>   		.hash_reg_file		= 1,
>>   		.unbound_nonreg_file	= 1,
>>   	},
>> +	[IORING_OP_IOCTL] = {
>> +		.needs_file             = 1,
>> +		.work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_FILES
>> +	},
>>   };
>>   
>>   enum io_mem_account {
>> @@ -4819,6 +4831,45 @@ static int io_connect(struct io_kiocb *req, bool force_nonblock,
>>   }
>>   #endif /* CONFIG_NET */
>>   
>> +static int io_ioctl_prep(struct io_kiocb *req,
>> +			 const struct io_uring_sqe *sqe)
>> +{
>> +	if (sqe->ioprio || sqe->buf_index || sqe->rw_flags)
>> +		return -EINVAL;
>> +	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>> +		return -EINVAL;
>> +
>> +	req->ioctl.fd = READ_ONCE(sqe->fd);
>> +	req->ioctl.cmd = READ_ONCE(sqe->len);
>> +	req->ioctl.arg = READ_ONCE(sqe->addr);
>> +	return 0;
>> +}
>> +
>> +static int io_ioctl(struct io_kiocb *req, bool force_nonblock)
>> +{
>> +	int ret;
>> +
>> +	if (force_nonblock)
>> +		return -EAGAIN;
>> +
>> +	if (!req->file)
>> +		return -EBADF;
>> +
>> +	ret = security_file_ioctl(req->file, req->ioctl.cmd, req->ioctl.arg);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = do_vfs_ioctl(req->file, req->ioctl.fd, req->ioctl.cmd, req->ioctl.arg);
>> +	if (ret == -ENOIOCTLCMD)
>> +		ret = vfs_ioctl(req->file, req->ioctl.cmd, req->ioctl.arg);
>> +
>> +out:
>> +	if (ret)
>> +		req_set_fail_links(req);
>> +	io_req_complete(req, ret);
>> +	return 0;
>> +}
>> +
>>   struct io_poll_table {
>>   	struct poll_table_struct pt;
>>   	struct io_kiocb *req;
>> @@ -5742,6 +5793,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>   		return io_remove_buffers_prep(req, sqe);
>>   	case IORING_OP_TEE:
>>   		return io_tee_prep(req, sqe);
>> +	case IORING_OP_IOCTL:
>> +		return io_ioctl_prep(req, sqe);
>>   	}
>>   
>>   	printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
>> @@ -5985,6 +6038,9 @@ static int io_issue_sqe(struct io_kiocb *req, bool force_nonblock,
>>   	case IORING_OP_TEE:
>>   		ret = io_tee(req, force_nonblock);
>>   		break;
>> +	case IORING_OP_IOCTL:
>> +		ret = io_ioctl(req, force_nonblock);
>> +		break;
>>   	default:
>>   		ret = -EINVAL;
>>   		break;
>> diff --git a/fs/ioctl.c b/fs/ioctl.c
>> index 4e6cc0a7d69c..4ff2eb0d8ee0 100644
>> --- a/fs/ioctl.c
>> +++ b/fs/ioctl.c
>> @@ -664,8 +664,8 @@ static int ioctl_file_dedupe_range(struct file *file,
>>    * When you add any new common ioctls to the switches above and below,
>>    * please ensure they have compatible arguments in compat mode.
>>    */
>> -static int do_vfs_ioctl(struct file *filp, unsigned int fd,
>> -			unsigned int cmd, unsigned long arg)
>> +int do_vfs_ioctl(struct file *filp, unsigned int fd,
>> +		unsigned int cmd, unsigned long arg)
>>   {
>>   	void __user *argp = (void __user *)arg;
>>   	struct inode *inode = file_inode(filp);
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 0bd126418bb6..ad62aa6f6136 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1732,7 +1732,8 @@ int vfs_mkobj(struct dentry *, umode_t,
>>   int vfs_utimes(const struct path *path, struct timespec64 *times);
>>   
>>   extern long vfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
>> -
>> +extern int do_vfs_ioctl(struct file *filp, unsigned int fd,
>> +			unsigned int cmd, unsigned long arg);
>>   #ifdef CONFIG_COMPAT
>>   extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
>>   					unsigned long arg);
>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>> index 98d8e06dea22..4919b4e94c12 100644
>> --- a/include/uapi/linux/io_uring.h
>> +++ b/include/uapi/linux/io_uring.h
>> @@ -132,6 +132,7 @@ enum {
>>   	IORING_OP_PROVIDE_BUFFERS,
>>   	IORING_OP_REMOVE_BUFFERS,
>>   	IORING_OP_TEE,
>> +	IORING_OP_IOCTL,
>>   
>>   	/* this goes last, obviously */
>>   	IORING_OP_LAST,
>>
>