Re: [PATCH v6 8/9] io_uring: add support for IORING_OP_SYMLINKAT

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

On 6/24/21 12:14 PM, Dmitry Kadashev wrote:
> IORING_OP_SYMLINKAT behaves like symlinkat(2) and takes the same flags
> and arguments.

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

> 
> Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
> Link: https://lore.kernel.org/io-uring/20210514145259.wtl4xcsp52woi6ab@wittgenstein/
> Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
> Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
> ---
>  fs/internal.h                 |  1 +
>  fs/io_uring.c                 | 66 +++++++++++++++++++++++++++++++++++
>  fs/namei.c                    |  3 +-
>  include/uapi/linux/io_uring.h |  1 +
>  4 files changed, 69 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/internal.h b/fs/internal.h
> index 207a455e32d3..3b3954214385 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -78,6 +78,7 @@ int may_linkat(struct user_namespace *mnt_userns, struct path *link);
>  int do_renameat2(int olddfd, struct filename *oldname, int newdfd,
>  		 struct filename *newname, unsigned int flags);
>  int do_mkdirat(int dfd, struct filename *name, umode_t mode);
> +int do_symlinkat(struct filename *from, int newdfd, struct filename *to);
>  
>  /*
>   * namespace.c
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 7aa08ed78452..c161f06a3cea 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -680,6 +680,13 @@ struct io_mkdir {
>  	struct filename			*filename;
>  };
>  
> +struct io_symlink {
> +	struct file			*file;
> +	int				new_dfd;
> +	struct filename			*oldpath;
> +	struct filename			*newpath;
> +};
> +
>  struct io_completion {
>  	struct file			*file;
>  	struct list_head		list;
> @@ -833,6 +840,7 @@ struct io_kiocb {
>  		struct io_rename	rename;
>  		struct io_unlink	unlink;
>  		struct io_mkdir		mkdir;
> +		struct io_symlink	symlink;
>  		/* use only after cleaning per-op data, see io_clean_op() */
>  		struct io_completion	compl;
>  	};
> @@ -1048,6 +1056,7 @@ static const struct io_op_def io_op_defs[] = {
>  	[IORING_OP_RENAMEAT] = {},
>  	[IORING_OP_UNLINKAT] = {},
>  	[IORING_OP_MKDIRAT] = {},
> +	[IORING_OP_SYMLINKAT] = {},
>  };
>  
>  static bool io_disarm_next(struct io_kiocb *req);
> @@ -3599,6 +3608,54 @@ static int io_mkdirat(struct io_kiocb *req, int issue_flags)
>  	return 0;
>  }
>  
> +static int io_symlinkat_prep(struct io_kiocb *req,
> +			    const struct io_uring_sqe *sqe)
> +{
> +	struct io_symlink *sl = &req->symlink;
> +	const char __user *oldpath, *newpath;
> +
> +	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
> +		return -EINVAL;
> +	if (sqe->ioprio || sqe->len || sqe->rw_flags || sqe->buf_index)
> +		return -EINVAL;
> +	if (unlikely(req->flags & REQ_F_FIXED_FILE))
> +		return -EBADF;
> +
> +	sl->new_dfd = READ_ONCE(sqe->fd);
> +	oldpath = u64_to_user_ptr(READ_ONCE(sqe->addr));
> +	newpath = u64_to_user_ptr(READ_ONCE(sqe->addr2));
> +
> +	sl->oldpath = getname(oldpath);
> +	if (IS_ERR(sl->oldpath))
> +		return PTR_ERR(sl->oldpath);
> +
> +	sl->newpath = getname(newpath);
> +	if (IS_ERR(sl->newpath)) {
> +		putname(sl->oldpath);
> +		return PTR_ERR(sl->newpath);
> +	}
> +
> +	req->flags |= REQ_F_NEED_CLEANUP;
> +	return 0;
> +}
> +
> +static int io_symlinkat(struct io_kiocb *req, int issue_flags)
> +{
> +	struct io_symlink *sl = &req->symlink;
> +	int ret;
> +
> +	if (issue_flags & IO_URING_F_NONBLOCK)
> +		return -EAGAIN;
> +
> +	ret = do_symlinkat(sl->oldpath, sl->new_dfd, sl->newpath);
> +
> +	req->flags &= ~REQ_F_NEED_CLEANUP;
> +	if (ret < 0)
> +		req_set_fail(req);
> +	io_req_complete(req, ret);
> +	return 0;
> +}
> +
>  static int io_shutdown_prep(struct io_kiocb *req,
>  			    const struct io_uring_sqe *sqe)
>  {
> @@ -6009,6 +6066,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  		return io_unlinkat_prep(req, sqe);
>  	case IORING_OP_MKDIRAT:
>  		return io_mkdirat_prep(req, sqe);
> +	case IORING_OP_SYMLINKAT:
> +		return io_symlinkat_prep(req, sqe);
>  	}
>  
>  	printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
> @@ -6173,6 +6232,10 @@ static void io_clean_op(struct io_kiocb *req)
>  		case IORING_OP_MKDIRAT:
>  			putname(req->mkdir.filename);
>  			break;
> +		case IORING_OP_SYMLINKAT:
> +			putname(req->symlink.oldpath);
> +			putname(req->symlink.newpath);
> +			break;
>  		}
>  	}
>  	if ((req->flags & REQ_F_POLLED) && req->apoll) {
> @@ -6304,6 +6367,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>  	case IORING_OP_MKDIRAT:
>  		ret = io_mkdirat(req, issue_flags);
>  		break;
> +	case IORING_OP_SYMLINKAT:
> +		ret = io_symlinkat(req, issue_flags);
> +		break;
>  	default:
>  		ret = -EINVAL;
>  		break;
> diff --git a/fs/namei.c b/fs/namei.c
> index f99de6e294ad..f5b0379d2f8c 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -4208,8 +4208,7 @@ int vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
>  }
>  EXPORT_SYMBOL(vfs_symlink);
>  
> -static int do_symlinkat(struct filename *from, int newdfd,
> -		  struct filename *to)
> +int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
>  {
>  	int error;
>  	struct dentry *dentry;
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 49a24a149eeb..796f37ab4ce3 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -138,6 +138,7 @@ enum {
>  	IORING_OP_RENAMEAT,
>  	IORING_OP_UNLINKAT,
>  	IORING_OP_MKDIRAT,
> +	IORING_OP_SYMLINKAT,
>  
>  	/* this goes last, obviously */
>  	IORING_OP_LAST,
> 

-- 
Pavel Begunkov