Re: [PATCH v10 4/5] io_uring: add fsetxattr and setxattr support

[Al Viro <viro@zeniv.linux.org.uk>]

On Wed, Dec 29, 2021 at 12:30:01PM -0800, Stefan Roesch wrote:

> +static int io_setxattr_prep(struct io_kiocb *req,
> +			const struct io_uring_sqe *sqe)
> +{
> +	struct io_xattr *ix = &req->xattr;
> +	const char __user *path;
> +	int ret;
> +
> +	ret = __io_setxattr_prep(req, sqe);
> +	if (ret)
> +		return ret;
> +
> +	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
> +
> +	ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
> +	if (IS_ERR(ix->filename)) {
> +		ret = PTR_ERR(ix->filename);
> +		ix->filename = NULL;
> +	}
> +
> +	return ret;
> +}

Same question as for getxattr side.  Why bother doing getname in prep
and open-coding the ESTALE retry loop in io_setxattr() proper?

Again, if you have hit the retry_estale() returning true, you are already
on a very slow path; trying to save on getname is completely pointless.
Moreover, had there been a situation where it might have been warranted
(and I really can't imagine one), why would that only be applicable in
io_uring case?