On 23/02/2020 18:07, Jens Axboe wrote:
> On 2/23/20 7:58 AM, Jens Axboe wrote:
>> On 2/23/20 7:49 AM, Jens Axboe wrote:
>>>> Anyway, creds handling is too scattered across the code, and this do a
>>>> lot of useless refcounting and bouncing. It's better to find it a
>>>> better place in the near future.
>>>
>>> I think a good cleanup on top of this would be to move the personality
>>> lookup to io_req_defer_prep(), and kill it from io_submit_sqe(). Now
>>> __io_issue_sqe() does the right thing, and it'll just fall out nicely
>>> with that as far as I can tell.
>>>
>>> Care to send a patch for that?
>>
>> Since we also need it for non-deferral, how about just leaving the
>> lookup in there and removing the assignment? That means we only do that
>> juggling in one spot, which makes more sense. I think this should just
>> be folded into the previous patch.
>
> Tested, we need a ref grab on the creds when assigning since we're
> dropped at the other end.
Nice, this looks much better.
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index cead1a0602b4..d83f113f22fd 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4923,7 +4923,6 @@ static inline void io_queue_link_head(struct io_kiocb *req)
> static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> struct io_submit_state *state, struct io_kiocb **link)
> {
> - const struct cred *old_creds = NULL;
> struct io_ring_ctx *ctx = req->ctx;
> unsigned int sqe_flags;
> int ret, id;
> @@ -4938,14 +4937,12 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
>
> id = READ_ONCE(sqe->personality);
> if (id) {
> - const struct cred *personality_creds;
> -
> - personality_creds = idr_find(&ctx->personality_idr, id);
> - if (unlikely(!personality_creds)) {
> + req->work.creds = idr_find(&ctx->personality_idr, id);
> + if (unlikely(!req->work.creds)) {
> ret = -EINVAL;
> goto err_req;
> }
> - old_creds = override_creds(personality_creds);
> + get_cred(req->work.creds);
> }
>
> /* same numerical values with corresponding REQ_F_*, safe to copy */
> @@ -4957,8 +4954,6 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> err_req:
> io_cqring_add_event(req, ret);
> io_double_put_req(req);
> - if (old_creds)
> - revert_creds(old_creds);
> return false;
> }
>
> @@ -5019,8 +5014,6 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> }
> }
>
> - if (old_creds)
> - revert_creds(old_creds);
> return true;
> }
>
>
--
Pavel Begunkov
