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SubjectRe: [PATCH 1/3] io_uring: pass sqe for link head
Date
On 05/02/2020 22:07, Pavel Begunkov wrote:
> Save an sqe for a head of a link, so it doesn't go through switch in
> io_req_defer_prep() nor allocating an async context in advance.
>
> Also, it's fixes potenial memleak for double-preparing head requests.
> E.g. prep in io_submit_sqe() and then prep in io_req_defer(),
> which leaks iovec for vectored read/writes.

Looking through -rc1, remembered that Jens already fixed this. So, this may be
striked out.


>
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
> fs/io_uring.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index f00c2c9c67c0..e18056af5672 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4721,20 +4721,22 @@ static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> }
> }
>
> -static inline void io_queue_link_head(struct io_kiocb *req)
> +static inline void io_queue_link_head(struct io_kiocb *req,
> + const struct io_uring_sqe *sqe)
> {
> if (unlikely(req->flags & REQ_F_FAIL_LINK)) {
> io_cqring_add_event(req, -ECANCELED);
> io_double_put_req(req);
> } else
> - io_queue_sqe(req, NULL);
> + io_queue_sqe(req, sqe);
> }
>
> #define SQE_VALID_FLAGS (IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK| \
> IOSQE_IO_HARDLINK | IOSQE_ASYNC)
>
> static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> - struct io_submit_state *state, struct io_kiocb **link)
> + struct io_submit_state *state, struct io_kiocb **link,
> + const struct io_uring_sqe **link_sqe)
> {
> const struct cred *old_creds = NULL;
> struct io_ring_ctx *ctx = req->ctx;
> @@ -4812,7 +4814,7 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
>
> /* last request of a link, enqueue the link */
> if (!(sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK))) {
> - io_queue_link_head(head);
> + io_queue_link_head(head, *link_sqe);
> *link = NULL;
> }
> } else {
> @@ -4823,10 +4825,8 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> if (sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) {
> req->flags |= REQ_F_LINK;
> INIT_LIST_HEAD(&req->link_list);
> - ret = io_req_defer_prep(req, sqe);
> - if (ret)
> - req->flags |= REQ_F_FAIL_LINK;
> *link = req;
> + *link_sqe = sqe;
> } else {
> io_queue_sqe(req, sqe);
> }
> @@ -4924,6 +4924,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
> struct io_kiocb *link = NULL;
> int i, submitted = 0;
> bool mm_fault = false;
> + const struct io_uring_sqe *link_sqe = NULL;
>
> /* if we have a backlog and couldn't flush it all, return BUSY */
> if (test_bit(0, &ctx->sq_check_overflow)) {
> @@ -4983,7 +4984,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
> req->needs_fixed_file = async;
> trace_io_uring_submit_sqe(ctx, req->opcode, req->user_data,
> true, async);
> - if (!io_submit_sqe(req, sqe, statep, &link))
> + if (!io_submit_sqe(req, sqe, statep, &link, &link_sqe))
> break;
> }
>
> @@ -4993,7 +4994,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
> percpu_ref_put_many(&ctx->refs, nr - ref_used);
> }
> if (link)
> - io_queue_link_head(link);
> + io_queue_link_head(link, link_sqe);
> if (statep)
> io_submit_state_end(&state);
>
>

--
Pavel Begunkov

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