Re: [PATCH 1/3] io_uring: pass sqe for link head

From: Pavel Begunkov
Date: Wed Feb 05 2020 - 16:44:40 EST


On 06/02/2020 00:39, Pavel Begunkov wrote:
> 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.

Just to clarify, I was talking about removing the last argument in the patch
message.

>
>
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
>> ---
>> 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

Attachment: signature.asc
Description: OpenPGP digital signature