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io_uring: fix failed linkchain code logic

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Given a linkchain like this:
req0(link_flag)-->req1(link_flag)-->...-->reqn(no link_flag)

There is a problem:
 - if some intermediate linked req like req1 's submittion fails, reqs
   after it won't be cancelled.

   - sqpoll disabled: maybe it's ok since users can get the error info
     of req1 and stop submitting the following sqes.

   - sqpoll enabled: definitely a problem, the following sqes will be
     submitted in the next round.

The solution is to refactor the code logic to:
 - if a linked req's submittion fails, just mark it and the head(if it
   exists) as REQ_F_FAIL. Leverage req->result to indicate whether it
   is failed or cancelled.
 - submit or fail the whole chain when we come to the end of it.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/20210827094609.36052-3-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Hao Xu 2021-08-27 17:46:09 +08:00 committed by Jens Axboe
parent 14afdd6ee3
commit a8295b982c
1 changed files with 47 additions and 14 deletions
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61
fs/io_uring.c
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@ -1188,6 +1188,12 @@ static inline void req_set_fail(struct io_kiocb *req)
req->flags |= REQ_F_FAIL;
}
static inline void req_fail_link_node(struct io_kiocb *req, int res)
{
req_set_fail(req);
req->result = res;
}
static void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);
@ -1957,11 +1963,16 @@ static void io_fail_links(struct io_kiocb *req)
req->link = NULL;
while (link) {
long res = -ECANCELED;
if (link->flags & REQ_F_FAIL)
res = link->result;
nxt = link->link;
link->link = NULL;
trace_io_uring_fail_link(req, link);
io_cqring_fill_event(link->ctx, link->user_data, -ECANCELED, 0);
io_cqring_fill_event(link->ctx, link->user_data, res, 0);
io_put_req_deferred(link);
link = nxt;
}
@ -6622,8 +6633,10 @@ static inline void io_queue_sqe(struct io_kiocb *req)
if (unlikely(req->ctx->drain_active) && io_drain_req(req))
return;
if (likely(!(req->flags & REQ_F_FORCE_ASYNC))) {
if (likely(!(req->flags & (REQ_F_FORCE_ASYNC | REQ_F_FAIL)))) {
__io_queue_sqe(req);
} else if (req->flags & REQ_F_FAIL) {
io_req_complete_failed(req, req->result);
} else {
int ret = io_req_prep_async(req);
@ -6732,19 +6745,34 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
ret = io_init_req(ctx, req, sqe);
if (unlikely(ret)) {
fail_req:
/* fail even hard links since we don't submit */
if (link->head) {
/* fail even hard links since we don't submit */
io_req_complete_failed(link->head, -ECANCELED);
link->head = NULL;
/*
* we can judge a link req is failed or cancelled by if
* REQ_F_FAIL is set, but the head is an exception since
* it may be set REQ_F_FAIL because of other req's failure
* so let's leverage req->result to distinguish if a head
* is set REQ_F_FAIL because of its failure or other req's
* failure so that we can set the correct ret code for it.
* init result here to avoid affecting the normal path.
*/
if (!(link->head->flags & REQ_F_FAIL))
req_fail_link_node(link->head, -ECANCELED);
} else if (!(req->flags & (REQ_F_LINK | REQ_F_HARDLINK))) {
/*
* the current req is a normal req, we should return
* error and thus break the submittion loop.
*/
io_req_complete_failed(req, ret);
return ret;
}
io_req_complete_failed(req, ret);
return ret;
req_fail_link_node(req, ret);
} else {
ret = io_req_prep(req, sqe);
if (unlikely(ret))
goto fail_req;
}
ret = io_req_prep(req, sqe);
if (unlikely(ret))
goto fail_req;
/* don't need @sqe from now on */
trace_io_uring_submit_sqe(ctx, req, req->opcode, req->user_data,
req->flags, true,
@ -6760,9 +6788,14 @@ fail_req:
if (link->head) {
struct io_kiocb *head = link->head;
ret = io_req_prep_async(req);
if (unlikely(ret))
goto fail_req;
if (!(req->flags & REQ_F_FAIL)) {
ret = io_req_prep_async(req);
if (unlikely(ret)) {
req_fail_link_node(req, ret);
if (!(head->flags & REQ_F_FAIL))
req_fail_link_node(head, -ECANCELED);
}
}
trace_io_uring_link(ctx, req, head);
link->last->link = req;
link->last = req;