From: Hao Xu <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected], Pavel Begunkov <[email protected]>,
Joseph Qi <[email protected]>
Subject: [PATCH 2/2] io_uring: fix failed linkchain code logic
Date: Fri, 27 Aug 2021 17:46:09 +0800 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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 <[email protected]>
---
fs/io_uring.c | 61 +++++++++++++++++++++++++++++++++++++++------------
1 file changed, 47 insertions(+), 14 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3598319b1340..4c83ec227d85 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1175,6 +1175,12 @@ 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);
@@ -1931,11 +1937,16 @@ 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;
}
@@ -6519,8 +6530,10 @@ 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);
@@ -6629,19 +6642,34 @@ 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,
@@ -6657,9 +6685,14 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *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;
--
2.24.4
next prev parent reply other threads:[~2021-08-27 9:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-27 9:46 [PATCH for-5.15 v3 0/2] fix failed linkchain code logic Hao Xu
2021-08-27 9:46 ` [PATCH 1/2] io_uring: remove redundant req_set_fail() Hao Xu
2021-08-27 9:46 ` Hao Xu [this message]
2021-08-27 11:01 ` [PATCH for-5.15 v3 0/2] fix failed linkchain code logic Pavel Begunkov
2021-08-27 13:27 ` Jens Axboe
2021-08-27 17:04 ` Hao Xu
-- strict thread matches above, loose matches on Subject: below --
2021-08-23 3:25 [PATCH for-5.15 v2 " Hao Xu
2021-08-23 3:25 ` [PATCH 2/2] io_uring: " Hao Xu
2021-08-23 11:02 ` Pavel Begunkov
2021-08-23 17:12 ` Pavel Begunkov
2021-08-23 18:45 ` Hao Xu
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