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Date: Sat, 2 May 2020 15:07:13 +0300
From: Pavel Begunkov <asml.silence@...il.com>
To: Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] io_uring: trigger timeout after any sqe->off CQEs
sequence mode timeouts wait not for sqe->off CQEs, but rather
sqe->off + number of prior inflight requests with a quirk ignoring other
timeouts completions. Wait exactly for sqe->off using completion count
(tail) for accounting.
Reported-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
fs/io_uring.c | 120 +++++++++++++++++++-------------------------------
1 file changed, 46 insertions(+), 74 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 65458eda2127..148f61734572 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -384,7 +384,8 @@ struct io_timeout {
struct file *file;
u64 addr;
int flags;
- u32 count;
+ u32 off;
+ u32 target_seq;
};
struct io_rw {
@@ -986,23 +987,6 @@ static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx)
return NULL;
}
-static struct io_kiocb *io_get_timeout_req(struct io_ring_ctx *ctx)
-{
- struct io_kiocb *req;
-
- req = list_first_entry_or_null(&ctx->timeout_list, struct io_kiocb, list);
- if (req) {
- if (req->flags & REQ_F_TIMEOUT_NOSEQ)
- return NULL;
- if (!__req_need_defer(req)) {
- list_del_init(&req->list);
- return req;
- }
- }
-
- return NULL;
-}
-
static void __io_commit_cqring(struct io_ring_ctx *ctx)
{
struct io_rings *rings = ctx->rings;
@@ -1118,12 +1102,42 @@ static void io_kill_timeouts(struct io_ring_ctx *ctx)
spin_unlock_irq(&ctx->completion_lock);
}
+static inline bool io_check_in_range(u32 pos, u32 start, u32 end)
+{
+ /* if @end < @start, check for [end, MAX_UINT] + [MAX_UINT, start] */
+ return (pos - start) <= (end - start);
+}
+
+static void __io_flush_timeouts(struct io_ring_ctx *ctx)
+{
+ u32 end, start;
+
+ start = end = ctx->cached_cq_tail;
+ do {
+ struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
+ struct io_kiocb, list);
+
+ if (req->flags & REQ_F_TIMEOUT_NOSEQ)
+ break;
+ /*
+ * multiple timeouts may have the same target,
+ * check that @req is in [first_tail, cur_tail]
+ */
+ if (!io_check_in_range(req->timeout.target_seq, start, end))
+ break;
+
+ list_del_init(&req->list);
+ io_kill_timeout(req);
+ end = ctx->cached_cq_tail;
+ } while (!list_empty(&ctx->timeout_list));
+}
+
static void io_commit_cqring(struct io_ring_ctx *ctx)
{
struct io_kiocb *req;
- while ((req = io_get_timeout_req(ctx)) != NULL)
- io_kill_timeout(req);
+ if (!list_empty(&ctx->timeout_list))
+ __io_flush_timeouts(ctx);
__io_commit_cqring(ctx);
@@ -4582,20 +4596,8 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
* We could be racing with timeout deletion. If the list is empty,
* then timeout lookup already found it and will be handling it.
*/
- if (!list_empty(&req->list)) {
- struct io_kiocb *prev;
-
- /*
- * Adjust the reqs sequence before the current one because it
- * will consume a slot in the cq_ring and the cq_tail
- * pointer will be increased, otherwise other timeout reqs may
- * return in advance without waiting for enough wait_nr.
- */
- prev = req;
- list_for_each_entry_continue_reverse(prev, &ctx->timeout_list, list)
- prev->sequence++;
+ if (!list_empty(&req->list))
list_del_init(&req->list);
- }
io_cqring_fill_event(req, -ETIME);
io_commit_cqring(ctx);
@@ -4675,18 +4677,19 @@ static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
{
struct io_timeout_data *data;
unsigned flags;
+ u32 off = READ_ONCE(sqe->off);
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
return -EINVAL;
if (sqe->ioprio || sqe->buf_index || sqe->len != 1)
return -EINVAL;
- if (sqe->off && is_timeout_link)
+ if (off && is_timeout_link)
return -EINVAL;
flags = READ_ONCE(sqe->timeout_flags);
if (flags & ~IORING_TIMEOUT_ABS)
return -EINVAL;
- req->timeout.count = READ_ONCE(sqe->off);
+ req->timeout.off = off;
if (!req->io && io_alloc_async_ctx(req))
return -ENOMEM;
@@ -4710,68 +4713,37 @@ static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
static int io_timeout(struct io_kiocb *req)
{
struct io_ring_ctx *ctx = req->ctx;
- struct io_timeout_data *data;
+ struct io_timeout_data *data = &req->io->timeout;
struct list_head *entry;
- unsigned span = 0;
- u32 count = req->timeout.count;
- u32 seq = req->sequence;
+ u32 tail, off = req->timeout.off;
- data = &req->io->timeout;
+ spin_lock_irq(&ctx->completion_lock);
/*
* sqe->off holds how many events that need to occur for this
* timeout event to be satisfied. If it isn't set, then this is
* a pure timeout request, sequence isn't used.
*/
- if (!count) {
+ if (!off) {
req->flags |= REQ_F_TIMEOUT_NOSEQ;
- spin_lock_irq(&ctx->completion_lock);
entry = ctx->timeout_list.prev;
goto add;
}
- req->sequence = seq + count;
+ tail = ctx->cached_cq_tail;
+ req->timeout.target_seq = tail + off;
/*
* Insertion sort, ensuring the first entry in the list is always
* the one we need first.
*/
- spin_lock_irq(&ctx->completion_lock);
list_for_each_prev(entry, &ctx->timeout_list) {
struct io_kiocb *nxt = list_entry(entry, struct io_kiocb, list);
- unsigned nxt_seq;
- long long tmp, tmp_nxt;
- u32 nxt_offset = nxt->timeout.count;
-
- if (nxt->flags & REQ_F_TIMEOUT_NOSEQ)
- continue;
-
- /*
- * Since seq + count can overflow, use type long
- * long to store it.
- */
- tmp = (long long)seq + count;
- nxt_seq = nxt->sequence - nxt_offset;
- tmp_nxt = (long long)nxt_seq + nxt_offset;
+ u32 nxt_off = nxt->timeout.target_seq - tail;
- /*
- * cached_sq_head may overflow, and it will never overflow twice
- * once there is some timeout req still be valid.
- */
- if (seq < nxt_seq)
- tmp += UINT_MAX;
-
- if (tmp > tmp_nxt)
+ if (!(nxt->flags & REQ_F_TIMEOUT_NOSEQ) && (off >= nxt_off))
break;
-
- /*
- * Sequence of reqs after the insert one and itself should
- * be adjusted because each timeout req consumes a slot.
- */
- span++;
- nxt->sequence++;
}
- req->sequence -= span;
add:
list_add(&req->list, entry);
data->timer.function = io_timeout_fn;
--
2.24.0
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