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authoryangerkun <yangerkun@huawei.com>2019-10-15 21:59:29 +0800
committerJens Axboe <axboe@kernel.dk>2019-10-15 08:55:50 -0600
commit5da0fb1ab34ccfe6d49210b4f5a739c59fcbf25e (patch)
treec9eaf517afbc8c7dc8e2f9633ec17d6f0416e647 /fs
parent7a7c5e715e722c86d602c56a09e77f000364e263 (diff)
downloadlinux-5da0fb1ab34ccfe6d49210b4f5a739c59fcbf25e.tar.bz2
io_uring: consider the overflow of sequence for timeout req
Now we recalculate the sequence of timeout with 'req->sequence = ctx->cached_sq_head + count - 1', judge the right place to insert for timeout_list by compare the number of request we still expected for completion. But we have not consider about the situation of overflow: 1. ctx->cached_sq_head + count - 1 may overflow. And a bigger count for the new timeout req can have a small req->sequence. 2. cached_sq_head of now may overflow compare with before req. And it will lead the timeout req with small req->sequence. This overflow will lead to the misorder of timeout_list, which can lead to the wrong order of the completion of timeout_list. Fix it by reuse req->submit.sequence to store the count, and change the logic of inserting sort in io_timeout. Signed-off-by: yangerkun <yangerkun@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
-rw-r--r--fs/io_uring.c27
1 files changed, 21 insertions, 6 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 38d274fc0f25..d2cb277da2f4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1884,7 +1884,7 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
- unsigned count, req_dist, tail_index;
+ unsigned count;
struct io_ring_ctx *ctx = req->ctx;
struct list_head *entry;
struct timespec64 ts;
@@ -1907,21 +1907,36 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
count = 1;
req->sequence = ctx->cached_sq_head + count - 1;
+ /* reuse it to store the count */
+ req->submit.sequence = count;
req->flags |= REQ_F_TIMEOUT;
/*
* Insertion sort, ensuring the first entry in the list is always
* the one we need first.
*/
- tail_index = ctx->cached_cq_tail - ctx->rings->sq_dropped;
- req_dist = req->sequence - tail_index;
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 dist;
+ unsigned nxt_sq_head;
+ long long tmp, tmp_nxt;
- dist = nxt->sequence - tail_index;
- if (req_dist >= dist)
+ /*
+ * Since cached_sq_head + count - 1 can overflow, use type long
+ * long to store it.
+ */
+ tmp = (long long)ctx->cached_sq_head + count - 1;
+ nxt_sq_head = nxt->sequence - nxt->submit.sequence + 1;
+ tmp_nxt = (long long)nxt_sq_head + nxt->submit.sequence - 1;
+
+ /*
+ * cached_sq_head may overflow, and it will never overflow twice
+ * once there is some timeout req still be valid.
+ */
+ if (ctx->cached_sq_head < nxt_sq_head)
+ tmp_nxt += UINT_MAX;
+
+ if (tmp >= tmp_nxt)
break;
}
list_add(&req->list, entry);