diff options
author | yangerkun <yangerkun@huawei.com> | 2019-10-15 21:59:29 +0800 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2019-10-15 08:55:50 -0600 |
commit | 5da0fb1ab34ccfe6d49210b4f5a739c59fcbf25e (patch) | |
tree | c9eaf517afbc8c7dc8e2f9633ec17d6f0416e647 /fs | |
parent | 7a7c5e715e722c86d602c56a09e77f000364e263 (diff) |
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.c | 27 |
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); |