On 2019/10/15 4:10, Jens Axboe wrote:
On 10/14/19 5:51 AM, yangerkun wrote:
The sequence for timeout req may overflow, and it will lead to wrong
order of timeout req list. And we should consider two situation:
1. ctx->cached_sq_head + count - 1 may overflow;
2. cached_sq_head of now may overflow compare with before
cached_sq_head.
Fix the wrong logic by add record of count and use type long long to
record the overflow.
Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
---
fs/io_uring.c | 31 +++++++++++++++++++++++++------
1 file changed, 25 insertions(+), 6 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 76fdbe84aff5..c8dbf85c1c91 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -288,6 +288,7 @@ struct io_poll_iocb {
struct io_timeout {
struct file *file;
struct hrtimer timer;
+ unsigned count;
};
Can we reuse io_kiocb->submit->sequence for this? Unfortunately doing it
the way that you did, which does make the most logical sense, means that
struct io_kiocb will now spill into a 4th cacheline.
Or maybe fold ->sequence and ->submit.sequence to reclaim that space?
Yeah, prefer to reuse ->submit.sequence to dump the count. I have never
thought about the cacheline before. Thanks a lot!
@@ -1907,21 +1908,39 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
count = 1;
req->sequence = ctx->cached_sq_head + count - 1;
+ req->timeout.count = 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)
+ /* count bigger than before should break directly. */
+ if (count >= nxt->timeout.count)
+ break;
Took me a bit, but I guess that's true. It's an optimization, maybe it'd be
cleaner if we just stuck to the sequence checking?
It's a good idea and thanks for you suggestion! I will resend the patch
soon!
Thanks,
Kun.
