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io_uring: fix an issue when IOSQE_IO_LINK is inserted into defer list

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This patch may fix two issues:

First, when IOSQE_IO_DRAIN set, the next IOs need to be inserted into
defer list to delay execution, but link io will be actively scheduled to
run by calling io_queue_sqe.

Second, when multiple LINK_IOs are inserted together with defer_list,
the LINK_IO is no longer keep order.

   |-------------|
   |   LINK_IO   |      ----> insert to defer_list  -----------
   |-------------|                                            |
   |   LINK_IO   |      ----> insert to defer_list  ----------|
   |-------------|                                            |
   |   LINK_IO   |      ----> insert to defer_list  ----------|
   |-------------|                                            |
   |   NORMAL_IO |      ----> insert to defer_list  ----------|
   |-------------|                                            |
                                                              |
                              queue_work at same time   <-----|

Fixes: 9e645e1105c ("io_uring: add support for sqe links")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jackie Liu 2019-08-14 17:35:22 +08:00 committed by Jens Axboe
parent 7b6620d7db
commit a982eeb09b
1 changed files with 9 additions and 7 deletions
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16
fs/io_uring.c
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@ -2023,6 +2023,15 @@ static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
{
int ret;
ret = io_req_defer(ctx, req, s->sqe);
if (ret) {
if (ret != -EIOCBQUEUED) {
io_free_req(req);
io_cqring_add_event(ctx, s->sqe->user_data, ret);
}
return 0;
}
ret = __io_submit_sqe(ctx, req, s, true);
if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) {
struct io_uring_sqe *sqe_copy;
@ -2095,13 +2104,6 @@ err:
return;
}
ret = io_req_defer(ctx, req, s->sqe);
if (ret) {
if (ret != -EIOCBQUEUED)
goto err_req;
return;
}
/*
* If we already have a head request, queue this one for async
* submittal once the head completes. If we don't have a head but