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io_uring: fix counter inc/dec mismatch in async_list 

We could queue a work for each req in defer and link list without
increasing async_list->cnt, so we shouldn't decrease it while exiting
from workqueue as well if we didn't process the req in async list.

Thanks to Jens Axboe <axboe@kernel.dk> for his guidance.

Fixes: 31b5151064 ("io_uring: allow workqueue item to handle multiple buffered requests")
Signed-off-by: Zhengyuan Liu <liuzhengyuan@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Zhengyuan Liu 2019-07-16 23:26:14 +08:00 committed by Jens Axboe
parent c56cbfae62
commit f7b76ac9d1
1 changed files with 8 additions and 1 deletions
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9
fs/io_uring.c
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@ -333,7 +333,8 @@ struct io_kiocb {
#define REQ_F_IO_DRAIN 16 /* drain existing IO first */
#define REQ_F_IO_DRAINED 32 /* drain done */
#define REQ_F_LINK 64 /* linked sqes */
#define REQ_F_FAIL_LINK 128 /* fail rest of links */
#define REQ_F_LINK_DONE 128 /* linked sqes done */
#define REQ_F_FAIL_LINK 256 /* fail rest of links */
u64 user_data;
u32 result;
u32 sequence;
@ -632,6 +633,7 @@ static void io_req_link_next(struct io_kiocb *req)
nxt->flags |= REQ_F_LINK;
}
nxt->flags |= REQ_F_LINK_DONE;
INIT_WORK(&nxt->work, io_sq_wq_submit_work);
queue_work(req->ctx->sqo_wq, &nxt->work);
}
@ -1844,6 +1846,10 @@ static void io_sq_wq_submit_work(struct work_struct *work)
/* async context always use a copy of the sqe */
kfree(sqe);
/* req from defer and link list needn't decrease async cnt */
if (req->flags & (REQ_F_IO_DRAINED | REQ_F_LINK_DONE))
goto out;
if (!async_list)
break;
if (!list_empty(&req_list)) {
@ -1891,6 +1897,7 @@ static void io_sq_wq_submit_work(struct work_struct *work)
}
}
out:
if (cur_mm) {
set_fs(old_fs);
unuse_mm(cur_mm);