io_uring: fix sleeping under spin in __io_clean_op

[ 27.629441] BUG: sleeping function called from invalid context
at fs/file.c:402
[ 27.631317] in_atomic(): 1, irqs_disabled(): 1, non_block: 0,
pid: 1012, name: io_wqe_worker-0
[ 27.633220] 1 lock held by io_wqe_worker-0/1012:
[ 27.634286] #0: ffff888105e26c98 (&ctx->completion_lock)
{....}-{2:2}, at: __io_req_complete.part.102+0x30/0x70
[ 27.649249] Call Trace:
[ 27.649874] dump_stack+0xac/0xe3
[ 27.650666] ___might_sleep+0x284/0x2c0
[ 27.651566] put_files_struct+0xb8/0x120
[ 27.652481] __io_clean_op+0x10c/0x2a0
[ 27.653362] __io_cqring_fill_event+0x2c1/0x350
[ 27.654399] __io_req_complete.part.102+0x41/0x70
[ 27.655464] io_openat2+0x151/0x300
[ 27.656297] io_issue_sqe+0x6c/0x14e0
[ 27.660991] io_wq_submit_work+0x7f/0x240
[ 27.662890] io_worker_handle_work+0x501/0x8a0
[ 27.664836] io_wqe_worker+0x158/0x520
[ 27.667726] kthread+0x134/0x180
[ 27.669641] ret_from_fork+0x1f/0x30

Instead of cleaning files on overflow, return back overflow cancellation
into io_uring_cancel_files(). Previously it was racy to clean
REQ_F_OVERFLOW flag, but we got rid of it, and can do it through
repetitive attempts targeting all matching requests.

Reported-by: Abaci <[e-mail]>
Reported-by: Joseph Qi <[e-mail]>
Cc: Xiaoguang Wang <[e-mail]>
Signed-off-by: Pavel Begunkov <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

fs/io_uring.c

···
 static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
 			     const struct iovec *fast_iov,
 			     struct iov_iter *iter, bool force);
+static void io_req_drop_files(struct io_kiocb *req);
 
 static struct kmem_cache *req_cachep;
 
···
 
 static inline void io_clean_op(struct io_kiocb *req)
 {
-	if (req->flags & (REQ_F_NEED_CLEANUP | REQ_F_BUFFER_SELECTED |
-			  REQ_F_INFLIGHT))
+	if (req->flags & (REQ_F_NEED_CLEANUP | REQ_F_BUFFER_SELECTED))
 		__io_clean_op(req);
 }
 
···
 			free_fs_struct(fs);
 		req->work.flags &= ~IO_WQ_WORK_FS;
 	}
+	if (req->flags & REQ_F_INFLIGHT)
+		io_req_drop_files(req);
 
 	io_put_identity(req->task->io_uring, req);
 }
···
 		}
 		req->flags &= ~REQ_F_NEED_CLEANUP;
 	}
-
-	if (req->flags & REQ_F_INFLIGHT)
-		io_req_drop_files(req);
 }
 
 static int io_issue_sqe(struct io_kiocb *req, bool force_nonblock,
···
 		io_wq_cancel_cb(ctx->io_wq, io_cancel_task_cb, &cancel, true);
 		io_poll_remove_all(ctx, task, files);
 		io_kill_timeouts(ctx, task, files);
+		io_cqring_overflow_flush(ctx, true, task, files);
 		/* cancellations _may_ trigger task work */
 		io_run_task_work();
 		schedule();