Re: [PATCH] io_uring: don't issue reqs in iopoll mode when ctx is dying

[Pavel Begunkov <asml.silence@gmail.com>]

On 24/02/2021 09:46, Pavel Begunkov wrote:
>> Are you sure? We just don't want to reissue it, we need to fail it.
>> Hence if we catch it at reissue time, that should be enough. But I'm
>> open to clue batting :-)
> 
> Jens, IOPOLL can happen from a different task, so
> 1) we don't want to grab io_wq_work context from it. As always we can pass it
> through task_work, or should be solved with your io-wq patches.
> 
> 2) it happens who knows when in time, so iovec may be gone already -- same
> reasoning why io_[read,write]() copy it before going to io-wq.

The diff below should solve the second problem by failing them (not tested).
1) can be left to the io-wq patches.


diff --git a/fs/io_uring.c b/fs/io_uring.c
index bf9ad810c621..561c29b20463 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2610,8 +2610,11 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
 		list_del(&req->inflight_entry);
 
 		if (READ_ONCE(req->result) == -EAGAIN) {
+			bool reissue = req->async_data ||
+				!io_op_defs[req->opcode].needs_async_data;
+
 			req->iopoll_completed = 0;
-			if (io_rw_reissue(req))
+			if (reissue && io_rw_reissue(req))
 				continue;
 		}
 


-- 
Pavel Begunkov