We currently have a race where we recycle the selected buffer if poll
returns IO_APOLL_OK. But that's too late, as the poll could already be
triggering or have triggered. If that race happens, then we're putting a
buffer that's already being used.
Fix this by recycling before we arm poll. This does mean that we'll
sometimes almost instantly re-select the buffer, but it's rare enough in
testing that it should not pose a performance issue.
Fixes:
b1c62645758e ("io_uring: recycle provided buffers if request goes async")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
req->flags |= REQ_F_POLLED;
ipt.pt._qproc = io_async_queue_proc;
+ io_kbuf_recycle(req);
+
ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask);
if (ret || ipt.error)
return ret ? IO_APOLL_READY : IO_APOLL_ABORTED;
io_queue_async_work(req, NULL);
break;
case IO_APOLL_OK:
- io_kbuf_recycle(req);
break;
}