On Wed, 2021-06-09 at 15:19 -0400, Olivier Langlois wrote: > the man page says the following: > > If succesful, the resulting CQE will have IORING_CQE_F_BUFFER set > in the flags part of the struct, and the upper > IORING_CQE_BUFFER_SHIFT > bits will contain the ID of the selected buffers. > > based on my understanding of the kernel code (it could wrong. testing > is still ongoing to be 100% sure), the buffer will be returned even > if > the underlying syscall fails. (I have only checked io_read() for > IORING_OP_READ). > > At the minimum, the man page should be clarified to better reflect > the > code behavior. (and there is a missing 's' in succesful) > > ideally, imho, I believe the code should be modified to do what the > man > page says because: > > 1. doing otherwise is counter-intuitive and error-prone (I cannot > think > of a single example of a syscall failing and still require the user > to > free the allocated resources) > > 2. it is inefficient because the buffer is unneeded since there is no > data to transfer back to the user and the buffer will need to be > returned back to io_uring to avoid a leak. > I have confirmed that a buffer was returned and needed to be provided back io_uring even when read() syscall was failing. It failed with ECONNRESET with obviously no data and I still had to return back the buffer to avoid a leak (which my app was suffering of). Unless someone says that it works as designed, I'll figure out a way to fix that with a patch. It should be trivial to do. Greetings, Olivier
