On Wed, Dec 4, 2024 at 9:22 AM David Wei <dw@xxxxxxxxxxx> wrote: > > From: Pavel Begunkov <asml.silence@xxxxxxxxx> > > Some page pool memory providers like io_uring need to catch the point > when the page pool is asked to be destroyed. ->destroy is not enough > because it relies on the page pool to wait for its buffers first, but > for that to happen a provider might need to react, e.g. to collect all > buffers that are currently given to the user space. > > Add a new provider's scrub callback serving the purpose and called off > the pp's generic (cold) scrubbing path, i.e. page_pool_scrub(). > > Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> > Signed-off-by: David Wei <dw@xxxxxxxxxxx> I think after numerous previous discussions on this op, I guess I finally see the point. AFAIU on destruction tho io_uring instance will destroy the page_pool, but we need to drop the user reference in the memory region. So the io_uring instance will destroy the pool, then the scrub callback tells io_uring that the pool is being destroyed, which drops the user references. I would have preferred if io_uring drops the user references before destroying the pool, which I think would have accomplished the same thing without adding a memory provider callback that is a bit specific to this use case, but I guess it's all the same. Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx> -- Thanks, Mina
