Re: [PATCH v4 7/8] io_uring/zcrx: add refcount to ifq and remove ifq->ctx

On 10/29/25 16:16, Pavel Begunkov wrote:

On 10/29/25 15:22, Pavel Begunkov wrote:

quoted

On 10/28/25 17:46, David Wei wrote:

...>>>   void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)

quoted

quoted

  {
      struct io_zcrx_ifq *ifq;

@@ -743,7 +730,10 @@ void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)

          }
          if (!ifq)
              break;
-        io_zcrx_ifq_free(ifq);
+        if (refcount_dec_and_test(&ifq->refs)) {
+            io_zcrx_scrub(ifq);
+            io_zcrx_ifq_free(ifq);
+        }
      }
      xa_destroy(&ctx->zcrx_ctxs);

@@ -894,15 +884,11 @@ static int io_pp_zc_init(struct page_pool *pp)

      if (ret)
          return ret;
-    percpu_ref_get(&ifq->ctx->refs);
      return 0;

refcount_inc();

Which would add another ref cycle problem, the same that IIRC
was solved with two step shutdown + release. I'll take a closer
look.

The simplest solution is to keep the two 2 level release and
split refcounting for sharing. It's still better as now
shutdown can be folded into the io_uring ifq unregstration
helper.

https://github.com/isilence/linux.git zcrx/zcrx-sharing
https://github.com/isilence/liburing.git zcrx/zcrx-sharing

I fixed up synchronisation and drafted the export/import via
a file part, take a look.

-- 
Pavel Begunkov