[PATCH v2 3/6] io_uring/zcrx: notify user on frag copy fallback
From: Clément Léger
Date: Mon May 18 2026 - 11:39:08 EST
Add a ZCRX_NOTIF_COPY notification type to signal userspace when a
received fragment could not be delivered using zero-copy and was
instead copied into a buffer.
Signed-off-by: Clément Léger <cleger@xxxxxxxx>
---
include/uapi/linux/io_uring/zcrx.h | 1 +
io_uring/zcrx.c | 7 ++++++-
io_uring/zcrx.h | 2 +-
3 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/io_uring/zcrx.h b/include/uapi/linux/io_uring/zcrx.h
index 67185566ad3c..3f7b72b09878 100644
--- a/include/uapi/linux/io_uring/zcrx.h
+++ b/include/uapi/linux/io_uring/zcrx.h
@@ -70,6 +70,7 @@ enum zcrx_features {
enum zcrx_notification_type {
ZCRX_NOTIF_NO_BUFFERS,
+ ZCRX_NOTIF_COPY,
__ZCRX_NOTIF_TYPE_LAST,
};
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 463fbaead35b..f31f2ca0f7ec 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -1534,8 +1534,13 @@ static int io_zcrx_copy_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
const skb_frag_t *frag, int off, int len)
{
struct page *page = skb_frag_page(frag);
+ int ret;
+
+ ret = io_zcrx_copy_chunk(req, ifq, page, off + skb_frag_off(frag), len);
+ if (ret > 0)
+ zcrx_send_notif(ifq, ZCRX_NOTIF_COPY);
- return io_zcrx_copy_chunk(req, ifq, page, off + skb_frag_off(frag), len);
+ return ret;
}
static int io_zcrx_recv_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index cca10d0d02ac..203b3049e14b 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -11,7 +11,7 @@
#define ZCRX_SUPPORTED_REG_FLAGS (ZCRX_REG_IMPORT | ZCRX_REG_NODEV)
#define ZCRX_FEATURES (ZCRX_FEATURE_RX_PAGE_SIZE |\
ZCRX_FEATURE_NOTIFICATION)
-#define ZCRX_NOTIF_TYPE_MASK (1U << ZCRX_NOTIF_NO_BUFFERS)
+#define ZCRX_NOTIF_TYPE_MASK ((1U << ZCRX_NOTIF_NO_BUFFERS) | (1U << ZCRX_NOTIF_COPY))
struct io_zcrx_mem {
unsigned long size;
--
2.53.0-Meta