[PATCH 6.18 305/314] xsk: introduce helper to determine rxq->frag_size

Sasha Levin
2026-03-10T11:30:15Z

From: Larysa Zaremba <larysa.zaremba@intel.com>

[ Upstream commit 16394d80539937d348dd3b9ea32415c54e67a81b ]

rxq->frag_size is basically a step between consecutive strictly aligned
frames. In ZC mode, chunk size fits exactly, but if chunks are unaligned,
there is no safe way to determine accessible space to grow tailroom.

Report frag_size to be zero, if chunks are unaligned, chunk_size otherwise.

Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://patch.msgid.link/20260305111253.2317394-3-larysa.zaremba@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/xdp_sock_drv.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 99b6c3358e363..33e072768de9d 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -47,6 +47,11 @@ static inline u32 xsk_pool_get_rx_frame_size(struct xsk_buff_pool *pool)
return xsk_pool_get_chunk_size(pool) - xsk_pool_get_headroom(pool);
}

+static inline u32 xsk_pool_get_rx_frag_step(struct xsk_buff_pool *pool)
+{
+ return pool->unaligned ? 0 : xsk_pool_get_chunk_size(pool);
+}
+
static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
struct xdp_rxq_info *rxq)
{
@@ -333,6 +338,11 @@ static inline u32 xsk_pool_get_rx_frame_size(struct xsk_buff_pool *pool)
return 0;
}

+static inline u32 xsk_pool_get_rx_frag_step(struct xsk_buff_pool *pool)
+{
+ return 0;
+}
+
static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
struct xdp_rxq_info *rxq)
{
--
2.51.0