netdev - [PATCH bpf-next v5 1/7] bpf: Clear pfmemalloc flag when freeing all fragments

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Message-ID: <20250919182100.1925352-2-ameryhung@gmail.com>
Date: Fri, 19 Sep 2025 11:20:54 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	alexei.starovoitov@...il.com,
	andrii@...nel.org,
	daniel@...earbox.net,
	paul.chaignon@...il.com,
	kuba@...nel.org,
	stfomichev@...il.com,
	martin.lau@...nel.org,
	mohsin.bashr@...il.com,
	noren@...dia.com,
	dtatulea@...dia.com,
	saeedm@...dia.com,
	tariqt@...dia.com,
	mbloch@...dia.com,
	maciej.fijalkowski@...el.com,
	kernel-team@...a.com
Subject: [PATCH bpf-next v5 1/7] bpf: Clear pfmemalloc flag when freeing all fragments

It is possible for bpf_xdp_adjust_tail() to free all fragments. The
kfunc currently clears the XDP_FLAGS_HAS_FRAGS bit, but not
XDP_FLAGS_FRAGS_PF_MEMALLOC. So far, this has not caused a issue when
building sk_buff from xdp_buff since all readers of xdp_buff->flags
use the flag only when there are fragments. Clear the
XDP_FLAGS_FRAGS_PF_MEMALLOC bit as well to make the flags correct.

Signed-off-by: Amery Hung <ameryhung@...il.com>
---
 include/net/xdp.h | 5 +++++
 net/core/filter.c | 1 +
 2 files changed, 6 insertions(+)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index b40f1f96cb11..f288c348a6c1 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -115,6 +115,11 @@ static __always_inline void xdp_buff_set_frag_pfmemalloc(struct xdp_buff *xdp)
 	xdp->flags |= XDP_FLAGS_FRAGS_PF_MEMALLOC;
 }
 
+static __always_inline void xdp_buff_clear_frag_pfmemalloc(struct xdp_buff *xdp)
+{
+	xdp->flags &= ~XDP_FLAGS_FRAGS_PF_MEMALLOC;
+}
+
 static __always_inline void
 xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
 {
diff --git a/net/core/filter.c b/net/core/filter.c
index 63f3baee2daf..5837534f4352 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4210,6 +4210,7 @@ static int bpf_xdp_frags_shrink_tail(struct xdp_buff *xdp, int offset)
 
 	if (unlikely(!sinfo->nr_frags)) {
 		xdp_buff_clear_frags_flag(xdp);
+		xdp_buff_clear_frag_pfmemalloc(xdp);
 		xdp->data_end -= offset;
 	}
 
-- 
2.47.3