netdev - [PATCH v2 1/2] net: Add a test to see if a skb is freeable in irq context

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Date:	Tue, 01 Apr 2014 12:20:24 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Miller <davem@...emloft.net>
Cc:	'Bjørn Mork' <bjorn@...k.no>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	"stephen\@networkplumber.org" <stephen@...workplumber.org>,
	"netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
	"xiyou.wangcong\@gmail.com" <xiyou.wangcong@...il.com>,
	"mpm\@selenic.com" <mpm@...enic.com>,
	"satyam.sharma\@gmail.com" <satyam.sharma@...il.com>,
	David Laight <David.Laight@...LAB.COM>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Subject: [PATCH v2 1/2] net: Add a test to see if a skb is freeable in irq context


Currently netpoll and skb_release_head_state assume that a skb is
freeable in hard irq context except when skb->destructor is set.

The reality is far from this.  So add a function skb_irq_freeable to
compute the full test and in the process be the living documentation
of what the requirements are of actually freeing a skb in hard irq
context.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 include/linux/skbuff.h |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 18ef0224fb6a..113fee1b7b63 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2833,6 +2833,19 @@ static inline void skb_init_secmark(struct sk_buff *skb)
 { }
 #endif
 
+static inline bool skb_irq_freeable(struct sk_buff *skb)
+{
+	return !skb->destructor &&
+#if IS_ENABLED(CONFIG_XFRM)
+		!skb->sp &&
+#endif
+#if IS_ENABLED(CONFIG_NF_CONNTRACK)
+		!skb->nfct &&
+#endif
+		!skb->_skb_refdst &&
+		!skb_has_frag_list(skb);
+}
+
 static inline void skb_set_queue_mapping(struct sk_buff *skb, u16 queue_mapping)
 {
 	skb->queue_mapping = queue_mapping;
-- 
1.7.10.4

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