linux-kernel - [PATCH] inet: inet_defrag: Removing the usage of refcount_inc_not

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Date: Mon, 15 Apr 2024 16:06:19 +0000
From: Abhinav Jain <jain.abhinav177@...il.com>
To: davem@...emloft.net,
	dsahern@...nel.org,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: skhan@...uxfoundation.org,
	javier.carrasco.cruz@...il.com,
	Abhinav Jain <jain.abhinav177@...il.com>
Subject: [PATCH] inet: inet_defrag: Removing the usage of refcount_inc_not_zero

Remove refcount_inc_not_zero as per the listed TODO in the file.
Used spin_(un)lock and refcount_* functions for synchronization.

Signed-off-by: Abhinav Jain <jain.abhinav177@...il.com>
---
 net/ipv4/inet_fragment.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index c88c9034d630..e4838bbe0abb 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -358,7 +358,6 @@ static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
 	return q;
 }
 
-/* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
 struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
 {
 	/* This pairs with WRITE_ONCE() in fqdir_pre_exit(). */
@@ -375,8 +374,14 @@ struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
 		fq = inet_frag_create(fqdir, key, &prev);
 	if (!IS_ERR_OR_NULL(prev)) {
 		fq = prev;
-		if (!refcount_inc_not_zero(&fq->refcnt))
+		spin_lock(&fq->lock);
+		if (refcount_read(&fq->refcnt) > 0) {
+			refcount_inc(&fq->refcnt);
+			spin_unlock(&fq->lock);
+		} else {
+			spin_unlock(&fq->lock);
 			fq = NULL;
+		}
 	}
 	rcu_read_unlock();
 	return fq;
-- 
2.34.1