netdev - Re: [PATCH] sunrpc: Pass lockdep expression to RCU lists

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Date:   Tue, 3 Mar 2020 11:37:34 -0500
From:   "J . Bruce Fields" <bfields@...ldses.org>
To:     Amol Grover <frextrite@...il.com>
Cc:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] sunrpc: Pass lockdep expression to RCU lists

On Wed, Feb 19, 2020 at 03:05:05PM +0530, Amol Grover wrote:
> detail->hash_table[] is traversed using hlist_for_each_entry_rcu
> outside an RCU read-side critical section but under the protection
> of detail->hash_lock.
> 
> Hence, add corresponding lockdep expression to silence false-positive
> warnings, and harden RCU lists.

Thanks, applying for 5.7.--b.

> 
> Signed-off-by: Amol Grover <frextrite@...il.com>
> ---
>  net/sunrpc/cache.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index f740cb51802a..5db5f5b94726 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -97,7 +97,8 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
>  	spin_lock(&detail->hash_lock);
>  
>  	/* check if entry appeared while we slept */
> -	hlist_for_each_entry_rcu(tmp, head, cache_list) {
> +	hlist_for_each_entry_rcu(tmp, head, cache_list,
> +				 lockdep_is_held(&detail->hash_lock)) {
>  		if (detail->match(tmp, key)) {
>  			if (cache_is_expired(detail, tmp)) {
>  				hlist_del_init_rcu(&tmp->cache_list);
> -- 
> 2.24.1