Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 4 Jul 2022 15:56:57 +0300
From:   Dan Aloni <dan.aloni@vastdata.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/4] SUNRPC: Clean up the AUTH cache code
Message-ID: <20220704125657.apczddzlpqng2ov3@gmail.com>
References: <20181023163404.27777-1-trond.myklebust@hammerspace.com>
 <20220703214628.2zzixg62do6d7jhh@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220703214628.2zzixg62do6d7jhh@gmail.com>
Precedence: bulk

On 2022-07-04 00:53:06, Dan Aloni wrote:
> On 2018-10-23 12:34:01, Trond Myklebust wrote:
> > @@ -456,32 +495,24 @@ rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
> >  
> >  		if (nr_to_scan-- == 0)
> >  			break;
> > +		if (atomic_read(&cred->cr_count) > 1) {
> > +			rpcauth_lru_remove_locked(cred);
> > +			continue;
> > +		}
> >  		/*
> >  		 * Enforce a 60 second garbage collection moratorium
> >  		 * Note that the cred_unused list must be time-ordered.
> >  		 */
> > -		if (time_in_range(cred->cr_expire, expired, jiffies) &&
> > -		    test_bit(RPCAUTH_CRED_HASHED, &cred->cr_flags) != 0) {
> > -			freed = SHRINK_STOP;
> > -			break;
> > -		}
> > -
> > -		list_del_init(&cred->cr_lru);
> > -		number_cred_unused--;
> > -		freed++;
> > -		if (atomic_read(&cred->cr_count) != 0)
> > +		if (!time_in_range(cred->cr_expire, expired, jiffies))
> > +			continue;
> > +		if (!rpcauth_unhash_cred(cred))
> >  			continue;
> 
> With `!` flipping the `time_in_range(...)` condition in this past
> change, looks like we are skipping the head of the LRU which should be
> pruned, so actual expiry does not happen at all in case there are more
> than about 100 old items in the LRU.
> 
> Reverting this, I saw the correct behavior taking place.

v2: Made a better explanation in the commit message.

 
-- >8 --
Subject: [PATCH] sunrpc: fix expiry of auth creds

Before this commit, with a large enough LRU of expired items (100), the
loop skipped all the expired items and was entirely ineffectual in
trimming the LRU list.

Fixes: 95cd623250ad ('SUNRPC: Clean up the AUTH cache code')
Signed-off-by: Dan Aloni <dan.aloni@vastdata.com>
---
 net/sunrpc/auth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 682fcd24bf43..2324d1e58f21 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -445,7 +445,7 @@ rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
 		 * Enforce a 60 second garbage collection moratorium
 		 * Note that the cred_unused list must be time-ordered.
 		 */
-		if (!time_in_range(cred->cr_expire, expired, jiffies))
+		if (time_in_range(cred->cr_expire, expired, jiffies))
 			continue;
 		if (!rpcauth_unhash_cred(cred))
 			continue;
-- 
2.23.0

-- 
Dan Aloni