From mboxrd@z Thu Jan 1 00:00:00 1970 From: Trond Myklebust Subject: Re: [PATCH 08/15] SUNRPC: Ensure rpcauth_prune_expired() respects the nr_to_scan parameter Date: Fri, 14 May 2010 13:13:20 -0400 Message-ID: <1273857200.4732.2.camel@localhost.localdomain> References: <1273784901-25599-1-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-2-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-3-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-4-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-5-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-6-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-7-git-send-email-Trond.Myklebust@netapp.com> <1273784901-25599-8-git-send-email-Trond.Myklebust@netapp.com> <4BED7BAD.20509@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: linux-nfs@vger.kernel.org To: Chuck Lever Return-path: Received: from mx2.netapp.com ([216.240.18.37]:51012 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752696Ab0ENRNX convert rfc822-to-8bit (ORCPT ); Fri, 14 May 2010 13:13:23 -0400 In-Reply-To: <4BED7BAD.20509@oracle.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, 2010-05-14 at 12:34 -0400, Chuck Lever wrote: > On 05/13/10 05:08 PM, Trond Myklebust wrote: > > Signed-off-by: Trond Myklebust > > --- > > net/sunrpc/auth.c | 5 ++--- > > 1 files changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c > > index 2213dc5..5fb02ac 100644 > > --- a/net/sunrpc/auth.c > > +++ b/net/sunrpc/auth.c > > @@ -236,6 +236,8 @@ rpcauth_prune_expired(struct list_head *free, int nr_to_scan) > > > > list_for_each_entry_safe(cred, next,&cred_unused, cr_lru) { > > > > + if (nr_to_scan-- == 0) > > + break; > > /* > > * Enforce a 60 second garbage collection moratorium > > * Note that the cred_unused list must be time-ordered. > > @@ -255,11 +257,8 @@ rpcauth_prune_expired(struct list_head *free, int nr_to_scan) > > get_rpccred(cred); > > list_add_tail(&cred->cr_lru, free); > > rpcauth_unhash_cred_locked(cred); > > - nr_to_scan--; > > } > > spin_unlock(cache_lock); > > - if (nr_to_scan == 0) > > - break; > > } > > return (number_cred_unused / 100) * sysctl_vfs_cache_pressure; > > } > > It looks to me like the mm calls our cache shrinker with nr_to_scan set > to zero when it just wants this return value, and nothing more. But the > logic here seems to assume that nr_to_scan == 0 means shrink as much as > you can. Am I reading this correctly? Look more carefully: the comparison contains a post-decrement operation, so if the nr_to_scan == 0, then we immediately exit the loop (after decrementing nr_to_scan, but who cares about that)... Cheers Trond