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<Trond.Myklebust@xxxxxxxxxx>
> > ---
> > 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
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