From: Sachin S. Prabhu <sprabhu@redhat.com>
Date: Fri, 13 Mar 2009 15:58:27 +0000
Subject: [nfs] add 'lookupcache' mount option for nfs shares
Message-id: 49BA82A3.3090504@redhat.com
O-Subject: Re: [RHEL5.4 PATCH 2/2]: Add fine grain control for lookup cache in nfs
Bugzilla: 489285
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

Sachin S. Prabhu wrote:
> Backport of the following upstream patch to add finer grained control
> over the lookup cache.
>
> --
> commit 4eec952e42314b53e48fef1f54dd89cbf9789734
> Author: Trond Myklebust <Trond.Myklebust@netapp.com>
> Date:   Tue Jul 15 17:58:13 2008 -0400
>
>     NFS: Add options for finer control of the lookup cache
>
>     Add the flag NFS_MOUNT_LOOKUP_CACHE_NONEG to turn off the caching of
>     negative dentries. In reality what we do is to force
>     nfs_lookup_revalidate() to always discard negative dentries.
>
>     Add the flag NFS_MOUNT_LOOKUP_CACHE_NONE for enforcing stricter
>     revalidation of dentries. It forces the revalidate code to always do a
>     lookup instead of just checking the cached mtime of the parent
> directory.
>
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> --
>
>

Backport of the following upstream patch to add lookupcache mount option to the nfs client to control the lookup cache.

diff --git a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c
index 330e4e9..c3860d1 100644
--- a/fs/nfs/nfsroot.c
+++ b/fs/nfs/nfsroot.c
@@ -123,7 +123,9 @@ enum {
 	Opt_soft, Opt_hard, Opt_intr,
 	Opt_nointr, Opt_posix, Opt_noposix, Opt_cto, Opt_nocto, Opt_ac, 
 	Opt_noac, Opt_lock, Opt_nolock, Opt_v2, Opt_v3, Opt_udp, Opt_tcp,
-	Opt_acl, Opt_noacl,
+	Opt_acl, Opt_noacl, Opt_lookupcache_all, Opt_lookupcache_positive,
+	Opt_lookupcache_none,
+	
 	/* Error token */
 	Opt_err
 };
@@ -160,6 +162,10 @@ static match_table_t __initdata tokens = {
 	{Opt_tcp, "tcp"},
 	{Opt_acl, "acl"},
 	{Opt_noacl, "noacl"},
+	{Opt_lookupcache_all, "lookupcache=all" },
+	{Opt_lookupcache_positive, "lookupcache=pos" },
+	{Opt_lookupcache_positive, "lookupcache=positive" },
+	{Opt_lookupcache_none, "lookupcache=none" },
 	{Opt_err, NULL}
 	
 };
@@ -274,6 +280,16 @@ static int __init root_nfs_parse(char *name, char *buf)
 			case Opt_noacl:
 				nfs_data.flags |= NFS_MOUNT_NOACL;
 				break;
+			case Opt_lookupcache_all:
+				nfs_data.flags &= ~(NFS_MOUNT_LOOKUP_CACHE_NONEG|NFS_MOUNT_LOOKUP_CACHE_NONE);
+				break;
+			case Opt_lookupcache_positive:
+				nfs_data.flags &= ~NFS_MOUNT_LOOKUP_CACHE_NONE;
+				nfs_data.flags |= NFS_MOUNT_LOOKUP_CACHE_NONEG;
+				break;
+			case Opt_lookupcache_none:
+				nfs_data.flags |= NFS_MOUNT_LOOKUP_CACHE_NONEG|NFS_MOUNT_LOOKUP_CACHE_NONE;
+				break;
 			default:
 				printk(KERN_WARNING "Root-NFS: unknown "
 					"option: %s\n", p);