From: Sachin S. Prabhu <sprabhu@redhat.com>
Date: Fri, 13 Mar 2009 15:56:08 +0000
Subject: [nfs] add fine grain control for lookup cache in nfs
Message-id: 49BA8218.5080004@redhat.com
O-Subject: [RHEL5.4 PATCH 1/2]: Add fine grain control for lookup cache in nfs
Bugzilla: 489285
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

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 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>
--

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 9630198..cdf2116 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -631,6 +631,8 @@ static inline int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
 {
 	if (IS_ROOT(dentry))
 		return 1;
+	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
+		return 0;
 	if (!nfs_verify_change_attribute(dir, dentry->d_time))
 		return 0;
 	/* Revalidate nfsi->cache_change_attribute before we declare a match */
@@ -712,6 +714,8 @@ int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
 	/* Don't revalidate a negative dentry if we're creating a new file */
 	if (nd != NULL && nfs_lookup_check_intent(nd, LOOKUP_CREATE) != 0)
 		return 0;
+	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)
+		return 1;
 	return !nfs_check_verifier(dir, dentry);
 }
 
diff --git a/include/linux/nfs_mount.h b/include/linux/nfs_mount.h
index 2bbae41..f3a2548 100644
--- a/include/linux/nfs_mount.h
+++ b/include/linux/nfs_mount.h
@@ -66,5 +66,8 @@ struct nfs_mount_data {
 #define NFS_MOUNT_UNSHARED  0x10000  /* 5 */
 #define NFS_MOUNT_FLAGMASK	0xFFFFF
 
+/* The following are for internal use only */
+#define NFS_MOUNT_LOOKUP_CACHE_NONEG	0x20000
+#define NFS_MOUNT_LOOKUP_CACHE_NONE	0x40000
 
 #endif