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>

2 files changed, 8 insertions, 0 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 74f92b717f78..49d565412827 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -667,6 +667,8 @@ static 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 */
@@ -750,6 +752,8 @@ 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 df7c6b7a7ebb..6549a06ac16e 100644
--- a/include/linux/nfs_mount.h
+++ b/include/linux/nfs_mount.h
@@ -65,4 +65,8 @@ struct nfs_mount_data {
 #define NFS_MOUNT_UNSHARED      0x8000  /* 5 */
 #define NFS_MOUNT_FLAGMASK      0xFFFF
 
+/* The following are for internal use only */
+#define NFS_MOUNT_LOOKUP_CACHE_NONEG    0x10000
+#define NFS_MOUNT_LOOKUP_CACHE_NONE     0x20000
+
 #endif