NFS: Fix a readdir/lookup inefficiency.

Make sure that nfs_readdir_lookup() handles negative dentries correctly.
If d_lookup() returns a negative dentry, then we need to d_drop() that
since readdir shows that it should be positive.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index bd269d268824..db29c7fa9620 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1123,8 +1123,14 @@ static struct dentry *nfs_readdir_lookup(nfs_readdir_descriptor_t *desc)
         }
         name.hash = full_name_hash(name.name, name.len);
         dentry = d_lookup(parent, &name);
-        if (dentry != NULL)
-                return dentry;
+        if (dentry != NULL) {
+                /* Is this a positive dentry? */
+                if (dentry->d_inode != NULL)
+                        return dentry;
+                /* No, so d_drop to allow one to be created */
+                d_drop(dentry);
+                dput(dentry);
+        }
         if (!desc->plus || !(entry->fattr->valid & NFS_ATTR_FATTR))
                 return NULL;
         /* Note: caller is already holding the dir->i_mutex! */