NFSv4: Defer inode revalidation when setting up a delegation

Currently we force a synchronous call to __nfs_revalidate_inode() in
nfs_inode_set_delegation(). This not only ensures that we cannot call
nfs_inode_set_delegation from an asynchronous context, but it also slows
down any call to open().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 56f4f6a..20ac403 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -124,10 +124,6 @@
 	struct nfs_delegation *delegation;
 	int status = 0;
 
-	/* Ensure we first revalidate the attributes and page cache! */
-	if ((nfsi->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_ATTR)))
-		__nfs_revalidate_inode(NFS_SERVER(inode), inode);
-
 	delegation = kmalloc(sizeof(*delegation), GFP_KERNEL);
 	if (delegation == NULL)
 		return -ENOMEM;
@@ -154,6 +150,12 @@
 			status = -EIO;
 		}
 	}
+
+	/* Ensure we revalidate the attributes and page cache! */
+	spin_lock(&inode->i_lock);
+	nfsi->cache_validity |= NFS_INO_REVAL_FORCED;
+	spin_unlock(&inode->i_lock);
+
 	spin_unlock(&clp->cl_lock);
 	kfree(delegation);
 	return status;