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: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/delegation.c

@@ -124,10 +124,6 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
 	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 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
 			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;

fs/nfs/inode.c

@@ -1072,8 +1072,10 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 		invalid &= ~NFS_INO_INVALID_DATA;
 	if (data_stable)
 		invalid &= ~(NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME|NFS_INO_REVAL_PAGECACHE);
-	if (!nfs_have_delegation(inode, FMODE_READ))
+	if (!nfs_have_delegation(inode, FMODE_READ) ||
+			(nfsi->cache_validity & NFS_INO_REVAL_FORCED))
 		nfsi->cache_validity |= invalid;
+	nfsi->cache_validity &= ~NFS_INO_REVAL_FORCED;
 
 	return 0;
  out_changed:

include/linux/nfs_fs.h

@@ -184,6 +184,7 @@ struct nfs_inode {
 #define NFS_INO_INVALID_ACCESS	0x0008		/* cached access cred invalid */
 #define NFS_INO_INVALID_ACL	0x0010		/* cached acls are invalid */
 #define NFS_INO_REVAL_PAGECACHE	0x0020		/* must revalidate pagecache */
+#define NFS_INO_REVAL_FORCED	0x0040		/* force revalidation ignoring a delegation */
 
 /*
  * Bit offsets in flags field