NFS: Ensure that we always drop inodes that have been marked as stale

There is no need to cache stale inodes.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -107,6 +107,12 @@ u64 nfs_compat_user_ino64(u64 fileid)
 	return ino;
 }
 
+int nfs_drop_inode(struct inode *inode)
+{
+	return NFS_STALE(inode) || generic_drop_inode(inode);
+}
+EXPORT_SYMBOL_GPL(nfs_drop_inode);
+
 void nfs_clear_inode(struct inode *inode)
 {
 	/*

fs/nfs/internal.h

@@ -296,6 +296,7 @@ extern struct workqueue_struct *nfsiod_workqueue;
 extern struct inode *nfs_alloc_inode(struct super_block *sb);
 extern void nfs_destroy_inode(struct inode *);
 extern int nfs_write_inode(struct inode *, struct writeback_control *);
+extern int nfs_drop_inode(struct inode *);
 extern void nfs_clear_inode(struct inode *);
 extern void nfs_evict_inode(struct inode *);
 void nfs_zap_acl_cache(struct inode *inode);

fs/nfs/nfs4super.c

@@ -51,6 +51,7 @@ static const struct super_operations nfs4_sops = {
 	.alloc_inode	= nfs_alloc_inode,
 	.destroy_inode	= nfs_destroy_inode,
 	.write_inode	= nfs4_write_inode,
+	.drop_inode	= nfs_drop_inode,
 	.put_super	= nfs_put_super,
 	.statfs		= nfs_statfs,
 	.evict_inode	= nfs4_evict_inode,

fs/nfs/super.c

@@ -308,6 +308,7 @@ const struct super_operations nfs_sops = {
 	.alloc_inode	= nfs_alloc_inode,
 	.destroy_inode	= nfs_destroy_inode,
 	.write_inode	= nfs_write_inode,
+	.drop_inode	= nfs_drop_inode,
 	.put_super	= nfs_put_super,
 	.statfs		= nfs_statfs,
 	.evict_inode	= nfs_evict_inode,