2 files changed, 29 insertions, 5 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 0b14f6910fc..86643302079 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -479,6 +479,14 @@ static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry
 	struct fs_struct *fs = current->fs;
 	struct dentry *parent = nd->path.dentry;
 
+	/*
+	 * It can be possible to revalidate the dentry that we started
+	 * the path walk with. force_reval_path may also revalidate the
+	 * dentry already committed to the nameidata.
+	 */
+	if (unlikely(parent == dentry))
+		return nameidata_drop_rcu(nd);
+
 	BUG_ON(!(nd->flags & LOOKUP_RCU));
 	if (nd->root.mnt) {
 		spin_lock(&fs->lock);
@@ -583,6 +591,13 @@ void release_open_intent(struct nameidata *nd)
 		fput(nd->intent.open.file);
 }
 
+/*
+ * Call d_revalidate and handle filesystems that request rcu-walk
+ * to be dropped. This may be called and return in rcu-walk mode,
+ * regardless of success or error. If -ECHILD is returned, the caller
+ * must return -ECHILD back up the path walk stack so path walk may
+ * be restarted in ref-walk mode.
+ */
 static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	int status;
@@ -673,6 +688,9 @@ force_reval_path(struct path *path, struct nameidata *nd)
 		return 0;
 
 	if (!status) {
+		/* Don't d_invalidate in rcu-walk mode */
+		if (nameidata_drop_rcu(nd))
+			return -ECHILD;
 		d_invalidate(dentry);
 		status = -ESTALE;
 	}
@@ -2105,11 +2123,13 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 		dir = nd->path.dentry;
 	case LAST_DOT:
 		if (need_reval_dot(dir)) {
-			error = d_revalidate(nd->path.dentry, nd);
-			if (!error)
-				error = -ESTALE;
-			if (error < 0)
+			int status = d_revalidate(nd->path.dentry, nd);
+			if (!status)
+				status = -ESTALE;
+			if (status < 0) {
+				error = status;
 				goto exit;
+			}
 		}
 		/* fallthrough */
 	case LAST_ROOT:
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 64ee240f3c8..df8c03a0216 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1406,11 +1406,15 @@ no_open:
 static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	struct dentry *parent = NULL;
-	struct inode *inode = dentry->d_inode;
+	struct inode *inode;
 	struct inode *dir;
 	struct nfs_open_context *ctx;
 	int openflags, ret = 0;
 
+	if (nd->flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = dentry->d_inode;
 	if (!is_atomic_open(nd) || d_mountpoint(dentry))
 		goto no_open;