vfs: make do_unlinkat retry once on ESTALE errors

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -3440,8 +3440,9 @@ static long do_unlinkat(int dfd, const char __user *pathname)
 	struct dentry *dentry;
 	struct nameidata nd;
 	struct inode *inode = NULL;
-
-	name = user_path_parent(dfd, pathname, &nd, 0);
+	unsigned int lookup_flags = 0;
+retry:
+	name = user_path_parent(dfd, pathname, &nd, lookup_flags);
 	if (IS_ERR(name))
 		return PTR_ERR(name);
 
@@ -3479,6 +3480,11 @@ exit2:
 exit1:
 	path_put(&nd.path);
 	putname(name);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		inode = NULL;
+		goto retry;
+	}
 	return error;
 
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