[PATCH v4 14/17] vfs: fix renameat to retry on ESTALE errors

[Jeff Layton <jlayton@redhat.com>]

...as always, rename is the messiest of the bunch. We have to track
whether to retry or not via a separate flag since the error handling
is already quite complex.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/namei.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 65e5177..7cf5e91 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3699,12 +3699,25 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
 	char *from;
 	char *to;
 	int error;
+	unsigned int try = 0;
+	bool should_retry = false;
+	unsigned int lookup_flags = LOOKUP_PARENT;
 
-	error = user_path_parent(olddfd, oldname, &oldnd, &from);
-	if (error)
+	from = getname(oldname);
+	if (IS_ERR(from))
+		return PTR_ERR(from);
+
+	to = getname(newname);
+	if (IS_ERR(to)) {
+		error = PTR_ERR(to);
 		goto exit;
+	}
+retry:
+	error = do_path_lookup(olddfd, from, lookup_flags, &oldnd);
+	if (error)
+		goto exit0;
 
-	error = user_path_parent(newdfd, newname, &newnd, &to);
+	error = do_path_lookup(newdfd, to, lookup_flags, &newnd);
 	if (error)
 		goto exit1;
 
@@ -3773,13 +3786,21 @@ exit4:
 	dput(old_dentry);
 exit3:
 	unlock_rename(new_dir, old_dir);
+	if (retry_estale(error, try++))
+		should_retry = true;
 exit2:
 	path_put(&newnd.path);
-	putname(to);
 exit1:
 	path_put(&oldnd.path);
-	putname(from);
+	if (should_retry) {
+		should_retry = false;
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
+exit0:
+	putname(to);
 exit:
+	putname(from);
 	return error;
 }
 
-- 
1.7.11.2