vfs: fix renameat to retry on ESTALE errors

...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>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 12 insertions, 3 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 8a262c2efff8..43a97ee1d4c8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3840,15 +3840,17 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
         struct nameidata oldnd, newnd;
         struct filename *from;
         struct filename *to;
+        unsigned int lookup_flags = 0;
+        bool should_retry = false;
         int error;
-
-        from = user_path_parent(olddfd, oldname, &oldnd, 0);
+retry:
+        from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
         if (IS_ERR(from)) {
                 error = PTR_ERR(from);
                 goto exit;
         }
 
-        to = user_path_parent(newdfd, newname, &newnd, 0);
+        to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
         if (IS_ERR(to)) {
                 error = PTR_ERR(to);
                 goto exit1;
@@ -3920,11 +3922,18 @@ exit3:
         unlock_rename(new_dir, old_dir);
         mnt_drop_write(oldnd.path.mnt);
 exit2:
+        if (retry_estale(error, lookup_flags))
+                should_retry = true;
         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;
+        }
 exit:
         return error;
 }