Unionfs: better error handling in rename code when copyups are involved

First, rewrite code slightly and document it better to explain why we appear
to ignore copyup errors (because we try the next branch to the left).

Second, change a BUG_ON to a printk(KERN_ERR), because a mild failure to
copyup a file should not cause an oops.  For example, some file systems
don't support UIDs/GIDs (e.g., VFAT) and others don't allow you to chmod a
symlink (e.g., jffs2), possibly resulting in mild copyup failures; that
shouldn't be considered so severe as to cause an oops.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>

diff --git a/fs/unionfs/rename.c b/fs/unionfs/rename.c
index 0316258d8584dee072d569c0f11147f5e138d585..1761f8b6ae48fb1a0ee241db8641c36967778ba8 100644 (file)
--- a/fs/unionfs/rename.c
+++ b/fs/unionfs/rename.c
@@ -230,14 +230,15 @@ static int do_unionfs_rename(struct inode *old_dir,
                                            old_dentry->d_name.name,
                                            old_dentry->d_name.len,
                                            NULL, old_dentry->d_inode->i_size);
-                       if (!err) {
-                               dput(wh_old);
-                               bwh_old = bindex;
-                               err = __unionfs_rename(old_dir, old_dentry,
-                                                      new_dir, new_dentry,
-                                                      bindex, &wh_old);
-                               break;
-                       }
+                       /* if copyup failed, try next branch to the left */
+                       if (err)
+                               continue;
+                       dput(wh_old);
+                       bwh_old = bindex;
+                       err = __unionfs_rename(old_dir, old_dentry,
+                                              new_dir, new_dentry,
+                                              bindex, &wh_old);
+                       break;
                }
        }
 
@@ -255,7 +256,13 @@ static int do_unionfs_rename(struct inode *old_dir,
         */
        if ((old_bstart != old_bend) || (do_copyup != -1)) {
                struct dentry *lower_parent;
-               BUG_ON(!wh_old || wh_old->d_inode || bwh_old < 0);
+               if (!wh_old || wh_old->d_inode || bwh_old < 0) {
+                       printk(KERN_ERR "unionfs: rename error "
+                              "(wh_old=%p/%p bwh_old=%d)\n", wh_old,
+                              (wh_old ? wh_old->d_inode : NULL), bwh_old);
+                       err = -EIO;
+                       goto out;
+               }
                lower_parent = lock_parent(wh_old);
                local_err = vfs_create(lower_parent->d_inode, wh_old, S_IRUGO,
                                       NULL);