unionfs: better handling when copying up permissions

When we copyup a file, directory, or symlink, we may be copying up from one
file system type to another.  The destination file system may not support
all of the features of the source file system, and the differences in
support may be minor.  For example jffs2 doesn't allow one to chmod a
symlink (and it returns a -EOPNOTSUPP).  So we ignore such harmless errors,
rather than propagating them up, which results in copyup errors and errors
returned back to users.

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

diff --git a/fs/unionfs/copyup.c b/fs/unionfs/copyup.c
index c9c0a645bbe74612d030a75fc05f383643e6d5ca..3e99a736b6565eece804f19b0c1e879cbc997e80 100644 (file)
--- a/fs/unionfs/copyup.c
+++ b/fs/unionfs/copyup.c
@@ -92,7 +92,14 @@ out:
 }
 #endif /* CONFIG_UNION_FS_XATTR */
 
-/* Determine the mode based on the copyup flags, and the existing dentry. */
+/*
+ * Determine the mode based on the copyup flags, and the existing dentry.
+ *
+ * Handle file systems which may not support certain options.  For example
+ * jffs2 doesn't allow one to chmod a symlink.  So we ignore such harmless
+ * errors, rather than propagating them up, which results in copyup errors
+ * and errors returned back to users.
+ */
 static int copyup_permissions(struct super_block *sb,
                              struct dentry *old_lower_dentry,
                              struct dentry *new_lower_dentry)
@@ -104,18 +111,28 @@ static int copyup_permissions(struct super_block *sb,
        newattrs.ia_atime = i->i_atime;
        newattrs.ia_mtime = i->i_mtime;
        newattrs.ia_ctime = i->i_ctime;
-
        newattrs.ia_gid = i->i_gid;
        newattrs.ia_uid = i->i_uid;
-
-       newattrs.ia_mode = i->i_mode;
-
        newattrs.ia_valid = ATTR_CTIME | ATTR_ATIME | ATTR_MTIME |
                ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_FORCE |
-               ATTR_GID | ATTR_UID | ATTR_MODE;
+               ATTR_GID | ATTR_UID;
+       err = notify_change(new_lower_dentry, &newattrs);
+       if (err)
+               goto out;
 
+       /* now try to change the mode and ignore EOPNOTSUPP on symlinks */
+       newattrs.ia_mode = i->i_mode;
+       newattrs.ia_valid = ATTR_MODE | ATTR_FORCE;
        err = notify_change(new_lower_dentry, &newattrs);
+       if (err == -EOPNOTSUPP &&
+           S_ISLNK(new_lower_dentry->d_inode->i_mode)) {
+               printk(KERN_WARNING
+                      "unionfs: changing \"%s\" symlink mode unsupported\n",
+                      new_lower_dentry->d_name.name);
+               err = 0;
+       }
 
+out:
        return err;
 }