8040 NFSv4 client: 3-way deadlock between nfs4_bio(), nfs4_do_delegreturn(), and nfs4_flush_pages()
Reviewed by: Arne Jansen <arne@die-jansens.de>
Reviewed by: Vitaliy Gusev <gusev.vitaliy@icloud.com>
Approved by: Gordon Ross <gordon.w.ross@gmail.com>

@@ -2594,16 +2594,10 @@
          */
         ASSERT(osp->os_ref_count >= 2);
         osp->os_ref_count--;
 
         if (ep->error == 0) {
-                /*
-                 * Avoid a deadlock with the r_serial thread waiting for
-                 * os_sync_lock in nfs4_get_otw_cred_by_osp() which might be
-                 * held by us. We will wait in nfs4_attr_cache() for the
-                 * completion of the r_serial thread.
-                 */
                 mutex_exit(&osp->os_sync_lock);
                 *have_sync_lockp = 0;
 
                 nfs4_attr_cache(vp,
                     &res.array[1].nfs_resop4_u.opgetattr.ga_res,