IB/fmr_pool: Flush all dirty FMRs from ib_fmr_pool_flush()

Commit a3cd7d90 ("IB/fmr_pool: ib_fmr_pool_flush() should flush all
dirty FMRs") caused a regression for iSER and was reverted in
e5507736.

This change attempts to redo the original patch so that all used FMR
entries are flushed when ib_flush_fmr_pool() is called without
affecting the normal FMR pool cleaning thread.  Simply move used
entries from the clean list onto the dirty list in ib_flush_fmr_pool()
before letting the cleanup thread do its job.
Signed-off-by: Pete Wyckoff <pw@osc.edu>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/fmr_pool.c

@@ -398,8 +398,23 @@ EXPORT_SYMBOL(ib_destroy_fmr_pool);
  */
 int ib_flush_fmr_pool(struct ib_fmr_pool *pool)
 {
-	int serial = atomic_inc_return(&pool->req_ser);
+	int serial;
+	struct ib_pool_fmr *fmr, *next;
+
+	/*
+	 * The free_list holds FMRs that may have been used
+	 * but have not been remapped enough times to be dirty.
+	 * Put them on the dirty list now so that the cleanup
+	 * thread will reap them too.
+	 */
+	spin_lock_irq(&pool->pool_lock);
+	list_for_each_entry_safe(fmr, next, &pool->free_list, list) {
+		if (fmr->remap_count > 0)
+			list_move(&fmr->list, &pool->dirty_list);
+	}
+	spin_unlock_irq(&pool->pool_lock);
 
+	serial = atomic_inc_return(&pool->req_ser);
 	wake_up_process(pool->thread);
 
 	if (wait_event_interruptible(pool->force_wait,