[PATCH] tidier atomic check in mempool_alloc()

From Hugh.

Be more explicit in the "can we sleep" test.  It doesn't change
anything unless someone is performing __GFP_IO && !__GFP_WAIT
allocations, which is nonsensical.

mm/mempool.c

@@ -221,7 +221,7 @@ void * mempool_alloc(mempool_t *pool, int gfp_mask)
 	spin_unlock_irqrestore(&pool->lock, flags);
 
 	/* We must not sleep in the GFP_ATOMIC case */
-	if (gfp_mask == gfp_nowait)
+	if (!(gfp_mask & __GFP_WAIT))
 		return NULL;
 
 	blk_run_queues();