[1/4] I/OAT: fix channel resources free for not allocated channels

If the ioatdma driver is loaded but not used it does not allocate descriptors.
Before it frees channel resources it should first be sure
that they have been previously allocated.

Cc: <stable@kernel.org>
Signed-off-by: NMaciej Sosnowski <maciej.sosnowski@intel.com>
Tested-by: NTom Picard <tom.s.picard@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/dma/ioat_dma.c

@@ -807,6 +807,12 @@ static void ioat_dma_free_chan_resources(struct dma_chan *chan)
 	struct ioat_desc_sw *desc, *_desc;
 	int in_use_descs = 0;
 
+	/* Before freeing channel resources first check
+	 * if they have been previously allocated for this channel.
+	 */
+	if (ioat_chan->desccount == 0)
+		return;
+
 	tasklet_disable(&ioat_chan->cleanup_task);
 	ioat_dma_memcpy_cleanup(ioat_chan);
 
@@ -869,6 +875,7 @@ static void ioat_dma_free_chan_resources(struct dma_chan *chan)
 	ioat_chan->last_completion = ioat_chan->completion_addr = 0;
 	ioat_chan->pending = 0;
 	ioat_chan->dmacount = 0;
+	ioat_chan->desccount = 0;
 	ioat_chan->watchdog_completion = 0;
 	ioat_chan->last_compl_desc_addr_hw = 0;
 	ioat_chan->watchdog_tcp_cookie =