rsxx: Disallow discards from being unmapped.

This patch fixes a bug in which discards were always
calling pci_unmap_page. Discards should never call the
pci_unmap_page function call because they are never mapped.

This caused a race condition on PowerPC systems when issuing
discards, writes, and reads all at the same time. The
pci_map_page function would eventually map logical address
0 for a read or write. Discards are always assigned a DMA
address of 0 because they are never mapped. So if
pci_map_page mapped address 0 for a DMA and a discard was
"unmapped" then the address would be freed and would cause
an EEH event to occur when Hardware accesses the address.

This was injected/uncovered in commit:
b347f9cf0bc8d42ee95ba1d3837fd93045ab336b

The pci_dma_mapping_error function declares -1 a DMA_ERROR
not 0 like initially thought So before we would never unmap
discards because they were considered NULL.

This patch should fall on top of commit id:
fc1967bb08a6184ed44ef990e1dd4389901b809c

Also, the driver version is being up dated.

Signed-off-by: Philip J Kelleher <pjk1939@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rsxx/dma.c

@@ -223,6 +223,7 @@ static void dma_intr_coal_auto_tune(struct rsxx_cardinfo *card)
 /*----------------- RSXX DMA Handling -------------------*/
 static void rsxx_free_dma(struct rsxx_dma_ctrl *ctrl, struct rsxx_dma *dma)
 {
+	if (dma->cmd != HW_CMD_BLK_DISCARD) {
 		if (!pci_dma_mapping_error(ctrl->card->dev, dma->dma_addr)) {
 			pci_unmap_page(ctrl->card->dev, dma->dma_addr,
 				       get_dma_size(dma),
@@ -230,6 +231,7 @@ static void rsxx_free_dma(struct rsxx_dma_ctrl *ctrl, struct rsxx_dma *dma)
 						   PCI_DMA_TODEVICE :
 						   PCI_DMA_FROMDEVICE);
 		}
+	}
 
 	kmem_cache_free(rsxx_dma_pool, dma);
 }
@@ -1057,11 +1059,14 @@ int rsxx_eeh_save_issued_dmas(struct rsxx_cardinfo *card)
 			else
 				card->ctrl[i].stats.reads_issued--;
 
+			if (dma->cmd != HW_CMD_BLK_DISCARD) {
 				pci_unmap_page(card->dev, dma->dma_addr,
 					       get_dma_size(dma),
 					       dma->cmd == HW_CMD_BLK_WRITE ?
 					       PCI_DMA_TODEVICE :
 					       PCI_DMA_FROMDEVICE);
+			}
+
 			list_add_tail(&dma->list, &issued_dmas[i]);
 			push_tracker(card->ctrl[i].trackers, j);
 			cnt++;

drivers/block/rsxx/rsxx_priv.h

@@ -52,7 +52,7 @@ struct proc_cmd;
 #define RS70_PCI_REV_SUPPORTED	4
 
 #define DRIVER_NAME "rsxx"
-#define DRIVER_VERSION "4.0.1.2498"
+#define DRIVER_VERSION "4.0.2.2510"
 
 /* Block size is 4096 */
 #define RSXX_HW_BLK_SHIFT		12