[PATCH 2/2] scsi: esp: make it working on SG_CHAIN

[Ming Lei <ming.lei@xxxxxxxxxx>]

The driver supporses that there isn't sg chain, and itereate the
list one by one. This way is obviously wrong.

Fixes it by sgl helper.

Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Ewan D. Milne <emilne@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 drivers/scsi/esp_scsi.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 76e7ca864d6a..58b4e059dcfb 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -371,6 +371,7 @@ static void esp_map_dma(struct esp *esp, struct scsi_cmnd *cmd)
 	struct esp_cmd_priv *spriv = ESP_CMD_PRIV(cmd);
 	struct scatterlist *sg = scsi_sglist(cmd);
 	int total = 0, i;
+	struct scatterlist *sgt;
 
 	if (cmd->sc_data_direction == DMA_NONE)
 		return;
@@ -381,14 +382,15 @@ static void esp_map_dma(struct esp *esp, struct scsi_cmnd *cmd)
 		 * a dma address, so perform an identity mapping.
 		 */
 		spriv->num_sg = scsi_sg_count(cmd);
-		for (i = 0; i < spriv->num_sg; i++) {
-			sg[i].dma_address = (uintptr_t)sg_virt(&sg[i]);
-			total += sg_dma_len(&sg[i]);
+
+		scsi_for_each_sg(cmd, sgt, spriv->num_sg, i) {
+			sgt->dma_address = (uintptr_t)sg_virt(sgt);
+			total += sg_dma_len(sgt);
 		}
 	} else {
 		spriv->num_sg = scsi_dma_map(cmd);
-		for (i = 0; i < spriv->num_sg; i++)
-			total += sg_dma_len(&sg[i]);
+		scsi_for_each_sg(cmd, sgt, spriv->num_sg, i)
+			total += sg_dma_len(sgt);
 	}
 	spriv->cur_residue = sg_dma_len(sg);
 	spriv->cur_sg = sg;
@@ -444,7 +446,7 @@ static void esp_advance_dma(struct esp *esp, struct esp_cmd_entry *ent,
 		p->tot_residue = 0;
 	}
 	if (!p->cur_residue && p->tot_residue) {
-		p->cur_sg++;
+		p->cur_sg = sg_next(p->cur_sg);
 		p->cur_residue = sg_dma_len(p->cur_sg);
 	}
 }
@@ -1610,6 +1612,22 @@ static void esp_msgin_extended(struct esp *esp)
 	scsi_esp_cmd(esp, ESP_CMD_SATN);
 }
 
+static struct scatterlist *esp_sg_prev(struct scsi_cmnd *cmd,
+		struct scatterlist *sg)
+{
+	int i;
+	struct scatterlist *tmp;
+	struct scatterlist *prev = NULL;
+
+	scsi_for_each_sg(cmd, tmp, scsi_sg_count(cmd), i) {
+		if (tmp == sg)
+			break;
+		prev = tmp;
+	}
+
+	return prev;
+}
+
 /* Analyze msgin bytes received from target so far.  Return non-zero
  * if there are more bytes needed to complete the message.
  */
@@ -1647,7 +1665,7 @@ static int esp_msgin_process(struct esp *esp)
 		spriv = ESP_CMD_PRIV(ent->cmd);
 
 		if (spriv->cur_residue == sg_dma_len(spriv->cur_sg)) {
-			spriv->cur_sg--;
+			spriv->cur_sg = esp_sg_prev(ent->cmd, spriv->cur_sg);
 			spriv->cur_residue = 1;
 		} else
 			spriv->cur_residue++;
-- 
2.20.1