[PATCH] sg traverse fix for __atapi_pio_bytes()

Problem:
Incorrect md5sum when using ATAPI PIO mode to verify a distro CD.

Root cause:  sg traverse problem.
In __atapi_pio_bytes(), if qc->cursg++ is increased and "goto
next_page" is executed, then sg is not updated to the new qc->cursg
and the old sg is overwritten with the new data.

Changes:
- Replace "goto next_page" with "goto next_sg" to make sg updated.
Signed-off-by: NAlbert Lee <albertcc@tw.ibm.com>

drivers/scsi/libata-core.c

@@ -2577,7 +2577,6 @@ static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 next_sg:
 	sg = &qc->sg[qc->cursg];
 
-next_page:
 	page = sg->page;
 	offset = sg->offset + qc->cursg_ofs;
 
@@ -2585,6 +2584,7 @@ static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 	page = nth_page(page, (offset >> PAGE_SHIFT));
 	offset %= PAGE_SIZE;
 
+	/* don't overrun current sg */
 	count = min(sg->length - qc->cursg_ofs, bytes);
 
 	/* don't cross page boundaries */
@@ -2609,8 +2609,6 @@ static void __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
 	kunmap(page);
 
 	if (bytes) {
-		if (qc->cursg_ofs < sg->length)
-			goto next_page;
 		goto next_sg;
 	}
 }