ata: pata_macio: Use WARN instead of BUG

The overflow/underflow conditions in pata_macio_qc_prep() should never
happen. But if they do there's no need to kill the system entirely, a
WARN and failing the IO request should be sufficient and might allow the
system to keep running.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

drivers/ata/pata_macio.c

@@ -554,7 +554,8 @@ static enum ata_completion_errors pata_macio_qc_prep(struct ata_queued_cmd *qc)
 
 		while (sg_len) {
 			/* table overflow should never happen */
-			BUG_ON (pi++ >= MAX_DCMDS);
+			if (WARN_ON_ONCE(pi >= MAX_DCMDS))
+				return AC_ERR_SYSTEM;
 
 			len = (sg_len < MAX_DBDMA_SEG) ? sg_len : MAX_DBDMA_SEG;
 			table->command = cpu_to_le16(write ? OUTPUT_MORE: INPUT_MORE);
@@ -566,11 +567,13 @@ static enum ata_completion_errors pata_macio_qc_prep(struct ata_queued_cmd *qc)
 			addr += len;
 			sg_len -= len;
 			++table;
+			++pi;
 		}
 	}
 
 	/* Should never happen according to Tejun */
-	BUG_ON(!pi);
+	if (WARN_ON_ONCE(!pi))
+		return AC_ERR_SYSTEM;
 
 	/* Convert the last command to an input/output */
 	table--;