[libata] scsi simulator improvements: MODE SENSE, SEEK(6,10), REZERO_UNIT

* SEEK(6), SEEK(10), and REZERO_UNIT are no-ops.  Unconditionally
  complete these commands with success.
* MODE SENSE caching page work:
	* correct page length
	* set bit, if read-ahead is disabled
	* set bit, if writeback caching is enabled
	  (previously, this bit was never set, even if
	   writeback caching was enabled)
* add MODE SENSE r/w error recovery page

drivers/scsi/libata-scsi.c

@@ -695,9 +695,17 @@ static void ata_msense_push(u8 **ptr_io, const u8 *last,
 static unsigned int ata_msense_caching(struct ata_device *dev, u8 **ptr_io,
 				       const u8 *last)
 {
-	u8 page[7] = { 0xf, 0, 0x10, 0, 0x8, 0xa, 0 };
-	if (dev->flags & ATA_DFLAG_WCACHE)
-		page[6] = 0x4;
+	u8 page[] = {
+		0x8,				/* page code */
+		0x12,				/* page length */
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 10 zeroes */
+		0, 0, 0, 0, 0, 0, 0, 0		/* 8 zeroes */
+	};
+
+	if (ata_id_wcache_enabled(dev))
+		page[2] |= (1 << 2);	/* write cache enable */
+	if (!ata_id_rahead_enabled(dev))
+		page[12] |= (1 << 5);	/* disable read ahead */
 
 	ata_msense_push(ptr_io, last, page, sizeof(page));
 	return sizeof(page);
@@ -723,6 +731,31 @@ static unsigned int ata_msense_ctl_mode(u8 **ptr_io, const u8 *last)
 	return sizeof(page);
 }
 
+/**
+ *	ata_msense_rw_recovery - Simulate MODE SENSE r/w error recovery page
+ *	@dev: Device associated with this MODE SENSE command
+ *	@ptr_io: (input/output) Location to store more output data
+ *	@last: End of output data buffer
+ *
+ *	Generate a generic MODE SENSE r/w error recovery page.
+ *
+ *	LOCKING:
+ *	None.
+ */
+
+static unsigned int ata_msense_rw_recovery(u8 **ptr_io, const u8 *last)
+{
+	const u8 page[] = {
+		0x1,			  /* page code */
+		0xa,			  /* page length */
+		(1 << 7) | (1 << 6),	  /* note auto r/w reallocation */
+		0, 0, 0, 0, 0, 0, 0, 0, 0 /* 9 zeroes */
+	};
+
+	ata_msense_push(ptr_io, last, page, sizeof(page));
+	return sizeof(page);
+}
+
 /**
  *	ata_scsiop_mode_sense - Simulate MODE SENSE 6, 10 commands
  *	@args: Port / device / SCSI command of interest.
@@ -762,6 +795,10 @@ unsigned int ata_scsiop_mode_sense(struct ata_scsi_args *args, u8 *rbuf,
 	last = rbuf + buflen - 1;
 
 	switch(scsicmd[2] & 0x3f) {
+	case 0x01:		/* r/w error recovery */
+		output_len += ata_msense_rw_recovery(&p, last);
+		break;
+
 	case 0x08:		/* caching */
 		output_len += ata_msense_caching(dev, &p, last);
 		break;
@@ -772,6 +809,7 @@ unsigned int ata_scsiop_mode_sense(struct ata_scsi_args *args, u8 *rbuf,
 		}
 
 	case 0x3f:		/* all pages */
+		output_len += ata_msense_rw_recovery(&p, last);
 		output_len += ata_msense_caching(dev, &p, last);
 		output_len += ata_msense_ctl_mode(&p, last);
 		break;
@@ -1118,6 +1156,10 @@ static void ata_scsi_simulate(struct ata_port *ap, struct ata_device *dev,
 	args.done = done;
 
 	switch(scsicmd[0]) {
+		/* no-op's, complete with success */
+		case REZERO_UNIT:
+		case SEEK_6:
+		case SEEK_10:
 		case TEST_UNIT_READY:
 		case FORMAT_UNIT:		/* FIXME: correct? */
 		case SEND_DIAGNOSTIC:		/* FIXME: correct? */

include/linux/ata.h

@@ -202,6 +202,7 @@ struct ata_taskfile {
 };
 
 #define ata_id_is_ata(dev)	(((dev)->id[0] & (1 << 15)) == 0)
+#define ata_id_rahead_enabled(dev) ((dev)->id[85] & (1 << 6))
 #define ata_id_wcache_enabled(dev) ((dev)->id[85] & (1 << 5))
 #define ata_id_has_lba48(dev)	((dev)->id[83] & (1 << 10))
 #define ata_id_has_wcache(dev)	((dev)->id[82] & (1 << 5))