[PATCH/RFC 4/4] CHS: optimize LBA28/LBA48 usage (resend)

[Albert Lee <albertcc@tw.ibm.com>]

(Resend for the tab problem)

Patch 4/4: optimize LBA28/LBA48 per Mark's advice.

Changes:
     - add lba_28_ok() and lba_48_ok() to ata.h
     - use lba_28_ok() for CHS range check
     - LBA28/LBA48 optimization

For your review, thanks.

Albert
Signed-off-by: Albert Lee <albertcc@tw.ibm.com>

=====

--- ch2/include/linux/ata.h	2005-10-05 18:11:12.000000000 +0800
+++ ch4/include/linux/ata.h	2005-10-05 18:12:09.000000000 +0800
@@ -291,4 +291,14 @@ static inline int ata_ok(u8 status)
  			== ATA_DRDY);
  }

+static inline int lba_28_ok(u64 block, u32 n_block)
+{
+	return (block < ((u64)1 << 28)) && (n_block <= 256);
+}
+
+static inline int lba_48_ok(u64 block, u32 n_block)
+{
+	return (block < ((u64)1 << 48)) && (n_block <= 65536);
+}
+
  #endif /* __LINUX_ATA_H__ */
--- ch3/drivers/scsi/libata-scsi.c	2005-10-05 18:11:12.000000000 +0800
+++ ch4/drivers/scsi/libata-scsi.c	2005-10-05 18:12:09.000000000 +0800
@@ -633,8 +633,12 @@ static unsigned int ata_scsi_verify_xlat
  	if (dev->flags & ATA_DFLAG_LBA) {
  		tf->flags |= ATA_TFLAG_LBA;

-		if (dev->flags & ATA_DFLAG_LBA48) {
-			if (n_block > (64 * 1024))
+		if (lba_28_ok(block, n_block)) {
+			/* use LBA28 */
+			tf->command = ATA_CMD_VERIFY;
+			tf->device |= (block >> 24) & 0xf;
+		} else if (lba_48_ok(block, n_block)) {
+			if (!(dev->flags & ATA_DFLAG_LBA48))
  				return 1;

  			/* use LBA48 */
@@ -646,14 +650,9 @@ static unsigned int ata_scsi_verify_xlat
  			tf->hob_lbah = (block >> 40) & 0xff;
  			tf->hob_lbam = (block >> 32) & 0xff;
  			tf->hob_lbal = (block >> 24) & 0xff;
-		} else {
-			if (n_block > 256)
-				return 1;
-
-			/* use LBA28 */
-			tf->command = ATA_CMD_VERIFY;
-			tf->device |= (block >> 24) & 0xf;
-		}
+		} else
+			/* request too large even for LBA48 */
+			return 1;

  		tf->nsect = n_block & 0xff;

@@ -666,7 +665,7 @@ static unsigned int ata_scsi_verify_xlat
  		/* CHS */
  		u32 sect, head, cyl, track;

-		if (n_block > 256)
+		if (!lba_28_ok(block, n_block))
  			return 1;

  		/* Convert LBA to CHS */
@@ -766,9 +765,11 @@ static unsigned int ata_scsi_rw_xlat(str
  	if (dev->flags & ATA_DFLAG_LBA) {
  		tf->flags |= ATA_TFLAG_LBA;

-		if (dev->flags & ATA_DFLAG_LBA48) {
-			/* The request -may- be too large for LBA48. */
-			if ((block >> 48) || (n_block > 65536))
+		if (lba_28_ok(block, n_block)) {
+			/* use LBA28 */
+			tf->device |= (block >> 24) & 0xf;
+		} else if (lba_48_ok(block, n_block)) {
+			if (!(dev->flags & ATA_DFLAG_LBA48))
  				return 1;

  			/* use LBA48 */
@@ -779,15 +780,9 @@ static unsigned int ata_scsi_rw_xlat(str
  			tf->hob_lbah = (block >> 40) & 0xff;
  			tf->hob_lbam = (block >> 32) & 0xff;
  			tf->hob_lbal = (block >> 24) & 0xff;
-		} else {
-			/* use LBA28 */
-
-			/* The request -may- be too large for LBA28. */
-			if ((block >> 28) || (n_block > 256))
-				return 1;
-
-			tf->device |= (block >> 24) & 0xf;
-		}
+		} else
+			/* request too large even for LBA48 */
+			return 1;

  		ata_rwcmd_protocol(qc);

@@ -804,7 +799,7 @@ static unsigned int ata_scsi_rw_xlat(str
  		u32 sect, head, cyl, track;

  		/* The request -may- be too large for CHS addressing. */
-		if ((block >> 28) || (n_block > 256))
+		if (!lba_28_ok(block, n_block))
  			return 1;

  		ata_rwcmd_protocol(qc);