[PATCH] libata CHS: LBA28/LBA48 optimization (revise #6)

     - add lba_28_ok() and lba_48_ok() to ata.h.
     - check ending block number instead of staring block number.
     - use lba_28_ok() for CHS range check
     - LBA28/LBA48 optimization

Suggested by Mark Lord and Alan Cox.

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

=====
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

drivers/scsi/libata-scsi.c

@@ -636,9 +636,13 @@ static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 	if (dev->flags & ATA_DFLAG_LBA) {
 		tf->flags |= ATA_TFLAG_LBA;
 
-		if (dev->flags & ATA_DFLAG_LBA48) {
-			if (n_block > (64 * 1024))
-				goto invalid_fld;
+		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))
+				goto out_of_range;
 
 			/* use LBA48 */
 			tf->flags |= ATA_TFLAG_LBA48;
@@ -649,15 +653,9 @@ static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 			tf->hob_lbah = (block >> 40) & 0xff;
 			tf->hob_lbam = (block >> 32) & 0xff;
 			tf->hob_lbal = (block >> 24) & 0xff;
-		} else {
-			if (n_block > 256)
-				goto invalid_fld;
-
-			/* use LBA28 */
-			tf->command = ATA_CMD_VERIFY;
-
-			tf->device |= (block >> 24) & 0xf;
-		}
+		} else
+			/* request too large even for LBA48 */
+			goto out_of_range;
 
 		tf->nsect = n_block & 0xff;
 
@@ -670,8 +668,8 @@ static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 		/* CHS */
 		u32 sect, head, cyl, track;
 
-		if (n_block > 256)
-			goto invalid_fld;
+		if (!lba_28_ok(block, n_block))
+			goto out_of_range;
 
 		/* Convert LBA to CHS */
 		track = (u32)block / dev->sectors;
@@ -784,9 +782,11 @@ static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 	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))
 				goto out_of_range;
 
 			/* use LBA48 */
@@ -797,15 +797,9 @@ static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 			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))
-				goto out_of_range;
-
-			tf->device |= (block >> 24) & 0xf;
-		}
+		} else
+			/* request too large even for LBA48 */
+			goto out_of_range;
 
 		ata_rwcmd_protocol(qc);
 
@@ -822,7 +816,7 @@ static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 		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))
 			goto out_of_range;
 
 		ata_rwcmd_protocol(qc);

include/linux/ata.h

@@ -291,4 +291,16 @@ static inline int ata_ok(u8 status)
 			== ATA_DRDY);
 }
 
+static inline int lba_28_ok(u64 block, u32 n_block)
+{
+	/* check the ending block number */
+	return ((block + n_block - 1) < ((u64)1 << 28)) && (n_block <= 256);
+}
+
+static inline int lba_48_ok(u64 block, u32 n_block)
+{
+	/* check the ending block number */
+	return ((block + n_block - 1) < ((u64)1 << 48)) && (n_block <= 65536);
+}
+
 #endif /* __LINUX_ATA_H__ */