[PATCH/RFC 3/3] irq-pio: reorganize "buf + offset"

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

Patch 3/3:
   use PageHighMem() to optimize the kmap_atomic() usage, as done in ide-scsi.c

For your review, thanks.

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

==========

--- himem2/drivers/scsi/libata-core.c	2005-10-06 16:10:33.000000000 +0800
+++ himem3/drivers/scsi/libata-core.c	2005-10-06 16:08:43.000000000 +0800
@@ -2748,7 +2748,6 @@ static void ata_pio_sector(struct ata_qu
  	struct page *page;
  	unsigned int offset;
  	unsigned char *buf;
-	unsigned long flags;

  	if (qc->cursect == (qc->nsect - 1))
  		ap->hsm_task_state = HSM_ST_LAST;
@@ -2762,14 +2761,21 @@ static void ata_pio_sector(struct ata_qu

  	DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

-	local_irq_save(flags);
-	buf = kmap_atomic(page, KM_IRQ0);
+	if (PageHighMem(page)) {
+		unsigned long flags;
+
+		local_irq_save(flags);
+		buf = kmap_atomic(page, KM_IRQ0);

-	/* do the actual data transfer */
-	ata_data_xfer(ap, buf + offset, ATA_SECT_SIZE, do_write);
+		/* do the actual data transfer */
+		ata_data_xfer(ap, buf + offset, ATA_SECT_SIZE, do_write);

-	kunmap_atomic(buf, KM_IRQ0);
-	local_irq_restore(flags);
+		kunmap_atomic(buf, KM_IRQ0);
+		local_irq_restore(flags);
+	} else {
+		buf = page_address(page);
+		ata_data_xfer(ap, buf + offset, ATA_SECT_SIZE, do_write);
+	}

  	qc->cursect++;
  	qc->cursg_ofs++;
@@ -2908,7 +2914,6 @@ static void __atapi_pio_bytes(struct ata
  	struct page *page;
  	unsigned char *buf;
  	unsigned int offset, count;
-	unsigned long flags;

  	if (qc->curbytes + bytes >= qc->nbytes)
  		ap->hsm_task_state = HSM_ST_LAST;
@@ -2954,14 +2959,21 @@ next_sg:

  	DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

-	local_irq_save(flags);
-	buf = kmap_atomic(page, KM_IRQ0);
+	if (PageHighMem(page)) {
+		unsigned long flags;
+
+		local_irq_save(flags);
+		buf = kmap_atomic(page, KM_IRQ0);

-	/* do the actual data transfer */
-	ata_data_xfer(ap, buf + offset, count, do_write);
+		/* do the actual data transfer */
+		ata_data_xfer(ap, buf + offset, count, do_write);

-	kunmap_atomic(buf, KM_IRQ0);
-	local_irq_restore(flags);
+		kunmap_atomic(buf, KM_IRQ0);
+		local_irq_restore(flags);
+	} else {
+		buf = page_address(page);
+		ata_data_xfer(ap, buf + offset, count, do_write);
+	}

  	bytes -= count;
  	qc->curbytes += count;