[PATCH] revert ide-scsi highmem cleanup

Jeff Garzik <jgarzik@pobox.com> points out that this was wrong: we need to
disable local interrupts while holding KM_IRQ0 due to IRQ sharing.

And holding interrupts off during a big PIO opration is expensive, so we only
want to do that if we know the page was highmem.

So revert commit 17fd47a

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/scsi/ide-scsi.c

@@ -180,12 +180,22 @@ static void idescsi_input_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsigne
 			return;
 		}
 		count = min(pc->sg->length - pc->b_count, bcount);
-		buf = kmap_atomic(pc->sg->page, KM_IRQ0);
-		drive->hwif->atapi_input_bytes(drive,
-				buf + pc->b_count + pc->sg->offset, count);
-		kunmap_atomic(buf, KM_IRQ0);
-		bcount -= count;
-		pc->b_count += count;
+		if (PageHighMem(pc->sg->page)) {
+			unsigned long flags;
+
+			local_irq_save(flags);
+			buf = kmap_atomic(pc->sg->page, KM_IRQ0) +
+					pc->sg->offset;
+			drive->hwif->atapi_input_bytes(drive,
+						buf + pc->b_count, count);
+			kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
+			local_irq_restore(flags);
+		} else {
+			buf = page_address(pc->sg->page) + pc->sg->offset;
+			drive->hwif->atapi_input_bytes(drive,
+						buf + pc->b_count, count);
+		}
+		bcount -= count; pc->b_count += count;
 		if (pc->b_count == pc->sg->length) {
 			pc->sg++;
 			pc->b_count = 0;
@@ -205,12 +215,22 @@ static void idescsi_output_buffers (ide_drive_t *drive, idescsi_pc_t *pc, unsign
 			return;
 		}
 		count = min(pc->sg->length - pc->b_count, bcount);
-		buf = kmap_atomic(pc->sg->page, KM_IRQ0);
-		drive->hwif->atapi_output_bytes(drive,
-				buf + pc->b_count + pc->sg->offset, count);
-		kunmap_atomic(buf, KM_IRQ0);
-		bcount -= count;
-		pc->b_count += count;
+		if (PageHighMem(pc->sg->page)) {
+			unsigned long flags;
+
+			local_irq_save(flags);
+			buf = kmap_atomic(pc->sg->page, KM_IRQ0) +
+						pc->sg->offset;
+			drive->hwif->atapi_output_bytes(drive,
+						buf + pc->b_count, count);
+			kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
+			local_irq_restore(flags);
+		} else {
+			buf = page_address(pc->sg->page) + pc->sg->offset;
+			drive->hwif->atapi_output_bytes(drive,
+						buf + pc->b_count, count);
+		}
+		bcount -= count; pc->b_count += count;
 		if (pc->b_count == pc->sg->length) {
 			pc->sg++;
 			pc->b_count = 0;