Change table chaining layout

Change the page member of the scatterlist structure to be an unsigned
long, and encode more stuff in the lower bits:

- Bits 0 and 1 zero: this is a normal sg entry. Next sg entry is located
  at sg + 1.
- Bit 0 set: this is a chain entry, the next real entry is at ->page_link
  with the two low bits masked off.
- Bit 1 set: this is the final entry in the sg entry. sg_next() will return
  NULL when passed such an entry.

It's thus important that sg table users use the proper accessors to get
and set the page member.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/asm-x86/dma-mapping_32.h b/include/asm-x86/dma-mapping_32.h
index 6a2d26cb5da6..55f01bd9e556 100644
--- a/include/asm-x86/dma-mapping_32.h
+++ b/include/asm-x86/dma-mapping_32.h
@@ -45,9 +45,9 @@ dma_map_sg(struct device *dev, struct scatterlist *sglist, int nents,
 	WARN_ON(nents == 0 || sglist[0].length == 0);
 
 	for_each_sg(sglist, sg, nents, i) {
-		BUG_ON(!sg->page);
+		BUG_ON(!sg_page(sg));
 
-		sg->dma_address = page_to_phys(sg->page) + sg->offset;
+		sg->dma_address = sg_phys(sg);
 	}
 
 	flush_write_buffers();