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>

3 files changed, 4 insertions, 4 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();
diff --git a/include/asm-x86/scatterlist_32.h b/include/asm-x86/scatterlist_32.h
index bd5164aa8f63..140a5b37fa77 100644
--- a/include/asm-x86/scatterlist_32.h
+++ b/include/asm-x86/scatterlist_32.h
@@ -4,7 +4,7 @@
 #include <asm/types.h>
 
 struct scatterlist {
-    struct page         *page;
+    unsigned long       page_link;
     unsigned int        offset;
     dma_addr_t          dma_address;
     unsigned int        length;
diff --git a/include/asm-x86/scatterlist_64.h b/include/asm-x86/scatterlist_64.h
index ef3986ba4b79..e3447846e03d 100644
--- a/include/asm-x86/scatterlist_64.h
+++ b/include/asm-x86/scatterlist_64.h
@@ -4,7 +4,7 @@
 #include <asm/types.h>
 
 struct scatterlist {
-    struct page         *page;
+    unsigned long       page_link;
     unsigned int        offset;
     unsigned int        length;
     dma_addr_t          dma_address;