diff -r 98b83cc57eca linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c	Thu Jul 14 14:01:21 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c	Thu Jul 14 16:30:07 2005
@@ -329,11 +329,11 @@
                 buffer_ma >> PAGE_SHIFT;
 
             ring_req->frame_and_sects[ring_req->nr_segments++] =
-                (((u32) ref) << 16) | (fsect << 3) | lsect;
+                blkif_fas_from_gref(ref, fsect, lsect);
 
 #else
             ring_req->frame_and_sects[ring_req->nr_segments++] =
-                buffer_ma | (fsect << 3) | lsect;
+                blkif_fas(buffer_ma, fsect, lsect);
 #endif
         }
     }
@@ -832,10 +832,10 @@
                 buffer_ma >> PAGE_SHIFT;
 
             req->frame_and_sects[req->nr_segments] =
-                (((u32) ref ) << 16) | (fsect << 3) | lsect;
+                blkif_fas_from_gref(ref, fsect, lsect);
 #else
             req->frame_and_sects[req->nr_segments] =
-                buffer_ma | (fsect << 3) | lsect;
+                blkif_fas(buffer_ma, fsect, lsect);
 #endif
             if ( ++req->nr_segments < BLKIF_MAX_SEGMENTS_PER_REQUEST )
                 sg_next_sect += nr_sectors;
@@ -887,9 +887,9 @@
 
     blk_shadow[xid].frame[0] = buffer_ma >> PAGE_SHIFT;
 
-    req->frame_and_sects[0] = (((u32) ref)<<16)  | (fsect<<3) | lsect;
+    req->frame_and_sects[0] = blkif_fas_from_gref(ref, fsect, lsect);
 #else
-    req->frame_and_sects[0] = buffer_ma | (fsect<<3) | lsect;
+    req->frame_and_sects[0] = blkif_fas(buffer_ma, fsect, lsect);
 #endif
 
     /* Keep a private copy so we can reissue requests when recovering. */    
@@ -1057,7 +1057,7 @@
 
     gnttab_grant_foreign_access_ref( ref, rdomid, address >> PAGE_SHIFT, 0 );
 
-    req->frame_and_sects[0] = (((u32) ref) << 16) | 7;
+    req->frame_and_sects[0] = blkif_fas_from_gref(ref, 0, (PAGE_SIZE/512)-1);
 
     blkif_control_send(req, rsp);
 }
diff -r 98b83cc57eca linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c	Thu Jul 14 14:01:21 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/blkfront/vbd.c	Thu Jul 14 16:30:07 2005
@@ -137,7 +137,7 @@
     blkif_control_probe_send(&req, &rsp,
                              (unsigned long)(virt_to_machine(buf)));
 #else
-    req.frame_and_sects[0] = virt_to_machine(buf) | 7;
+    req.frame_and_sects[0] = blkif_fas(virt_to_machine(buf), 0, ((PAGE_SIZE/512)-1);
 
     blkif_control_send(&req, &rsp);
 #endif
diff -r 98b83cc57eca xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h	Thu Jul 14 14:01:21 2005
+++ b/xen/include/public/io/blkif.h	Thu Jul 14 16:30:07 2005
@@ -36,7 +36,7 @@
     blkif_vdev_t   device;       /* only for read/write requests         */
     unsigned long  id;           /* private guest value, echoed in resp  */
     blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-    /* @f_a_s[2:0]=last_sect ; @f_a_s[5:3]=first_sect                        */
+    /* @f_a_s[4:0]=last_sect ; @f_a_s[9:5]=first_sect                        */
 #ifdef CONFIG_XEN_BLKDEV_GRANT
     /* @f_a_s[:16]= grant reference (16 bits)                                */
 #else
@@ -47,10 +47,12 @@
     unsigned long  frame_and_sects[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 } blkif_request_t;
 
-#define blkif_first_sect(_fas) (((_fas)>>3)&7)
-#define blkif_last_sect(_fas)  ((_fas)&7)
+#define blkif_fas(_addr, _fs, _ls) ((addr)|((_fs)<<5)|(_ls))
+#define blkif_first_sect(_fas) (((_fas)>>5)&31)
+#define blkif_last_sect(_fas)  ((_fas)&31)
 
 #ifdef CONFIG_XEN_BLKDEV_GRANT
+#define blkif_fas_from_gref(_gref, _fs, _ls) (((_gref)<<16)|((_fs)<<5)|(_ls))
 #define blkif_gref_from_fas(_fas) ((_fas)>>16)
 #endif