[PATCH] ia64: turn off ALLOW_IOV_BYPASS

Since the BIO-layer assumes that blocks can be merged virtually
at the granularity of BIO_VMERGE_BOUNDARY, independent of what device
is in use, we always need to go through the I/O MMU, even for 64-bit
devices.  Hopefully, the BIO-layer can be made smarter some day.

arch/ia64/hp/common/sba_iommu.c

@@ -47,8 +47,10 @@
 /*
 ** This option allows cards capable of 64bit DMA to bypass the IOMMU.  If
 ** not defined, all DMA will be 32bit and go through the TLB.
+** There's potentially a conflict in the bio merge code with us
+** advertising an iommu, but then bypassing it.  Disabled for now.
 */
-#define ALLOW_IOV_BYPASS
+#undef ALLOW_IOV_BYPASS
 
 /*
 ** If a device prefetches beyond the end of a valid pdir entry, it will cause