x86: remove dead BIO_VMERGE_BOUNDARY definition

Impact: cleanup, remove dead code

The block layer dropped the virtual merge feature
(b8b3e16cfe6435d961f6aaebcfd52a1ff2a988c5).

BIO_VMERGE_BOUNDARY definition is meaningless now.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 33513b9..05cfed4 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -80,8 +80,6 @@
 #define readq			readq
 #define writeq			writeq
 
-extern int iommu_bio_merge;
-
 #ifdef CONFIG_X86_32
 # include "io_32.h"
 #else
diff --git a/arch/x86/include/asm/io_64.h b/arch/x86/include/asm/io_64.h
index fea325a..563c162 100644
--- a/arch/x86/include/asm/io_64.h
+++ b/arch/x86/include/asm/io_64.h
@@ -232,8 +232,6 @@
 
 #define flush_write_buffers()
 
-#define BIO_VMERGE_BOUNDARY iommu_bio_merge
-
 /*
  * Convert a virtual cached pointer to an uncached pointer
  */
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 12eeb4b..da93c65 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -31,11 +31,6 @@
 /* Set this to 1 if there is a HW IOMMU in the system */
 int iommu_detected __read_mostly = 0;
 
-/* This tells the BIO block layer to assume merging. Default to off
-   because we cannot guarantee merging later. */
-int iommu_bio_merge __read_mostly = 0;
-EXPORT_SYMBOL(iommu_bio_merge);
-
 dma_addr_t bad_dma_address __read_mostly = 0;
 EXPORT_SYMBOL(bad_dma_address);
 
@@ -189,7 +184,6 @@
 		}
 
 		if (!strncmp(p, "biomerge", 8)) {
-			iommu_bio_merge = 4096;
 			iommu_merge = 1;
 			force_iommu = 1;
 		}