x86: remove dead BIO_VMERGE_BOUNDARY definition

Impact: cleanup, remove dead code

The block layer dropped the virtual merge feature
(b8b3e16c).

BIO_VMERGE_BOUNDARY definition is meaningless now.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NJens Axboe <jens.axboe@oracle.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/include/asm/io.h

@@ -80,8 +80,6 @@ static inline void writeq(__u64 val, volatile void __iomem *addr)
 #define readq			readq
 #define writeq			writeq
 
-extern int iommu_bio_merge;
-
 #ifdef CONFIG_X86_32
 # include "io_32.h"
 #else

arch/x86/include/asm/io_64.h

@@ -232,8 +232,6 @@ void memset_io(volatile void __iomem *a, int b, size_t c);
 
 #define flush_write_buffers()
 
-#define BIO_VMERGE_BOUNDARY iommu_bio_merge
-
 /*
  * Convert a virtual cached pointer to an uncached pointer
  */

arch/x86/kernel/pci-dma.c

@@ -31,11 +31,6 @@ int no_iommu __read_mostly;
 /* 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 @@ static __init int iommu_setup(char *p)
 		}
 
 		if (!strncmp(p, "biomerge", 8)) {
-			iommu_bio_merge = 4096;
 			iommu_merge = 1;
 			force_iommu = 1;
 		}