CONFIG_BOUNCE to avoid useless inclusion of bounce buffer logic

The bounce buffer logic is included on systems that do not need it.  If a
system does not have zones like ZONE_DMA and ZONE_HIGHMEM that can lead to
the use of bounce buffers then there is no need to reserve memory pools etc
etc.  This is true f.e.  for SGI Altix.

Also nicifies the Makefile and gets rid of the tricky "and" there.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 6 insertions, 4 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b32564a1e10..f78965fc642 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -624,7 +624,7 @@ extern unsigned long blk_max_low_pfn, blk_max_pfn;
  */
 #define BLK_DEFAULT_SG_TIMEOUT  (60 * HZ)
 
-#ifdef CONFIG_MMU
+#ifdef CONFIG_BOUNCE
 extern int init_emergency_isa_pool(void);
 extern void blk_queue_bounce(request_queue_t *q, struct bio **bio);
 #else
diff --git a/mm/Kconfig b/mm/Kconfig
index 086af703da4..86187221e78 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -163,6 +163,10 @@ config ZONE_DMA_FLAG
         default "0" if !ZONE_DMA
         default "1"
 
+config BOUNCE
+        def_bool y
+        depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
+
 config NR_QUICK
         int
         depends on QUICKLIST
diff --git a/mm/Makefile b/mm/Makefile
index a9148ea329a..245e33ab00c 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -13,9 +13,7 @@ obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
                            prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
                            $(mmu-y)
 
-ifeq ($(CONFIG_MMU)$(CONFIG_BLOCK),yy)
-obj-y                   += bounce.o
-endif
+obj-$(CONFIG_BOUNCE)    += bounce.o
 obj-$(CONFIG_SWAP)      += page_io.o swap_state.o swapfile.o thrash.o
 obj-$(CONFIG_HUGETLBFS) += hugetlb.o
 obj-$(CONFIG_NUMA)      += mempolicy.o