[PATCH 1/2] block: Reduce BLK_MIN_SEGMENT_SIZE

[Bart Van Assche <bvanassche@acm.org>]

The current value of BLK_MIN_SEGMENT_SIZE, 4096 bytes, makes it
impossible to test small DMA segment size support on systems with a
virtual memory page size of 4096 bytes. Hence reduce
BLK_MIN_SEGMENT_SIZE to 512. There is nothing special about this value -
any other value that is a divisor of 4096 and that doesn't cause
lim->max_segments to be exceeded would also work.

Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk.h b/block/blk.h
index 7082dd5a87f9..7c792c012b0d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -23,7 +23,7 @@ struct elv_change_ctx;
 #define BLK_DEF_MAX_SECTORS_CAP	(SZ_4M >> SECTOR_SHIFT)
 
 #define	BLK_DEV_MAX_SECTORS	(LLONG_MAX >> 9)
-#define	BLK_MIN_SEGMENT_SIZE	4096
+#define	BLK_MIN_SEGMENT_SIZE	512
 
 /* Max future timer expiry for timeouts */
 #define BLK_MAX_TIMEOUT		(5 * HZ)