block: mark bio_split_pool static

Since all bio_split calls refer the same single bio_split_pool, the bio_split
function can use bio_split_pool directly instead of the mempool_t parameter;

then the mempool_t parameter can be removed from bio_split param list, and
bio_split_pool is only referred in fs/bio.c file, can be marked static.

Signed-off-by: Denis ChengRq <crquan@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index e1a90bb..0e07715 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -2544,7 +2544,7 @@
 		if (last_zone != zone) {
 			BUG_ON(last_zone != zone + pd->settings.size);
 			first_sectors = last_zone - bio->bi_sector;
-			bp = bio_split(bio, bio_split_pool, first_sectors);
+			bp = bio_split(bio, first_sectors);
 			BUG_ON(!bp);
 			pkt_make_request(q, &bp->bio1);
 			pkt_make_request(q, &bp->bio2);
diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index c80ea90..b9cbee68 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -353,7 +353,7 @@
 		 * split it.
 		 */
 		struct bio_pair *bp;
-		bp = bio_split(bio, bio_split_pool,
+		bp = bio_split(bio,
 			       ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
 		if (linear_make_request(q, &bp->bio1))
 			generic_make_request(&bp->bio1);
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f52f442..53508a8 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -427,7 +427,7 @@
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
 		 */
-		bp = bio_split(bio, bio_split_pool, chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
+		bp = bio_split(bio, chunk_sects - (bio->bi_sector & (chunk_sects - 1)));
 		if (raid0_make_request(q, &bp->bio1))
 			generic_make_request(&bp->bio1);
 		if (raid0_make_request(q, &bp->bio2))
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5f99013..8bdc9bf 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -817,7 +817,7 @@
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
 		 */
-		bp = bio_split(bio, bio_split_pool,
+		bp = bio_split(bio,
 			       chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
 		if (make_request(q, &bp->bio1))
 			generic_make_request(&bp->bio1);