xfs: use kmem_zone_zalloc for buffers

To replace the alloc/memset pair.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fs/xfs/xfs_buf.c

@@ -178,7 +178,7 @@ xfs_buf_alloc(
 {
 	struct xfs_buf		*bp;
 
-	bp = kmem_zone_alloc(xfs_buf_zone, xb_to_km(flags));
+	bp = kmem_zone_zalloc(xfs_buf_zone, xb_to_km(flags));
 	if (unlikely(!bp))
 		return NULL;
 
@@ -187,7 +187,6 @@ xfs_buf_alloc(
 	 */
 	flags &= ~(XBF_LOCK|XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);
 
-	memset(bp, 0, sizeof(xfs_buf_t));
 	atomic_set(&bp->b_hold, 1);
 	atomic_set(&bp->b_lru_ref, 1);
 	init_completion(&bp->b_iowait);