xfs: Remove kmem_zone_zalloc() usage

Use kmem_cache_zalloc() directly.

With the exception of xlog_ticket_alloc() which will be dealt on the
next patch for readability.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index dda0c94..d4cdcb6 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -214,9 +214,7 @@ _xfs_buf_alloc(
 	int			i;
 
 	*bpp = NULL;
-	bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
-	if (unlikely(!bp))
-		return -ENOMEM;
+	bp = kmem_cache_zalloc(xfs_buf_zone, GFP_NOFS | __GFP_NOFAIL);
 
 	/*
 	 * We don't want certain flags to appear in b_flags unless they are