From d9070c4379711e41865db46d083a24805b1b1265 Mon Sep 17 00:00:00 2001
From: Jakub Jirutka <jakub@jirutka.cz>
Date: Wed, 11 Oct 2017 16:58:42 +0200
Subject: [PATCH] Do not discard blocks on NBD image when creating FS

It's useless for NBD image and probably causes the following error:

    > Formatting image to ext4
    mke2fs 1.43.4 (31-Jan-2017)
    Discarding device blocks:    4096/1310720               failed - I/O error
---
 alpine-make-vm-image | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/alpine-make-vm-image b/alpine-make-vm-image
index 5307f83..6920df3 100755
--- a/alpine-make-vm-image
+++ b/alpine-make-vm-image
@@ -287,8 +287,10 @@ nbd_dev=$(attach_image "$IMAGE_FILE" "$IMAGE_FORMAT")
 #-----------------------------------------------------------------------
 einfo "Formatting image to $ROOTFS"
 
-# syslinux 6.0.3 cannot boot from ext4 w/ 64bit feature enabled
-[ "$ROOTFS" = ext4 ] && mkfs_args='-O ^64bit' || mkfs_args=''
+# syslinux 6.0.3 cannot boot from ext4 w/ 64bit feature enabled.
+# -E nodiscard / -K - do not attempt to discard blocks at mkfs time (it's
+# useless for NBD image and prints confusing error).
+[ "$ROOTFS" = ext4 ] && mkfs_args='-O ^64bit -E nodiscard' || mkfs_args='-K'
 
 mkfs.$ROOTFS -L root $mkfs_args "$nbd_dev"