From 41357d98dd7ba5a17a5bf3e3e21d4050018a4966 Mon Sep 17 00:00:00 2001
From: Jonathan Bauer
Date: Mon, 18 Nov 2019 15:08:02 +0100
Subject: [slx-dmsetup] back to sparse files

since preallocating the cow file did not work well with overprovisioned
tmpfs
---
 builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device b/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
index 5d5ec267..64b12047 100755
--- a/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
+++ b/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
@@ -153,15 +153,8 @@ ramdisk_fallback() {
 	fi
 
 	local file="$(mktemp -u -p "$cow_tmpfs" dnbd_cow.XXX)"
-	local fail_count=0
-	while ! fallocate -l "${cow_size}K" "$file" ; do
-		(( cow_size -= 4 ))
-		if [ "$(( fail_count ++ ))" -eq 1000 ]; then
-			break
-		fi
-	done
-	if [ "$fail_count" -eq 1000 ]; then
-		emergency_shell "Failed to allocate CoW file $file after 1000 tries. :("
+	if ! dd of="$file" seek="$cow_size" bs=1k count=0 &> /dev/null; then
+		emergency_shell "Failed to allocate CoW file $file."
 	fi
 	writable_device="$(losetup --show --find "$file")"
 	cow_device_candidate="root"
-- 
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