Adding function for more resilient detachment of loopback devices.

1 files changed, 25 insertions, 2 deletions

diff --git a/functions/losetup.sh b/functions/losetup.sh
index df7e2d27f..039ff3ec1 100755
--- a/functions/losetup.sh
+++ b/functions/losetup.sh
@@ -7,6 +7,29 @@
 ## This is free software, and you are welcome to redistribute it
 ## under certain conditions; see COPYING for details.
 
+Lodetach ()
+{
+	DEVICE="${1}"
+	ATTEMPT="${2:-1}"
+
+	if [ "${ATTEMPT}" -gt 3 ]
+	then
+		Echo_error "Failed to detach loop device '${DEVICE}'."
+		exit 1
+	fi
+
+	# Changes to block devices result in uevents which trigger rules which in
+	# turn access the loop device (ex. udisks-part-id, blkid) which can cause
+	# a race condition. We call 'udevadm settle' to help avoid this.
+	${LB_ROOT_COMMAND} udevadm settle
+
+	# Loop back devices aren't the most reliable when it comes to writes.
+	# We sleep and sync for good measure - better than build failure.
+	sync
+	sleep 1
+
+	${LB_ROOT_COMMAND} ${LB_LOSETUP} -d "${DEVICE}" || Lodetach "${DEVICE}" "$(expr ${ATTEMPT} + 1)"
+}
 
 Losetup ()
 {
@@ -14,9 +37,9 @@ Losetup ()
 	FILE="${2}"
 	PARTITION="${3:-1}"
 
-	${LB_ROOT_COMMAND} ${LB_LOSETUP} "${DEVICE}" "${FILE}"
+	${LB_ROOT_COMMAND} ${LB_LOSETUP} --read-only "${DEVICE}" "${FILE}"
 	FDISK_OUT="$(${LB_FDISK} -l -u ${DEVICE} 2>&1)"
-	${LB_ROOT_COMMAND} ${LB_LOSETUP} -d "${DEVICE}"
+	Lodetach "${DEVICE}"
 
 	LOOPDEVICE="$(echo ${DEVICE}p${PARTITION})"