Merge ~mwhudson/ubuntu/+source/casper:lp-1489855-harder into ubuntu/+source/casper:ubuntu/eoan-proposed

[Michael Hudson-Doyle]

    * Use udev-created symlinks to find filesystems by label.
    * Fix find_cow_device and find_files to not unmount filesystems that were
      already mounted (LP: #1489855)

This "seems to work" in my testing so far.

[Michael Hudson-Doyle (mwhudson)]

I've now tested this in three scenarios as described in the bug report, with both the desktop and live-server ISO. I'm happy enough with it but I'll leave this here over my weekend in case someone wants to review it.

Unmerged commits

a452b0b... by Michael Hudson-Doyle on 2019-07-19

Use udev-created symlinks to find filesystems by label.

* Use udev-created symlinks to find filesystems by label.
* Fix find_cow_device and find_files to not unmount filesystems that were
  already mounted (LP: #1489855)

38f1ac5... by Michael Hudson-Doyle on 2019-07-16

Import patches-unapplied version 1.413 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 0e52b46ea2a0eff48e0e8b26cb6a7174989ceb27

New changelog entries:
  * Fix ftbfs by restoring empty conf.d missing from git import.

0e52b46... by Michael Hudson-Doyle on 2019-07-16

Import patches-unapplied version 1.412 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: ffbe569742513eeff619206775c15a842cc723d0

New changelog entries:
  * Try to mount partitions of a block device before mounting the block device
    itself (if both work, the former is preferable). (LP: #1489855)

ffbe569... by Dimitri John Ledkov on 2019-07-01

Import patches-unapplied version 1.411 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 21653d164262d107b3acf397836a72852b330401

New changelog entries:
  * 1.409 only added parsing for NFSROOT, also add parsing for NETBOOT as
    it was intended.

21653d1... by Dimitri John Ledkov on 2019-06-20

Import patches-unapplied version 1.410 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 9512917f738e5701175e146003a6652bec46008d

New changelog entries:
  * Drop casper-bottom/23networking and rely on stock configure_networking
    only. As that one knows netplan... However this drops ',' separated
    syntax for ip= command which is very weird. And baked-in networking
    config on the images should switch to netplan too.

9512917... by Dimitri John Ledkov on 2019-06-20

Import patches-unapplied version 1.409 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 78a580214c8bba7f3ef89ff70ad6e1d37f9ee40b

New changelog entries:
  * Reintroduce netboot= => export NETBOOT option parsing in casper, as it
    was dropped in initramfs-tools.

78a5802... by Sebastien Bacher on 2019-06-05

Import patches-unapplied version 1.408 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 43f12281f98ddefb74fb80ebf6a37342a8a66e1e

New changelog entries:
  * ubiquity-hooks/30accessibility:
    - enable accessibility for gdm as well as for lightdm which was still
      the only option being handled (lp: #1825112)

43f1228... by Dimitri John Ledkov on 2019-04-25

Import patches-unapplied version 1.407 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: 41d58850dce25631976f69a1c0517f0fb33cd2f5

New changelog entries:
  * Upload 1.396 partially reverted 1.395, but it didn't restore the
    systemd job, thus the net effect is that password was not cleared at
    all for anyone. Restore 1.395 codepath, but do not clear the password
    when ssdm is present.
  * Add a 99casperboot hook, and make casper-stop sensitive to that, since
    boot=casper is gone from the default kernel cmdline.

41d5885... by Dimitri John Ledkov on 2019-04-23

Import patches-unapplied version 1.406 to ubuntu/eoan-proposed

Imported using git-ubuntu import.

Changelog parent: f4c05cc8c0d7bf5e7790bd3e166a9ec8260cfbdf

New changelog entries:
  * When generating casper inird with UUID, also default boot= arg to
    casper. This way, we can drop boot=casper from all the iso's default
    cmdline.

f4c05cc... by Alberto Milone on 2019-04-16

Import patches-unapplied version 1.405 to ubuntu/disco-proposed

Imported using git-ubuntu import.

Changelog parent: 762b2bb689974c4fecd95d9fd8797e8e25ae9b06

New changelog entries:
  [ Dimitri John Ledkov ]
  * scripts/casper-bottom/25adduser:
    - Make boot non-degraded, by clearing the lock. As otherwise
      systemd-sysusers fails and boots the system degraded on multi-lower
      subiquity images.
  [ Alberto Milone ]
  * scripts/casper-bottom/56override_nvidia_udev_rule:
    - Prevent udev from repeatedly trying to modprobe the nvidia modules
      and to start the relevant daemons on the live image (LP: #1824177).

diff --git a/debian/changelog b/debian/changelog
index 43a2f49..3d6784b 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,11 @@
+casper (1.414) UNRELEASED; urgency=medium
+
+  * Use udev-created symlinks to find filesystems by label.
+  * Fix find_cow_device and find_files to not unmount filesystems that were
+    already mounted (LP: #1489855)
+
+ -- Michael Hudson-Doyle <[e-mail]>  Fri, 19 Jul 2019 14:34:03 +1200
+
 casper (1.413) eoan; urgency=medium
 
   * Fix ftbfs by restoring empty conf.d missing from git import. 
diff --git a/scripts/casper-helpers b/scripts/casper-helpers
index 0127bb9..ad961ae 100644
--- a/scripts/casper-helpers
+++ b/scripts/casper-helpers
@@ -169,35 +169,16 @@ setup_loop() {
     fi
 }
 
-# Returns 0 on success
-# panics if remount- or bind-mount fails
-# returns 1 on failure otherwise
-try_mount ()
-{
-    dev="${1}"
-    mountp="${2}"
-    opts="${3}"
+find_cow_device() {
+    pers_label="${1}"
 
-    if where_is_mounted ${dev} > /dev/null; then
-        if [ "${opts}" != "ro" ]; then
-            mount -o remount,"${opts}" ${dev} $(where_is_mounted ${dev}) || panic "Remounting failed"
-            return 0
-        fi
-        mount -o bind $(where_is_mounted ${dev}) ${mountp} || panic "Cannot bind-mount"
-        return 0
-    else
-        mount -t $(get_fstype "${dev}") -o "${opts}" "${dev}" "${mountp}"
-        ret=$?
-        if [ $ret -ne 0 ]; then
-            log_warning_msg "Cannot mount ${dev} on ${mountp}"
-            return 1
-        fi
+    udevadm settle
+
+    if [ -e "/dev/disk/by-label/${pers_label}" ]; then
+        echo /dev/disk/by-label/${pers_label}
         return 0
     fi
-}
 
-find_cow_device() {
-    pers_label="${1}"
     cow_backing="/${pers_label}-backing"
 
     if [ -z "${PERSISTENT_PATH}" ]; then
@@ -214,22 +195,30 @@ find_cow_device() {
         fi
         for dev in $(subdevices "${sysblock}"); do
             devname=$(sys2dev "${dev}")
-            if [ "$(/sbin/blkid -s LABEL -o value $devname 2>/dev/null)" = "${pers_label}" ]; then
-                echo "$devname"
-                return
             # Do not add any filesystem types here that might be able to
             # mount a journalled filesystem and replay the journal. Doing so
             # will cause data loss when a live CD is booted on a system
             # where filesystems are in use by hibernated operating systems.
-            elif [ "$(get_fstype ${devname})" = "vfat" ]; then
+            case "$(get_fstype ${devname})" in
+                vfat)
+                    :;;
+                *)
+                    continue;;
+            esac
+            where_mounted=$(where_is_mounted "${devname}")
+            if [ $? -eq 0 ]; then
+                if [ -e "${where_mounted}/${pers_fpath}" ]; then
+                    mount -o remount,rw ${devname} ${where_mounted} || continue
+                    echo $(setup_loop "${where_mounted}/${pers_fpath}" "loop" "/sys/block/loop*")
+                fi
+            else
                 mkdir -p "${cow_backing}"
-                try_mount "${devname}" "${cow_backing}" "rw" || continue
-                cow_backing_mp=$(where_is_mounted "${devname}")
-                if [ -e "${cow_backing_mp}/${pers_fpath}" ]; then
-                    echo $(setup_loop "${cow_backing_mp}/${pers_fpath}" "loop" "/sys/block/loop*")
+                mount "${devname}" "${cow_backing}" || continue
+                if [ -e "${cow_backing}/${pers_fpath}" ]; then
+                    echo $(setup_loop "${cow_backing}/${pers_fpath}" "loop" "/sys/block/loop*")
                     return 0
                 else
-                    umount ${cow_backing_mp}
+                    umount ${cow_backing}
                 fi
             fi
         done
@@ -241,21 +230,31 @@ find_files()
 # FIXME: merge with above function
 {
     filenames="${1}"
-    snap_backing="/snap-backing"
     for sysblock in $(echo /sys/block/* | tr ' ' '\n' | grep -v loop); do
         for dev in $(subdevices "${sysblock}"); do
             devname=$(sys2dev "${dev}")
-            devfstype="$(get_fstype ${devname})"
-            if [ "${devfstype}" = "vfat" ] ||  [ "${devfstype}" = "ext2" ] ; then # FIXME: all supported block devices should be scanned
-                mkdir -p "${snap_backing}"
-                try_mount "${devname}" "${snap_backing}" "ro" || continue
-                for filename in ${filenames}; do
-                    if [ -e "${snap_backing}/${filename}" ]; then
-                        echo "${devname} ${snap_backing} ${filename}"
-                        return 0
-                    fi
-                done
-                umount ${snap_backing}
+            case "$(get_fstype ${devname})" in
+                vfat|ext2)
+                    :;;
+                *)
+                    continue;;
+            esac
+            doumount=
+            mntpoint=$(where_is_mounted "${devname}")
+            if [ $? -ne 0 ]; then
+                doumount=1
+                mntpoint="/snap-backing"
+                mkdir -p "${mntpoint}"
+                mount -o ro "${devname}" "${mntpoint}"
+            fi
+            for filename in ${filenames}; do
+                if [ -e "${mntpoint}/${filename}" ]; then
+                    echo "${devname} ${mntpoint} ${filename}"
+                    return 0
+                fi
+            done
+            if [ -n "${doumount}" ]; then
+                umount "${mntpoint}"
             fi
         done
     done