From 2f529e9a07eb351510a880a4256111014bcf9235 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Wed, 16 Apr 2025 10:27:25 +0100
Subject: [PATCH] daemon: inspect: Resolve Ubuntu 22+
 /dev/disk/by-id/dm-uuid-LVM-... in fstab

Linux + LVM supports device names like /dev/disk/by-id/dm-uuid-LVM-
followed by two concatenated UUIDs, firstly for the volume group and
secondly for the logical volume.  We can reverse those to get the
device name (/dev/VG/LV).

fstab entries look like:

  # / was on /dev/vg0/lv-0 during curtin installation
  /dev/disk/by-id/dm-uuid-LVM-OzFWT6NHkstr1hcmrWRRMDGPn9xdZj1YOOycQ533186x288FdU6UubU3OlnWJz6D / ext4 defaults 0 1
  # /usr was on /dev/vg0/lv-1 during curtin installation
  /dev/disk/by-id/dm-uuid-LVM-OzFWT6NHkstr1hcmrWRRMDGPn9xdZj1YZu53m4ZssZ8Jeb3I14RAJwIj5YlHIb9P /usr ext4 defaults 0 1

The upshot of this fix is that we are now able to correctly inspect
and run virt-v2v on Ubuntu 22+ guests with split /usr.  In particular,
we correctly map /etc/fstab entries like the above to LV device names,
which means that /usr merging now works correctly.

Reported-by: Jaroslav Spanko
Thanks: Daniel Berrange
Fixes: https://issues.redhat.com/browse/RHEL-87493
(cherry picked from commit e43ca1912973b3ddfa73b09a4690aa8bb26e08af)
(cherry picked from commit 180293338e0d127d0545fe03b6141ed04e22e441)
---
 daemon/inspect_fs_unix_fstab.ml | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/daemon/inspect_fs_unix_fstab.ml b/daemon/inspect_fs_unix_fstab.ml
index 45c62175..dcbdab3c 100644
--- a/daemon/inspect_fs_unix_fstab.ml
+++ b/daemon/inspect_fs_unix_fstab.ml
@@ -27,6 +27,7 @@ open Inspect_utils
 
 let re_cciss = PCRE.compile "^/dev/(cciss/c\\d+d\\d+)(?:p(\\d+))?$"
 let re_diskbyid = PCRE.compile "^/dev/disk/by-id/.*-part(\\d+)$"
+let re_dmuuid = PCRE.compile "^/dev/disk/by-id/dm-uuid-LVM-([0-9a-zA-Z]{32})([0-9a-zA-Z]{32})$"
 let re_freebsd_gpt = PCRE.compile "^/dev/(ada{0,1}|vtbd)(\\d+)p(\\d+)$"
 let re_freebsd_mbr = PCRE.compile "^/dev/(ada{0,1}|vtbd)(\\d+)s(\\d+)([a-z])$"
 let re_hurd_dev = PCRE.compile "^/dev/(h)d(\\d+)s(\\d+)$"
@@ -407,6 +408,26 @@ and resolve_fstab_device spec md_map os_type =
       Failure _ -> default
   )
 
+  (* Ubuntu 22+ uses /dev/disk/by-id/dm-uuid-LVM-... followed by a
+   * double UUID which identifies an LV.  The first part of the UUID
+   * is the VG UUID.  The second part is the LV UUID.
+   *)
+  else if PCRE.matches re_dmuuid spec then (
+    debug_matching "dmuuid";
+    let vg_uuid_spec = PCRE.sub 1 and lv_uuid_spec = PCRE.sub 2 in
+    try
+      (* Get the list of all VGs and LVs. *)
+      let vgs = Lvm_full.vgs_full () and lvs = Lvm_full.lvs_full () in
+      (* Find one VG & LV (hopefully) that matches the UUIDs. *)
+      let vg =
+        List.find (fun { Structs.vg_uuid } -> vg_uuid = vg_uuid_spec) vgs
+      and lv =
+        List.find (fun { Structs.lv_uuid } -> lv_uuid = lv_uuid_spec) lvs in
+      Mountable.of_device (sprintf "/dev/%s/%s" vg.vg_name lv.lv_name)
+    with
+      Failure _ | Not_found -> default
+  )
+
   else if PCRE.matches re_freebsd_gpt spec then (
     debug_matching "FreeBSD GPT";
     (* group 1 (type) is not used *)