Re: Future of installing GRUB to LVM volumes (and loop devices)

[Andrei Borzenkov <arvidjaar@gmail.com>]

В Fri, 22 May 2015 00:17:50 +0200
"Vladimir 'phcoder' Serbinenko" <phcoder@gmail.com> пишет:

> Le 21 mai 2015 23:48, "Sebastian Pipping" <sebastian@pipping.org> a écrit :
> >
> > There is not device map and there was no need for one previously.
> > I'm happy to add that to the ticket, give me a second.
> >
> It worked only by lack of support for devmapper, not because it was
> designed so or because it's reasonable to. It was just a bug which happened
> to do what you wanted

The actual bug is that device.map does not work anymore for
device-mapper devices that LVM happens to be:

opensuse:/home/bor # grub2-install --boot-directory /tmp/x/boot /dev/mapper/vg-lv
Выполняется установка для платформы i386-pc.
grub2-install: ошибка: диск «lvmid/AxK0hm-Xmee-kRPP-dqU3-ycoo-EfcX-Vs3mk2/aot5OT-H8ZH-FXKe-Kz8e-gw6r-PI6v-9IdcGb» не найден.
opensuse:/home/bor # grub2-install --boot-directory /tmp/x/boot '(hd0)'
Выполняется установка для платформы i386-pc.
grub2-install: ошибка: диск «hd0» не найден.
opensuse:/home/bor # cat /tmp/x/boot/grub/device.map 
(hd0) /dev/mapper/vg-lv


This is fixed with patch below. And yes, with this patch it does not
require device.map which itself is a bug and should be fixed but it is
much more intrusive.

From: Andrei Borzenkov <arvidjaar@gmail.com>
Subject: [PATCH] check for abstraction in grub_util_get_devmapper_grub_dev

If user added device to device.map we should respect it.

---
 grub-core/osdep/devmapper/getroot.c | 33 ++++++++++++++++++++-------------
 grub-core/osdep/linux/getroot.c     |  2 +-
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/grub-core/osdep/devmapper/getroot.c b/grub-core/osdep/devmapper/getroot.c
index 0a77a04..f830f9c 100644
--- a/grub-core/osdep/devmapper/getroot.c
+++ b/grub-core/osdep/devmapper/getroot.c
@@ -224,11 +224,14 @@ grub_util_get_devmapper_grub_dev (const char *os_dev)
   uuid = get_dm_uuid (os_dev);
   if (!uuid)
     return NULL;
-  
-  if (strncmp (uuid, "LVM-", sizeof ("LVM-") - 1) == 0)
+
+  switch (grub_util_get_dev_abstraction (os_dev))
     {
+    case GRUB_DEV_ABSTRACTION_LVM:
+      {
 	unsigned i;
 	int dashes[] = { 0, 6, 10, 14, 18, 22, 26, 32, 38, 42, 46, 50, 54, 58};
+
 	grub_dev = xmalloc (grub_strlen (uuid) + 40);
 	optr = grub_stpcpy (grub_dev, "lvmid/");
 	for (i = 0; i < ARRAY_SIZE (dashes) - 1; i++)
@@ -246,19 +249,23 @@ grub_util_get_devmapper_grub_dev (const char *os_dev)
 	return grub_dev;
       }
 
-  if (strncmp (uuid, "CRYPT-LUKS1-", sizeof ("CRYPT-LUKS1-") - 1) == 0)
-    {
-      char *dash;
-      dash = grub_strchr (uuid + sizeof ("CRYPT-LUKS1-") - 1, '-');
-      if (dash)
-	*dash = 0;
-      grub_dev = grub_xasprintf ("cryptouuid/%s",
-				 uuid + sizeof ("CRYPT-LUKS1-") - 1);
+    case GRUB_DEV_ABSTRACTION_LUKS:
+      {
+	char *dash;
+
+	dash = grub_strchr (uuid + sizeof ("CRYPT-LUKS1-") - 1, '-');
+	if (dash)
+	  *dash = 0;
+	grub_dev = grub_xasprintf ("cryptouuid/%s",
+				   uuid + sizeof ("CRYPT-LUKS1-") - 1);
+	grub_free (uuid);
+	return grub_dev;
+      }
+
+    default:
       grub_free (uuid);
-      return grub_dev;
+      return NULL;
     }
-  grub_free (uuid);
-  return NULL;
 }
 
 char *
diff --git a/grub-core/osdep/linux/getroot.c b/grub-core/osdep/linux/getroot.c
index a2e360f..bc79eaa 100644
--- a/grub-core/osdep/linux/getroot.c
+++ b/grub-core/osdep/linux/getroot.c
@@ -1075,7 +1075,7 @@ grub_util_get_grub_dev_os (const char *os_dev)
   switch (grub_util_get_dev_abstraction (os_dev))
     {
       /* Fallback for non-devmapper build. In devmapper-builds LVM is handled
-	 in rub_util_get_devmapper_grub_dev and this point isn't reached.
+	 in grub_util_get_devmapper_grub_dev and this point isn't reached.
        */
     case GRUB_DEV_ABSTRACTION_LVM:
       {
-- 
tg: (f4e62af..) u/devmapper-check-abstraction (depends on: master)