[PATCH] zfs: fix LINUX_ROOT_DEVICE when grub-probe fails

[Doug Goldstein]

When grub-probe fails, the current code is to just stuff an empty result
in which causes the user to not knowingly have a system that no longer
boots. grub-probe can fail because the ZFS pool that contains the root
filesystem might have features that grub does not yet support which is a
common configuration for people with a rpool and a bpool. This behavior
uses the zdb utility to dump the same value as the filesystem label
would print.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
---
 util/grub.d/10_linux.in     | 2 +-
 util/grub.d/20_linux_xen.in | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/util/grub.d/10_linux.in b/util/grub.d/10_linux.in
index e8b01c0d0..33a25ba8f 100644
--- a/util/grub.d/10_linux.in
+++ b/util/grub.d/10_linux.in
@@ -71,7 +71,7 @@ case x"$GRUB_FS" in
            GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} 
${GRUB_CMDLINE_LINUX}"
        fi;;
     xzfs)
-       rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 
2>/dev/null || true`
+       rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 
2>/dev/null || zdb -l ${GRUB_DEVICE} | awk -F \' '/ name/ { print $2 }'`
        bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
        LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs%/}"
        ;;
diff --git a/util/grub.d/20_linux_xen.in b/util/grub.d/20_linux_xen.in
index 3b1f47049..96210c24d 100644
--- a/util/grub.d/20_linux_xen.in
+++ b/util/grub.d/20_linux_xen.in
@@ -79,7 +79,7 @@ case x"$GRUB_FS" in
            GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} 
${GRUB_CMDLINE_LINUX}"
        fi;;
     xzfs)
-       rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 
2>/dev/null || true`
+       rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 
2>/dev/null || zdb -l ${GRUB_DEVICE} | awk -F \' '/ name/ { print $2 }'`
        bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
        LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs%/}"
        ;;
-- 
2.24.3 (Apple Git-128)