From 4562d80ec231e8b84089b17a3ca05889529c1bce Mon Sep 17 00:00:00 2001
From: Lichen Liu <lichliu@redhat.com>
Date: Fri, 19 Sep 2025 16:43:19 +0800
Subject: [PATCH 1/2] mkdumprd: basic support for btrfs subvol

The kdump scripts previously could not correctly handle cases where the
dump target was located on a btrfs subvolume. The logic for finding
the mount point did not account for the way subvolumes are represented,
leading to failures in identifying the target device and checking for
available space.

This patch introduces support for btrfs subvolumes by:

1.  Adding a new helper function `get_btrfs_subvol_from_mntopt` to
    extract the subvolume name from mount options.
2.  Modifying `get_mntpoint_from_target` to accept a subvolume
    name. When a subvolume is provided, it correctly identifies the
    mount point by looking for the source entry that includes the
    subvolume name (e.g., `/dev/sda1[/subvol]`).
3.  Updating various functions in `mkdumprd`, `kdump-lib.sh`, and the
    dracut module setup scripts to detect if the target is on a btrfs
    filesystem, parse the subvolume, and pass it to the relevant
    functions for mount point resolution and free space checks.

This ensures that kdump can now be reliably configured with a dump
target located on a btrfs subvolume.

Signed-off-by: Lichen Liu <lichliu@redhat.com>
---
 dracut/99kdumpbase/module-setup.sh | 11 ++++++++---
 kdump-lib-initramfs.sh             | 22 ++++++++++++++++++----
 kdump-lib.sh                       | 13 ++++++-------
 mkdumprd                           | 24 ++++++++++++++++--------
 4 files changed, 48 insertions(+), 22 deletions(-)

diff --git a/dracut/99kdumpbase/module-setup.sh b/dracut/99kdumpbase/module-setup.sh
index 4dc11ac6..32819ab5 100755
--- a/dracut/99kdumpbase/module-setup.sh
+++ b/dracut/99kdumpbase/module-setup.sh
@@ -683,16 +683,21 @@ kdump_install_pre_post_conf() {
 }
 
 default_dump_target_install_conf() {
-    local _target _fstype
+    local _target _fstype _subvol _options
     local _mntpoint _save_path
 
     is_user_configured_dump_target && return
 
     _save_path=$(get_bind_mount_source "$(get_save_path)")
     _target=$(get_target_from_path "$_save_path")
-    _mntpoint=$(get_mntpoint_from_target "$_target")
-
+    _options=$(get_mount_info OPTIONS target "$_save_path" -f)
     _fstype=$(get_fs_type_from_target "$_target")
+    if [[ $_fstype == btrfs ]]; then
+        _subvol=$(get_btrfs_subvol_from_mntopt "$_options")
+    fi
+
+    _mntpoint=$(get_mntpoint_from_target "$_target" "$_subvol")
+
     if is_fs_type_nfs "$_fstype"; then
         kdump_collect_netif_usage "$_target"
         _fstype="nfs"
diff --git a/kdump-lib-initramfs.sh b/kdump-lib-initramfs.sh
index c4bc6d2e..39e52a6f 100755
--- a/kdump-lib-initramfs.sh
+++ b/kdump-lib-initramfs.sh
@@ -110,15 +110,29 @@ get_fs_type_from_target()
 
 get_mntpoint_from_target()
 {
-	# get the first TARGET when SOURCE doesn't end with ].
-	# In most cases, a SOURCE ends with ] when fsroot or subvol exists.
-	_mntpoint=$(get_mount_info TARGET,SOURCE source "$1" | grep -v "\]$" | awk 'NR==1 { print $1 }')
-
+	_subvol="$2"
+	if [ -z "$_subvol" ]; then
+		# get the first TARGET when SOURCE doesn't end with ].
+		# In most cases, a SOURCE ends with ] when fsroot or subvol exists.
+		_mntpoint=$(get_mount_info TARGET,SOURCE source "$1" | grep -v "\]$" | awk 'NR==1 { print $1 }')
+	else
+		# btrfs with subvol
+		_mntpoint=$(get_mount_info TARGET,SOURCE source "$1" | grep "\[$_subvol\]$" | awk 'NR==1 { print $1 }')
+	fi
 	# fallback to the old way when _mntpoint is empty.
 	[ -n "$_mntpoint" ] || _mntpoint=$(get_mount_info TARGET source "$1" -f)
 	echo "$_mntpoint"
 }
 
+get_btrfs_subvol_from_mntopt()
+{
+	_subvol=${1#*subvol=}
+	# mount option may not contain subvol
+	[ "$1" != "$_subvol" ] || return 0
+	_subvol=${_subvol%%,*}
+	echo "$_subvol"
+}
+
 is_ssh_dump_target()
 {
 	kdump_get_conf_val ssh | grep -q @
diff --git a/kdump-lib.sh b/kdump-lib.sh
index 232d065f..4196b0e5 100755
--- a/kdump-lib.sh
+++ b/kdump-lib.sh
@@ -177,7 +177,7 @@ get_kdump_targets()
 # part is the bind mounted directory which quotes by bracket "[]".
 get_bind_mount_source()
 {
-	local _mnt _path _src _opt _fstype
+	local _mnt _path _src _opt _fstype _subvol
 	local _fsroot _src_nofsroot
 
 	_mnt=$(df "$1" | tail -1 | awk '{print $NF}')
@@ -200,15 +200,13 @@ get_bind_mount_source()
 
 	_fsroot=${_src#"${_src_nofsroot}"[}
 	_fsroot=${_fsroot%]}
-	_mnt=$(get_mntpoint_from_target "$_src_nofsroot")
-
 	# for btrfs, _fsroot will also contain the subvol value as well, strip it
 	if [[ $_fstype == btrfs ]]; then
-		local _subvol
-		_subvol=${_opt#*subvol=}
-		_subvol=${_subvol%,*}
+		_subvol=$(get_btrfs_subvol_from_mntopt "$_opt")
 		_fsroot=${_fsroot#"$_subvol"}
 	fi
+	_mnt=$(get_mntpoint_from_target "$_src_nofsroot" "$_subvol")
+
 	echo "$_mnt$_fsroot$_path"
 }
 
@@ -219,11 +217,12 @@ get_mntopt_from_target()
 
 # Get the path where the target will be mounted in kdump kernel
 # $1: kdump target device
+# $2: btrfs subvol
 get_kdump_mntpoint_from_target()
 {
 	local _mntpoint
 
-	_mntpoint=$(get_mntpoint_from_target "$1")
+	_mntpoint=$(get_mntpoint_from_target "$1" "$2")
 	# mount under /sysroot if dump to root disk or mount under
 	# mount under /kdumproot if dump target is not mounted in first kernel
 	# mount under /kdumproot/$_mntpoint in other cases in 2nd kernel.
diff --git a/mkdumprd b/mkdumprd
index e0392da9..06174de1 100644
--- a/mkdumprd
+++ b/mkdumprd
@@ -76,10 +76,13 @@ to_mount()
 {
 	local _target=$1 _fstype=$2 _options=$3 _sed_cmd _new_mntpoint _pdev
 
-	_new_mntpoint=$(get_kdump_mntpoint_from_target "$_target")
 	_fstype="${_fstype:-$(get_fs_type_from_target "$_target")}"
 	_options="${_options:-$(get_mntopt_from_target "$_target")}"
 	_options="${_options:-defaults}"
+	if [[ $_fstype == btrfs ]]; then
+		_subvol=$(get_btrfs_subvol_from_mntopt "$_options")
+	fi
+	_new_mntpoint=$(get_kdump_mntpoint_from_target "$_target" "$_subvol")
 
 	if [[ $_fstype == "nfs"* ]]; then
 		_pdev=$_target
@@ -146,7 +149,7 @@ mkdir_save_path_ssh()
 #$1=dump target
 get_fs_size()
 {
-	df --output=avail "$(get_mntpoint_from_target "$1")/$SAVE_PATH" | tail -1
+	df --output=avail "$(get_mntpoint_from_target "$1" "$2")/$SAVE_PATH" | tail -1
 }
 
 #Function: get_raw_size
@@ -159,6 +162,7 @@ get_raw_size()
 #Function: check_size
 #$1: dump type string ('raw', 'fs', 'ssh')
 #$2: dump target
+#$3: btrfs subvol
 check_size()
 {
 	local avail memtotal
@@ -172,7 +176,7 @@ check_size()
 		avail=$(get_ssh_size "$2")
 		;;
 	fs)
-		avail=$(get_fs_size "$2")
+		avail=$(get_fs_size "$2" "$3")
 		;;
 	*)
 		return
@@ -302,20 +306,24 @@ add_mount()
 #handle the case user does not specify the dump target explicitly
 handle_default_dump_target()
 {
-	local _target
-	local _mntpoint
+	local _target _mntpoint _fstype _subvol _options
 
 	is_user_configured_dump_target && return
 
 	check_save_path_fs "$SAVE_PATH"
 
 	_save_path=$(get_bind_mount_source "$SAVE_PATH")
+	_options=$(get_mount_info OPTIONS target "$_save_path" -f)
 	_target=$(get_target_from_path "$_save_path")
-	_mntpoint=$(get_mntpoint_from_target "$_target")
+	_fstype=$(get_fs_type_from_target "$_target")
+	if [[ $_fstype == btrfs ]]; then
+		_subvol=$(get_btrfs_subvol_from_mntopt "$_options")
+	fi
 
+	_mntpoint=$(get_mntpoint_from_target "$_target" "$_subvol")
 	SAVE_PATH=${_save_path##"$_mntpoint"}
-	add_mount "$_target"
-	check_size fs "$_target"
+	add_mount "$_target" "$_fstype" "$_options"
+	check_size fs "$_target" "$_subvol"
 }
 
 # firstly get right SSH_KEY_LOCATION

From 44601272651ea8eae26967b5b090442fb212885e Mon Sep 17 00:00:00 2001
From: Lichen Liu <lichliu@redhat.com>
Date: Thu, 30 Oct 2025 16:59:56 +0800
Subject: [PATCH 2/2] unit tests: Add cases for btrfs subvol

Add test cases to verify new and modified logic for handling btrfs
subvolumes as kdump targets.

Assisted-by: Claude (Anthropic)
Signed-off-by: Lichen Liu <lichliu@redhat.com>
---
 spec/kdump-lib-initramfs_spec.sh | 50 ++++++++++++++++++++++++++++----
 spec/kdump-lib_spec.sh           | 48 ++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+), 6 deletions(-)

diff --git a/spec/kdump-lib-initramfs_spec.sh b/spec/kdump-lib-initramfs_spec.sh
index acabc2ff..d12b758d 100644
--- a/spec/kdump-lib-initramfs_spec.sh
+++ b/spec/kdump-lib-initramfs_spec.sh
@@ -67,6 +67,12 @@ Describe 'kdump-lib-initramfs'
 				else
 					printf '/var %s[/ostree/deploy/default/var]\n/sysroot %s\n' "$7" "$7"
 				fi
+			elif [[ "$7" == '/dev/nvme0n1p3' ]]; then
+				if [[ "$8" == "-f" ]]; then
+					printf '/ /dev/nvme0n1p3[/root]\n'
+				else
+					printf '/ /dev/nvme0n1p3[/root]\n/var /dev/nvme0n1p3[/var]\n'
+				fi
 			fi
 		}
 
@@ -76,19 +82,51 @@ Describe 'kdump-lib-initramfs'
 			#  - IPv6 NFS target also contain '[' in the export
 			#  - local dumping target that has '[' in the name
 			#  - has bind mint
+			#  - has subvol
 			Parameters
-				'eng.redhat.com:/srv/[nfs]' '/mnt'
-				'[2620:52:0:a1:217:38ff:fe01:131]:/srv/[nfs]' '/mnt'
-				'/dev/mapper/rhel[disk]' '/'
-				'/dev/vda4' '/sysroot'
+				'eng.redhat.com:/srv/[nfs]' '' '/mnt'
+				'[2620:52:0:a1:217:38ff:fe01:131]:/srv/[nfs]' '' '/mnt'
+				'/dev/mapper/rhel[disk]' '' '/'
+				'/dev/vda4' '' '/sysroot'
+				'/dev/nvme0n1p3' '/var' '/var'
 			End
 
 			It 'should handle all cases correctly'
-				When call get_mntpoint_from_target "$1"
-				The output should equal "$2"
+				When call get_mntpoint_from_target "$1" "$2"
+				The output should equal "$3"
 			End
 		End
 
 	End
 
+	Describe 'Test get_btrfs_subvol_from_mntopt'
+		Context 'Given different mount option formats'
+			# Test the following cases:
+			#  - Standard subvol option at the beginning
+			#  - Standard subvol option in the middle
+			#  - Standard subvol option at the end
+			#  - Subvol with @ prefix (common btrfs pattern)
+			#  - Subvol with complex path
+			#  - No subvol option present
+			#  - Empty mount options
+			#  - Subvol option with no value
+			#  - Similar but different option names
+			Parameters
+				"subvol=/home,rw,relatime" "/home"
+				"rw,subvol=/root,defaults" "/root"
+				"rw,relatime,subvol=/root" "/root"
+				"subvol=@home" "@home"
+				"subvol=/path/to/subvolume,rw" "/path/to/subvolume"
+				"rw,relatime,defaults" ""
+				true ''
+				"subvol=,rw" ""
+				"rw,subvolume=@home" ""
+			End
+
+			It 'should extract subvolume correctly'
+				When call get_btrfs_subvol_from_mntopt "$1"
+				The output should equal "$2"
+			End
+		End
+	End
 End
diff --git a/spec/kdump-lib_spec.sh b/spec/kdump-lib_spec.sh
index 41755a40..8ced9172 100644
--- a/spec/kdump-lib_spec.sh
+++ b/spec/kdump-lib_spec.sh
@@ -133,4 +133,52 @@ Describe 'kdump-lib'
 		End
 	End
 
+	Describe "get_kdump_mntpoint_from_target with btrfs subvolume support"
+		# Mock get_mntpoint_from_target to simulate different mount scenarios
+		get_mntpoint_from_target() {
+			local device="$1" subvol="$2"
+			case "$device" in
+				'/dev/sda1')
+					if [[ "$subvol" == "@home" ]]; then
+						echo "/mnt/btrfs"
+					elif [[ "$subvol" == "/root" ]]; then
+						echo "/"
+					else
+						echo "/"
+					fi
+					;;
+				'/dev/sdb1')
+					if [[ "$subvol" == "@backup" ]]; then
+						echo "/backup"
+					else
+						echo "/backup"
+					fi
+					;;
+				*)
+					echo "/"
+					;;
+			esac
+		}
+
+		Context 'Given various mount point scenarios with subvolumes'
+			# Test the following cases:
+			#  - Root filesystem with @ subvolume -> /sysroot
+			#  - Home subvolume on non-root -> /kdumproot/mnt/btrfs
+			#  - Backup subvolume -> /kdumproot/backup
+			#  - Regular filesystem without subvolume -> /sysroot
+			Parameters
+				'/dev/sda1 /root /sysroot'
+				'/dev/sda1 @home /kdumproot/mnt/btrfs'
+				'/dev/sdb1 @backup /kdumproot/backup'
+				'/dev/vda2 "" /sysroot'
+			End
+
+			It 'should handle btrfs subvolumes correctly'
+				# Parse parameters: device subvol expected_result
+				read -r device subvol expected_result <<< "$1"
+				When call get_kdump_mntpoint_from_target "$device" "$subvol"
+				The output should equal "$expected_result"
+			End
+		End
+	End
 End