From eafa39fbc3dbbadeda320a9bf418eaab75a88e41 Mon Sep 17 00:00:00 2001
From: Timothy Day <tday141@gmail.com>
Date: Fri, 29 May 2026 16:40:14 +0000
Subject: [PATCH] build: add ZFS_DEBUG Kconfig for copy-builtin

... so we can toggle ZFS debug assertions from the
Linux kernel build without having to regenerate the
ZFS patch.

Update the qemu test script to also set this kernel
config.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Timothy Day <timday@thelustrecollective.com>
Co-authored-by: Timothy Day <timday@thelustrecollective.com>
Closes #18595
---
 .github/workflows/scripts/qemu-6-tests.sh |  1 +
 config/zfs-build.m4                       | 12 ++++++++++++
 copy-builtin                              | 11 +++++++++++
 module/Kbuild.in                          | 11 +++++++++--
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/scripts/qemu-6-tests.sh b/.github/workflows/scripts/qemu-6-tests.sh
index c261cbfca06..41c34511357 100755
--- a/.github/workflows/scripts/qemu-6-tests.sh
+++ b/.github/workflows/scripts/qemu-6-tests.sh
@@ -79,6 +79,7 @@ function do_builtin_build() {
 
   cd $HOME/linux-$fullver
   ./scripts/config --enable ZFS
+  ./scripts/config --enable ZFS_DEBUG
   yes "" | make oldconfig
   make -j `nproc`
   ) &> /var/tmp/builtin.txt || rc=$?
diff --git a/config/zfs-build.m4 b/config/zfs-build.m4
index 1e1485c4cf4..7aabad3868b 100644
--- a/config/zfs-build.m4
+++ b/config/zfs-build.m4
@@ -39,6 +39,18 @@ dnl # (If INVARIANTS is detected, we need to force DEBUG, or strange panics
 dnl # can ensue.)
 dnl #
 AC_DEFUN([ZFS_AC_DEBUG], [
+	dnl #
+	dnl # In the Linux kernel copy-builtin build, assertion/debug support
+	dnl # is selected by CONFIG_ZFS_DEBUG (Kconfig).
+	dnl #
+	AH_BOTTOM([
+#ifdef CONFIG_ZFS
+#undef ZFS_DEBUG
+#ifdef CONFIG_ZFS_DEBUG
+#define ZFS_DEBUG 1
+#endif
+#endif])
+
 	AC_MSG_CHECKING([whether assertion support will be enabled])
 	AC_ARG_ENABLE([debug],
 		[AS_HELP_STRING([--enable-debug],
diff --git a/copy-builtin b/copy-builtin
index 9a430bfb289..d412437f556 100755
--- a/copy-builtin
+++ b/copy-builtin
@@ -43,6 +43,17 @@ config ZFS
 
 	  To compile this file system support as a module, choose M here.
 
+	  If unsure, say N.
+
+config ZFS_DEBUG
+	bool "ZFS debugging"
+	depends on ZFS
+	help
+	  Enable ZFS debugging. This turns on all ASSERT() assertions,
+	  enables additional debug-only code paths, and promotes
+	  compiler warnings to errors. This should only be enabled for
+	  development or troubleshooting.
+
 	  If unsure, say N.
 EOF
 
diff --git a/module/Kbuild.in b/module/Kbuild.in
index ff2c96b85ae..fa4085c84b0 100644
--- a/module/Kbuild.in
+++ b/module/Kbuild.in
@@ -4,9 +4,11 @@
 
 ZFS_MODULE_CFLAGS += -std=gnu11 -Wno-declaration-after-statement
 ZFS_MODULE_CFLAGS += -Wmissing-prototypes
-ZFS_MODULE_CFLAGS += @KERNEL_DEBUG_CFLAGS@ @KERNEL_NO_FORMAT_ZERO_LENGTH@
+ZFS_MODULE_CFLAGS += @KERNEL_NO_FORMAT_ZERO_LENGTH@
 
 ifneq ($(KBUILD_EXTMOD),)
+ZFS_MODULE_CFLAGS += @KERNEL_DEBUG_CFLAGS@
+ZFS_MODULE_CPPFLAGS += @KERNEL_DEBUG_CPPFLAGS@
 zfs_include = @abs_top_srcdir@/include
 icp_include = @abs_srcdir@/icp/include
 zstd_include = @abs_srcdir@/zstd/include
@@ -16,6 +18,12 @@ ZFS_MODULE_CFLAGS += -I@abs_top_builddir@/include
 src = @abs_srcdir@
 obj = @abs_builddir@
 else
+ifeq ($(CONFIG_ZFS_DEBUG),y)
+ZFS_MODULE_CFLAGS += -Werror
+ZFS_MODULE_CPPFLAGS += -DDEBUG -UNDEBUG -DZFS_DEBUG
+else
+ZFS_MODULE_CPPFLAGS += -UDEBUG -DNDEBUG
+endif
 zfs_include = $(srctree)/include/zfs
 icp_include = $(src)/icp/include
 zstd_include = $(src)/zstd/include
@@ -28,7 +36,6 @@ ZFS_MODULE_CFLAGS += -I$(zfs_include)/os/linux/spl
 ZFS_MODULE_CFLAGS += -I$(zfs_include)/os/linux/zfs
 ZFS_MODULE_CFLAGS += -I$(zfs_include)
 ZFS_MODULE_CPPFLAGS += -D_KERNEL
-ZFS_MODULE_CPPFLAGS += @KERNEL_DEBUG_CPPFLAGS@
 
 # KASAN enables -Werror=frame-larger-than=1024, which
 # breaks oh so many parts of our build.