dnl #
dnl # Default ZFS kernel configuration
dnl #
AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
	AM_COND_IF([BUILD_LINUX], [
		dnl # Setup the kernel build environment.
		ZFS_AC_KERNEL
		ZFS_AC_QAT

		dnl # Sanity checks for module building and CONFIG_* defines
		ZFS_AC_KERNEL_CONFIG_DEFINED
		ZFS_AC_MODULE_SYMVERS

		dnl # Sequential ZFS_LINUX_TRY_COMPILE tests
		ZFS_AC_KERNEL_FPU_HEADER
		ZFS_AC_KERNEL_OBJTOOL_HEADER
		ZFS_AC_KERNEL_WAIT_QUEUE_ENTRY_T
		ZFS_AC_KERNEL_MISC_MINOR
		ZFS_AC_KERNEL_DECLARE_EVENT_CLASS

		dnl # Parallel ZFS_LINUX_TEST_SRC / ZFS_LINUX_TEST_RESULT tests
		ZFS_AC_KERNEL_TEST_SRC
		ZFS_AC_KERNEL_TEST_RESULT

		AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
			KERNEL_MAKE="$KERNEL_MAKE O=$LINUX_OBJ"
		])

		AC_SUBST(KERNEL_MAKE)
	])
])

dnl #
dnl # Generate and compile all of the kernel API test cases to determine
dnl # which interfaces are available.  By invoking the kernel build system
dnl # only once the compilation can be done in parallel significantly
dnl # speeding up the process.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
	ZFS_AC_KERNEL_SRC_TYPES
	ZFS_AC_KERNEL_SRC_OBJTOOL
	ZFS_AC_KERNEL_SRC_GLOBAL_PAGE_STATE
	ZFS_AC_KERNEL_SRC_ACCESS_OK_TYPE
	ZFS_AC_KERNEL_SRC_PDE_DATA
	ZFS_AC_KERNEL_SRC_FALLOCATE
	ZFS_AC_KERNEL_SRC_FADVISE
	ZFS_AC_KERNEL_SRC_GENERIC_FADVISE
	ZFS_AC_KERNEL_SRC_2ARGS_ZLIB_DEFLATE_WORKSPACESIZE
	ZFS_AC_KERNEL_SRC_RWSEM
	ZFS_AC_KERNEL_SRC_SCHED
	ZFS_AC_KERNEL_SRC_USLEEP_RANGE
	ZFS_AC_KERNEL_SRC_KMEM_CACHE
	ZFS_AC_KERNEL_SRC_KVMALLOC
	ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL
	ZFS_AC_KERNEL_SRC_WAIT
	ZFS_AC_KERNEL_SRC_INODE_TIMES
	ZFS_AC_KERNEL_SRC_INODE_LOCK
	ZFS_AC_KERNEL_SRC_GROUP_INFO_GID
	ZFS_AC_KERNEL_SRC_RW
	ZFS_AC_KERNEL_SRC_TIMER_SETUP
	ZFS_AC_KERNEL_SRC_SUPER_USER_NS
	ZFS_AC_KERNEL_SRC_PROC_OPERATIONS
	ZFS_AC_KERNEL_SRC_BLOCK_DEVICE_OPERATIONS
	ZFS_AC_KERNEL_SRC_BIO
	ZFS_AC_KERNEL_SRC_BLKDEV
	ZFS_AC_KERNEL_SRC_BLK_QUEUE
	ZFS_AC_KERNEL_SRC_GENHD_FLAGS
	ZFS_AC_KERNEL_SRC_REVALIDATE_DISK
	ZFS_AC_KERNEL_SRC_GET_DISK_RO
	ZFS_AC_KERNEL_SRC_GENERIC_READLINK_GLOBAL
	ZFS_AC_KERNEL_SRC_DISCARD_GRANULARITY
	ZFS_AC_KERNEL_SRC_INODE_OWNER_OR_CAPABLE
	ZFS_AC_KERNEL_SRC_XATTR
	ZFS_AC_KERNEL_SRC_ACL
	ZFS_AC_KERNEL_SRC_INODE_SETATTR
	ZFS_AC_KERNEL_SRC_INODE_GETATTR
	ZFS_AC_KERNEL_SRC_INODE_SET_FLAGS
	ZFS_AC_KERNEL_SRC_INODE_SET_IVERSION
	ZFS_AC_KERNEL_SRC_SHOW_OPTIONS
	ZFS_AC_KERNEL_SRC_FILE_INODE
	ZFS_AC_KERNEL_SRC_FILE_DENTRY
	ZFS_AC_KERNEL_SRC_FSYNC
	ZFS_AC_KERNEL_SRC_AIO_FSYNC
	ZFS_AC_KERNEL_SRC_EVICT_INODE
	ZFS_AC_KERNEL_SRC_DIRTY_INODE
	ZFS_AC_KERNEL_SRC_SHRINKER
	ZFS_AC_KERNEL_SRC_MKDIR
	ZFS_AC_KERNEL_SRC_LOOKUP_FLAGS
	ZFS_AC_KERNEL_SRC_CREATE
	ZFS_AC_KERNEL_SRC_PERMISSION
	ZFS_AC_KERNEL_SRC_GET_LINK
	ZFS_AC_KERNEL_SRC_PUT_LINK
	ZFS_AC_KERNEL_SRC_TMPFILE
	ZFS_AC_KERNEL_SRC_AUTOMOUNT
	ZFS_AC_KERNEL_SRC_ENCODE_FH_WITH_INODE
	ZFS_AC_KERNEL_SRC_COMMIT_METADATA
	ZFS_AC_KERNEL_SRC_CLEAR_INODE
	ZFS_AC_KERNEL_SRC_SETATTR_PREPARE
	ZFS_AC_KERNEL_SRC_INSERT_INODE_LOCKED
	ZFS_AC_KERNEL_SRC_DENTRY
	ZFS_AC_KERNEL_SRC_DENTRY_ALIAS_D_U
	ZFS_AC_KERNEL_SRC_TRUNCATE_SETSIZE
	ZFS_AC_KERNEL_SRC_SECURITY_INODE
	ZFS_AC_KERNEL_SRC_FST_MOUNT
	ZFS_AC_KERNEL_SRC_BDI
	ZFS_AC_KERNEL_SRC_SET_NLINK
	ZFS_AC_KERNEL_SRC_SGET
	ZFS_AC_KERNEL_SRC_LSEEK_EXECUTE
	ZFS_AC_KERNEL_SRC_VFS_FILEMAP_DIRTY_FOLIO
	ZFS_AC_KERNEL_SRC_VFS_READ_FOLIO
	ZFS_AC_KERNEL_SRC_VFS_GETATTR
	ZFS_AC_KERNEL_SRC_VFS_FSYNC_2ARGS
	ZFS_AC_KERNEL_SRC_VFS_ITERATE
	ZFS_AC_KERNEL_SRC_VFS_DIRECT_IO
	ZFS_AC_KERNEL_SRC_VFS_READPAGES
	ZFS_AC_KERNEL_SRC_VFS_SET_PAGE_DIRTY_NOBUFFERS
	ZFS_AC_KERNEL_SRC_VFS_RW_ITERATE
	ZFS_AC_KERNEL_SRC_VFS_GENERIC_WRITE_CHECKS
	ZFS_AC_KERNEL_SRC_VFS_IOV_ITER
	ZFS_AC_KERNEL_SRC_VFS_COPY_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_GENERIC_COPY_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_SPLICE_COPY_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_REMAP_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_CLONE_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_DEDUPE_FILE_RANGE
	ZFS_AC_KERNEL_SRC_VFS_FILE_OPERATIONS_EXTEND
	ZFS_AC_KERNEL_SRC_KMAP_ATOMIC_ARGS
	ZFS_AC_KERNEL_SRC_KMAP_LOCAL_PAGE
	ZFS_AC_KERNEL_SRC_FOLLOW_DOWN_ONE
	ZFS_AC_KERNEL_SRC_MAKE_REQUEST_FN
	ZFS_AC_KERNEL_SRC_GENERIC_IO_ACCT
	ZFS_AC_KERNEL_SRC_FPU
	ZFS_AC_KERNEL_SRC_FMODE_T
	ZFS_AC_KERNEL_SRC_KUIDGID_T
	ZFS_AC_KERNEL_SRC_KUID_HELPERS
	ZFS_AC_KERNEL_SRC_RENAME
	ZFS_AC_KERNEL_SRC_CURRENT_TIME
	ZFS_AC_KERNEL_SRC_USERNS_CAPABILITIES
	ZFS_AC_KERNEL_SRC_IN_COMPAT_SYSCALL
	ZFS_AC_KERNEL_SRC_KTIME
	ZFS_AC_KERNEL_SRC_TOTALRAM_PAGES_FUNC
	ZFS_AC_KERNEL_SRC_TOTALHIGH_PAGES
	ZFS_AC_KERNEL_SRC_KSTRTOUL
	ZFS_AC_KERNEL_SRC_PERCPU
	ZFS_AC_KERNEL_SRC_CPU_HOTPLUG
	ZFS_AC_KERNEL_SRC_GENERIC_FILLATTR
	ZFS_AC_KERNEL_SRC_MKNOD
	ZFS_AC_KERNEL_SRC_SYMLINK
	ZFS_AC_KERNEL_SRC_BIO_MAX_SEGS
	ZFS_AC_KERNEL_SRC_SIGNAL_STOP
	ZFS_AC_KERNEL_SRC_SIGINFO
	ZFS_AC_KERNEL_SRC_SYSFS
	ZFS_AC_KERNEL_SRC_SET_SPECIAL_STATE
	ZFS_AC_KERNEL_SRC_STANDALONE_LINUX_STDARG
	ZFS_AC_KERNEL_SRC_STRLCPY
	ZFS_AC_KERNEL_SRC_STRSCPY
	ZFS_AC_KERNEL_SRC_PAGEMAP_FOLIO_WAIT_BIT
	ZFS_AC_KERNEL_SRC_ADD_DISK
	ZFS_AC_KERNEL_SRC_KTHREAD
	ZFS_AC_KERNEL_SRC_ZERO_PAGE
	ZFS_AC_KERNEL_SRC___COPY_FROM_USER_INATOMIC
	ZFS_AC_KERNEL_SRC_USER_NS_COMMON_INUM
	ZFS_AC_KERNEL_SRC_IDMAP_MNT_API
	ZFS_AC_KERNEL_SRC_IDMAP_NO_USERNS
	ZFS_AC_KERNEL_SRC_IATTR_VFSID
	ZFS_AC_KERNEL_SRC_FILEMAP
	ZFS_AC_KERNEL_SRC_WRITEPAGE_T
	ZFS_AC_KERNEL_SRC_RECLAIMED
	ZFS_AC_KERNEL_SRC_REGISTER_SYSCTL_TABLE
	ZFS_AC_KERNEL_SRC_COPY_SPLICE_READ
	ZFS_AC_KERNEL_SRC_SYNC_BDEV
	ZFS_AC_KERNEL_SRC_MM_PAGE_SIZE
	case "$host_cpu" in
		powerpc*)
			ZFS_AC_KERNEL_SRC_CPU_HAS_FEATURE
			ZFS_AC_KERNEL_SRC_FLUSH_DCACHE_PAGE
			;;
		riscv*)
			ZFS_AC_KERNEL_SRC_FLUSH_DCACHE_PAGE
			;;
	esac

	AC_MSG_CHECKING([for available kernel interfaces])
	ZFS_LINUX_TEST_COMPILE_ALL([kabi])
	AC_MSG_RESULT([done])
])

dnl #
dnl # Check results of kernel interface tests.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
	ZFS_AC_KERNEL_TYPES
	ZFS_AC_KERNEL_ACCESS_OK_TYPE
	ZFS_AC_KERNEL_GLOBAL_PAGE_STATE
	ZFS_AC_KERNEL_OBJTOOL
	ZFS_AC_KERNEL_PDE_DATA
	ZFS_AC_KERNEL_FALLOCATE
	ZFS_AC_KERNEL_FADVISE
	ZFS_AC_KERNEL_GENERIC_FADVISE
	ZFS_AC_KERNEL_2ARGS_ZLIB_DEFLATE_WORKSPACESIZE
	ZFS_AC_KERNEL_RWSEM
	ZFS_AC_KERNEL_SCHED
	ZFS_AC_KERNEL_USLEEP_RANGE
	ZFS_AC_KERNEL_KMEM_CACHE
	ZFS_AC_KERNEL_KVMALLOC
	ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL
	ZFS_AC_KERNEL_WAIT
	ZFS_AC_KERNEL_INODE_TIMES
	ZFS_AC_KERNEL_INODE_LOCK
	ZFS_AC_KERNEL_GROUP_INFO_GID
	ZFS_AC_KERNEL_RW
	ZFS_AC_KERNEL_TIMER_SETUP
	ZFS_AC_KERNEL_SUPER_USER_NS
	ZFS_AC_KERNEL_PROC_OPERATIONS
	ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS
	ZFS_AC_KERNEL_BIO
	ZFS_AC_KERNEL_BLKDEV
	ZFS_AC_KERNEL_BLK_QUEUE
	ZFS_AC_KERNEL_GENHD_FLAGS
	ZFS_AC_KERNEL_REVALIDATE_DISK
	ZFS_AC_KERNEL_GET_DISK_RO
	ZFS_AC_KERNEL_GENERIC_READLINK_GLOBAL
	ZFS_AC_KERNEL_DISCARD_GRANULARITY
	ZFS_AC_KERNEL_INODE_OWNER_OR_CAPABLE
	ZFS_AC_KERNEL_XATTR
	ZFS_AC_KERNEL_ACL
	ZFS_AC_KERNEL_INODE_SETATTR
	ZFS_AC_KERNEL_INODE_GETATTR
	ZFS_AC_KERNEL_INODE_SET_FLAGS
	ZFS_AC_KERNEL_INODE_SET_IVERSION
	ZFS_AC_KERNEL_SHOW_OPTIONS
	ZFS_AC_KERNEL_FILE_INODE
	ZFS_AC_KERNEL_FILE_DENTRY
	ZFS_AC_KERNEL_FSYNC
	ZFS_AC_KERNEL_AIO_FSYNC
	ZFS_AC_KERNEL_EVICT_INODE
	ZFS_AC_KERNEL_DIRTY_INODE
	ZFS_AC_KERNEL_SHRINKER
	ZFS_AC_KERNEL_MKDIR
	ZFS_AC_KERNEL_LOOKUP_FLAGS
	ZFS_AC_KERNEL_CREATE
	ZFS_AC_KERNEL_PERMISSION
	ZFS_AC_KERNEL_GET_LINK
	ZFS_AC_KERNEL_PUT_LINK
	ZFS_AC_KERNEL_TMPFILE
	ZFS_AC_KERNEL_AUTOMOUNT
	ZFS_AC_KERNEL_ENCODE_FH_WITH_INODE
	ZFS_AC_KERNEL_COMMIT_METADATA
	ZFS_AC_KERNEL_CLEAR_INODE
	ZFS_AC_KERNEL_SETATTR_PREPARE
	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
	ZFS_AC_KERNEL_DENTRY
	ZFS_AC_KERNEL_DENTRY_ALIAS_D_U
	ZFS_AC_KERNEL_TRUNCATE_SETSIZE
	ZFS_AC_KERNEL_SECURITY_INODE
	ZFS_AC_KERNEL_FST_MOUNT
	ZFS_AC_KERNEL_BDI
	ZFS_AC_KERNEL_SET_NLINK
	ZFS_AC_KERNEL_SGET
	ZFS_AC_KERNEL_LSEEK_EXECUTE
	ZFS_AC_KERNEL_VFS_FILEMAP_DIRTY_FOLIO
	ZFS_AC_KERNEL_VFS_READ_FOLIO
	ZFS_AC_KERNEL_VFS_GETATTR
	ZFS_AC_KERNEL_VFS_FSYNC_2ARGS
	ZFS_AC_KERNEL_VFS_ITERATE
	ZFS_AC_KERNEL_VFS_DIRECT_IO
	ZFS_AC_KERNEL_VFS_READPAGES
	ZFS_AC_KERNEL_VFS_SET_PAGE_DIRTY_NOBUFFERS
	ZFS_AC_KERNEL_VFS_RW_ITERATE
	ZFS_AC_KERNEL_VFS_GENERIC_WRITE_CHECKS
	ZFS_AC_KERNEL_VFS_IOV_ITER
	ZFS_AC_KERNEL_VFS_COPY_FILE_RANGE
	ZFS_AC_KERNEL_VFS_GENERIC_COPY_FILE_RANGE
	ZFS_AC_KERNEL_VFS_SPLICE_COPY_FILE_RANGE
	ZFS_AC_KERNEL_VFS_REMAP_FILE_RANGE
	ZFS_AC_KERNEL_VFS_CLONE_FILE_RANGE
	ZFS_AC_KERNEL_VFS_DEDUPE_FILE_RANGE
	ZFS_AC_KERNEL_VFS_FILE_OPERATIONS_EXTEND
	ZFS_AC_KERNEL_KMAP_ATOMIC_ARGS
	ZFS_AC_KERNEL_KMAP_LOCAL_PAGE
	ZFS_AC_KERNEL_FOLLOW_DOWN_ONE
	ZFS_AC_KERNEL_MAKE_REQUEST_FN
	ZFS_AC_KERNEL_GENERIC_IO_ACCT
	ZFS_AC_KERNEL_FPU
	ZFS_AC_KERNEL_FMODE_T
	ZFS_AC_KERNEL_KUIDGID_T
	ZFS_AC_KERNEL_KUID_HELPERS
	ZFS_AC_KERNEL_RENAME
	ZFS_AC_KERNEL_CURRENT_TIME
	ZFS_AC_KERNEL_USERNS_CAPABILITIES
	ZFS_AC_KERNEL_IN_COMPAT_SYSCALL
	ZFS_AC_KERNEL_KTIME
	ZFS_AC_KERNEL_TOTALRAM_PAGES_FUNC
	ZFS_AC_KERNEL_TOTALHIGH_PAGES
	ZFS_AC_KERNEL_KSTRTOUL
	ZFS_AC_KERNEL_PERCPU
	ZFS_AC_KERNEL_CPU_HOTPLUG
	ZFS_AC_KERNEL_GENERIC_FILLATTR
	ZFS_AC_KERNEL_MKNOD
	ZFS_AC_KERNEL_SYMLINK
	ZFS_AC_KERNEL_BIO_MAX_SEGS
	ZFS_AC_KERNEL_SIGNAL_STOP
	ZFS_AC_KERNEL_SIGINFO
	ZFS_AC_KERNEL_SYSFS
	ZFS_AC_KERNEL_SET_SPECIAL_STATE
	ZFS_AC_KERNEL_STANDALONE_LINUX_STDARG
	ZFS_AC_KERNEL_STRLCPY
	ZFS_AC_KERNEL_STRSCPY
	ZFS_AC_KERNEL_PAGEMAP_FOLIO_WAIT_BIT
	ZFS_AC_KERNEL_ADD_DISK
	ZFS_AC_KERNEL_KTHREAD
	ZFS_AC_KERNEL_ZERO_PAGE
	ZFS_AC_KERNEL___COPY_FROM_USER_INATOMIC
	ZFS_AC_KERNEL_USER_NS_COMMON_INUM
	ZFS_AC_KERNEL_IDMAP_MNT_API
	ZFS_AC_KERNEL_IDMAP_NO_USERNS
	ZFS_AC_KERNEL_IATTR_VFSID
	ZFS_AC_KERNEL_FILEMAP
	ZFS_AC_KERNEL_WRITEPAGE_T
	ZFS_AC_KERNEL_RECLAIMED
	ZFS_AC_KERNEL_REGISTER_SYSCTL_TABLE
	ZFS_AC_KERNEL_COPY_SPLICE_READ
	ZFS_AC_KERNEL_SYNC_BDEV
	ZFS_AC_KERNEL_MM_PAGE_SIZE
	case "$host_cpu" in
		powerpc*)
			ZFS_AC_KERNEL_CPU_HAS_FEATURE
			ZFS_AC_KERNEL_FLUSH_DCACHE_PAGE
			;;
		riscv*)
			ZFS_AC_KERNEL_FLUSH_DCACHE_PAGE
			;;
	esac
])

dnl #
dnl # Detect name used for Module.symvers file in kernel
dnl #
AC_DEFUN([ZFS_AC_MODULE_SYMVERS], [
	modpost=$LINUX/scripts/Makefile.modpost
	AC_MSG_CHECKING([kernel file name for module symbols])
	AS_IF([test "x$enable_linux_builtin" != xyes -a -f "$modpost"], [
		AS_IF([grep -q Modules.symvers $modpost], [
			LINUX_SYMBOLS=Modules.symvers
		], [
			LINUX_SYMBOLS=Module.symvers
		])

		AS_IF([test ! -f "$LINUX_OBJ/$LINUX_SYMBOLS"], [
			AC_MSG_ERROR([
	*** Please make sure the kernel devel package for your distribution
	*** is installed.  If you are building with a custom kernel, make sure
	*** the kernel is configured, built, and the '--with-linux=PATH'
	*** configure option refers to the location of the kernel source.
			])
		])
	], [
		LINUX_SYMBOLS=NONE
	])
	AC_MSG_RESULT($LINUX_SYMBOLS)
	AC_SUBST(LINUX_SYMBOLS)
])

dnl #
dnl # Detect the kernel to be built against
dnl #
dnl # Most modern Linux distributions have separate locations for bare
dnl # source (source) and prebuilt (build) files. Additionally, there are
dnl # `source` and `build` symlinks in `/lib/modules/$(KERNEL_VERSION)`
dnl # pointing to them. The directory search order is now:
dnl # 
dnl # - `configure` command line values if both `--with-linux` and
dnl #   `--with-linux-obj` were defined
dnl # 
dnl # - If only `--with-linux` was defined, `--with-linux-obj` is assumed
dnl #   to have the same value as `--with-linux`
dnl # 
dnl # - If neither `--with-linux` nor `--with-linux-obj` were defined
dnl #   autodetection is used:
dnl # 
dnl #   - `/lib/modules/$(uname -r)/{source,build}` respectively, if exist.
dnl # 
dnl #   - If only `/lib/modules/$(uname -r)/build` exists, it is assumed
dnl #     to be both source and build directory.
dnl # 
dnl #   - The first directory in `/lib/modules` with the highest version
dnl #     number according to `sort -V` which contains both `source` and
dnl #     `build` symlinks/directories. If module directory contains only
dnl #     `build` component, it is assumed to be both source and build
dnl #     directory.
dnl # 
dnl #   - Last resort: the first directory matching `/usr/src/kernels/*`
dnl #     and `/usr/src/linux-*` with the highest version number according
dnl #     to `sort -V` is assumed to be both source and build directory.
dnl #
AC_DEFUN([ZFS_AC_KERNEL], [
	AC_ARG_WITH([linux],
		AS_HELP_STRING([--with-linux=PATH],
		[Path to kernel source]),
		[kernelsrc="$withval"])

	AC_ARG_WITH(linux-obj,
		AS_HELP_STRING([--with-linux-obj=PATH],
		[Path to kernel build objects]),
		[kernelbuild="$withval"])

	AC_MSG_CHECKING([kernel source and build directories])
	AS_IF([test -n "$kernelsrc" && test -z "$kernelbuild"], [
		kernelbuild="$kernelsrc"
	], [test -z "$kernelsrc"], [
		AS_IF([test -e "/lib/modules/$(uname -r)/source" && \
		       test -e "/lib/modules/$(uname -r)/build"], [
			src="/lib/modules/$(uname -r)/source"
			build="/lib/modules/$(uname -r)/build"
		], [test -e "/lib/modules/$(uname -r)/build"], [
			build="/lib/modules/$(uname -r)/build"
			src="$build"
		], [
			src=

			for d in $(ls -1d /lib/modules/* 2>/dev/null | sort -Vr); do
				if test -e "$d/source" && test -e "$d/build"; then
					src="$d/source"
					build="$d/build"
					break
				fi

				if test -e "$d/build"; then
					src="$d/build"
					build="$d/build"
					break
				fi
			done

			# the least reliable method
			if test -z "$src"; then
				src=$(ls -1d /usr/src/kernels/* /usr/src/linux-* \
				      2>/dev/null | grep -v obj | sort -Vr | head -1)
				build="$src"
			fi
		])

		AS_IF([test -n "$src" && test -e "$src"], [
			kernelsrc=$(readlink -e "$src")
		], [
			kernelsrc="[Not found]"
		])
		AS_IF([test -n "$build" && test -e "$build"], [
			kernelbuild=$(readlink -e "$build")
		], [
			kernelbuild="[Not found]"
		])
	], [
		AS_IF([test "$kernelsrc" = "NONE"], [
			kernsrcver=NONE
		])
		withlinux=yes
	])

	AC_MSG_RESULT([done])
	AC_MSG_CHECKING([kernel source directory])
	AC_MSG_RESULT([$kernelsrc])
	AC_MSG_CHECKING([kernel build directory])
	AC_MSG_RESULT([$kernelbuild])
	AS_IF([test ! -d "$kernelsrc" || test ! -d "$kernelbuild"], [
		AC_MSG_ERROR([
	*** Please make sure the kernel devel package for your distribution
	*** is installed and then try again.  If that fails, you can specify the
	*** location of the kernel source and build with the '--with-linux=PATH' and
	*** '--with-linux-obj=PATH' options respectively.])
	])

	AC_MSG_CHECKING([kernel source version])
	utsrelease1=$kernelbuild/include/linux/version.h
	utsrelease2=$kernelbuild/include/linux/utsrelease.h
	utsrelease3=$kernelbuild/include/generated/utsrelease.h
	AS_IF([test -r $utsrelease1 && grep -qF UTS_RELEASE $utsrelease1], [
		utsrelease=$utsrelease1
	], [test -r $utsrelease2 && grep -qF UTS_RELEASE $utsrelease2], [
		utsrelease=$utsrelease2
	], [test -r $utsrelease3 && grep -qF UTS_RELEASE $utsrelease3], [
		utsrelease=$utsrelease3
	])

	AS_IF([test -n "$utsrelease"], [
		kernsrcver=$($AWK '/UTS_RELEASE/ { gsub(/"/, "", $[3]); print $[3] }' $utsrelease)
		AS_IF([test -z "$kernsrcver"], [
			AC_MSG_RESULT([Not found])
			AC_MSG_ERROR([
	*** Cannot determine kernel version.
			])
		])
	], [
		AC_MSG_RESULT([Not found])
		if test "x$enable_linux_builtin" != xyes; then
			AC_MSG_ERROR([
	*** Cannot find UTS_RELEASE definition.
			])
		else
			AC_MSG_ERROR([
	*** Cannot find UTS_RELEASE definition.
	*** Please run 'make prepare' inside the kernel source tree.])
		fi
	])

	AC_MSG_RESULT([$kernsrcver])

	AS_VERSION_COMPARE([$kernsrcver], [$ZFS_META_KVER_MIN], [
		 AC_MSG_ERROR([
	*** Cannot build against kernel version $kernsrcver.
	*** The minimum supported kernel version is $ZFS_META_KVER_MIN.
		])
	])

	LINUX=${kernelsrc}
	LINUX_OBJ=${kernelbuild}
	LINUX_VERSION=${kernsrcver}

	AC_SUBST(LINUX)
	AC_SUBST(LINUX_OBJ)
	AC_SUBST(LINUX_VERSION)
])

dnl #
dnl # Detect the QAT module to be built against, QAT provides hardware
dnl # acceleration for data compression:
dnl #
dnl # https://01.org/intel-quickassist-technology
dnl #
dnl # 1) Download and install QAT driver from the above link
dnl # 2) Start QAT driver in your system:
dnl # 	 service qat_service start
dnl # 3) Enable QAT in ZFS, e.g.:
dnl # 	 ./configure --with-qat=<qat-driver-path>/QAT1.6
dnl # 	 make
dnl # 4) Set GZIP compression in ZFS dataset:
dnl # 	 zfs set compression = gzip <dataset>
dnl #
dnl # Then the data written to this ZFS pool is compressed by QAT accelerator
dnl # automatically, and de-compressed by QAT when read from the pool.
dnl #
dnl # 1) Get QAT hardware statistics with:
dnl #	 cat /proc/icp_dh895xcc_dev/qat
dnl # 2) To disable QAT:
dnl # 	 insmod zfs.ko zfs_qat_disable=1
dnl #
AC_DEFUN([ZFS_AC_QAT], [
	AC_ARG_WITH([qat],
		AS_HELP_STRING([--with-qat=PATH],
		[Path to qat source]),
		AS_IF([test "$withval" = "yes"],
			AC_MSG_ERROR([--with-qat=PATH requires a PATH]),
			[qatsrc="$withval"]))

	AC_ARG_WITH([qat-obj],
		AS_HELP_STRING([--with-qat-obj=PATH],
		[Path to qat build objects]),
		[qatbuild="$withval"])

	AS_IF([test ! -z "${qatsrc}"], [
		AC_MSG_CHECKING([qat source directory])
		AC_MSG_RESULT([$qatsrc])
		QAT_SRC="${qatsrc}/quickassist"
		AS_IF([ test ! -e "$QAT_SRC/include/cpa.h"], [
			AC_MSG_ERROR([
	*** Please make sure the qat driver package is installed
	*** and specify the location of the qat source with the
	*** '--with-qat=PATH' option then try again. Failed to
	*** find cpa.h in:
	${QAT_SRC}/include])
		])
	])

	AS_IF([test ! -z "${qatsrc}"], [
		AC_MSG_CHECKING([qat build directory])
		AS_IF([test -z "$qatbuild"], [
			qatbuild="${qatsrc}/build"
		])

		AC_MSG_RESULT([$qatbuild])
		QAT_OBJ=${qatbuild}
		AS_IF([ ! test -e "$QAT_OBJ/icp_qa_al.ko" && ! test -e "$QAT_OBJ/qat_api.ko"], [
			AC_MSG_ERROR([
	*** Please make sure the qat driver is installed then try again.
	*** Failed to find icp_qa_al.ko or qat_api.ko in:
	$QAT_OBJ])
		])

		AC_SUBST(QAT_SRC)
		AC_SUBST(QAT_OBJ)

		AC_DEFINE(HAVE_QAT, 1,
		[qat is enabled and existed])
	])

	dnl #
	dnl # Detect the name used for the QAT Module.symvers file.
	dnl #
	AS_IF([test ! -z "${qatsrc}"], [
		AC_MSG_CHECKING([qat file for module symbols])
		QAT_SYMBOLS=$QAT_SRC/lookaside/access_layer/src/Module.symvers

		AS_IF([test -r $QAT_SYMBOLS], [
			AC_MSG_RESULT([$QAT_SYMBOLS])
			AC_SUBST(QAT_SYMBOLS)
		],[
			AC_MSG_ERROR([
	*** Please make sure the qat driver is installed then try again.
	*** Failed to find Module.symvers in:
	$QAT_SYMBOLS
			])
		])
	])
])

dnl #
dnl # ZFS_LINUX_CONFTEST_H
dnl #
AC_DEFUN([ZFS_LINUX_CONFTEST_H], [
test -d build/$2 || mkdir -p build/$2
cat - <<_ACEOF >build/$2/$2.h
$1
_ACEOF
])

dnl #
dnl # ZFS_LINUX_CONFTEST_C
dnl #
AC_DEFUN([ZFS_LINUX_CONFTEST_C], [
test -d build/$2 || mkdir -p build/$2
cat confdefs.h - <<_ACEOF >build/$2/$2.c
$1
_ACEOF
])

dnl #
dnl # ZFS_LINUX_CONFTEST_MAKEFILE
dnl #
dnl # $1 - test case name
dnl # $2 - add to top-level Makefile
dnl # $3 - additional build flags
dnl #
AC_DEFUN([ZFS_LINUX_CONFTEST_MAKEFILE], [
	test -d build || mkdir -p build
	test -d build/$1 || mkdir -p build/$1

	file=build/$1/Makefile

	dnl # Example command line to manually build source.
	cat - <<_ACEOF >$file
# Example command line to manually build source
# make modules -C $LINUX_OBJ $ARCH_UM M=$PWD/build/$1

ccflags-y := -Werror $FRAME_LARGER_THAN
_ACEOF

	dnl # Additional custom CFLAGS as requested.
	m4_ifval($3, [echo "ccflags-y += $3" >>$file], [])

	dnl # Test case source
	echo "obj-m := $1.o" >>$file

	AS_IF([test "x$2" = "xyes"], [echo "obj-m += $1/" >>build/Makefile], [])
])

dnl #
dnl # ZFS_LINUX_TEST_PROGRAM(C)([PROLOGUE], [BODY])
dnl #
m4_define([ZFS_LINUX_TEST_PROGRAM], [
#include <linux/module.h>
$1

int
main (void)
{
$2
	;
	return 0;
}

MODULE_DESCRIPTION("conftest");
MODULE_AUTHOR(ZFS_META_AUTHOR);
MODULE_VERSION(ZFS_META_VERSION "-" ZFS_META_RELEASE);
MODULE_LICENSE($3);
])

dnl #
dnl # ZFS_LINUX_TEST_REMOVE
dnl #
dnl # Removes the specified test source and results.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_REMOVE], [
	test -d build/$1 && rm -Rf build/$1
	test -f build/Makefile && sed '/$1/d' build/Makefile
])

dnl #
dnl # ZFS_LINUX_COMPILE
dnl #
dnl # $1 - build dir
dnl # $2 - test command
dnl # $3 - pass command
dnl # $4 - fail command
dnl # $5 - set KBUILD_MODPOST_NOFINAL='yes'
dnl # $6 - set KBUILD_MODPOST_WARN='yes'
dnl #
dnl # Used internally by ZFS_LINUX_TEST_{COMPILE,MODPOST}
dnl #
AC_DEFUN([ZFS_LINUX_COMPILE], [
	AC_ARG_VAR([KERNEL_CC], [C compiler for
		building kernel modules])
	AC_ARG_VAR([KERNEL_LD], [Linker for
		building kernel modules])
	AC_ARG_VAR([KERNEL_LLVM], [Binary option to
		build kernel modules with LLVM/CLANG toolchain])
	AC_TRY_COMMAND([
	    KBUILD_MODPOST_NOFINAL="$5" KBUILD_MODPOST_WARN="$6"
	    make modules -k -j$TEST_JOBS ${KERNEL_CC:+CC=$KERNEL_CC}
	    ${KERNEL_LD:+LD=$KERNEL_LD} ${KERNEL_LLVM:+LLVM=$KERNEL_LLVM}
	    CONFIG_MODULES=y CFLAGS_MODULE=-DCONFIG_MODULES
	    -C $LINUX_OBJ $ARCH_UM M=$PWD/$1 >$1/build.log 2>&1])
	AS_IF([AC_TRY_COMMAND([$2])], [$3], [$4])
])

dnl #
dnl # ZFS_LINUX_TEST_COMPILE
dnl #
dnl # Perform a full compile excluding the final modpost phase.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_COMPILE], [
	ZFS_LINUX_COMPILE([$2], [test -f $2/build.log], [
		mv $2/Makefile $2/Makefile.compile.$1
		mv $2/build.log $2/build.log.$1
	],[
	        AC_MSG_ERROR([
        *** Unable to compile test source to determine kernel interfaces.])
	], [yes], [])
])

dnl #
dnl # ZFS_LINUX_TEST_MODPOST
dnl #
dnl # Perform a full compile including the modpost phase.  This may
dnl # be an incremental build if the objects have already been built.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_MODPOST], [
	ZFS_LINUX_COMPILE([$2], [test -f $2/build.log], [
		mv $2/Makefile $2/Makefile.modpost.$1
		cat $2/build.log >>build/build.log.$1
	],[
	        AC_MSG_ERROR([
        *** Unable to modpost test source to determine kernel interfaces.])
	], [], [yes])
])

dnl #
dnl # Perform the compilation of the test cases in two phases.
dnl #
dnl # Phase 1) attempt to build the object files for all of the tests
dnl #          defined by the ZFS_LINUX_TEST_SRC macro.  But do not
dnl #          perform the final modpost stage.
dnl #
dnl # Phase 2) disable all tests which failed the initial compilation,
dnl #          then invoke the final modpost step for the remaining tests.
dnl #
dnl # This allows us efficiently build the test cases in parallel while
dnl # remaining resilient to build failures which are expected when
dnl # detecting the available kernel interfaces.
dnl #
dnl # The maximum allowed parallelism can be controlled by setting the
dnl # TEST_JOBS environment variable.  Otherwise, it default to $(nproc).
dnl #
AC_DEFUN([ZFS_LINUX_TEST_COMPILE_ALL], [
	dnl # Phase 1 - Compilation only, final linking is skipped.
	ZFS_LINUX_TEST_COMPILE([$1], [build])

	dnl #
	dnl # Phase 2 - When building external modules disable test cases
	dnl # which failed to compile and invoke modpost to verify the
	dnl # final linking.
	dnl #
	dnl # Test names suffixed with '_license' call modpost independently
	dnl # to ensure that a single incompatibility does not result in the
	dnl # modpost phase exiting early.  This check is not performed on
	dnl # every symbol since the majority are compatible and doing so
	dnl # would significantly slow down this phase.
	dnl #
	dnl # When configuring for builtin (--enable-linux-builtin)
	dnl # fake the linking step artificially create the expected .ko
	dnl # files for tests which did compile.  This is required for
	dnl # kernels which do not have loadable module support or have
	dnl # not yet been built.
	dnl #
	AS_IF([test "x$enable_linux_builtin" = "xno"], [
		for dir in $(awk '/^obj-m/ { print [$]3 }' \
		    build/Makefile.compile.$1); do
			name=${dir%/}
			AS_IF([test -f build/$name/$name.o], [
				AS_IF([test "${name##*_}" = "license"], [
					ZFS_LINUX_TEST_MODPOST([$1],
					    [build/$name])
					echo "obj-n += $dir" >>build/Makefile
				], [
					echo "obj-m += $dir" >>build/Makefile
				])
			], [
				echo "obj-n += $dir" >>build/Makefile
			])
		done

		ZFS_LINUX_TEST_MODPOST([$1], [build])
	], [
		for dir in $(awk '/^obj-m/ { print [$]3 }' \
		    build/Makefile.compile.$1); do
			name=${dir%/}
			AS_IF([test -f build/$name/$name.o], [
				touch build/$name/$name.ko
			])
		done
	])
])

dnl #
dnl # ZFS_LINUX_TEST_SRC
dnl #
dnl # $1 - name
dnl # $2 - global
dnl # $3 - source
dnl # $4 - extra cflags
dnl # $5 - check license-compatibility
dnl #
dnl # Check if the test source is buildable at all and then if it is
dnl # license compatible.
dnl #
dnl # N.B because all of the test cases are compiled in parallel they
dnl # must never depend on the results of previous tests.  Each test
dnl # needs to be entirely independent.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_SRC], [
	ZFS_LINUX_CONFTEST_C([ZFS_LINUX_TEST_PROGRAM([[$2]], [[$3]],
	    [["Dual BSD/GPL"]])], [$1])
	ZFS_LINUX_CONFTEST_MAKEFILE([$1], [yes], [$4])

	AS_IF([ test -n "$5" ], [
		ZFS_LINUX_CONFTEST_C([ZFS_LINUX_TEST_PROGRAM(
		    [[$2]], [[$3]], [[$5]])], [$1_license])
		ZFS_LINUX_CONFTEST_MAKEFILE([$1_license], [yes], [$4])
	])
])

dnl #
dnl # ZFS_LINUX_TEST_RESULT
dnl #
dnl # $1 - name of a test source (ZFS_LINUX_TEST_SRC)
dnl # $2 - run on success (valid .ko generated)
dnl # $3 - run on failure (unable to compile)
dnl #
AC_DEFUN([ZFS_LINUX_TEST_RESULT], [
	AS_IF([test -d build/$1], [
		AS_IF([test -f build/$1/$1.ko], [$2], [$3])
	], [
		AC_MSG_ERROR([
	*** No matching source for the "$1" test, check that
	*** both the test source and result macros refer to the same name.
		])
	])
])

dnl #
dnl # ZFS_LINUX_TEST_ERROR
dnl #
dnl # Generic error message which can be used when none of the expected
dnl # kernel interfaces were detected.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_ERROR], [
	AC_MSG_ERROR([
	*** None of the expected "$1" interfaces were detected.
	*** This may be because your kernel version is newer than what is
	*** supported, or you are using a patched custom kernel with
	*** incompatible modifications.
	***
	*** ZFS Version: $ZFS_META_ALIAS
	*** Compatible Kernels: $ZFS_META_KVER_MIN - $ZFS_META_KVER_MAX
	])
])

dnl #
dnl # ZFS_LINUX_TEST_RESULT_SYMBOL
dnl #
dnl # Like ZFS_LINUX_TEST_RESULT except ZFS_CHECK_SYMBOL_EXPORT is called to
dnl # verify symbol exports, unless --enable-linux-builtin was provided to
dnl # configure.
dnl #
AC_DEFUN([ZFS_LINUX_TEST_RESULT_SYMBOL], [
	AS_IF([ ! test -f build/$1/$1.ko], [
		$5
	], [
		AS_IF([test "x$enable_linux_builtin" != "xyes"], [
			ZFS_CHECK_SYMBOL_EXPORT([$2], [$3], [$4], [$5])
		], [
			$4
		])
	])
])

dnl #
dnl # ZFS_LINUX_COMPILE_IFELSE
dnl #
AC_DEFUN([ZFS_LINUX_COMPILE_IFELSE], [
	ZFS_LINUX_TEST_REMOVE([conftest])

	m4_ifvaln([$1], [ZFS_LINUX_CONFTEST_C([$1], [conftest])])
	m4_ifvaln([$5], [ZFS_LINUX_CONFTEST_H([$5], [conftest])],
	    [ZFS_LINUX_CONFTEST_H([], [conftest])])

	ZFS_LINUX_CONFTEST_MAKEFILE([conftest], [no],
	    [m4_ifvaln([$5], [-I$PWD/build/conftest], [])])
	ZFS_LINUX_COMPILE([build/conftest], [$2], [$3], [$4], [], [])
])

dnl #
dnl # ZFS_LINUX_TRY_COMPILE
dnl #
dnl # $1 - global
dnl # $2 - source
dnl # $3 - run on success (valid .ko generated)
dnl # $4 - run on failure (unable to compile)
dnl #
dnl # When configuring as builtin (--enable-linux-builtin) for kernels
dnl # without loadable module support (CONFIG_MODULES=n) only the object
dnl # file is created.  See ZFS_LINUX_TEST_COMPILE_ALL for details.
dnl #
AC_DEFUN([ZFS_LINUX_TRY_COMPILE], [
	AS_IF([test "x$enable_linux_builtin" = "xyes"], [
		ZFS_LINUX_COMPILE_IFELSE(
		    [ZFS_LINUX_TEST_PROGRAM([[$1]], [[$2]],
		    [[ZFS_META_LICENSE]])],
		    [test -f build/conftest/conftest.o], [$3], [$4])
	], [
		ZFS_LINUX_COMPILE_IFELSE(
		    [ZFS_LINUX_TEST_PROGRAM([[$1]], [[$2]],
		    [[ZFS_META_LICENSE]])],
		    [test -f build/conftest/conftest.ko], [$3], [$4])
	])
])

dnl #
dnl # ZFS_CHECK_SYMBOL_EXPORT
dnl #
dnl # Check if a symbol is exported on not by consulting the symbols
dnl # file, or optionally the source code.
dnl #
AC_DEFUN([ZFS_CHECK_SYMBOL_EXPORT], [
	grep -q -E '[[[:space:]]]$1[[[:space:]]]' \
		$LINUX_OBJ/$LINUX_SYMBOLS 2>/dev/null
	rc=$?
	if test $rc -ne 0; then
		export=0
		for file in $2; do
			grep -q -E "EXPORT_SYMBOL.*($1)" \
				"$LINUX/$file" 2>/dev/null
			rc=$?
			if test $rc -eq 0; then
				export=1
				break;
			fi
		done
		if test $export -eq 0; then :
			$4
		else :
			$3
		fi
	else :
		$3
	fi
])

dnl #
dnl # ZFS_LINUX_TRY_COMPILE_SYMBOL
dnl #
dnl # Like ZFS_LINUX_TRY_COMPILER except ZFS_CHECK_SYMBOL_EXPORT is called
dnl # to verify symbol exports, unless --enable-linux-builtin was provided
dnl # to configure.
dnl #
AC_DEFUN([ZFS_LINUX_TRY_COMPILE_SYMBOL], [
	ZFS_LINUX_TRY_COMPILE([$1], [$2], [rc=0], [rc=1])
	if test $rc -ne 0; then :
		$6
	else
		if test "x$enable_linux_builtin" != xyes; then
			ZFS_CHECK_SYMBOL_EXPORT([$3], [$4], [rc=0], [rc=1])
		fi
		if test $rc -ne 0; then :
			$6
		else :
			$5
		fi
	fi
])

dnl #
dnl # ZFS_LINUX_TRY_COMPILE_HEADER
dnl # like ZFS_LINUX_TRY_COMPILE, except the contents conftest.h are
dnl # provided via the fifth parameter
dnl #
AC_DEFUN([ZFS_LINUX_TRY_COMPILE_HEADER], [
	AS_IF([test "x$enable_linux_builtin" = "xyes"], [
		ZFS_LINUX_COMPILE_IFELSE(
		    [ZFS_LINUX_TEST_PROGRAM([[$1]], [[$2]],
		    [[ZFS_META_LICENSE]])],
		    [test -f build/conftest/conftest.o], [$3], [$4], [$5])
	], [
		ZFS_LINUX_COMPILE_IFELSE(
		    [ZFS_LINUX_TEST_PROGRAM([[$1]], [[$2]],
		    [[ZFS_META_LICENSE]])],
		    [test -f build/conftest/conftest.ko], [$3], [$4], [$5])
	])
])

dnl #
dnl # AS_VERSION_COMPARE_LE
dnl # like AS_VERSION_COMPARE_LE, but runs $3 if (and only if) $1 <= $2
dnl # AS_VERSION_COMPARE_LE (version-1, version-2, [action-if-less-or-equal], [action-if-greater])
dnl #
AC_DEFUN([AS_VERSION_COMPARE_LE], [
	AS_VERSION_COMPARE([$1], [$2], [$3], [$3], [$4])
])

dnl #
dnl # ZFS_LINUX_REQUIRE_API
dnl # like ZFS_LINUX_TEST_ERROR, except only fails if the kernel is
dnl # at least some specified version.
dnl #
AC_DEFUN([ZFS_LINUX_REQUIRE_API], [
	AS_VERSION_COMPARE_LE([$2], [$kernsrcver], [
		AC_MSG_ERROR([
		*** None of the expected "$1" interfaces were detected. This
		*** interface is expected for kernels version "$2" and above.
		*** This may be because your kernel version is newer than what is
		*** supported, or you are using a patched custom kernel with
		*** incompatible modifications.  Newer kernels may have incompatible
		*** APIs.
		***
		*** ZFS Version: $ZFS_META_ALIAS
		*** Compatible Kernels: $ZFS_META_KVER_MIN - $ZFS_META_KVER_MAX
		])
	], [
		AC_MSG_RESULT(no)
	])
])