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_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_ACCESS_OK_TYPE
	ZFS_AC_KERNEL_SRC_PDE_DATA
	ZFS_AC_KERNEL_SRC_GENERIC_FADVISE
	ZFS_AC_KERNEL_SRC_SCHED
	ZFS_AC_KERNEL_SRC_USLEEP_RANGE
	ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL
	ZFS_AC_KERNEL_SRC_INODE_TIMES
	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_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_SHOW_OPTIONS
	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_TMPFILE
	ZFS_AC_KERNEL_SRC_AUTOMOUNT
	ZFS_AC_KERNEL_SRC_COMMIT_METADATA
	ZFS_AC_KERNEL_SRC_SETATTR_PREPARE
	ZFS_AC_KERNEL_SRC_INSERT_INODE_LOCKED
	ZFS_AC_KERNEL_SRC_TRUNCATE_SETSIZE
	ZFS_AC_KERNEL_SRC_SECURITY_INODE
	ZFS_AC_KERNEL_SRC_FST_MOUNT
	ZFS_AC_KERNEL_SRC_SET_NLINK
	ZFS_AC_KERNEL_SRC_SGET
	ZFS_AC_KERNEL_SRC_VFS_FILEMAP_DIRTY_FOLIO
	ZFS_AC_KERNEL_SRC_VFS_READ_FOLIO
	ZFS_AC_KERNEL_SRC_VFS_MIGRATE_FOLIO
	ZFS_AC_KERNEL_SRC_VFS_FSYNC_2ARGS
	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_IOV_ITER
	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_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_TOTALRAM_PAGES_FUNC
	ZFS_AC_KERNEL_SRC_TOTALHIGH_PAGES
	ZFS_AC_KERNEL_SRC_PERCPU
	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_SIGINFO
	ZFS_AC_KERNEL_SRC_SYSFS
	ZFS_AC_KERNEL_SRC_STANDALONE_LINUX_STDARG
	ZFS_AC_KERNEL_SRC_STRLCPY
	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_IDMAP_MNT_API
	ZFS_AC_KERNEL_SRC_IDMAP_NO_USERNS
	ZFS_AC_KERNEL_SRC_IATTR_VFSID
	ZFS_AC_KERNEL_SRC_WRITEPAGE_T
	ZFS_AC_KERNEL_SRC_RECLAIMED
	ZFS_AC_KERNEL_SRC_REGISTER_SYSCTL_TABLE
	ZFS_AC_KERNEL_SRC_REGISTER_SYSCTL_SZ
	ZFS_AC_KERNEL_SRC_PROC_HANDLER_CTL_TABLE_CONST
	ZFS_AC_KERNEL_SRC_COPY_SPLICE_READ
	ZFS_AC_KERNEL_SRC_SYNC_BDEV
	ZFS_AC_KERNEL_SRC_MM_PAGE_FLAGS
	ZFS_AC_KERNEL_SRC_MM_PAGE_SIZE
	ZFS_AC_KERNEL_SRC_MM_PAGE_MAPPING
	ZFS_AC_KERNEL_SRC_FILE
	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_OBJTOOL
	ZFS_AC_KERNEL_PDE_DATA
	ZFS_AC_KERNEL_GENERIC_FADVISE
	ZFS_AC_KERNEL_SCHED
	ZFS_AC_KERNEL_USLEEP_RANGE
	ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL
	ZFS_AC_KERNEL_INODE_TIMES
	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_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_SHOW_OPTIONS
	ZFS_AC_KERNEL_SHRINKER
	ZFS_AC_KERNEL_MKDIR
	ZFS_AC_KERNEL_LOOKUP_FLAGS
	ZFS_AC_KERNEL_CREATE
	ZFS_AC_KERNEL_PERMISSION
	ZFS_AC_KERNEL_TMPFILE
	ZFS_AC_KERNEL_AUTOMOUNT
	ZFS_AC_KERNEL_COMMIT_METADATA
	ZFS_AC_KERNEL_SETATTR_PREPARE
	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
	ZFS_AC_KERNEL_TRUNCATE_SETSIZE
	ZFS_AC_KERNEL_SECURITY_INODE
	ZFS_AC_KERNEL_FST_MOUNT
	ZFS_AC_KERNEL_SET_NLINK
	ZFS_AC_KERNEL_SGET
	ZFS_AC_KERNEL_VFS_FILEMAP_DIRTY_FOLIO
	ZFS_AC_KERNEL_VFS_READ_FOLIO
	ZFS_AC_KERNEL_VFS_MIGRATE_FOLIO
	ZFS_AC_KERNEL_VFS_FSYNC_2ARGS
	ZFS_AC_KERNEL_VFS_DIRECT_IO
	ZFS_AC_KERNEL_VFS_READPAGES
	ZFS_AC_KERNEL_VFS_SET_PAGE_DIRTY_NOBUFFERS
	ZFS_AC_KERNEL_VFS_IOV_ITER
	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_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_TOTALRAM_PAGES_FUNC
	ZFS_AC_KERNEL_TOTALHIGH_PAGES
	ZFS_AC_KERNEL_PERCPU
	ZFS_AC_KERNEL_GENERIC_FILLATTR
	ZFS_AC_KERNEL_MKNOD
	ZFS_AC_KERNEL_SYMLINK
	ZFS_AC_KERNEL_BIO_MAX_SEGS
	ZFS_AC_KERNEL_SIGINFO
	ZFS_AC_KERNEL_SYSFS
	ZFS_AC_KERNEL_STANDALONE_LINUX_STDARG
	ZFS_AC_KERNEL_STRLCPY
	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_IDMAP_MNT_API
	ZFS_AC_KERNEL_IDMAP_NO_USERNS
	ZFS_AC_KERNEL_IATTR_VFSID
	ZFS_AC_KERNEL_WRITEPAGE_T
	ZFS_AC_KERNEL_RECLAIMED
	ZFS_AC_KERNEL_REGISTER_SYSCTL_TABLE
	ZFS_AC_KERNEL_REGISTER_SYSCTL_SZ
	ZFS_AC_KERNEL_PROC_HANDLER_CTL_TABLE_CONST
	ZFS_AC_KERNEL_COPY_SPLICE_READ
	ZFS_AC_KERNEL_SYNC_BDEV
	ZFS_AC_KERNEL_MM_PAGE_FLAGS
	ZFS_AC_KERNEL_MM_PAGE_SIZE
	ZFS_AC_KERNEL_MM_PAGE_MAPPING
	ZFS_AC_KERNEL_1ARG_ASSIGN_STR
	ZFS_AC_KERNEL_FILE
	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])

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

	AC_ARG_ENABLE([linux-experimental],
		AS_HELP_STRING([--enable-linux-experimental],
		[Allow building against some unsupported kernel versions]))

	AX_COMPARE_VERSION([$kernsrcver], [ge], [$ZFS_META_KVER_MAX], [
		AX_COMPARE_VERSION([$kernsrcver], [eq2], [$ZFS_META_KVER_MAX], [
			kern_max_version_ok=yes
		], [
			kern_max_version_ok=no
		])
	], [
		kern_max_version_ok=yes
	])

	AS_IF([test "x$kern_max_version_ok" != "xyes"], [
		AS_IF([test "x$enable_linux_experimental" == "xyes"], [
			AC_DEFINE(HAVE_LINUX_EXPERIMENTAL, 1,
			    [building against unsupported kernel version])
		], [
			AC_MSG_ERROR([
	*** Cannot build against kernel version $kernsrcver.
	*** The maximum supported kernel version is $ZFS_META_KVER_MAX.
			])
		])
	])

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

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

AC_DEFUN([ZFS_AC_KERNEL_VERSION_WARNING], [
	AS_IF([test "x$enable_linux_experimental" = "xyes" && \
	    test "x$kern_max_version_ok" != "xyes"], [
		AC_MSG_WARN([

	You are building OpenZFS against Linux version $kernsrcver.

	This combination is considered EXPERIMENTAL by the OpenZFS project.
	Even if it appears to build and run correctly, there may be bugs that
	can cause SERIOUS DATA LOSS.

	YOU HAVE BEEN WARNED!

	If you choose to continue, we'd appreciate if you could report your
	results on the OpenZFS issue tracker at:

	    https://github.com/openzfs/zfs/issues/new

	Your feedback will help us prepare a new OpenZFS release that supports
	this version of Linux.
		])
	])
])

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)
	])
])