freebsd-dev/config/kernel.m4
Brian Behlendorf dba1d70566 Fix arc_adapt() spinning in iterate_supers_type()
The iterate_supers_type() function which was introduced in the
3.0 kernel was supposed to provide a safe way to call an arbitrary
function on all super blocks of a specific type.  Unfortunately,
because a list_head was used a bug was introduced which made it
possible for iterate_supers_type() to get stuck spinning on a
super block which was just deactivated.

This can occur because when the list head is removed from the
fs_supers list it is reinitialized to point to itself.  If the
iterate_supers_type() function happened to be processing the
removed list_head it will get stuck spinning on that list_head.

The bug was fixed in the 3.3 kernel by converting the list_head
to an hlist_node.  However, to resolve the issue for existing
3.0 - 3.2 kernels we detect when a list_head is used.  Then to
prevent the spinning from occurring the .next pointer is set to
the fs_supers list_head which ensures the iterate_supers_type()
function will always terminate.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1045
Closes #861
Closes #790
2013-07-17 09:28:06 -07:00

603 lines
16 KiB
Plaintext

dnl #
dnl # Default ZFS kernel configuration
dnl #
AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL
ZFS_AC_SPL
ZFS_AC_TEST_MODULE
ZFS_AC_KERNEL_CONFIG
ZFS_AC_KERNEL_BDEV_BLOCK_DEVICE_OPERATIONS
ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID
ZFS_AC_KERNEL_TYPE_FMODE_T
ZFS_AC_KERNEL_KOBJ_NAME_LEN
ZFS_AC_KERNEL_3ARG_BLKDEV_GET
ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH
ZFS_AC_KERNEL_OPEN_BDEV_EXCLUSIVE
ZFS_AC_KERNEL_LOOKUP_BDEV
ZFS_AC_KERNEL_INVALIDATE_BDEV_ARGS
ZFS_AC_KERNEL_BDEV_LOGICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BDEV_PHYSICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BIO_FAILFAST
ZFS_AC_KERNEL_BIO_FAILFAST_DTD
ZFS_AC_KERNEL_REQ_FAILFAST_MASK
ZFS_AC_KERNEL_BIO_END_IO_T_ARGS
ZFS_AC_KERNEL_BIO_RW_SYNC
ZFS_AC_KERNEL_BIO_RW_SYNCIO
ZFS_AC_KERNEL_REQ_SYNC
ZFS_AC_KERNEL_BLK_END_REQUEST
ZFS_AC_KERNEL_BLK_QUEUE_FLUSH
ZFS_AC_KERNEL_BLK_QUEUE_MAX_HW_SECTORS
ZFS_AC_KERNEL_BLK_QUEUE_MAX_SEGMENTS
ZFS_AC_KERNEL_BLK_QUEUE_PHYSICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BLK_QUEUE_IO_OPT
ZFS_AC_KERNEL_BLK_QUEUE_NONROT
ZFS_AC_KERNEL_BLK_QUEUE_DISCARD
ZFS_AC_KERNEL_BLK_FETCH_REQUEST
ZFS_AC_KERNEL_BLK_REQUEUE_REQUEST
ZFS_AC_KERNEL_BLK_RQ_BYTES
ZFS_AC_KERNEL_BLK_RQ_POS
ZFS_AC_KERNEL_BLK_RQ_SECTORS
ZFS_AC_KERNEL_GET_DISK_RO
ZFS_AC_KERNEL_GET_GENDISK
ZFS_AC_KERNEL_RQ_IS_SYNC
ZFS_AC_KERNEL_RQ_FOR_EACH_SEGMENT
ZFS_AC_KERNEL_DISCARD_GRANULARITY
ZFS_AC_KERNEL_CONST_XATTR_HANDLER
ZFS_AC_KERNEL_XATTR_HANDLER_GET
ZFS_AC_KERNEL_XATTR_HANDLER_SET
ZFS_AC_KERNEL_SHOW_OPTIONS
ZFS_AC_KERNEL_FSYNC
ZFS_AC_KERNEL_EVICT_INODE
ZFS_AC_KERNEL_DIRTY_INODE_WITH_FLAGS
ZFS_AC_KERNEL_NR_CACHED_OBJECTS
ZFS_AC_KERNEL_FREE_CACHED_OBJECTS
ZFS_AC_KERNEL_FALLOCATE
ZFS_AC_KERNEL_MKDIR_UMODE_T
ZFS_AC_KERNEL_LOOKUP_NAMEIDATA
ZFS_AC_KERNEL_CREATE_NAMEIDATA
ZFS_AC_KERNEL_TRUNCATE_RANGE
ZFS_AC_KERNEL_AUTOMOUNT
ZFS_AC_KERNEL_ENCODE_FH_WITH_INODE
ZFS_AC_KERNEL_COMMIT_METADATA
ZFS_AC_KERNEL_CLEAR_INODE
ZFS_AC_KERNEL_INSERT_INODE_LOCKED
ZFS_AC_KERNEL_D_MAKE_ROOT
ZFS_AC_KERNEL_D_OBTAIN_ALIAS
ZFS_AC_KERNEL_D_SET_D_OP
ZFS_AC_KERNEL_D_REVALIDATE_NAMEIDATA
ZFS_AC_KERNEL_CONST_DENTRY_OPERATIONS
ZFS_AC_KERNEL_CHECK_DISK_SIZE_CHANGE
ZFS_AC_KERNEL_TRUNCATE_SETSIZE
ZFS_AC_KERNEL_6ARGS_SECURITY_INODE_INIT_SECURITY
ZFS_AC_KERNEL_CALLBACK_SECURITY_INODE_INIT_SECURITY
ZFS_AC_KERNEL_MOUNT_NODEV
ZFS_AC_KERNEL_SHRINK
ZFS_AC_KERNEL_S_INSTANCES_LIST_HEAD
ZFS_AC_KERNEL_S_D_OP
ZFS_AC_KERNEL_BDI
ZFS_AC_KERNEL_BDI_SETUP_AND_REGISTER
ZFS_AC_KERNEL_SET_NLINK
ZFS_AC_KERNEL_ELEVATOR_CHANGE
ZFS_AC_KERNEL_5ARG_SGET
ZFS_AC_KERNEL_LSEEK_EXECUTE
AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"
])
AC_SUBST(KERNELMAKE_PARAMS)
dnl # -Wall -fno-strict-aliasing -Wstrict-prototypes and other
dnl # compiler options are added by the kernel build system.
KERNELCPPFLAGS="$KERNELCPPFLAGS $NO_UNUSED_BUT_SET_VARIABLE"
KERNELCPPFLAGS="$KERNELCPPFLAGS -DHAVE_SPL -D_KERNEL"
KERNELCPPFLAGS="$KERNELCPPFLAGS -DTEXT_DOMAIN=\\\"zfs-linux-kernel\\\""
AC_SUBST(KERNELCPPFLAGS)
])
dnl #
dnl # Detect name used for Module.symvers file in kernel
dnl #
AC_DEFUN([ZFS_AC_MODULE_SYMVERS], [
modpost=$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 #
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 directory])
AS_IF([test -z "$kernelsrc"], [
AS_IF([test -e "/lib/modules/$(uname -r)/source"], [
headersdir="/lib/modules/$(uname -r)/source"
sourcelink=$(readlink -f "$headersdir")
], [test -e "/lib/modules/$(uname -r)/build"], [
headersdir="/lib/modules/$(uname -r)/build"
sourcelink=$(readlink -f "$headersdir")
], [
sourcelink=$(ls -1d /usr/src/kernels/* \
/usr/src/linux-* \
2>/dev/null | grep -v obj | tail -1)
])
AS_IF([test -n "$sourcelink" && test -e ${sourcelink}], [
kernelsrc=`readlink -f ${sourcelink}`
], [
kernelsrc="[Not found]"
])
], [
AS_IF([test "$kernelsrc" = "NONE"], [
kernsrcver=NONE
])
])
AC_MSG_RESULT([$kernelsrc])
AS_IF([test ! -d "$kernelsrc"], [
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 with the '--with-linux=PATH' option.])
])
AC_MSG_CHECKING([kernel build directory])
AS_IF([test -z "$kernelbuild"], [
AS_IF([test -e "/lib/modules/$(uname -r)/build"], [
kernelbuild=`readlink -f /lib/modules/$(uname -r)/build`
], [test -d ${kernelsrc}-obj/${target_cpu}/${target_cpu}], [
kernelbuild=${kernelsrc}-obj/${target_cpu}/${target_cpu}
], [test -d ${kernelsrc}-obj/${target_cpu}/default], [
kernelbuild=${kernelsrc}-obj/${target_cpu}/default
], [test -d `dirname ${kernelsrc}`/build-${target_cpu}], [
kernelbuild=`dirname ${kernelsrc}`/build-${target_cpu}
], [
kernelbuild=${kernelsrc}
])
])
AC_MSG_RESULT([$kernelbuild])
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 && fgrep -q UTS_RELEASE $utsrelease1], [
utsrelease=linux/version.h
], [test -r $utsrelease2 && fgrep -q UTS_RELEASE $utsrelease2], [
utsrelease=linux/utsrelease.h
], [test -r $utsrelease3 && fgrep -q UTS_RELEASE $utsrelease3], [
utsrelease=generated/utsrelease.h
])
AS_IF([test "$utsrelease"], [
kernsrcver=`(echo "#include <$utsrelease>";
echo "kernsrcver=UTS_RELEASE") |
cpp -I $kernelbuild/include |
grep "^kernsrcver=" | cut -d \" -f 2`
AS_IF([test -z "$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])
LINUX=${kernelsrc}
LINUX_OBJ=${kernelbuild}
LINUX_VERSION=${kernsrcver}
AC_SUBST(LINUX)
AC_SUBST(LINUX_OBJ)
AC_SUBST(LINUX_VERSION)
ZFS_AC_MODULE_SYMVERS
])
dnl #
dnl # Detect the SPL module to be built against
dnl #
AC_DEFUN([ZFS_AC_SPL], [
AC_ARG_WITH([spl],
AS_HELP_STRING([--with-spl=PATH],
[Path to spl source]),
[splsrc="$withval"])
AC_ARG_WITH([spl-obj],
AS_HELP_STRING([--with-spl-obj=PATH],
[Path to spl build objects]),
[splbuild="$withval"])
AC_ARG_WITH([spl-timeout],
AS_HELP_STRING([--with-spl-timeout=SECS],
[Wait SECS for SPL header and symver file @<:@default=0@:>@]),
[timeout="$withval"], [timeout=0])
dnl #
dnl # The existence of spl.release.in is used to identify a valid
dnl # source directory. In order of preference:
dnl #
splsrc0="/var/lib/dkms/spl/${VERSION}/build"
splsrc1="/usr/src/spl-${VERSION}/${LINUX_VERSION}"
splsrc2="/usr/src/spl-${VERSION}"
splsrc3="../spl/"
splsrc4="$LINUX"
AC_MSG_CHECKING([spl source directory])
AS_IF([test -z "${splsrc}"], [
AS_IF([ test -e "${splsrc0}/spl.release.in"], [
splsrc=${splsrc0}
], [ test -e "${splsrc1}/spl.release.in"], [
splsrc=${splsrc1}
], [ test -e "${splsrc2}/spl.release.in"], [
splsrc=${splsrc2}
], [ test -e "${splsrc3}/spl.release.in"], [
splsrc=$(readlink -f "${splsrc3}")
], [ test -e "${splsrc4}/spl.release.in" ], [
splsrc=${splsrc4}
], [
splsrc="[Not found]"
])
], [
AS_IF([test "$splsrc" = "NONE"], [
splbuild=NONE
splsrcver=NONE
])
])
AC_MSG_RESULT([$splsrc])
AS_IF([ test ! -e "$splsrc/spl.release.in"], [
AC_MSG_ERROR([
*** Please make sure the kmod spl devel package for your distribution
*** is installed then try again. If that fails you can specify the
*** location of the spl source with the '--with-spl=PATH' option.])
])
dnl #
dnl # The existence of the spl_config.h is used to identify a valid
dnl # spl object directory. In many cases the object and source
dnl # directory are the same, however the objects may also reside
dnl # is a subdirectory named after the kernel version.
dnl #
dnl # This file is supposed to be available after DKMS finishes
dnl # building the SPL kernel module for the target kernel. The
dnl # '--with-spl-timeout' option can be passed to pause here,
dnl # waiting for the file to appear from a concurrently building
dnl # SPL package.
dnl #
AC_MSG_CHECKING([spl build directory])
while true; do
AS_IF([test -z "$splbuild"], [
AS_IF([ test -e "${splsrc}/${LINUX_VERSION}/spl_config.h" ], [
splbuild="${splsrc}/${LINUX_VERSION}"
], [ test -e "${splsrc}/spl_config.h" ], [
splbuild="${splsrc}"
], [
splbuild="[Not found]"
])
])
AS_IF([test -e "$splbuild/spl_config.h" -o $timeout -le 0], [
break;
], [
sleep 1
timeout=$((timeout-1))
])
done
AC_MSG_RESULT([$splbuild])
AS_IF([ ! test -e "$splbuild/spl_config.h"], [
AC_MSG_ERROR([
*** Please make sure the kmod spl devel <kernel> package for your
*** distribution is installed then try again. If that fails you
*** can specify the location of the spl objects with the
*** '--with-spl-obj=PATH' option.])
])
AC_MSG_CHECKING([spl source version])
AS_IF([test -r $splbuild/spl_config.h &&
fgrep -q SPL_META_VERSION $splbuild/spl_config.h], [
splsrcver=`(echo "#include <spl_config.h>";
echo "splsrcver=SPL_META_VERSION-SPL_META_RELEASE") |
cpp -I $splbuild |
grep "^splsrcver=" | tr -d \" | cut -d= -f2`
])
AS_IF([test -z "$splsrcver"], [
AC_MSG_RESULT([Not found])
AC_MSG_ERROR([
*** Cannot determine the version of the spl source.
*** Please prepare the spl source before running this script])
])
AC_MSG_RESULT([$splsrcver])
SPL=${splsrc}
SPL_OBJ=${splbuild}
SPL_VERSION=${splsrcver}
AC_SUBST(SPL)
AC_SUBST(SPL_OBJ)
AC_SUBST(SPL_VERSION)
dnl #
dnl # Detect the name used for the SPL Module.symvers file. If one
dnl # does not exist this is likely because the SPL has been configured
dnl # but not built. The '--with-spl-timeout' option can be passed
dnl # to pause here, waiting for the file to appear from a concurrently
dnl # building SPL package. If the file does not appear in time, a good
dnl # guess is made as to what this file will be named based on what it
dnl # is named in the kernel build products. This file will first be
dnl # used at link time so if the guess is wrong the build will fail
dnl # then. This unfortunately means the ZFS package does not contain a
dnl # reliable mechanism to detect symbols exported by the SPL at
dnl # configure time.
dnl #
AC_MSG_CHECKING([spl file name for module symbols])
SPL_SYMBOLS=NONE
while true; do
AS_IF([test -r $SPL_OBJ/Module.symvers], [
SPL_SYMBOLS=Module.symvers
], [test -r $SPL_OBJ/Modules.symvers], [
SPL_SYMBOLS=Modules.symvers
], [test -r $SPL_OBJ/module/Module.symvers], [
SPL_SYMBOLS=Module.symvers
], [test -r $SPL_OBJ/module/Modules.symvers], [
SPL_SYMBOLS=Modules.symvers
])
AS_IF([test $SPL_SYMBOLS != NONE -o $timeout -le 0], [
break;
], [
sleep 1
timeout=$((timeout-1))
])
done
AS_IF([test "$SPL_SYMBOLS" = NONE], [
SPL_SYMBOLS=$LINUX_SYMBOLS
])
AC_MSG_RESULT([$SPL_SYMBOLS])
AC_SUBST(SPL_SYMBOLS)
])
dnl #
dnl # Basic toolchain sanity check.
dnl #
AC_DEFUN([ZFS_AC_TEST_MODULE],
[AC_MSG_CHECKING([whether modules can be built])
ZFS_LINUX_TRY_COMPILE([],[],[
AC_MSG_RESULT([yes])
],[
AC_MSG_RESULT([no])
if test "x$enable_linux_builtin" != xyes; then
AC_MSG_ERROR([*** Unable to build an empty module.])
else
AC_MSG_ERROR([
*** Unable to build an empty module.
*** Please run 'make scripts' inside the kernel source tree.])
fi
])
])
dnl #
dnl # Certain kernel build options are not supported. These must be
dnl # detected at configure time and cause a build failure. Otherwise
dnl # modules may be successfully built that behave incorrectly.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_CONFIG], [
AS_IF([test "$ZFS_META_LICENSE" = GPL], [
AC_DEFINE([HAVE_GPL_ONLY_SYMBOLS], [1],
[Define to 1 if licensed under the GPL])
])
ZFS_AC_KERNEL_CONFIG_DEBUG_LOCK_ALLOC
])
dnl #
dnl # Check CONFIG_DEBUG_LOCK_ALLOC
dnl #
dnl # This is typically only set for debug kernels because it comes with
dnl # a performance penalty. However, when it is set it maps the non-GPL
dnl # symbol mutex_lock() to the GPL-only mutex_lock_nested() symbol.
dnl # This will cause a failure at link time which we'd rather know about
dnl # at compile time.
dnl #
dnl # Since we plan to pursue making mutex_lock_nested() a non-GPL symbol
dnl # with the upstream community we add a check to detect this case.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_CONFIG_DEBUG_LOCK_ALLOC], [
ZFS_LINUX_CONFIG([DEBUG_LOCK_ALLOC], [
AC_MSG_CHECKING([whether mutex_lock() is GPL-only])
tmp_flags="$EXTRA_KCFLAGS"
ZFS_LINUX_TRY_COMPILE([
#include <linux/module.h>
#include <linux/mutex.h>
MODULE_LICENSE("$ZFS_META_LICENSE");
],[
struct mutex lock;
mutex_init(&lock);
mutex_lock(&lock);
mutex_unlock(&lock);
],[
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(yes)
AC_MSG_ERROR([
*** Kernel built with CONFIG_DEBUG_LOCK_ALLOC which is incompatible
*** with the CDDL license and will prevent the module linking stage
*** from succeeding. You must rebuild your kernel without this
*** option enabled.])
])
EXTRA_KCFLAGS="$tmp_flags"
], [])
])
dnl #
dnl # ZFS_LINUX_CONFTEST
dnl #
AC_DEFUN([ZFS_LINUX_CONFTEST], [
cat confdefs.h - <<_ACEOF >conftest.c
$1
_ACEOF
])
dnl #
dnl # ZFS_LANG_PROGRAM(C)([PROLOGUE], [BODY])
dnl #
m4_define([ZFS_LANG_PROGRAM], [
$1
int
main (void)
{
dnl Do *not* indent the following line: there may be CPP directives.
dnl Don't move the `;' right after for the same reason.
$2
;
return 0;
}
])
dnl #
dnl # ZFS_LINUX_COMPILE_IFELSE / like AC_COMPILE_IFELSE
dnl #
AC_DEFUN([ZFS_LINUX_COMPILE_IFELSE], [
m4_ifvaln([$1], [ZFS_LINUX_CONFTEST([$1])])
rm -Rf build && mkdir -p build && touch build/conftest.mod.c
echo "obj-m := conftest.o" >build/Makefile
modpost_flag=''
test "x$enable_linux_builtin" = xyes && modpost_flag='modpost=true' # fake modpost stage
AS_IF(
[AC_TRY_COMMAND(cp conftest.c build && make [$2] -C $LINUX_OBJ EXTRA_CFLAGS="-Werror $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build $modpost_flag) >/dev/null && AC_TRY_COMMAND([$3])],
[$4],
[_AC_MSG_LOG_CONFTEST m4_ifvaln([$5],[$5])]
)
rm -Rf build
])
dnl #
dnl # ZFS_LINUX_TRY_COMPILE like AC_TRY_COMPILE
dnl #
AC_DEFUN([ZFS_LINUX_TRY_COMPILE],
[ZFS_LINUX_COMPILE_IFELSE(
[AC_LANG_SOURCE([ZFS_LANG_PROGRAM([[$1]], [[$2]])])],
[modules],
[test -s build/conftest.o],
[$3], [$4])
])
dnl #
dnl # ZFS_LINUX_CONFIG
dnl #
AC_DEFUN([ZFS_LINUX_CONFIG],
[AC_MSG_CHECKING([whether Linux was built with CONFIG_$1])
ZFS_LINUX_TRY_COMPILE([
#include <linux/module.h>
],[
#ifndef CONFIG_$1
#error CONFIG_$1 not #defined
#endif
],[
AC_MSG_RESULT([yes])
$2
],[
AC_MSG_RESULT([no])
$3
])
])
dnl #
dnl # ZFS_CHECK_SYMBOL_EXPORT
dnl # check symbol exported or not
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 # like ZFS_LINUX_TRY_COMPILE, except ZFS_CHECK_SYMBOL_EXPORT
dnl # is called if not compiling for builtin
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
])