config: remove HAVE_KVMALLOC

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes openzfs#16479

config/kernel-kmem.m4

@@ -57,31 +57,6 @@ AC_DEFUN([SPL_AC_DEBUG_KMEM_TRACKING], [
 	AC_MSG_RESULT([$enable_debug_kmem_tracking])
 ])
 
-dnl #
-dnl # 4.12 API,
-dnl # Added kvmalloc allocation strategy
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_KVMALLOC], [
-	ZFS_LINUX_TEST_SRC([kvmalloc], [
-		#include <linux/mm.h>
-		#include <linux/slab.h>
-	],[
-		void *p __attribute__ ((unused));
-
-		p = kvmalloc(0, GFP_KERNEL);
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_KVMALLOC], [
-	AC_MSG_CHECKING([whether kvmalloc(ptr, flags) is available])
-	ZFS_LINUX_TEST_RESULT([kvmalloc], [
-		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_KVMALLOC, 1, [kvmalloc exists])
-	],[
-		AC_MSG_RESULT(no)
-	])
-])
-
 dnl #
 dnl # 5.8 API,
 dnl # __vmalloc PAGE_KERNEL removal
@@ -106,4 +81,4 @@ AC_DEFUN([ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL], [
 		AC_MSG_RESULT(no)
 	])
 ])
--
+-

config/kernel.m4

@@ -45,7 +45,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_GENERIC_FADVISE
 	ZFS_AC_KERNEL_SRC_SCHED
 	ZFS_AC_KERNEL_SRC_USLEEP_RANGE
-	ZFS_AC_KERNEL_SRC_KVMALLOC
 	ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_SRC_WAIT
 	ZFS_AC_KERNEL_SRC_INODE_TIMES
@@ -161,7 +160,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_GENERIC_FADVISE
 	ZFS_AC_KERNEL_SCHED
 	ZFS_AC_KERNEL_USLEEP_RANGE
-	ZFS_AC_KERNEL_KVMALLOC
 	ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_WAIT
 	ZFS_AC_KERNEL_INODE_TIMES

module/os/linux/spl/spl-kmem.c

@@ -134,7 +134,6 @@ EXPORT_SYMBOL(kmem_strfree);
 void *
 spl_kvmalloc(size_t size, gfp_t lflags)
 {
-#ifdef HAVE_KVMALLOC
 	/*
 	 * GFP_KERNEL allocations can safely use kvmalloc which may
 	 * improve performance by avoiding a) high latency caused by
@@ -146,7 +145,6 @@ spl_kvmalloc(size_t size, gfp_t lflags)
 	 */
 	if ((lflags & GFP_KERNEL) == GFP_KERNEL)
 		return (kvmalloc(size, lflags));
-#endif
 
 	gfp_t kmalloc_lflags = lflags;