config: remove HAVE_KMEM_CACHE_CREATE_USERCOPY

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.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_KMEM_CACHE
 	ZFS_AC_KERNEL_SRC_KVMALLOC
 	ZFS_AC_KERNEL_SRC_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_SRC_WAIT
@@ -163,7 +162,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_GENERIC_FADVISE
 	ZFS_AC_KERNEL_SCHED
 	ZFS_AC_KERNEL_USLEEP_RANGE
-	ZFS_AC_KERNEL_KMEM_CACHE
 	ZFS_AC_KERNEL_KVMALLOC
 	ZFS_AC_KERNEL_VMALLOC_PAGE_KERNEL
 	ZFS_AC_KERNEL_WAIT

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

@@ -786,25 +786,8 @@ spl_kmem_cache_create(const char *name, size_t size, size_t align,
 		if (skc->skc_flags & KMC_RECLAIMABLE)
 			slabflags |= SLAB_RECLAIM_ACCOUNT;
 
-#if defined(SLAB_USERCOPY)
-		/*
-		 * Required for PAX-enabled kernels if the slab is to be
-		 * used for copying between user and kernel space.
-		 */
-		slabflags |= SLAB_USERCOPY;
-#endif
-
-#if defined(HAVE_KMEM_CACHE_CREATE_USERCOPY)
-		/*
-		 * Newer grsec patchset uses kmem_cache_create_usercopy()
-		 * instead of SLAB_USERCOPY flag
-		 */
 		skc->skc_linux_cache = kmem_cache_create_usercopy(
 		    skc->skc_name, size, align, slabflags, 0, size, NULL);
-#else
-		skc->skc_linux_cache = kmem_cache_create(
-		    skc->skc_name, size, align, slabflags, NULL);
-#endif
 		if (skc->skc_linux_cache == NULL)
 			goto out;
 	}