tunables: ensure tunable and variable have same define gate

If a variable is only available in the kernel, then the tunable should
also only be available there.

This matters very little so long as we don't have userspace tunables,
but its still good hygeine.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Pavel Snajdr <snajpa@snajpa.net>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17377

Author: robn

module/zfs/arc.c

@@ -382,8 +382,8 @@ static int zfs_arc_overflow_shift = 8;
 /* log2(fraction of arc to reclaim) */
 uint_t arc_shrink_shift = 7;
 
-/* percent of pagecache to reclaim arc to */
 #ifdef _KERNEL
+/* percent of pagecache to reclaim arc to */
 uint_t zfs_arc_pc_percent = 0;
 #endif
 
@@ -10829,8 +10829,10 @@ ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, grow_retry, param_set_arc_int,
 ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, shrink_shift, param_set_arc_int,
 	param_get_uint, ZMOD_RW, "log2(fraction of ARC to reclaim)");
 
+#ifdef _KERNEL
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, pc_percent, UINT, ZMOD_RW,
 	"Percent of pagecache to reclaim ARC to");
+#endif
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, average_blocksize, UINT, ZMOD_RD,
 	"Target average block size");

module/zfs/fm.c

@@ -1368,7 +1368,8 @@ fm_fini(void)
 		fm_ksp = NULL;
 	}
 }
-#endif /* _KERNEL */
 
 ZFS_MODULE_PARAM(zfs_zevent, zfs_zevent_, len_max, UINT, ZMOD_RW,
 	"Max event queue length");
+
+#endif /* _KERNEL */

module/zfs/spa_config.c

@@ -635,5 +635,7 @@ ZFS_MODULE_PARAM(zfs_spa, spa_, config_path, STRING, ZMOD_RD,
 	"SPA config file (/etc/zfs/zpool.cache)");
 #endif
 
+#ifdef _KERNEL
 ZFS_MODULE_PARAM(zfs, zfs_, autoimport_disable, INT, ZMOD_RW,
 	"Disable pool import at module load");
+#endif