spa: expose max_missing_tvds_cachefile and _scan on Linux

Register the two siblings of zfs_max_missing_tvds via
ZFS_MODULE_PARAM in spa.c

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Christos Longros <chris.longros@gmail.com>
Closes #18589

man/man4/zfs.4

@@ -918,6 +918,19 @@ but that was not proven to be useful.
 Number of missing top-level vdevs which will be allowed during
 pool import (only in read-only mode).
 .
+.It Sy zfs_max_missing_tvds_cachefile Ns = Ns Sy 2 Pq u64
+Number of missing top-level vdevs tolerated when importing a pool
+from a cachefile, before the trusted config is read from the MOS.
+A cachefile can fall out of sync with the on-disk config after a
+device removal that did not rewrite the cachefile, so the default
+of 2 still lets the import reach a copy of the MOS.
+.
+.It Sy zfs_max_missing_tvds_scan Ns = Ns Sy 0 Pq u64
+Number of missing top-level vdevs tolerated when importing a pool
+by scanning device paths, before the trusted config is read from
+the MOS.
+Defaults to 0 because a scan should detect every present device.
+.
 .It Sy zfs_max_nvlist_src_size Ns = Sy 0 Pq u64
 Maximum size in bytes allowed to be passed as
 .Sy zc_nvlist_src_size

module/os/freebsd/zfs/sysctl_os.c

@@ -381,18 +381,6 @@ SYSCTL_INT(_vfs_zfs, OID_AUTO, ccw_retry_interval,
 	"Configuration cache file write, retry after failure, interval"
 	" (seconds)");
 
-extern uint64_t zfs_max_missing_tvds_cachefile;
-
-SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, max_missing_tvds_cachefile,
-	CTLFLAG_RWTUN, &zfs_max_missing_tvds_cachefile, 0,
-	"Allow importing pools with missing top-level vdevs in cache file");
-
-extern uint64_t zfs_max_missing_tvds_scan;
-
-SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, max_missing_tvds_scan,
-	CTLFLAG_RWTUN, &zfs_max_missing_tvds_scan, 0,
-	"Allow importing pools with missing top-level vdevs during scan");
-
 /* spa_misc.c */
 
 extern int zfs_flags;

module/zfs/spa.c

@@ -11811,6 +11811,12 @@ ZFS_MODULE_PARAM(zfs, zfs_, max_missing_tvds, U64, ZMOD_RW,
 	"Allow importing pool with up to this number of missing top-level "
 	"vdevs (in read-only mode)");
 
+ZFS_MODULE_PARAM(zfs, zfs_, max_missing_tvds_cachefile, U64, ZMOD_RW,
+	"Allow importing pools with missing top-level vdevs in cache file");
+
+ZFS_MODULE_PARAM(zfs, zfs_, max_missing_tvds_scan, U64, ZMOD_RW,
+	"Allow importing pools with missing top-level vdevs during scan");
+
 ZFS_MODULE_PARAM(zfs_livelist_condense, zfs_livelist_condense_, zthr_pause, INT,
 	ZMOD_RW, "Set the livelist condense zthr to pause");