spa: make ccw_retry_interval tunable on Linux (#18681)

zfs_ccw_retry_interval sets the time interval after which a retry of a
failed write of the configuration cache file is attempted. It was only
exposed on FreeBSD. Make it Linux tunable with ZFS_MODULE_PARAM and
document it in zfs.4.

Signed-off-by: Christos Longros <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Richard Yao <[email protected]>

man/man4/zfs.4

@@ -1090,6 +1090,10 @@ and uses pages, unlike the Linux-specific
 .Sy zfs_arc_sys_free
 which is measured in bytes.
 .
+.It Sy zfs_ccw_retry_interval Ns = Ns Sy 300 Ns s Pq int
+Interval, in seconds, at which a failed write of the configuration cache file
+is retried.
+.
 .It Sy zfs_checksum_events_per_second Ns = Ns Sy 20 Ns /s Pq uint
 Rate limit checksum events to this many per second.
 Note that this should not be set below the ZED thresholds

module/os/freebsd/zfs/sysctl_os.c

@@ -306,15 +306,6 @@ param_set_multihost_interval(SYSCTL_HANDLER_ARGS)
 	return (0);
 }
 
-/* spa.c */
-
-extern int zfs_ccw_retry_interval;
-
-SYSCTL_INT(_vfs_zfs, OID_AUTO, ccw_retry_interval,
-	CTLFLAG_RWTUN, &zfs_ccw_retry_interval, 0,
-	"Configuration cache file write, retry after failure, interval"
-	" (seconds)");
-
 /* spa_misc.c */
 
 extern int zfs_flags;

module/zfs/spa.c

@@ -11866,3 +11866,7 @@ ZFS_MODULE_VIRTUAL_PARAM_CALL(zfs_zio, zio_, taskq_free,
 
 ZFS_MODULE_PARAM(zfs_zio, zio_, taskq_write_tpq, UINT, ZMOD_RW,
 	"Number of CPUs per write issue taskq");
+
+ZFS_MODULE_PARAM(zfs, zfs_, ccw_retry_interval, INT, ZMOD_RW,
+	"Configuration cache file write, retry after failure, interval "
+	"(seconds)");