Cleanup: 64-bit kernel module parameters should use fixed width types

Various module parameters such as `zfs_arc_max` were originally
`uint64_t` on OpenSolaris/Illumos, but were changed to `unsigned long`
for Linux compatibility because Linux's kernel default module parameter
implementation did not support 64-bit types on 32-bit platforms. This
caused problems when porting OpenZFS to Windows because its LLP64 memory
model made `unsigned long` a 32-bit type on 64-bit, which created the
undesireable situation that parameters that should accept 64-bit values
could not on 64-bit Windows.

Upon inspection, it turns out that the Linux kernel module parameter
interface is extensible, such that we are allowed to define our own
types. Rather than maintaining the original type change via hacks to to
continue shrinking module parameters on 32-bit Linux, we implement
support for 64-bit module parameters on Linux.

After doing a review of all 64-bit kernel parameters (found via the man
page and also proposed changes by Andrew Innes), the kernel module
parameters fell into a few groups:

Parameters that were originally 64-bit on Illumos:

 * dbuf_cache_max_bytes
 * dbuf_metadata_cache_max_bytes
 * l2arc_feed_min_ms
 * l2arc_feed_secs
 * l2arc_headroom
 * l2arc_headroom_boost
 * l2arc_write_boost
 * l2arc_write_max
 * metaslab_aliquot
 * metaslab_force_ganging
 * zfetch_array_rd_sz
 * zfs_arc_max
 * zfs_arc_meta_limit
 * zfs_arc_meta_min
 * zfs_arc_min
 * zfs_async_block_max_blocks
 * zfs_condense_max_obsolete_bytes
 * zfs_condense_min_mapping_bytes
 * zfs_deadman_checktime_ms
 * zfs_deadman_synctime_ms
 * zfs_initialize_chunk_size
 * zfs_initialize_value
 * zfs_lua_max_instrlimit
 * zfs_lua_max_memlimit
 * zil_slog_bulk

Parameters that were originally 32-bit on Illumos:

 * zfs_per_txg_dirty_frees_percent - made 32-bit again

Parameters that were originally `ssize_t` on Illumos:

 * zfs_immediate_write_sz

Note that `ssize_t` is `int32_t` on 32-bit and `int64_t` on 64-bit. It
has been upgraded to 64-bit.

Parameters that were `long`/`unsigned long` because of Linux/FreeBSD
influence:

 * l2arc_rebuild_blocks_min_l2size
 * zfs_key_max_salt_uses
 * zfs_max_log_walking
 * zfs_max_logsm_summary_length
 * zfs_metaslab_max_size_cache_sec
 * zfs_min_metaslabs_to_flush
 * zfs_multihost_interval
 * zfs_unflushed_log_block_max
 * zfs_unflushed_log_block_min
 * zfs_unflushed_log_block_pct
 * zfs_unflushed_max_mem_amt
 * zfs_unflushed_max_mem_ppm

New parameters that do not exist in Illumos:

 * l2arc_trim_ahead
 * vdev_file_logical_ashift
 * vdev_file_physical_ashift
 * zfs_arc_dnode_limit
 * zfs_arc_dnode_limit_percent
 * zfs_arc_dnode_reduce_percent
 * zfs_arc_meta_limit_percent
 * zfs_arc_sys_free
 * zfs_deadman_ziotime_ms
 * zfs_delete_blocks
 * zfs_history_output_max
 * zfs_livelist_max_entries
 * zfs_max_async_dedup_frees
 * zfs_max_nvlist_src_size
 * zfs_rebuild_max_segment
 * zfs_rebuild_vdev_limit
 * zfs_unflushed_log_txg_max
 * zfs_vdev_max_auto_ashift
 * zfs_vdev_min_auto_ashift
 * zfs_vnops_read_chunk_size
 * zvol_max_discard_blocks

Rather than clutter the lists with commentary, the module parameters
that need comments are repeated below.

A few parameters were defined in Linux/FreeBSD specific code, where the
use of ulong/long is not an issue for portability, so we leave them
alone:

 * zfs_delete_blocks
 * zfs_key_max_salt_uses
 * zvol_max_discard_blocks

The documentation for a few parameters was found to be incorrect:

 * zfs_deadman_checktime_ms - incorrectly documented as int
 * zfs_delete_blocks - not documented as Linux only
 * zfs_history_output_max - incorrectly documented as int
 * zfs_vnops_read_chunk_size - incorrectly documented as long
 * zvol_max_discard_blocks - incorrectly documented as ulong

The documentation for these has been fixed, alongside the changes to
document the switch to fixed width types.

In addition, several kernel module parameters were percentages or held
ashift values, so being 64-bit never made sense for them. They have been
downgraded to 32-bit:

 * vdev_file_logical_ashift
 * vdev_file_physical_ashift
 * zfs_arc_dnode_limit_percent
 * zfs_arc_dnode_reduce_percent
 * zfs_arc_meta_limit_percent
 * zfs_unflushed_log_block_pct
 * zfs_vdev_max_auto_ashift
 * zfs_vdev_min_auto_ashift

Of special note are `zfs_vdev_max_auto_ashift` and
`zfs_vdev_min_auto_ashift`, which were already defined as `uint64_t`,
and passed to the kernel as `ulong`. This is inherently buggy on big
endian 32-bit Linux/FreeBSD, since the values would not be written to
the correct locations.

Lastly, a code comment suggests that `zfs_arc_sys_free` is
Linux-specific, but there is nothing to indicate to me that it is
Linux-specific. Nothing was done about that.

Original-patch-by: Andrew Innes <andrew.c12@gmail.com>
Original-patch-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>

Author: ryao

cmd/ztest.c

@@ -252,7 +252,7 @@ static const ztest_shared_opts_t ztest_opts_defaults = {
 
 extern uint64_t metaslab_force_ganging;
 extern uint64_t metaslab_df_alloc_threshold;
-extern unsigned long zfs_deadman_synctime_ms;
+extern uint64_t zfs_deadman_synctime_ms;
 extern uint_t metaslab_preload_limit;
 extern int zfs_compressed_arc_enabled;
 extern int zfs_abd_scatter_enabled;

config/kernel-mod-param.m4

@@ -17,7 +17,10 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_MODULE_PARAM_CALL_CONST], [
 			return (0);
 		}
 
-		module_param_call(p, param_set, param_get, NULL, 0644);
+		const struct kernel_param_ops spl_param_ops = {
+			.set = param_set,
+			.get = param_get,
+		};
 	],[])
 ])
 

include/os/freebsd/spl/sys/mod_os.h

@@ -52,17 +52,17 @@
 
 #define	ZFS_MODULE_VIRTUAL_PARAM_CALL ZFS_MODULE_PARAM_CALL
 
-#define	param_set_arc_long_args(var) \
-    CTLTYPE_ULONG, &var, 0, param_set_arc_long, "LU"
+#define	param_set_arc_u64_args(var) \
+    CTLTYPE_U64, &var, 0, param_set_arc_u64, "QU"
 
 #define	param_set_arc_int_args(var) \
     CTLTYPE_INT, &var, 0, param_set_arc_int, "I"
 
 #define	param_set_arc_min_args(var) \
-    CTLTYPE_ULONG, NULL, 0, param_set_arc_min, "LU"
+    CTLTYPE_U64, NULL, 0, param_set_arc_min, "QU"
 
 #define	param_set_arc_max_args(var) \
-    CTLTYPE_ULONG, NULL, 0, param_set_arc_max, "LU"
+    CTLTYPE_U64, NULL, 0, param_set_arc_max, "QU"
 
 #define	param_set_arc_free_target_args(var) \
     CTLTYPE_UINT, NULL, 0, param_set_arc_free_target, "IU"
@@ -74,22 +74,22 @@
     CTLTYPE_STRING, NULL, 0, param_set_deadman_failmode, "A"
 
 #define	param_set_deadman_synctime_args(var) \
-    CTLTYPE_ULONG, NULL, 0, param_set_deadman_synctime, "LU"
+    CTLTYPE_U64, NULL, 0, param_set_deadman_synctime, "QU"
 
 #define	param_set_deadman_ziotime_args(var) \
-    CTLTYPE_ULONG, NULL, 0, param_set_deadman_ziotime, "LU"
+    CTLTYPE_U64, NULL, 0, param_set_deadman_ziotime, "QU"
 
 #define	param_set_multihost_interval_args(var) \
-    CTLTYPE_ULONG, NULL, 0, param_set_multihost_interval, "LU"
+    CTLTYPE_U64, NULL, 0, param_set_multihost_interval, "QU"
 
 #define	param_set_slop_shift_args(var) \
     CTLTYPE_INT, NULL, 0, param_set_slop_shift, "I"
 
 #define	param_set_min_auto_ashift_args(var) \
-    CTLTYPE_U64, NULL, 0, param_set_min_auto_ashift, "QU"
+    CTLTYPE_UINT, NULL, 0, param_set_min_auto_ashift, "IU"
 
 #define	param_set_max_auto_ashift_args(var) \
-    CTLTYPE_U64, NULL, 0, param_set_max_auto_ashift, "QU"
+    CTLTYPE_UINT, NULL, 0, param_set_max_auto_ashift, "IU"
 
 #define	fletcher_4_param_set_args(var) \
     CTLTYPE_STRING, NULL, 0, fletcher_4_param, "A"

include/os/linux/kernel/linux/mod_compat.h

@@ -30,6 +30,15 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 
+/*
+ * Despite constifying struct kernel_param_ops, some older kernels define a
+ * `__check_old_set_param()` function in their headers that checks for a
+ * non-constified `->set()`. This has long been fixed in Linux mainline, but
+ * since we support older kernels, we workaround it by using a preprocessor
+ * definition to disable it.
+ */
+#define	__check_old_set_param(set) (set)
+
 /* Grsecurity kernel API change */
 #ifdef MODULE_PARAM_CALL_CONST
 typedef const struct kernel_param zfs_kernel_param_t;
@@ -40,14 +49,6 @@ typedef struct kernel_param zfs_kernel_param_t;
 #define	ZMOD_RW 0644
 #define	ZMOD_RD 0444
 
-#define	INT int
-#define	LONG long
-/* BEGIN CSTYLED */
-#define	UINT uint
-#define	ULONG ulong
-/* END CSTYLED */
-#define	STRING charp
-
 enum scope_prefix_types {
 	zfs,
 	zfs_arc,
@@ -80,6 +81,50 @@ enum scope_prefix_types {
 	zfs_zil
 };
 
+/*
+ * While we define our own s64/u64 types, there is no reason to reimplement the
+ * existing Linux kernel types, so we use the preprocessor to remap our
+ * "custom" implementations to the kernel ones. This is done because the CPP
+ * does not allow us to write conditional definitions. The fourth definition
+ * exists because the CPP will not allow us to replace things like INT with int
+ * before string concatenation.
+ */
+
+#define	spl_param_set_int param_set_int
+#define	spl_param_get_int param_get_int
+#define	spl_param_ops_int param_ops_int
+#define	spl_param_ops_INT param_ops_int
+
+#define	spl_param_set_long param_set_long
+#define	spl_param_get_long param_get_long
+#define	spl_param_ops_long param_ops_long
+#define	spl_param_ops_LONG param_ops_long
+
+#define	spl_param_set_uint param_set_uint
+#define	spl_param_get_uint param_get_uint
+#define	spl_param_ops_uint param_ops_uint
+#define	spl_param_ops_UINT param_ops_uint
+
+#define	spl_param_set_ulong param_set_ulong
+#define	spl_param_get_ulong param_get_ulong
+#define	spl_param_ops_ulong param_ops_ulong
+#define	spl_param_ops_ULONG param_ops_ulong
+
+#define	spl_param_set_charp param_set_charp
+#define	spl_param_get_charp param_get_charp
+#define	spl_param_ops_charp param_ops_charp
+#define	spl_param_ops_STRING param_ops_charp
+
+int spl_param_set_s64(const char *val, zfs_kernel_param_t *kp);
+extern int spl_param_get_s64(char *buffer, zfs_kernel_param_t *kp);
+extern const struct kernel_param_ops spl_param_ops_s64;
+#define	spl_param_ops_S64 spl_param_ops_s64
+
+extern int spl_param_set_u64(const char *val, zfs_kernel_param_t *kp);
+extern int spl_param_get_u64(char *buffer, zfs_kernel_param_t *kp);
+extern const struct kernel_param_ops spl_param_ops_u64;
+#define	spl_param_ops_U64 spl_param_ops_u64
+
 /*
  * Declare a module parameter / sysctl node
  *
@@ -112,7 +157,8 @@ enum scope_prefix_types {
 	_Static_assert( \
 	    sizeof (scope_prefix) == sizeof (enum scope_prefix_types), \
 	    "" #scope_prefix " size mismatch with enum scope_prefix_types"); \
-	module_param(name_prefix ## name, type, perm); \
+	module_param_cb(name_prefix ## name, &spl_param_ops_ ## type, \
+	    &name_prefix ## name, perm); \
 	MODULE_PARM_DESC(name_prefix ## name, desc)
 
 /*

include/sys/arc_impl.h

@@ -985,8 +985,8 @@ extern arc_state_t	ARC_mfu;
 extern arc_state_t	ARC_mru;
 extern uint_t zfs_arc_pc_percent;
 extern uint_t arc_lotsfree_percent;
-extern unsigned long zfs_arc_min;
-extern unsigned long zfs_arc_max;
+extern uint64_t zfs_arc_min;
+extern uint64_t zfs_arc_max;
 
 extern void arc_reduce_target_size(int64_t to_free);
 extern boolean_t arc_reclaim_needed(void);
@@ -1003,7 +1003,7 @@ extern void arc_tuning_update(boolean_t);
 extern void arc_register_hotplug(void);
 extern void arc_unregister_hotplug(void);
 
-extern int param_set_arc_long(ZFS_MODULE_PARAM_ARGS);
+extern int param_set_arc_u64(ZFS_MODULE_PARAM_ARGS);
 extern int param_set_arc_int(ZFS_MODULE_PARAM_ARGS);
 extern int param_set_arc_min(ZFS_MODULE_PARAM_ARGS);
 extern int param_set_arc_max(ZFS_MODULE_PARAM_ARGS);

include/sys/dmu_zfetch.h

@@ -36,7 +36,7 @@
 extern "C" {
 #endif
 
-extern unsigned long	zfetch_array_rd_sz;
+extern uint64_t	zfetch_array_rd_sz;
 
 struct dnode;				/* so we can reference dnode */
 

include/sys/dsl_deadlist.h

@@ -84,7 +84,7 @@ typedef struct livelist_condense_entry {
 	boolean_t cancelled;
 } livelist_condense_entry_t;
 
-extern unsigned long zfs_livelist_max_entries;
+extern uint64_t zfs_livelist_max_entries;
 extern int zfs_livelist_min_percent_shared;
 
 typedef int deadlist_iter_t(void *args, dsl_deadlist_entry_t *dle);

include/sys/dsl_pool.h

@@ -57,13 +57,13 @@ struct dsl_scan;
 struct dsl_crypto_params;
 struct dsl_deadlist;
 
-extern unsigned long zfs_dirty_data_max;
-extern unsigned long zfs_dirty_data_max_max;
-extern unsigned long zfs_wrlog_data_max;
+extern uint64_t zfs_dirty_data_max;
+extern uint64_t zfs_dirty_data_max_max;
+extern uint64_t zfs_wrlog_data_max;
 extern uint_t zfs_dirty_data_max_percent;
 extern uint_t zfs_dirty_data_max_max_percent;
 extern uint_t zfs_delay_min_dirty_percent;
-extern unsigned long zfs_delay_scale;
+extern uint64_t zfs_delay_scale;
 
 /* These macros are for indexing into the zfs_all_blkstats_t. */
 #define	DMU_OT_DEFERRED	DMU_OT_NONE

include/sys/mmp.h

@@ -64,7 +64,7 @@ extern void mmp_signal_all_threads(void);
 
 /* Global tuning */
 extern int param_set_multihost_interval(ZFS_MODULE_PARAM_ARGS);
-extern ulong_t zfs_multihost_interval;
+extern uint64_t zfs_multihost_interval;
 extern uint_t zfs_multihost_fail_intervals;
 extern uint_t zfs_multihost_import_intervals;
 

include/sys/spa.h

@@ -1218,9 +1218,9 @@ int param_set_deadman_failmode(ZFS_MODULE_PARAM_ARGS);
 
 extern spa_mode_t spa_mode_global;
 extern int zfs_deadman_enabled;
-extern unsigned long zfs_deadman_synctime_ms;
-extern unsigned long zfs_deadman_ziotime_ms;
-extern unsigned long zfs_deadman_checktime_ms;
+extern uint64_t zfs_deadman_synctime_ms;
+extern uint64_t zfs_deadman_ziotime_ms;
+extern uint64_t zfs_deadman_checktime_ms;
 
 extern kmem_cache_t *zio_buf_cache[];
 extern kmem_cache_t *zio_data_buf_cache[];