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

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_per_txg_dirty_frees_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, since the values would not be written to the
correct locations. 32-bit FreeBSD was unaffected because its sysctl code
correctly treated this as a `uint64_t`.

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.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
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>
Closes #13984
Closes #14004

module/zfs/dsl_pool.c

@@ -99,8 +99,8 @@
  * capped at zfs_dirty_data_max_max.  It can also be overridden with a module
  * parameter.
  */
-unsigned long zfs_dirty_data_max = 0;
-unsigned long zfs_dirty_data_max_max = 0;
+uint64_t zfs_dirty_data_max = 0;
+uint64_t zfs_dirty_data_max_max = 0;
 uint_t zfs_dirty_data_max_percent = 10;
 uint_t zfs_dirty_data_max_max_percent = 25;
 
@@ -109,7 +109,7 @@ uint_t zfs_dirty_data_max_max_percent = 25;
  * when approaching the limit until log data is cleared out after txg sync.
  * It only counts TX_WRITE log with WR_COPIED or WR_NEED_COPY.
  */
-unsigned long zfs_wrlog_data_max = 0;
+uint64_t zfs_wrlog_data_max = 0;
 
 /*
  * If there's at least this much dirty data (as a percentage of
@@ -138,7 +138,7 @@ uint_t zfs_delay_min_dirty_percent = 60;
  * Note: zfs_delay_scale * zfs_dirty_data_max must be < 2^64, due to the
  * multiply in dmu_tx_delay().
  */
-unsigned long zfs_delay_scale = 1000 * 1000 * 1000 / 2000;
+uint64_t zfs_delay_scale = 1000 * 1000 * 1000 / 2000;
 
 /*
  * This determines the number of threads used by the dp_sync_taskq.
@@ -1465,20 +1465,20 @@ ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max_percent, UINT, ZMOD_RD,
 ZFS_MODULE_PARAM(zfs, zfs_, delay_min_dirty_percent, UINT, ZMOD_RW,
 	"Transaction delay threshold");
 
-ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max, ULONG, ZMOD_RW,
+ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max, U64, ZMOD_RW,
 	"Determines the dirty space limit");
 
-ZFS_MODULE_PARAM(zfs, zfs_, wrlog_data_max, ULONG, ZMOD_RW,
+ZFS_MODULE_PARAM(zfs, zfs_, wrlog_data_max, U64, ZMOD_RW,
 	"The size limit of write-transaction zil log data");
 
 /* zfs_dirty_data_max_max only applied at module load in arc_init(). */
-ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max, ULONG, ZMOD_RD,
+ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_max_max, U64, ZMOD_RD,
 	"zfs_dirty_data_max upper bound in bytes");
 
 ZFS_MODULE_PARAM(zfs, zfs_, dirty_data_sync_percent, UINT, ZMOD_RW,
 	"Dirty data txg sync threshold as a percentage of zfs_dirty_data_max");
 
-ZFS_MODULE_PARAM(zfs, zfs_, delay_scale, ULONG, ZMOD_RW,
+ZFS_MODULE_PARAM(zfs, zfs_, delay_scale, U64, ZMOD_RW,
 	"How quickly delay approaches infinity");
 
 ZFS_MODULE_PARAM(zfs, zfs_, sync_taskq_batch_pct, INT, ZMOD_RW,