Zfs.exports - Revision history

Lundman: /* zfs.exports */

2021-04-15T02:48:36Z

‎zfs.exports

Lundman: /* zfs.exports */

2021-04-14T08:46:13Z

‎zfs.exports

Lundman at 09:32, 13 April 2021

2021-04-13T09:32:09Z

Lundman: /* zfs.exports */

2021-04-13T09:17:04Z

‎zfs.exports

Lundman: /* zfs.exports */

2021-04-13T09:09:14Z

‎zfs.exports

Lundman at 09:08, 13 April 2021

2021-04-13T09:08:26Z

Lundman: Created page with " == zfs.exports == We used to list functions from XNU's private.exports, and using a codeless kext let's us call them. With 2.0 re-port, we no longer use zfs.exports, but it ..."

2021-04-13T09:07:10Z

Created page with " == zfs.exports == We used to list functions from XNU's private.exports, and using a codeless kext let's us call them. With 2.0 re-port, we no longer use zfs.exports, but it ..."

New page

== zfs.exports ==

We used to list functions from XNU's private.exports, and using a codeless kext let's us call them. With
2.0 re-port, we no longer use zfs.exports, but it would be nice to have some calls back.

_cpu_number

Comment: Used to spread out lock contention, we use the lock at active-core-index
Alternative: None, only using [0]
Result: performance penalty

_fp_lookup
_fp_drop
_fp_drop_written
_fo_read
_fo_write

Comment: "zfs send" and "zfs recv" will either do IO on a file (vnode) or pipe. There is no
way to do IO on a pipe in a kext without private.exports.
Alternative: userland will mknod /tmp/.pipe, spawn a relay helper, and open(/tmp/.pipe) which passes
a vnode to kernel. This works, but is complicated, both setting up pipes, and cleaning up. Especially with
SIGINT involved. It would be nice to do pipe IO in kext.
Result: Complicated code, but already working. Pipes love to deadlock, so corner cases could exist.

_hostname

Comment: uses hostname for diagnostic messages, history logs and multihost mounting (failover would
display which host stopped and which host took over.)
Alternative: None. Some work arounds could be done, like passing hostname from userland. Hashing hostid as string.
Result: user confusion to which host was in use. (Until work around)

_virtual_space_start
_virtual_space_end
_vm_page_free_wanted
_vm_page_free_count
_vm_page_free_min
_vm_page_speculative_count
_vm_pool_low

Comment: used to detect memory pressure well before jettison.
Alternative: implement with optional hardcap limit, mach_vm_pressure_level_monitor and
mach_vm_pressure_monitor.
Result: Hopefully can be made to run the same, without stutter.

_VFS_ROOT
_rootvnode

Comment: Used with boot to know when root has been mounted. vfs_rootvnode()
does not check for NULL and will just panic.
Alternative: None, It would be better if vfs_rootvnode() would not panic.
Result: No boot support.

_cache_purgevfs

Comment: Used to drop all cache entires for a mount, for example "zfs rollback".
Alternative: Implemented with vnode_iterate(cache_purge_negatives() cache_purge()). Working.
Result: None. Happy to live without.

_vfs_context_kernel
Comment: Used at times when it is correct to use kernel context. Like hfs.kext does as well.
Alternative: None
Result: No idea, seems to run any way

_vnode_lookupat
Comment: Look up a "file" from a directory is useful.
Alternative: Implemented with vn_getpath() strcat("/file" and vnode_lookup().
Result: Some string work in kernel, not "that" expensive. Still, vnode_lookupat would be nice.

_kvtophys
__mh_execute_header
_gLoadedKextSummaries

Comment: Used only in debug/panic. To lookup symbols when dumping stack.
Alternatives: None, and even harder with arm64's PAC. Can live without.
Result: Stack dumps with addresses only, use lldb to resolve symbols.

_kauth_cred_getgroups

Comment: Getting a list of other groups, to check for permission.
Alternative: Get list of permissions, and compare with _kauth_cred_ismember_gid
Result: No difference, just #ifdef in upstream

_cpuid_info
Comment: Get CPU features, sse, avx, aes etc.
Alternative: inline asm { cpuid }, and create own bit checks.
Result: None, just a shame to not be able to use XNU existing API.

@@ Line 95: / Line 95: @@
   Result: None, just a shame to not be able to use XNU existing API.
   thread_set_cpulimit
   throttle_set_thread_io_policy
-  rottegift said something about something
+  Comment: throttle_set_io_policy() lets us passivate our threads so that if they generate IOKit calls they do not get

← Older revision		Revision as of 09:17, 13 April 2021
Line 88:		Line 88:
	Alternative: inline asm { cpuid }, and create own bit checks.		Alternative: inline asm { cpuid }, and create own bit checks.
	Result: None, just a shame to not be able to use XNU existing API.		Result: None, just a shame to not be able to use XNU existing API.
		+
		+	thread_set_cpulimit
		+	throttle_set_thread_io_policy
		+
		+	rottegift said something about something

@@ Line 5: / Line 5: @@
 .0 re-port, we no longer use zfs.exports, but it would be nice to have some calls back.
-  _cpu_number
+  _cpu_number ARM64
-−
   Comment: Used to spread out lock contention, we use the lock at active-core-index
-  Alternative: None, only using [0]
+  Alternative: None, only using [0] on arm64.
   Result: performance penalty

@@ Line 23: / Line 23: @@
   SIGINT involved. It would be nice to do pipe IO in kext.
   Result: Complicated code, but already working. Pipes love to deadlock, so corner cases could exist.
   _hostname

@@ Line 18: / Line 18: @@
   Comment: "zfs send" and "zfs recv" will either do IO on a file (vnode) or pipe. There is no
-way to do IO on a pipe in a kext without private.exports.
+ way to do IO on a pipe in a kext without private.exports.
   Alternative: userland will mknod /tmp/.pipe, spawn a relay helper, and open(/tmp/.pipe) which passes
-a vnode to kernel. This works, but is complicated, both setting up pipes, and cleaning up. Especially with
+ a vnode to kernel. This works, but is complicated, both setting up pipes, and cleaning up. Especially with
-SIGINT involved. It would be nice to do pipe IO in kext.
+ SIGINT involved. It would be nice to do pipe IO in kext.
   Result: Complicated code, but already working. Pipes love to deadlock, so corner cases could exist.
@@ Line 27: / Line 27: @@
   Comment: uses hostname for diagnostic messages, history logs and multihost mounting (failover would
-display which host stopped and which host took over.)
+ display which host stopped and which host took over.)
   Alternative: None. Some work arounds could be done, like passing hostname from userland. Hashing hostid as string.
   Result: user confusion to which host was in use. (Until work around)
@@ Line 41: / Line 41: @@
   Comment: used to detect memory pressure well before jettison.
   Alternative: implement with optional hardcap limit, mach_vm_pressure_level_monitor and
-mach_vm_pressure_monitor.
+ mach_vm_pressure_monitor.
   Result: Hopefully can be made to run the same, without stutter.
@@ Line 48: / Line 48: @@
   Comment: Used with boot to know when root has been mounted. vfs_rootvnode()
-does not check for NULL and will just panic.
+ does not check for NULL and will just panic.
   Alternative: None, It would be better if vfs_rootvnode() would not panic.
   Result: No boot support.