illumos gate

Is this one of the issues you guys have a fix for already?

Looking at the arc_read_nolock fuction, we can see that the types for which DTrace is struggling are the const ones:

2814int
2815arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
2816 arc_done_func_t *done, void *private, int priority, int zio_flags,
2817 uint32_t *arc_flags, const zbookmark_t *zb)

From the kernel, DTrace exposes types with a module qualifier:

1. dtrace c 'dtrace -n arc_read:entry -lv' -n 'syscall::ioctl:entry/pid $target && arg1 1685352969/{ self>a = arg2; } syscall::ioctl:return/self->a/{ print(*(dtrace_argdesc_t *)copyin(self->a, sizeof (dtrace_argdesc_t))); self->a = 0; }'
   dtrace: description 'syscall::ioctl:entry' matched 2 probes
   ID PROVIDER MODULE FUNCTION NAME
   47431 fbt zfs arc_read entry

   Probe Description Attributes
   Identifier Names: Private
   Data Semantics: Private
   Dependency Class: Unknown

   Argument Attributes
   Identifier Names: Private
   Data Semantics: Private
   Dependency Class: ISA

   Argument Types
   args⁰: zio_t *
   args¹: spa_t *
   args²: blkptr_t *
   args³: arc_done_func_t *
   args⁴: void *
   args⁵: int
   args⁶: int
   args⁷: uint32_t *
   args⁸: zbookmark_t *

dtrace: pid 237776 has exited
CPU ID FUNCTION:NAME
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0
int dtargd_mapping = 0
char [128] dtargd_native = [ "zfs`zio_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x1
int dtargd_mapping = 0x1
char [128] dtargd_native = [ "zfs`spa_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x2
int dtargd_mapping = 0x2
char [128] dtargd_native = [ "const zfs`blkptr_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x3
int dtargd_mapping = 0x3
char [128] dtargd_native = [ "zfs`arc_done_func_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x4
int dtargd_mapping = 0x4
char [128] dtargd_native = [ "zfs`void *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x5
int dtargd_mapping = 0x5
char [128] dtargd_native = [ "zfs`int" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x6
int dtargd_mapping = 0x6
char [128] dtargd_native = [ "zfs`int" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x7
int dtargd_mapping = 0x7
char [128] dtargd_native = [ "zfs`uint32_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0x8
int dtargd_mapping = 0x8
char [128] dtargd_native = [ "const zfs`zbookmark_t *" ]
char [128] dtargd_xlate = [ "" ]
}
1 11564 ioctl:return dtrace_argdesc_t {
dtrace_id_t dtargd_id = 0xb947
int dtargd_ndx = 0xffffffff
int dtargd_mapping = 0x9
char [128] dtargd_native = [ "" ]
char [128] dtargd_xlate = [ "" ]
}

"const zfs`bookmark_t *" for example is just as valid a type name as "zfs`bookmark_t"