vfs: Fix vop_stdis_text()

[markj]

Summary

atomic(9) primitives are documented as operating on unsigned types.
Here, we need a cast to avoid a tautological comparison.

Reported by: NetApp
Sponsored by: Klara, Inc.
Sponsored by: NetApp, Inc.
Fixes: e511bd1406fa ("vfs: fully lockless v_writecount adjustment")

[kib]

So currently ETXTBSY does not work?

[markj]

In D47672#1087062, @kib wrote:

So currently ETXTBSY does not work?

It's not that bad. It means that access(write perms) will return 0 even if the file is being executed (it should return ETXTBUSY to userspace), but VOP_ADD_WRITECOUNT will still fail.

I will write a quick regression test.

[markj]

Add a regression test

[kib]

contrib/netbsd-tests/lib/libc/sys/t_access.c

193

It might be somewhat harder to code, but use of sysctl kern.proc.pathname.-1 is more appropriate there IMO.

[markj]

Use sysctl.