nfs: stop using SAVESTART

[mjg]

Summary

Only the name is wanted which is already always provided.

[rmacklem]

It crashes almost instantly for NFSv4.
Basically, it does a vrele(ni_startdir);

Now, if you got rid of all the vrele(ni_startdir) calls (there are quite
a few of them), would it work ok?
I honestly do not know.

Here's the crash info, in case you are interested:
Fatal trap 12: page fault while in kernel mode

cpuid = 0; apic id = 00

fault virtual address = 0x1ac

fault code = supervisor write data, page not present

instruction pointer = 0x20:0xffffffff80cf0e2c

stack pointer = 0x28:0xfffffe00cd080c80

frame pointer = 0x28:0xfffffe00cd080c80

code segment = base 0x0, limit 0xfffff, type 0x1b

			= DPL 0, pres 1, long 1, def32 0, gran 1

processor eflags = interrupt enabled, resume, IOPL = 0

current process = 990 (nfsd: master)

trap number = 12

panic: page fault

cpuid = 0

time = 1646870012

KDB: stack backtrace:

db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00cd080a40

vpanic() at vpanic+0x17f/frame 0xfffffe00cd080a90

panic() at panic+0x43/frame 0xfffffe00cd080af0

trap_fatal() at trap_fatal+0x385/frame 0xfffffe00cd080b50

trap_pfault() at trap_pfault+0xab/frame 0xfffffe00cd080bb0

calltrap() at calltrap+0x8/frame 0xfffffe00cd080bb0

• trap 0xc, rip = 0xffffffff80cf0e2c, rsp = 0xfffffe00cd080c80, rbp = 0xfffffe00cd080c80 ---

vrele() at vrele+0xc/frame 0xfffffe00cd080c80

nfsvno_open() at nfsvno_open+0x143/frame 0xfffffe00cd080d00

nfsrvd_open() at nfsrvd_open+0xe2b/frame 0xfffffe00cd0811d0

nfsrvd_dorpc() at nfsrvd_dorpc+0x1319/frame 0xfffffe00cd081400

nfssvc_program() at nfssvc_program+0x5f9/frame 0xfffffe00cd0815e0

svc_run_internal() at svc_run_internal+0xa42/frame 0xfffffe00cd081710

svc_run() at svc_run+0x230/frame 0xfffffe00cd081770

nfsrvd_nfsd() at nfsrvd_nfsd+0x338/frame 0xfffffe00cd0818d0

nfssvc_nfsd() at nfssvc_nfsd+0x4af/frame 0xfffffe00cd081de0

sys_nfssvc() at sys_nfssvc+0xae/frame 0xfffffe00cd081e00

amd64_syscall() at amd64_syscall+0x12e/frame 0xfffffe00cd081f30

fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe00cd081f30

• syscall (155, FreeBSD ELF64, sys_nfssvc), rip = 0x2011bd332c0a, rsp = 0x7fffffffe4d8, rbp = 0x7fffffffe770 ---

KDB: enter: panic

[mjg]

Sorry about previous instance, this is a new & tested patch. Can you validate yourself just in case?

[rmacklem]

I will test this, but I probably don't have time until
around next weekend.

[rmacklem]

Looks fine to me now and tested out ok.

sys/fs/nfsserver/nfs_nfsdserv.c

1326

Very minor nit..it looks a little weird to have LOCKPARENT
in brackets, but it is up to you whether or not you leave it
that way.