[9fans] Corrupted meta data

[9fans] Corrupted meta data

[Brian L. Stuart]

How do you remove a file with corrupted meta data?
I was in 9vx and trying to recompile a kernel so
I could get a boot file with the local method
and it locked.  After I killed 9vx and started it
up again, I can't mk because main.8 has corrupted
meta data.  check in fossilcons reports it, but
apparently can't fix it.  I also can't remove
it in fossilcons any more than I can from an rc
prompt.

Any magic?

Thanks,
BLS

Re: [9fans] Corrupted meta data

[Russ Cox]

> How do you remove a file with corrupted meta data?
> I was in 9vx and trying to recompile a kernel so
> I could get a boot file with the local method
> and it locked.  After I killed 9vx and started it
> up again, I can't mk because main.8 has corrupted
> meta data.  check in fossilcons reports it, but
> apparently can't fix it.  I also can't remove
> it in fossilcons any more than I can from an rc
> prompt.
>
> Any magic?

Can you clri the file from fossilcons?

Russ

Re: [9fans] Corrupted meta data

[Brian L. Stuart]

> Can you clri the file from fossilcons?

Unfortunately, that just reports the corrupted meta data too.
Interestingly, when I started it up this morning, the check
didn't report an error with it.  But then after trying to
access it, check now reports:
error: could not unpack meta block: /active/sys/src/9/pc[3]: corrupted meta data
What does the 3 refer to?  The 3rd block of the pc directory,
maybe?

The pc directory itself seems fine.  I can see everything
else there.  main.8 doesn't show up in an lc.  If my current
directory is elsewhere and I try to ls -l /n/fossil/sys/src/9/pc/main.8,
it comes up as not existing.  But if my current directory
is /n/fossil/sys/src/9/pc, then I get the corrupted meta
data error.

I haven't changed anything in that directory, so in principle,
I guess i could blow away the directory (clri if necessary)
and copy it all back from a venti snapshot.  But before I
do that, I'd like to see if a more direct recovery is possible.

BTW, I had it lock up again this morning.  I've noticed that
when it does, it uses 100% of the CPU.  It's acting like
it's stuck in a spin lock.  I can't say for sure, so this
may be a red herring, but it has seemed that every time
it's locked up, it's been when doing I/O to the sdloop
device.

Thanks,
BLS

Re: [9fans] Corrupted meta data

[Russ Cox]

> error: could not unpack meta block: /active/sys/src/9/pc[3]: corrupted meta data
> What does the 3 refer to?  The 3rd block of the pc directory,
> maybe?

Yes.

Your best bet is probably to clri /active/sys/src/9/pc
and not look back.

> BTW, I had it lock up again this morning.  I've noticed that
> when it does, it uses 100% of the CPU.  It's acting like
> it's stuck in a spin lock.  I can't say for sure, so this
> may be a red herring, but it has seemed that every time
> it's locked up, it's been when doing I/O to the sdloop
> device.

Locks on Plan 9 don't use 100% of the cpu.
Even spin locks start sleeping after enough
contention.

It's more likely in a bad loop somewhere.
Is it repeatedly doing I/O during the 100% cpu?

Russ

Re: [9fans] Corrupted meta data

[Brian L. Stuart]

> Your best bet is probably to clri /active/sys/src/9/pc
> and not look back.

clri /active/sys/src/9/pc
no_lb_mode = 1 ;

It is happy now.

> It's more likely in a bad loop somewhere.
> Is it repeatedly doing I/O during the 100% cpu?

I don't honestly know.  Next time it happens, I'll
check and see.

BLS

Re: [9fans] Corrupted meta data

[Brian L. Stuart]

> It's more likely in a bad loop somewhere.
> Is it repeatedly doing I/O during the 100% cpu?

It just locked again.  Here's what I'm seeing.  In
top, the first thread is using 100% of the CPU and
all the other threads are in the S state with no run
time.  I don't see any indications either in vmstat
or in load from p9p that there is any I/O going
on to speak of or an unusual number of system calls
being issued.  If there's anything else I can
check, let me know.

Thanks,
BLS