Re: [9fans] Using cwfs

[cinap_lenrek@gmx.de]

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check if you have the latest version of /sys/src/cmd/cwfs/wren.c
from sources.

the old wrenread()/wrenwrite() used non atomic seek/read/write
sequence that leaves a window for another process moving the file offset
arround under you. this caused wired checktag errors when i tried
to copy my main fileserver to another freshly created cwfs.

--
cinap

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From: Akshat Kumar <akumar@mail.nanosouffle.net>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] Using cwfs
Date: Mon, 24 Aug 2009 16:38:51 -0400
Message-ID: <fe41879c0908241338o309657d0t7a9ab0702891055a@mail.gmail.com>

I believe there may be an inconsistency somewhere
in the dump records themselves. When I tried to
copy back the file from the dump, into the active
fs, after a while of copying, cwfs panicked with:

main grow ...
    tag = 5/23; expected 757/7 -- not flushed
panic: cwio: checktag c bucket
halted ...

So I ran a `check' after starting up cwfs again, but
nbad = 0
nqbad = 0
although
nmiss = 224455
and still I don't know whether the nmiss is something
that ought to be fixed, or how.
Anyways, the check doesn't seem to reveal any
tag inconsistencies - any suggestions for further tests
in revealing what might be the issue? Or possible
fixes?


Thanks,
ak