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Date:      Fri, 19 Oct 2001 10:43:08 -0700 (PDT)
From:      Matthew Dillon <dillon@apollo.backplane.com>
To:        Stephen McKay <mckay@thehub.com.au>
Cc:        hackers@FreeBSD.ORG
Subject:   Re: vmiodirenable vs isofs, some proof
Message-ID:  <200110191743.f9JHh8G47321@apollo.backplane.com>
References:   <200110191315.f9JDFHS20600@dungeon.home>

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					-Matt
					Matthew Dillon 
					<dillon@backplane.com>


:About a month ago I suggested that vfs.vmiodirenable=1 and the cd9660
:file system interract badly.  I have not got absolute proof, but I
:think fairly good evidence of a causal link.
:...
:I set vfs.vmiodirenable=0 and copied again.  Exactly the same incorrect
:files.  In other words, the corruption, whatever it is, was not magically
:removed by disabling vmiodirenable while the cache remained.

    Turning off vmiodirenable does not effect things that are already
    VMIO backed, so this is expected.

:I unmounted and remounted the CD.  A copy operation was flawless at this
:point (vmiodirenable still off).
:
:I enabled vmiodirenable and the next copy was corrupt in the same manner
:(cross linked files), but the set of cross links was different than before.
:(Dang, I can't remember if I did another unmount/remount cycle before
:this copy.  Oh well.)
:
:At this point, I noticed that the cross links were actual hard links
:in my HD copies.  (I should have noticed how fast they were copying, I
:suppose).
:..
:Is this enough for you to form a theory?  Any more experiments you
:think would be worthwhile?
:
:Stephen.

    It sure looks like you can reproduce the bug at will, which is great!
    Now I need to reproduce it over here.  If you could email me an 
    ls -liaR of the CD with vmiodirenable turned off, and another ls -liaR
    of the CD with vmiodirenable turned on and the corruption present,
    I should be able to use that to burn a junk CD of my own to try to
    reproduce the bug.

					-Matt


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