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Date:      Tue, 2 Oct 2001 19:24:18 -0700 (PDT)
From:      Matt Dillon <dillon@earth.backplane.com>
To:        Peter Wemm <peter@wemm.org>
Cc:        Ian Dowse <iedowse@maths.tcd.ie>, Yevgeniy Aleynikov <eugenea@infospace.com>, ache@FreeBSD.ORG, mckusick@mckusick.com, Ken Pizzini <kenp@infospace.com>, hackers@FreeBSD.ORG
Subject:   Re: patch #3 (was Re: bleh. Re: ufs_rename panic) 
Message-ID:  <200110030224.f932OIO62159@earth.backplane.com>
References:   <20011003021435.0EE48380A@overcee.netplex.com.au>

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:
:Matt Dillon wrote:
:>     Here is the latest patch I have.  It appears to completely solve the
:>     problem.  I have shims in unionfs and nfs for the moment.
:
:This seems rather large compared to Ian Dowse's version..  Are you sure that
:you're doing this the right way?  Adding a whole new locking mechanism
:when the simple VRENAME flag to be enough seems like a bit of overkill..

    Ian's doesn't fix any of the filesystem semantics bugs, it only prevents
    the panic from occuring.  For example, if you have two hardlinked files
    residing in different directories both get renamed simultaniously, one
    of the rename()s can fail even though there is no conflict.  If you
    have a simultanious rmdir() and rename(), the rename() can return an
    unexpected error code.  And so forth.

    If you remove the filesystem semantics fixes from my patch you 
    essentially get Ian's patch except that I integrated the vnode flag
    in namei/lookup whereas Ian handles it manually in the syscall code.

    Also, Ian's patch only effects system calls.  It doesn't do the same
    fixes for nfs (server side) or unionfs.

						-Matt

:I'm not criticizing your work, I am just wondering if you have considered
:Ian's work and feel that it is wrong or the wrong direction..  His certainly
:appears more elegant than yours so I want to understand why you feel yours
:is better than his.
:
:freebsd-hackers
:Message-id: <200110022152.aa36964@salmon.maths.tcd.ie>
:
:Cheers,
:-Peter
:--
:Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
:"All of this is for nothing if we don't go to the stars" - JMS/B5

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