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Date:      Sun, 29 Aug 1999 23:51:49 -0700 (PDT)
From:      Matthew Dillon <dillon@apollo.backplane.com>
To:        Greg Lehey <grog@lemis.com>
Cc:        Bernd Walter <ticso@cicely.de>, Mike Smith <mike@smith.net.au>, Parag Patel <parag@cgt.com>, freebsd-current@FreeBSD.ORG
Subject:   Re: 4.0-CURRENT SMP crash with vinum raid-5 and softupdates
Message-ID:  <199908300651.XAA10557@apollo.backplane.com>
References:  <199908292224.PAA15435@dingo.cdrom.com> <199908292348.QAA07774@apollo.backplane.com> <19990830075311.A30271@cicely8.cicely.de> <199908300559.WAA09987@apollo.backplane.com> <19990830160155.G13904@freebie.lemis.com> <199908300636.XAA10399@apollo.backplane.com> <19990830161633.J13904@freebie.lemis.com>

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:>>
:>> What's a pbuf?
:>
:>     Sorry, it isn't a pbuf.
:
:OK.  But what is a pbuf?  I've never heard that term before.

    A pbuf is a 'physical buffer'.  Specifically, it is a struct buf 
    structure used by low level device drivers to issue their own I/O.

    pbuf's are used by a number of modules.  For example, they are used
    by the VFS clustering code to create a 'super buffer' that encompasses
    a number of smaller filesystem buffers.  They are also used by the swapper
    to initiate low level disk I/O, and the VN device for same.

:>     That could cause long term problems but is neither here nor
:>     there at the moment, we'll deal with it later.
:
:I discussed it with Kirk, who wasn't too concerned.  Do you have other
:issues?
:
:Greg

    Naw, when we finally fix the struct buf's we'll deal with everything
    that uses them.  As long as you do not special case structural fields
    (use them in a manner for which they were not designed), there shouldn't
    be any problem.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>


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