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Date:      Wed, 25 Sep 2002 08:04:16 +0200
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        Jeff Roberson <jroberson@chesapeake.net>
Cc:        Robert Watson <rwatson@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/sys lockmgr.h 
Message-ID:  <13689.1032933856@critter.freebsd.dk>
In-Reply-To: Your message of "Wed, 25 Sep 2002 00:50:29 EDT." <20020925003055.L97589-100000@mail.chesapeake.net> 

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In message <20020925003055.L97589-100000@mail.chesapeake.net>, Jeff Roberson wr
ites:

>I'd like to get rid of the redundant *_fsync code.  These are probably all
>copies of ufs from different points and are broken in many different ways.

I agree.

>In terms of SMP safing vfs, it looks like struct buf needs a mutex.  I
>figured out the lock order, it would be something like:
>
>vn lock
>buf lock
>vn interlock
>buf interlock

Beware of vinum.

>Also, the namecache has to be locked down.  This is nontrivial.  An early
>attempt to use a big global lock failed.  The mount structure has not been
>locked down.  The vnode/device relationship needs some more looking.

vnode/device locking can be done in specfs, there exists no other paths
between them (I hope!)

If I manage to make DEVFS mandatory, that will be devfs instead of specfs.

>In short, there is still much to do.  As I have said before, my goal is to
>have at least the top layer of VFS out from underneath Giant by 5.0.

Can't we also put a lock per mountpoint and pull the filesystems out that
way ?

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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