From owner-freebsd-hackers@FreeBSD.ORG  Thu Apr 22 19:53:36 2004
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Date: Thu, 22 Apr 2004 19:53:35 -0700 (PDT)
From: Matthew Dillon <dillon@apollo.backplane.com>
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To: Stephan Uphoff <ups@tree.com>,
	Julian Elischer <julian@elischer.org>
References: <200404230103.VAA18066@stups.com>
cc: hackers@freebsd.org
Subject: Re: how to flush out cache.? 
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    (taking hackers off to reduce noise)

    I think all that needs to happen to fix this problem is to call
    vm_object_page_remove() with the clean_only flag set to TRUE instead
    of FALSE.

    Wired pages, e.g. pages in the buffer cache, will not be removed, but
    that's ok because memory-mapped pages tend to not get buffer cache
    associations until the system decides to flush the pages.

    Fixing the buffer cache issue would have to occur in the actual
    VNODE I/O operation, which would only occur for VM_PROT_WRITE operations,
    which I think is just fine.  The I/O op will have access to the
    invalidation request as a flag and it can simply do what NFS does which
    is flag the buffer to be destroyed on I/O completion.  If that is done,
    then by the time we get to the second pass the buffer should be gone and
    the vm_object_page_remove() function will find a normal, unwired page and
    properly remove it.

    I'll test this out in DragonFly and email Stephan and Julian a followup.

						-Matt