To: "Bryan O'Sullivan" <bos@pathscale.com>
Cc: rolandd@cisco.com, gregkh@suse.de, akpm@osdl.org, davem@davemloft.net,
       linux-kernel@vger.kernel.org, openib-general@openib.org
Subject: Re: [PATCH 10 of 20] ipath - support for userspace apps using core driver
References: <71644dd19420ddb07a75.1141922823@localhost.localdomain>
	<ada4q27fban.fsf@cisco.com>
	<1141948516.10693.55.camel@serpentine.pathscale.com>
	<ada1wxbdv7a.fsf@cisco.com>
	<1141949262.10693.69.camel@serpentine.pathscale.com>
From: Roland Dreier <rdreier@cisco.com>
Date: Thu, 09 Mar 2006 16:32:46 -0800
In-Reply-To: <1141949262.10693.69.camel@serpentine.pathscale.com> (Bryan O'Sullivan's message of "Thu, 09 Mar 2006 16:07:42 -0800")
Message-ID: <adawtf3cf69.fsf@cisco.com>
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    Bryan> We're mapping some memory that the chip DMAs to into
    Bryan> userspace, so that user processes can spin on memory
    Bryan> locations without going through the kernel.  The
    Bryan> SetPageReserved hack is an attempt to stop the VM from
    Bryan> reclaiming those pages from us once a user process exits.

    Bryan> I realise that it's surely bogus, and I'd be thrilled to do
    Bryan> something correct instead.  We've tried doing both
    Bryan> SetPageReserved and get_page, but it hasn't work out too
    Bryan> well so far.

What's wrong with doing get_page()?  Surely the VM won't take pages
that you hold a reference to.

 - R.
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