Date: Tue, 28 Dec 1999 02:10:23 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Proposed patch to fix VN device (again) Message-ID: <9890.946343423@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 27 Dec 1999 17:01:55 PST." <199912280101.RAA34874@apollo.backplane.com>
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In message <199912280101.RAA34874@apollo.backplane.com>, Matthew Dillon writes: > First, you are confusing the underlying swap devices that we swapon on > with the parent swap device that controls them. The parent swap device > needs to have a dev_t - it does not currently have one, and this is > the entry point that the buffers are going into. The underlying swap > devices *already* have a dev_t. My kernel crashes on a NULL bp->b_dev. > In fact, it also crashes on a NULL vp->v_rdev. And where in the code does this crash happen ? > Second, the clustering done above the VN device is done by the > filesystem and has no understanding of whether the underlying media > controlled by the VN device can itself be clustered in the same way. > When using swap as backing store what may appear to be clusterable > by the filesystem may actually *NOT* be clusterable when you get into > the swap device due to potentially non-contiguous mappings as well > as border-crossings between interleaved swap devices. So you need to cluster all the way through the VN device ? Obviously clustering on just one side will not buy you anything. Tough luck... It sounds more and more like the mistake here is for VN to have a specfs VOP vector on top, I think it needs its own VOP vector so it can get hold of the VOP_BMAP function... -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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