Date: 01 Jun 1999 09:14:49 +0300 From: Ville-Pertti Keinonen <will@iki.fi> To: Ustimenko Semen <semen@iclub.nsu.ru> Cc: current@freebsd.org Subject: Re: FS Driver writing tactic Message-ID: <864skse9ba.fsf@not.demophon.com> In-Reply-To: Ustimenko Semen's message of "1 Jun 1999 00:50:28 %2B0300" References: <Pine.BSF.4.05.9906010444460.70646-100000@iclub.nsu.ru.newsgate.clinet.fi>
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Ustimenko Semen <semen@iclub.nsu.ru> writes: > Is this a good tactic to write working VOP_BMAP and > VOP_STRATEGY handlers, and implement VOP_READ and VOP_WRITE > via bread and bwrite of own vnodes? Considering that that's how the primary filesystem layers (ufs/ffs) do it, it should be fair to assume that it's at least a reasonable way of doing things. If you *don't* do it that way...the alternative (unless you want to bypass the cache) is to bread/bwrite the underlying device from VOP_READ/VOP_WRITE, which avoids a layer of indirection when the cache doesn't get hit (not very useful). The problem is, you're not going to be able to associate cached data with vm_objects usefully because you're buffers are associated with the underlying (device) vnode rather than the file vnode. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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