Date: Sat, 9 Jun 2001 18:01:12 -0400 From: Alfred Perlstein <bright@rush.net> To: Matt Dillon <dillon@earth.backplane.com> Cc: Peter Wemm <peter@wemm.org>, tlambert2@mindspring.com, "Patrick W. Penzias Dirks" <pwd@apple.com>, FreeBSD-FS@FreeBSD.ORG, FreeBSD-Arch@FreeBSD.ORG Subject: Re: Support for pivot_root-like system call? Message-ID: <20010609180111.M1832@superconductor.rush.net> In-Reply-To: <200106091651.f59GpgF07875@earth.backplane.com>; from dillon@earth.backplane.com on Sat, Jun 09, 2001 at 09:51:42AM -0700 References: <3B2096AB.309B2D14@mindspring.com> <20010608153011.D7AF1380C@overcee.netplex.com.au> <20010608130128.E1832@superconductor.rush.net> <200106091651.f59GpgF07875@earth.backplane.com>
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* Matt Dillon <dillon@earth.backplane.com> [010609 12:51] wrote: > > :The cache coherency bugs are not fixed for all cases, being able to > :ask the underlying filesystem for the vm_object does not solve the > :problem. > : > :What if i have a stacking layer where each page alternates > :between two files that i'm stacked on top of? > : > :Passing the vm_object back doesn't work for this. Unless something > :else has been done. > : > :-Alfred Perlstein [alfred@freebsd.org] > > Well, I suppose a vm_map would solve this, though for the specific > alternating case (or a RAID configuration of some sort) it would be > really expensive to do with a vm_map. We would need some kind of > synthesized translation capability in the vm_map to make it efficient. I think the proper method would be to use GET/PUTPAGES, where a GETPAGES would require a subsequent PUT/UNLOCKPAGES. The problem is that a bunch of code digs into the backing data of the vm and vfs structures without bothering to query the vm/vfs and ask if it's ok (besideds respecting locks, and even that's not always true). -- -Alfred Perlstein [alfred@freebsd.org] Instead of asking why a piece of software is using "1970s technology," start asking why software is ignoring 30 years of accumulated wisdom. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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