Date: Thu, 7 Jan 1999 22:08:22 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Alfred Perlstein <bright@hotjobs.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: (mfs idea) Re: questions/problems with vm_fault() in Stable Message-ID: <199901080608.WAA37994@apollo.backplane.com>
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:The buffer is just marked as dirty so that the FFS doesn't overwrite it.
:MFS _must_ reclaim them into it's own address space to avoid being
:overwritten.
:
:Since i assume that when a buffer is flushed it should then be free
:you have to 'give something back'
:...
I think I understand. The problem is that the system has no clue that
the vm_page needs to be returned to MFS. Once MFS gives the page away,
that is the end of the matter as far as the system is concerned.
Now, of course, we could *make* the system aware that it needs to do
something special with the page -- but if we do not create a generally
useful mechanism it would be nothing more then a bad hack. Any mechanism
that we would create to handle this situation would have to handle
moving the page across an arbitrary number of VFS layers, and then either
handed back down through the same layers or handed back to the original
layer... we cannot assume it will be moved across only two VFS layers.
Essentially, the vm_alias mechanism that I described would be able to
handle this sort of situation. Could we hack in something simpler?
Probably, but it might not be generic enough to be useable in other
situations.
-Matt
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications & God knows what else.
<dillon@backplane.com> (Please include original email in any response)
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