Messages in this thread | | | Date | Mon, 3 Mar 2003 17:56:57 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: [patch] remap-file-pages-2.5.63-A0 |
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On Mon, 3 Mar 2003, Linus Torvalds wrote:
> > the attached patch, against BK-curr, is a preparation to make > > remap_file_pages() usable on swappable vmas as well. When 'swapping out' > > shared-named mappings the page offset is written into the pte. > > > > it takes one bit from the swap-type bits, otherwise it does not change the > > pte layout - so it should be easy to adapt any other architecture to this > > change as well. (this patch does not introduce the protection-bits-in-pte > > approach used in my previous patch.) > > One question: Why? > > What's wrong with just using the value we use now (0), and just > calculating the page from the vma/offset information? Why hide the > offset in the page tables, when there is no need for it?
you mean why in the normal, linear mapping case? No reason, just for testing. At zap-time we could test whether that pte is linear or not, and only store it in the swap entry as a file-pte if it's nonlinear.
for swappable sys_file_remap_pages() support it's necessary though, as they break up the linear mapping without splitting up the vma into zillions of pieces.
Ingo
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