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[Xen-devel] Re: [RFC PATCH 30/35] Add generic_page_range() function
Chris Wright wrote:
Add a new mm function generic_page_range() which applies a given function to every pte in a given virtual address range in a given mm structure. This is a generic alternative to cut-and-pasting the Linux idiomatic pagetable walking code in every place that a sequence of PTEs must be accessed. Although this interface is intended to be useful in a wide range of situations, it is currently used specifically by several Xen subsystems, for example: to ensure that pagetables have been allocated for a virtual address range, and to construct batched special pagetable update requests to map I/O memory (in ioremap()).
I raised the idea when we were tossing around ideas for the page table walking crapectomy. Of course it was rejected due to use of the indirect function, however I gues it makes sense for code outside mm/ Couple of issues with the current code though: firstly, the name. secondly, I think you confuse our (confusing) terminology: the page that holds pte_ts is not the pte_page, the pte_page is the page that a pte points to lastly, you don't allow any control over the type of pages that are walked: this could well be unusably slow for some cases. At least you should proably design the interface so we can iterate over present, not present, all, etc so it becomes widely usable. Normally I'd say to wait until users come up but in this case the function isn't a speed demon anyway, and you also don't want to give people any excuses not to use it. -- SUSE Labs, Novell Inc.Send instant messages to your online friends http://au.messenger.yahoo.com
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