On Mon, Jul 16, 2018 at 10:00:48AM -0700, Dan Williams wrote: > The foreach_order_pgoff() helper takes advantage of the ability to > insert multi-order entries into a radix. It is currently used by > devm_memremap_pages() to minimize the number of entries in the pgmap > radix. Instead of dividing a range by a constant power-of-2 sized unit > and inserting an entry for each unit, it determines the maximum > power-of-2 sized entry (subject to alignment offset) that can be > inserted at each iteration. > > Up-level this helper so it can be used for populating other radix > instances. For example asynchronous-memmap-initialization-thread lookups > arriving in a follow on change. Hopefully by the time you're back, I'll have this code replaced with the XArray. Here's my proposed API: old = xa_store_range(xa, first, last, ptr, GFP_KERNEL); and then you'd simply use xa_for_each() as an iterator. You'd do one iteration for each range in the XArray, not for each entry occupied. So there's a difference between: xa_store(xa, 1, ptr, GFP_KERNEL); xa_store(xa, 2, ptr, GFP_KERNEL); xa_store(xa, 3, ptr, GFP_KERNEL); and xa_store_range(xa, 1, 3, ptr, GFP_KERNEL); index = 0; i = 0; xa_for_each(xa, p, index, ULONG_MAX, XA_PRESENT) i++; will return i = 3 for the first case and i = 1 for the second.
