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>> + /* >> + * Only consider ranges containing hugepages if those pages are >> + * smaller than the requested contiguous region. e.g.: >> + * Move 2MB pages to free up a 1GB range. >> + * Don't move 1GB pages to free up a 2MB range. >> + * >> + * This makes contiguous allocation more reliable if multiple >> + * hugepage sizes are used without causing needless movement. >> + */ >> + if (PageHuge(page)) { >> + unsigned int order; >> + >> + if (!IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION)) >> + return false; >> + >> + if (skip_hugetlb) { >> + *skipped_hugetlb = true; >> + return false; >> + } >> + >> + page = compound_head(page); >> + order = compound_order(page); >> + if ((order >= MAX_FOLIO_ORDER) || >> + (nr_pages <= (1 << order))) >> + return false; >> + >> + /* >> + * Reaching this point means we've encounted a huge page >> + * smaller than nr_pages, skip all pfn's for that page. >> + * >> + * We can't get here from a tail-PageHuge, as it implies >> + * we started a scan in the middle of a hugepage larger >> + * than nr_pages - which the prior check filters for. >> + */ >> + i += (1 << order) - 1; > > Assuming page != compound_head(page), you'd be skipping too much. It might not happen based on my reasoning[1], but feel free to punch poles. :) [1] https://lore.kernel.org/all/7EED2D83-AE17-49CB-BDB6-954793EAFDBF@nvidia.com/ > > You'd only have to skip as many pages as pages are left in this compound page. > > I think we have similar code elsewhere: see has_unmovable_pages(). > > Apart from that LGTM. Best Regards, Yan, Zi