Commit d21b9e57 authored Jul 26, 2016 by Kirill A. Shutemov Committed by Linus Torvalds Jul 26, 2016

thp: handle file pages in split_huge_pmd()

Splitting THP PMD is simple: just unmap it as in DAX case. This way we
can avoid memory overhead on page table allocation to deposit.

It's probably a good idea to try to allocation page table with
GFP_ATOMIC in __split_huge_pmd_locked() to avoid refaulting the area,
but clearing pmd should be good enough for now.

Unlike DAX, we also remove the page from rmap and drop reference.
pmd_young() is transfered to PageReferenced().

Link: http://lkml.kernel.org/r/1466021202-61880-15-git-send-email-kirill.shutemov@linux.intel.com

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b5072380

mm/huge_memory.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -2987,10 +2987,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct vma, pmd_t pmd,

		count_vm_event(THP_SPLIT_PMD);

		if (vma_is_dax(vma)) {
		pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
		if (!vma_is_anonymous(vma)) {
		_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
		if (is_huge_zero_pmd(_pmd))
		put_huge_zero_page();
		if (vma_is_dax(vma))
		return;
		page = pmd_page(_pmd);
		if (!PageReferenced(page) && pmd_young(_pmd))
		SetPageReferenced(page);
		page_remove_rmap(page, true);
		put_page(page);
		add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
		return;
		} else if (is_huge_zero_pmd(*pmd)) {
		return __split_huge_zero_page_pmd(vma, haddr, pmd);