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thp: handle file pages in split_huge_pmd()

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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>
This commit is contained in:
Kirill A. Shutemov 2016-07-26 15:25:37 -07:00 committed by Linus Torvalds
parent b5072380eb
commit d21b9e57c7
1 changed files with 10 additions and 2 deletions
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12
mm/huge_memory.c
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@ -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);