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Commit 338a16ba authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

mm, thp: copying user pages must schedule on collapse 

We have encountered need_resched warnings in __collapse_huge_page_copy()
while doing {clear,copy}_user_highpage() over HPAGE_PMD_NR source pages.

mm->mmap_sem is held for write, but the iteration is well bounded.

Reschedule as needed.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1705101426380.109808@chino.kir.corp.google.com


Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 876f2946

mm/khugepaged.c

+3 −4
Original line number Diff line number Diff line
@@ -612,7 +612,8 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 
				      spinlock_t *ptl)

{

	pte_t *_pte;

	for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {

	for (_pte = pte; _pte < pte + HPAGE_PMD_NR;

				_pte++, page++, address += PAGE_SIZE) {

		pte_t pteval = *_pte;

		struct page *src_page;
@@ -651,9 +652,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 
			spin_unlock(ptl);

			free_page_and_swap_cache(src_page);

		}



		address += PAGE_SIZE;

		page++;

		cond_resched();

	}

}