Commit 338a16ba authored May 12, 2017 by David Rientjes Committed by Linus Torvalds May 12, 2017

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: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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();
		}
		}

Admin message