+ mm-thp-copying-user-pages-must-schedule-on-collapse.patch added to -mm tree

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The patch titled
     Subject: mm, thp: copying user pages must schedule on collapse
has been added to the -mm tree.  Its filename is
     mm-thp-copying-user-pages-must-schedule-on-collapse.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-copying-user-pages-must-schedule-on-collapse.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-copying-user-pages-must-schedule-on-collapse.patch

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------------------------------------------------------
From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/khugepaged.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff -puN mm/khugepaged.c~mm-thp-copying-user-pages-must-schedule-on-collapse mm/khugepaged.c
--- a/mm/khugepaged.c~mm-thp-copying-user-pages-must-schedule-on-collapse
+++ a/mm/khugepaged.c
@@ -612,7 +612,8 @@ static void __collapse_huge_page_copy(pt
 				      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(pt
 			spin_unlock(ptl);
 			free_page_and_swap_cache(src_page);
 		}
-
-		address += PAGE_SIZE;
-		page++;
+		cond_resched();
 	}
 }
 
_

Patches currently in -mm which might be from rientjes@xxxxxxxxxx are

mm-thp-copying-user-pages-must-schedule-on-collapse.patch
fs-epoll-short-circuit-fetching-events-if-thread-has-been-killed.patch

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