From: David Rientjes <rientjes@google.com>
Date: Fri, 23 Jun 2017 22:08:38 +0000 (-0700)
Subject: mm, thp: remove cond_resched from __collapse_huge_page_copy
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=c891d9f6bf2a78c9c657656872a60807820db4c8;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

mm, thp: remove cond_resched from __collapse_huge_page_copy

This is a partial revert of commit 338a16ba1549 ("mm, thp: copying user
pages must schedule on collapse") which added a cond_resched() to
__collapse_huge_page_copy().

On x86 with CONFIG_HIGHPTE, __collapse_huge_page_copy is called in
atomic context and thus scheduling is not possible.  This is only a
possible config on arm and i386.

Although need_resched has been shown to be set for over 100 jiffies
while doing the iteration in __collapse_huge_page_copy, this is better
than doing

	if (in_atomic())
		cond_resched()

to cover only non-CONFIG_HIGHPTE configs.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1706191341550.97821@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 945fd1ca49b5..df4ebdb2b10a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -652,7 +652,6 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
 			spin_unlock(ptl);
 			free_page_and_swap_cache(src_page);
 		}
-		cond_resched();
 	}
 }