linux-kernel - [PATCH 4.9 27/47] mm: add cond_resched() in gather_pte

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Message-Id: <20210415144414.326518538@linuxfoundation.org>
Date:   Thu, 15 Apr 2021 16:47:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Chen si <cici.cs@...baba-inc.com>,
        Baoyou Xie <baoyou.xie@...yun.com>,
        Wen Yang <wenyang@...ux.alibaba.com>,
        Zijiang Huang <zijiang.hzj@...baba-inc.com>
Subject: [PATCH 4.9 27/47] mm: add cond_resched() in gather_pte_stats()

From: Hugh Dickins <hughd@...gle.com>

commit a66c0410b97c07a5708881198528ce724f7a3226 upstream.

The other pagetable walks in task_mmu.c have a cond_resched() after
walking their ptes: add a cond_resched() in gather_pte_stats() too, for
reading /proc/<id>/numa_maps.  Only pagemap_pmd_range() has a
cond_resched() in its (unusually expensive) pmd_trans_huge case: more
should probably be added, but leave them unchanged for now.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052157400.13021@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Reported-by: Chen si <cici.cs@...baba-inc.com>
Signed-off-by: Baoyou Xie <baoyou.xie@...yun.com>
Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
Signed-off-by: Zijiang Huang <zijiang.hzj@...baba-inc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/proc/task_mmu.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1609,6 +1609,7 @@ static int gather_pte_stats(pmd_t *pmd,
 
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 	pte_unmap_unlock(orig_pte, ptl);
+	cond_resched();
 	return 0;
 }
 #ifdef CONFIG_HUGETLB_PAGE