Commit 3db19aa3 authored Dec 15, 2020 by Alex Shi Committed by Linus Torvalds Dec 15, 2020

mm/mlock: remove lru_lock on TestClearPageMlocked

In the func munlock_vma_page, comments mentained lru_lock needed for
serialization with split_huge_pages.  But the page must be PageLocked as
well as pages in split_huge_page series funcs.  Thus the PageLocked is
enough to serialize both funcs.

Further more, Hugh Dickins pointed: before splitting in
split_huge_page_to_list, the page was unmap_page() to remove pmd/ptes
which protect the page from munlock.  Thus, no needs to guard
__split_huge_page_tail for mlock clean, just keep the lru_lock there for
isolation purpose.

LKP found a preempt issue on __mod_zone_page_state which need change to
mod_zone_page_state.  Thanks!

Link: https://lkml.kernel.org/r/1604566549-62481-13-git-send-email-alex.shi@linux.alibaba.com


Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: "Chen, Rong A" <rong.a.chen@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent afca9157

mm/mlock.c

+5 −21

Original line number	Diff line number	Diff line
		@@ -187,40 +187,24 @@ static void __munlock_isolation_failed(struct page *page)
		unsigned int munlock_vma_page(struct page *page)
		{
		int nr_pages;
		pg_data_t *pgdat = page_pgdat(page);

		/* For try_to_munlock() and to serialize with page migration */
		BUG_ON(!PageLocked(page));

		VM_BUG_ON_PAGE(PageTail(page), page);

		/*
		* Serialize with any parallel __split_huge_page_refcount() which
		* might otherwise copy PageMlocked to part of the tail pages before
		* we clear it in the head page. It also stabilizes thp_nr_pages().
		*/
		spin_lock_irq(&pgdat->lru_lock);

		if (!TestClearPageMlocked(page)) {
		/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
		nr_pages = 1;
		goto unlock_out;
		return 0;
		}

		nr_pages = thp_nr_pages(page);
		__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
		mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);

		if (__munlock_isolate_lru_page(page, true)) {
		spin_unlock_irq(&pgdat->lru_lock);
		if (!isolate_lru_page(page))
		__munlock_isolated_page(page);
		goto out;
		}
		else
		__munlock_isolation_failed(page);

		unlock_out:
		spin_unlock_irq(&pgdat->lru_lock);

		out:
		return nr_pages - 1;
		}

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