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/[email protected]
Signed-off-by: Alex Shi <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: "Chen, Rong A" <[email protected]>
Cc: Daniel Jordan <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mika Penttilä <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: Yang Shi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 5 insertions, 21 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index 884b1216da6a..796c726a0407 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -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;
-	}
-	__munlock_isolation_failed(page);
-
-unlock_out:
-	spin_unlock_irq(&pgdat->lru_lock);
+	else
+		__munlock_isolation_failed(page);
 
-out:
 	return nr_pages - 1;
 }