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>

diff --git a/mm/mlock.c b/mm/mlock.c
index 884b121..796c726 100644 (file)
--- 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;
 }