mm/vmscan: remove unnecessary lruvec adding

We don't have to add a freeable page into lru and then remove from it.
This change saves a couple of actions and makes the moving more clear.

The SetPageLRU needs to be kept before put_page_testzero for list
integrity, otherwise:

  #0 move_pages_to_lru             #1 release_pages
  if !put_page_testzero
     			           if (put_page_testzero())
     			              !PageLRU //skip lru_lock
     SetPageLRU()
     list_add(&page->lru,)
                                         list_add(&page->lru,)

[akpm@linux-foundation.org: coding style fixes]

Link: https://lkml.kernel.org/r/1604566549-62481-6-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: Tejun Heo <tj@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
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@linux.intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
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: 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/vmscan.c b/mm/vmscan.c
index 2423685..1c3df77 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1851,26 +1851,30 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
        while (!list_empty(list)) {
                page = lru_to_page(list);
                VM_BUG_ON_PAGE(PageLRU(page), page);
+               list_del(&page->lru);
                if (unlikely(!page_evictable(page))) {
-                       list_del(&page->lru);
                        spin_unlock_irq(&pgdat->lru_lock);
                        putback_lru_page(page);
                        spin_lock_irq(&pgdat->lru_lock);
                        continue;
                }
-               lruvec = mem_cgroup_page_lruvec(page, pgdat);
 
+               /*
+                * The SetPageLRU needs to be kept here for list integrity.
+                * Otherwise:
+                *   #0 move_pages_to_lru             #1 release_pages
+                *   if !put_page_testzero
+                *                                    if (put_page_testzero())
+                *                                      !PageLRU //skip lru_lock
+                *     SetPageLRU()
+                *     list_add(&page->lru,)
+                *                                        list_add(&page->lru,)
+                */
                SetPageLRU(page);
-               lru = page_lru(page);
 
-               nr_pages = thp_nr_pages(page);
-               update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
-               list_move(&page->lru, &lruvec->lists[lru]);
-
-               if (put_page_testzero(page)) {
+               if (unlikely(put_page_testzero(page))) {
                        __ClearPageLRU(page);
                        __ClearPageActive(page);
-                       del_page_from_lru_list(page, lruvec, lru);
 
                        if (unlikely(PageCompound(page))) {
                                spin_unlock_irq(&pgdat->lru_lock);
@@ -1878,11 +1882,19 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
                                spin_lock_irq(&pgdat->lru_lock);
                        } else
                                list_add(&page->lru, &pages_to_free);
-               } else {
-                       nr_moved += nr_pages;
-                       if (PageActive(page))
-                               workingset_age_nonresident(lruvec, nr_pages);
+
+                       continue;
                }
+
+               lruvec = mem_cgroup_page_lruvec(page, pgdat);
+               lru = page_lru(page);
+               nr_pages = thp_nr_pages(page);
+
+               update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
+               list_add(&page->lru, &lruvec->lists[lru]);
+               nr_moved += nr_pages;
+               if (PageActive(page))
+                       workingset_age_nonresident(lruvec, nr_pages);
        }
 
        /*