mm: add __clear_page_lru_flags() to replace page_off_lru()

Similar to page_off_lru(), the new function does non-atomic clearing
of PageLRU() in addition to PageActive() and PageUnevictable(), on a
page that has no references left.

If PageActive() and PageUnevictable() are both set, refuse to clear
either and leave them to bad_page(). This is a behavior change that
is meant to help debug.

Link: https://lore.kernel.org/linux-mm/20201207220949.830352-7-yuzhao@google.com/
Link: https://lkml.kernel.org/r/20210122220600.906146-7-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index ffacc6273678a32ac2edec47d5a7e3e0dae20663..ef3fd79222e5ced54445222e95d5cc95efd5fa42 100644 (file)
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -61,27 +61,19 @@ static inline enum lru_list page_lru_base_type(struct page *page)
 }
 
 /**
- * page_off_lru - which LRU list was page on? clearing its lru flags.
- * @page: the page to test
- *
- * Returns the LRU list a page was on, as an index into the array of LRU
- * lists; and clears its Unevictable or Active flags, ready for freeing.
+ * __clear_page_lru_flags - clear page lru flags before releasing a page
+ * @page: the page that was on lru and now has a zero reference
  */
-static __always_inline enum lru_list page_off_lru(struct page *page)
+static __always_inline void __clear_page_lru_flags(struct page *page)
 {
-       enum lru_list lru;
+       __ClearPageLRU(page);
 
-       if (PageUnevictable(page)) {
-               __ClearPageUnevictable(page);
-               lru = LRU_UNEVICTABLE;
-       } else {
-               lru = page_lru_base_type(page);
-               if (PageActive(page)) {
-                       __ClearPageActive(page);
-                       lru += LRU_ACTIVE;
-               }
-       }
-       return lru;
+       /* this shouldn't happen, so leave the flags to bad_page() */
+       if (PageActive(page) && PageUnevictable(page))
+               return;
+
+       __ClearPageActive(page);
+       __ClearPageUnevictable(page);
 }
 
 /**

diff --git a/mm/swap.c b/mm/swap.c
index ff910f636df2d04b49f4f5d14211ae15f09ca82a..1455fa56a0ee004e60970d50208f0cffd1b5c63a 100644 (file)
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -84,9 +84,8 @@ static void __page_cache_release(struct page *page)
 
                lruvec = lock_page_lruvec_irqsave(page, &flags);
                VM_BUG_ON_PAGE(!PageLRU(page), page);
-               __ClearPageLRU(page);
                del_page_from_lru_list(page, lruvec);
-               page_off_lru(page);
+               __clear_page_lru_flags(page);
                unlock_page_lruvec_irqrestore(lruvec, flags);
        }
        __ClearPageWaiters(page);
@@ -911,9 +910,8 @@ void release_pages(struct page **pages, int nr)
                                lock_batch = 0;
 
                        VM_BUG_ON_PAGE(!PageLRU(page), page);
-                       __ClearPageLRU(page);
                        del_page_from_lru_list(page, lruvec);
-                       page_off_lru(page);
+                       __clear_page_lru_flags(page);
                }
 
                __ClearPageWaiters(page);

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7c65d47e6612ebae0ba77dd39d5da5655bffa0eb..452dd3818aa32be346a60e71a3004e0a85022d1b 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1849,8 +1849,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
                SetPageLRU(page);
 
                if (unlikely(put_page_testzero(page))) {
-                       __ClearPageLRU(page);
-                       __ClearPageActive(page);
+                       __clear_page_lru_flags(page);
 
                        if (unlikely(PageCompound(page))) {
                                spin_unlock_irq(&lruvec->lru_lock);