z3fold: fix stale list handling

Fix the situation when clear_bit() is called for page->private before
the page pointer is actually assigned.  While at it, remove work_busy()
check because it is costly and does not give 100% guarantee anyway.

Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/mm/z3fold.c b/mm/z3fold.c
index b04fa3ba1bf2..b2ba2ba585f3 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -250,6 +250,7 @@ static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 
         WARN_ON(!list_empty(&zhdr->buddy));
         set_bit(PAGE_STALE, &page->private);
+        clear_bit(NEEDS_COMPACTING, &page->private);
         spin_lock(&pool->lock);
         if (!list_empty(&page->lru))
                 list_del(&page->lru);
@@ -303,7 +304,6 @@ static void free_pages_work(struct work_struct *w)
                 list_del(&zhdr->buddy);
                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
                         continue;
-                clear_bit(NEEDS_COMPACTING, &page->private);
                 spin_unlock(&pool->stale_lock);
                 cancel_work_sync(&zhdr->work);
                 free_z3fold_page(page);
@@ -624,10 +624,8 @@ lookup:
          * stale pages list. cancel_work_sync() can sleep so we must make
          * sure it won't be called in case we're in atomic context.
          */
-        if (zhdr && (can_sleep || !work_pending(&zhdr->work) ||
-            !unlikely(work_busy(&zhdr->work)))) {
+        if (zhdr && (can_sleep || !work_pending(&zhdr->work))) {
                 list_del(&zhdr->buddy);
-                clear_bit(NEEDS_COMPACTING, &page->private);
                 spin_unlock(&pool->stale_lock);
                 if (can_sleep)
                         cancel_work_sync(&zhdr->work);