mm/khugepaged: collapse_shmem() without freezing new_page

[sfrench/cifs-2.6.git] / mm / khugepaged.c

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 9d4e9ff1af95ebf444b14d63449bcb4214236ab2..55930cbed3fd5e6f5ddc885b362ef4b0ac0a925f 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1287,7 +1287,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
  * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
  *
  * Basic scheme is simple, details are more complex:
- *  - allocate and freeze a new huge page;
+ *  - allocate and lock a new huge page;
  *  - scan page cache replacing old pages with the new one
  *    + swap in pages if necessary;
  *    + fill in gaps;
@@ -1295,11 +1295,11 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
  *  - if replacing succeeds:
  *    + copy data over;
  *    + free old pages;
- *    + unfreeze huge page;
+ *    + unlock huge page;
  *  - if replacing failed;
  *    + put all pages back and unfreeze them;
  *    + restore gaps in the page cache;
- *    + free huge page;
+ *    + unlock and free huge page;
  */
 static void collapse_shmem(struct mm_struct *mm,
                struct address_space *mapping, pgoff_t start,
@@ -1333,13 +1333,11 @@ static void collapse_shmem(struct mm_struct *mm,
        __SetPageSwapBacked(new_page);
        new_page->index = start;
        new_page->mapping = mapping;
-       BUG_ON(!page_ref_freeze(new_page, 1));
 
        /*
-        * At this point the new_page is 'frozen' (page_count() is zero),
-        * locked and not up-to-date. It's safe to insert it into the page
-        * cache, because nobody would be able to map it or use it in other
-        * way until we unfreeze it.
+        * At this point the new_page is locked and not up-to-date.
+        * It's safe to insert it into the page cache, because nobody would
+        * be able to map it or use it in another way until we unlock it.
         */
 
        /* This will be less messy when we use multi-index entries */
@@ -1491,9 +1489,8 @@ xa_unlocked:
                        index++;
                }
 
-               /* Everything is ready, let's unfreeze the new_page */
                SetPageUptodate(new_page);
-               page_ref_unfreeze(new_page, HPAGE_PMD_NR);
+               page_ref_add(new_page, HPAGE_PMD_NR - 1);
                set_page_dirty(new_page);
                mem_cgroup_commit_charge(new_page, memcg, false, true);
                lru_cache_add_anon(new_page);
@@ -1541,8 +1538,6 @@ xa_unlocked:
                VM_BUG_ON(nr_none);
                xas_unlock_irq(&xas);
 
-               /* Unfreeze new_page, caller would take care about freeing it */
-               page_ref_unfreeze(new_page, 1);
                mem_cgroup_cancel_charge(new_page, memcg, true);
                new_page->mapping = NULL;
        }