Merge branch 'for-5.1/nfit/ars' into libnvdimm-for-next

Merge several updates to the ARS implementation. Highlights include:

* Support retrieval of short-ARS results if the ARS state is "requires
  continuation", and even if the "no_init_ars" module parameter is
  specified.
* Allow busy-polling of the kernel ARS state by allowing root to reset
  the exponential back-off timer.
* Filter potentially stale ARS results by tracking query-ARS relative to
  the previous start-ARS.

1 files changed, 5 insertions, 7 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index a16b15090df3..d4fd680be3b0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -709,7 +709,6 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head,
         /* Simple case, sync compaction */
         if (mode != MIGRATE_ASYNC) {
                 do {
-                        get_bh(bh);
                         lock_buffer(bh);
                         bh = bh->b_this_page;
 
@@ -720,18 +719,15 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head,
 
         /* async case, we cannot block on lock_buffer so use trylock_buffer */
         do {
-                get_bh(bh);
                 if (!trylock_buffer(bh)) {
                         /*
                          * We failed to lock the buffer and cannot stall in
                          * async migration. Release the taken locks
                          */
                         struct buffer_head *failed_bh = bh;
-                        put_bh(failed_bh);
                         bh = head;
                         while (bh != failed_bh) {
                                 unlock_buffer(bh);
-                                put_bh(bh);
                                 bh = bh->b_this_page;
                         }
                         return false;
@@ -818,7 +814,6 @@ unlock_buffers:
         bh = head;
         do {
                 unlock_buffer(bh);
-                put_bh(bh);
                 bh = bh->b_this_page;
 
         } while (bh != head);
@@ -1135,10 +1130,13 @@ out:
          * If migration is successful, decrease refcount of the newpage
          * which will not free the page because new page owner increased
          * refcounter. As well, if it is LRU page, add the page to LRU
-         * list in here.
+         * list in here. Use the old state of the isolated source page to
+         * determine if we migrated a LRU page. newpage was already unlocked
+         * and possibly modified by its owner - don't rely on the page
+         * state.
          */
         if (rc == MIGRATEPAGE_SUCCESS) {
-                if (unlikely(__PageMovable(newpage)))
+                if (unlikely(!is_lru))
                         put_page(newpage);
                 else
                         putback_lru_page(newpage);