These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / fs / btrfs / locking.c

diff --git a/kernel/fs/btrfs/locking.c b/kernel/fs/btrfs/locking.c
index f8229ef..8077461 100644 (file)
--- a/kernel/fs/btrfs/locking.c
+++ b/kernel/fs/btrfs/locking.c
@@ -79,6 +79,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
                write_lock(&eb->lock);
                WARN_ON(atomic_read(&eb->spinning_writers));
                atomic_inc(&eb->spinning_writers);
+               /*
+                * atomic_dec_and_test implies a barrier for waitqueue_active
+                */
                if (atomic_dec_and_test(&eb->blocking_writers) &&
                    waitqueue_active(&eb->write_lock_wq))
                        wake_up(&eb->write_lock_wq);
@@ -86,6 +89,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
                BUG_ON(atomic_read(&eb->blocking_readers) == 0);
                read_lock(&eb->lock);
                atomic_inc(&eb->spinning_readers);
+               /*
+                * atomic_dec_and_test implies a barrier for waitqueue_active
+                */
                if (atomic_dec_and_test(&eb->blocking_readers) &&
                    waitqueue_active(&eb->read_lock_wq))
                        wake_up(&eb->read_lock_wq);
@@ -229,6 +235,9 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
        }
        btrfs_assert_tree_read_locked(eb);
        WARN_ON(atomic_read(&eb->blocking_readers) == 0);
+       /*
+        * atomic_dec_and_test implies a barrier for waitqueue_active
+        */
        if (atomic_dec_and_test(&eb->blocking_readers) &&
            waitqueue_active(&eb->read_lock_wq))
                wake_up(&eb->read_lock_wq);
@@ -241,6 +250,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
  */
 void btrfs_tree_lock(struct extent_buffer *eb)
 {
+       WARN_ON(eb->lock_owner == current->pid);
 again:
        wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
        wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
@@ -279,6 +289,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb)
        if (blockers) {
                WARN_ON(atomic_read(&eb->spinning_writers));
                atomic_dec(&eb->blocking_writers);
+               /*
+                * Make sure counter is updated before we wake up waiters.
+                */
                smp_mb();
                if (waitqueue_active(&eb->write_lock_wq))
                        wake_up(&eb->write_lock_wq);