Merge branch 'fix/waitqueue-barriers' of git://git.kernel.org/pub/scm/linux/kernel...

[cascardo/linux.git] / fs / btrfs / transaction.c

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 76354bb..47fd270 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -82,6 +82,12 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
 static void clear_btree_io_tree(struct extent_io_tree *tree)
 {
        spin_lock(&tree->lock);
+       /*
+        * Do a single barrier for the waitqueue_active check here, the state
+        * of the waitqueue should not change once clear_btree_io_tree is
+        * called.
+        */
+       smp_mb();
        while (!RB_EMPTY_ROOT(&tree->state)) {
                struct rb_node *node;
                struct extent_state *state;
@@ -856,6 +862,9 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
        atomic_dec(&cur_trans->num_writers);
        extwriter_counter_dec(cur_trans, trans->type);
 
+       /*
+        * Make sure counter is updated before we wake up waiters.
+        */
        smp_mb();
        if (waitqueue_active(&cur_trans->writer_wait))
                wake_up(&cur_trans->writer_wait);