waitqueue_active should be preceded by a barrier, in this function we
don't need to call it all the time.
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
fs/btrfs/transaction.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 74bc3338418b..e8e5b5a10719 100644
--- 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;
--
2.1.3
--
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