btrfs: add comments to barriers before waitqueue_active
Reduce number of undocumented barriers out there.
Signed-off-by: David Sterba <[email protected]>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 57ee8ca..3a9317c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -839,6 +839,9 @@
btrfs_compress_op[idx]->free_workspace(workspace);
atomic_dec(alloc_workspace);
wake:
+ /*
+ * Make sure counter is updated before we wake up waiters.
+ */
smp_mb();
if (waitqueue_active(workspace_wait))
wake_up(workspace_wait);
