5 files changed, 16 insertions, 2 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 57ee8ca29b06..3a9317ce67f8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -839,6 +839,9 @@ static void free_workspace(int type, struct list_head *workspace)
         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);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9f9604201333..59eb92f65c62 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10363,8 +10363,7 @@ void btrfs_end_write_no_snapshoting(struct btrfs_root *root)
 {
         percpu_counter_dec(&root->subv_writers->counter);
         /*
-         * Make sure counter is updated before we wake up
-         * waiters.
+         * Make sure counter is updated before we wake up waiters.
          */
         smp_mb();
         if (waitqueue_active(&root->subv_writers->wait))
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index d7e6baf1b205..03f8630dbaf2 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -280,6 +280,9 @@ 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);
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 52170cf1757e..071005f008c1 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -345,6 +345,9 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
 
         if (entry->bytes_left == 0) {
                 ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
+                /*
+                 * Implicit memory barrier after test_and_set_bit
+                 */
                 if (waitqueue_active(&entry->wait))
                         wake_up(&entry->wait);
         } else {
@@ -409,6 +412,9 @@ have_entry:
 
         if (entry->bytes_left == 0) {
                 ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
+                /*
+                 * Implicit memory barrier after test_and_set_bit
+                 */
                 if (waitqueue_active(&entry->wait))
                         wake_up(&entry->wait);
         } else {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index e8e5b5a10719..3fd70f797b7d 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -861,6 +861,9 @@ 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);