Btrfs: barrier before waitqueue_active
We need a barrir before calling waitqueue_active otherwise we will miss
wakeups. So in places that do atomic_dec(); then atomic_read() use
atomic_dec_return() which imply a memory barrier (see memory-barriers.txt)
and then add an explicit memory barrier everywhere else that need them.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 00deed4e..07d5eeb 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -512,8 +512,8 @@
rb_erase(&delayed_item->rb_node, root);
delayed_item->delayed_node->count--;
- atomic_dec(&delayed_root->items);
- if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND &&
+ if (atomic_dec_return(&delayed_root->items) <
+ BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);
}
@@ -1056,8 +1056,7 @@
delayed_node->count--;
delayed_root = delayed_node->root->fs_info->delayed_root;
- atomic_dec(&delayed_root->items);
- if (atomic_read(&delayed_root->items) <
+ if (atomic_dec_return(&delayed_root->items) <
BTRFS_DELAYED_BACKGROUND &&
waitqueue_active(&delayed_root->wait))
wake_up(&delayed_root->wait);