btrfs: do not start relocation until in progress drops are done

[sfrench/cifs-2.6.git] / fs / btrfs / transaction.c

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c3cfdfd8de9b2d2ec040343f9f1dadca6cfe624e..f17bf3764ce86c07cc1df0017f99b8e88ef34bd8 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1319,6 +1319,32 @@ again:
        return 0;
 }
 
+/*
+ * If we had a pending drop we need to see if there are any others left in our
+ * dead roots list, and if not clear our bit and wake any waiters.
+ */
+void btrfs_maybe_wake_unfinished_drop(struct btrfs_fs_info *fs_info)
+{
+       /*
+        * We put the drop in progress roots at the front of the list, so if the
+        * first entry doesn't have UNFINISHED_DROP set we can wake everybody
+        * up.
+        */
+       spin_lock(&fs_info->trans_lock);
+       if (!list_empty(&fs_info->dead_roots)) {
+               struct btrfs_root *root = list_first_entry(&fs_info->dead_roots,
+                                                          struct btrfs_root,
+                                                          root_list);
+               if (test_bit(BTRFS_ROOT_UNFINISHED_DROP, &root->state)) {
+                       spin_unlock(&fs_info->trans_lock);
+                       return;
+               }
+       }
+       spin_unlock(&fs_info->trans_lock);
+
+       btrfs_wake_unfinished_drop(fs_info);
+}
+
 /*
  * dead roots are old snapshots that need to be deleted.  This allocates
  * a dirty root struct and adds it into the list of dead roots that need to
@@ -1331,7 +1357,12 @@ void btrfs_add_dead_root(struct btrfs_root *root)
        spin_lock(&fs_info->trans_lock);
        if (list_empty(&root->root_list)) {
                btrfs_grab_root(root);
-               list_add_tail(&root->root_list, &fs_info->dead_roots);
+
+               /* We want to process the partially complete drops first. */
+               if (test_bit(BTRFS_ROOT_UNFINISHED_DROP, &root->state))
+                       list_add(&root->root_list, &fs_info->dead_roots);
+               else
+                       list_add_tail(&root->root_list, &fs_info->dead_roots);
        }
        spin_unlock(&fs_info->trans_lock);
 }