btrfs: clean snapshots one by one

[firefly-linux-kernel-4.4.55.git] / fs / btrfs / transaction.c

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 6c0a72ab6de04ea415a6f5ba5332050fc0ee9266..5a5ea99f29ed6cd741b27241e754322c4f55b26a 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -948,7 +948,7 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 int btrfs_add_dead_root(struct btrfs_root *root)
 {
        spin_lock(&root->fs_info->trans_lock);
-       list_add(&root->root_list, &root->fs_info->dead_roots);
+       list_add_tail(&root->root_list, &root->fs_info->dead_roots);
        spin_unlock(&root->fs_info->trans_lock);
        return 0;
 }
@@ -1873,31 +1873,49 @@ cleanup_transaction:
 }
 
 /*
- * interface function to delete all the snapshots we have scheduled for deletion
+ * return < 0 if error
+ * 0 if there are no more dead_roots at the time of call
+ * 1 there are more to be processed, call me again
+ *
+ * The return value indicates there are certainly more snapshots to delete, but
+ * if there comes a new one during processing, it may return 0. We don't mind,
+ * because btrfs_commit_super will poke cleaner thread and it will process it a
+ * few seconds later.
  */
-int btrfs_clean_old_snapshots(struct btrfs_root *root)
+int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
 {
-       LIST_HEAD(list);
+       int ret;
        struct btrfs_fs_info *fs_info = root->fs_info;
 
+       if (fs_info->sb->s_flags & MS_RDONLY) {
+               pr_debug("btrfs: cleaner called for RO fs!\n");
+               return 0;
+       }
+
        spin_lock(&fs_info->trans_lock);
-       list_splice_init(&fs_info->dead_roots, &list);
+       if (list_empty(&fs_info->dead_roots)) {
+               spin_unlock(&fs_info->trans_lock);
+               return 0;
+       }
+       root = list_first_entry(&fs_info->dead_roots,
+                       struct btrfs_root, root_list);
+       list_del(&root->root_list);
        spin_unlock(&fs_info->trans_lock);
 
-       while (!list_empty(&list)) {
-               int ret;
-
-               root = list_entry(list.next, struct btrfs_root, root_list);
-               list_del(&root->root_list);
+       pr_debug("btrfs: cleaner removing %llu\n",
+                       (unsigned long long)root->objectid);
 
-               btrfs_kill_all_delayed_nodes(root);
+       btrfs_kill_all_delayed_nodes(root);
 
-               if (btrfs_header_backref_rev(root->node) <
-                   BTRFS_MIXED_BACKREF_REV)
-                       ret = btrfs_drop_snapshot(root, NULL, 0, 0);
-               else
-                       ret =btrfs_drop_snapshot(root, NULL, 1, 0);
-               BUG_ON(ret < 0);
-       }
-       return 0;
+       if (btrfs_header_backref_rev(root->node) <
+                       BTRFS_MIXED_BACKREF_REV)
+               ret = btrfs_drop_snapshot(root, NULL, 0, 0);
+       else
+               ret = btrfs_drop_snapshot(root, NULL, 1, 0);
+       /*
+        * If we encounter a transaction abort during snapshot cleaning, we
+        * don't want to crash here
+        */
+       BUG_ON(ret < 0 && ret != -EAGAIN && ret != -EROFS);
+       return 1;
 }