1 files changed, 37 insertions, 19 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 6c0a72ab6de0..5a5ea99f29ed 100644
--- 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;
 }