Btrfs: Add the ability to find and remove dead roots after a crash.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 47 insertions, 7 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 321f8852755b..85a2a5e27148 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -85,11 +85,15 @@ struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 
         if (root != root->fs_info->tree_root && root->last_trans <
             running_trans_id) {
-                radix_tree_tag_set(&root->fs_info->fs_roots_radix,
-                                   (unsigned long)root->root_key.objectid,
-                                   BTRFS_ROOT_TRANS_TAG);
-                root->commit_root = root->node;
-                get_bh(root->node);
+                if (root->root_item.refs != 0) {
+                        radix_tree_tag_set(&root->fs_info->fs_roots_radix,
+                                           (unsigned long)root->root_key.objectid,
+                                           BTRFS_ROOT_TRANS_TAG);
+                        root->commit_root = root->node;
+                        get_bh(root->node);
+                } else {
+                        WARN_ON(1);
+                }
         }
         root->last_trans = running_trans_id;
         h->transid = running_trans_id;
@@ -208,8 +212,24 @@ struct dirty_root {
         struct btrfs_key snap_key;
         struct buffer_head *commit_root;
         struct btrfs_root *root;
+        int free_on_drop;
 };
 
+int btrfs_add_dead_root(struct btrfs_root *root, struct list_head *dead_list)
+{
+        struct dirty_root *dirty;
+
+        dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
+        if (!dirty)
+                return -ENOMEM;
+        memcpy(&dirty->snap_key, &root->root_key, sizeof(root->root_key));
+        dirty->commit_root = root->node;
+        dirty->root = root;
+        dirty->free_on_drop = 1;
+        list_add(&dirty->list, dead_list);
+        return 0;
+}
+
 static int add_dirty_roots(struct btrfs_trans_handle *trans,
                            struct radix_tree_root *radix,
                            struct list_head *list)
@@ -217,9 +237,11 @@ static int add_dirty_roots(struct btrfs_trans_handle *trans,
         struct dirty_root *dirty;
         struct btrfs_root *gang[8];
         struct btrfs_root *root;
+        struct btrfs_root_item tmp_item;
         int i;
         int ret;
         int err = 0;
+        u32 refs;
 
         while(1) {
                 ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
@@ -246,6 +268,9 @@ static int add_dirty_roots(struct btrfs_trans_handle *trans,
                         dirty->commit_root = root->commit_root;
                         root->commit_root = NULL;
                         dirty->root = root;
+                        dirty->free_on_drop = 0;
+                        memcpy(&tmp_item, &root->root_item, sizeof(tmp_item));
+
                         root->root_key.offset = root->fs_info->generation;
                         btrfs_set_root_blocknr(&root->root_item,
                                                bh_blocknr(root->node));
@@ -254,7 +279,18 @@ static int add_dirty_roots(struct btrfs_trans_handle *trans,
                                                 &root->root_item);
                         if (err)
                                 break;
-                        list_add(&dirty->list, list);
+
+                        refs = btrfs_root_refs(&tmp_item);
+                        btrfs_set_root_refs(&tmp_item, refs - 1);
+                        err = btrfs_update_root(trans, root->fs_info->tree_root,
+                                                &dirty->snap_key,
+                                                &tmp_item);
+
+                        BUG_ON(err);
+                        if (refs == 1)
+                                list_add(&dirty->list, list);
+                        else
+                                kfree(dirty);
                 }
         }
         return err;
@@ -270,16 +306,20 @@ static int drop_dirty_roots(struct btrfs_root *tree_root,
                 mutex_lock(&tree_root->fs_info->fs_mutex);
                 dirty = list_entry(list->next, struct dirty_root, list);
                 list_del_init(&dirty->list);
+
                 trans = btrfs_start_transaction(tree_root, 1);
+printk("deleting root %Lu %u %Lu\n", dirty->snap_key.objectid, dirty->snap_key.flags, dirty->snap_key.offset);
                 ret = btrfs_drop_snapshot(trans, dirty->root,
                                           dirty->commit_root);
                 BUG_ON(ret);
-
                 ret = btrfs_del_root(trans, tree_root, &dirty->snap_key);
                 if (ret)
                         break;
                 ret = btrfs_end_transaction(trans, tree_root);
                 BUG_ON(ret);
+
+                if (dirty->free_on_drop)
+                        kfree(dirty->root);
                 kfree(dirty);
                 mutex_unlock(&tree_root->fs_info->fs_mutex);
                 btrfs_btree_balance_dirty(tree_root);