diff options
| -rw-r--r-- | fs/btrfs/relocation.c | 58 |
1 files changed, 48 insertions, 10 deletions
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 54724ae45380..022e5af66fba 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1368,6 +1368,7 @@ static void __del_reloc_root(struct btrfs_root *root) struct rb_node *rb_node; struct mapping_node *node = NULL; struct reloc_control *rc = fs_info->reloc_ctl; + bool put_ref = false; if (rc && root->node) { spin_lock(&rc->reloc_root_tree.lock); @@ -1383,9 +1384,22 @@ static void __del_reloc_root(struct btrfs_root *root) BUG_ON((struct btrfs_root *)node->data != root); } + /* + * We only put the reloc root here if it's on the list. There's a lot + * of places where the pattern is to splice the rc->reloc_roots, process + * the reloc roots, and then add the reloc root back onto + * rc->reloc_roots. If we call __del_reloc_root while it's off of the + * list we don't want the reference being dropped, because the guy + * messing with the list is in charge of the reference. + */ spin_lock(&fs_info->trans_lock); - list_del_init(&root->root_list); + if (!list_empty(&root->root_list)) { + put_ref = true; + list_del_init(&root->root_list); + } spin_unlock(&fs_info->trans_lock); + if (put_ref) + btrfs_put_root(root); kfree(node); } @@ -1500,6 +1514,9 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans, /* * create reloc tree for a given fs tree. reloc tree is just a * snapshot of the fs tree with special root objectid. + * + * The reloc_root comes out of here with two references, one for + * root->reloc_root, and another for being on the rc->reloc_roots list. */ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, struct btrfs_root *root) @@ -1539,7 +1556,7 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, ret = __add_reloc_root(reloc_root); BUG_ON(ret < 0); - root->reloc_root = reloc_root; + root->reloc_root = btrfs_grab_root(reloc_root); return 0; } @@ -1560,6 +1577,13 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans, reloc_root = root->reloc_root; root_item = &reloc_root->root_item; + /* + * We are probably ok here, but __del_reloc_root() will drop its ref of + * the root. We have the ref for root->reloc_root, but just in case + * hold it while we update the reloc root. + */ + btrfs_grab_root(reloc_root); + /* root->reloc_root will stay until current relocation finished */ if (fs_info->reloc_ctl->merge_reloc_tree && btrfs_root_refs(root_item) == 0) { @@ -1581,7 +1605,7 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans, ret = btrfs_update_root(trans, fs_info->tree_root, &reloc_root->root_key, root_item); BUG_ON(ret); - + btrfs_put_root(reloc_root); out: return 0; } @@ -2281,18 +2305,28 @@ static int clean_dirty_subvols(struct reloc_control *rc) */ smp_wmb(); clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state); - if (reloc_root) { + /* + * btrfs_drop_snapshot drops our ref we hold for + * ->reloc_root. If it fails however we must + * drop the ref ourselves. + */ ret2 = btrfs_drop_snapshot(reloc_root, 0, 1); - if (ret2 < 0 && !ret) - ret = ret2; + if (ret2 < 0) { + btrfs_put_root(reloc_root); + if (!ret) + ret = ret2; + } } btrfs_put_root(root); } else { /* Orphan reloc tree, just clean it up */ ret2 = btrfs_drop_snapshot(root, 0, 1); - if (ret2 < 0 && !ret) - ret = ret2; + if (ret2 < 0) { + btrfs_put_root(root); + if (!ret) + ret = ret2; + } } } return ret; @@ -4510,7 +4544,7 @@ int btrfs_recover_relocation(struct btrfs_root *root) err = __add_reloc_root(reloc_root); BUG_ON(err < 0); /* -ENOMEM or logic error */ - fs_root->reloc_root = reloc_root; + fs_root->reloc_root = btrfs_grab_root(reloc_root); btrfs_put_root(fs_root); } @@ -4698,6 +4732,10 @@ void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending, /* * called after snapshot is created. migrate block reservation * and create reloc root for the newly created snapshot + * + * This is similar to btrfs_init_reloc_root(), we come out of here with two + * references held on the reloc_root, one for root->reloc_root and one for + * rc->reloc_roots. */ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans, struct btrfs_pending_snapshot *pending) @@ -4730,7 +4768,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans, ret = __add_reloc_root(reloc_root); BUG_ON(ret < 0); - new_root->reloc_root = reloc_root; + new_root->reloc_root = btrfs_grab_root(reloc_root); if (rc->create_reloc_tree) ret = clone_backref_node(trans, rc, root, reloc_root); |