From 69e9c6c6dc87587d8846e447febedefe037c14f8 Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Thu, 5 Sep 2013 16:58:43 +0200 Subject: [PATCH] Btrfs: eliminate the exceptional root_tree refs=0 The fact that btrfs_root_refs() returned 0 for the tree_root caused bugs in the past, therefore it is set to 1 with this patch and (hopefully) all affected code is adapted to this change. I verified this change by temporarily adding WARN_ON() checks everywhere where btrfs_root_refs() is used, checking whether the logic of the code is changed by btrfs_root_refs() returning 1 instead of 0 for root->root_key.objectid == BTRFS_ROOT_TREE_OBJECTID. With these added checks, I ran the xfstests './check -g auto'. The two roots chunk_root and log_root_tree that are only referenced by the superblock and the log_roots below the log_root_tree still have btrfs_root_refs() == 0, only the tree_root is changed. Signed-off-by: Stefan Behrens Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/disk-io.c | 1 + fs/btrfs/inode-map.c | 3 +-- fs/btrfs/inode.c | 21 ++++++++------------- 3 files changed, 10 insertions(+), 15 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 62176ad89846..f724397b396b 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2670,6 +2670,7 @@ retry_root_backup: btrfs_set_root_node(&tree_root->root_item, tree_root->node); tree_root->commit_root = btrfs_root_node(tree_root); + btrfs_set_root_refs(&tree_root->root_item, 1); location.objectid = BTRFS_EXTENT_TREE_OBJECTID; location.type = BTRFS_ROOT_ITEM_KEY; diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c index 2c66ddbbe670..d11e1c6610b6 100644 --- a/fs/btrfs/inode-map.c +++ b/fs/btrfs/inode-map.c @@ -412,8 +412,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root, return 0; /* Don't save inode cache if we are deleting this root */ - if (btrfs_root_refs(&root->root_item) == 0 && - root != root->fs_info->tree_root) + if (btrfs_root_refs(&root->root_item) == 0) return 0; if (!btrfs_test_opt(root, INODE_MAP_CACHE)) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 51e3afa78354..dfc60aa40332 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4472,8 +4472,10 @@ void btrfs_evict_inode(struct inode *inode) trace_btrfs_inode_evict(inode); truncate_inode_pages(&inode->i_data, 0); - if (inode->i_nlink && (btrfs_root_refs(&root->root_item) != 0 || - btrfs_is_free_space_inode(inode))) + if (inode->i_nlink && + ((btrfs_root_refs(&root->root_item) != 0 && + root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID) || + btrfs_is_free_space_inode(inode))) goto no_delete; if (is_bad_inode(inode)) { @@ -4490,7 +4492,8 @@ void btrfs_evict_inode(struct inode *inode) } if (inode->i_nlink > 0) { - BUG_ON(btrfs_root_refs(&root->root_item) != 0); + BUG_ON(btrfs_root_refs(&root->root_item) != 0 && + root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID); goto no_delete; } @@ -4731,14 +4734,7 @@ static void inode_tree_del(struct inode *inode) } spin_unlock(&root->inode_lock); - /* - * Free space cache has inodes in the tree root, but the tree root has a - * root_refs of 0, so this could end up dropping the tree root as a - * snapshot, so we need the extra !root->fs_info->tree_root check to - * make sure we don't drop it. - */ - if (empty && btrfs_root_refs(&root->root_item) == 0 && - root != root->fs_info->tree_root) { + if (empty && btrfs_root_refs(&root->root_item) == 0) { synchronize_srcu(&root->fs_info->subvol_srcu); spin_lock(&root->inode_lock); empty = RB_EMPTY_ROOT(&root->inode_tree); @@ -7857,8 +7853,7 @@ int btrfs_drop_inode(struct inode *inode) return 1; /* the snap/subvol tree is on deleting */ - if (btrfs_root_refs(&root->root_item) == 0 && - root != root->fs_info->tree_root) + if (btrfs_root_refs(&root->root_item) == 0) return 1; else return generic_drop_inode(inode); -- 2.34.1