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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 <sbehrens@giantdisaster.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Stefan Behrens 2013-09-05 16:58:43 +02:00 committed by Chris Mason
parent 5e01dc7b26
commit 69e9c6c6dc
3 changed files with 10 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/btrfs/disk-io.c
View File

@ -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;

3
fs/btrfs/inode-map.c
View File

@ -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))

21
fs/btrfs/inode.c
View File

@ -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);