According to btree's balance algorithm, when we split a root into two parts,
we insert a new one to be their parent:
new root
node A / \
| x1 x2 x3 x4 x5 x6 | => node A node A'
| x1 x2 x3 - - - | | x4 x5 x6 - - - |
split
The original root won't be freed because it becomes a child of the new root,
and a move to keep balance is needed then.
So we should not add REMOVE_WHILE_FREEING keys for the old root, otherwise,
we will hit use-after-free since we first add REMOVE_WHILE_FREEING keys and
then add REMOVE keys, which is invalid.
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
---
fs/btrfs/ctree.c | 16 +++++++++-------
1 files changed, 9 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index b334362..26987ef 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -639,7 +639,8 @@ __tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
static noinline int
tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
struct extent_buffer *old_root,
- struct extent_buffer *new_root, gfp_t flags)
+ struct extent_buffer *new_root,
+ gfp_t flags, int free_old)
{
struct tree_mod_elem *tm;
int ret;
@@ -647,7 +648,8 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
if (tree_mod_dont_log(fs_info, NULL))
return 0;
- __tree_mod_log_free_eb(fs_info, old_root);
+ if (free_old)
+ __tree_mod_log_free_eb(fs_info, old_root);
ret = tree_mod_alloc(fs_info, flags, &tm);
if (ret < 0)
@@ -797,11 +799,11 @@ tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
static noinline void
tree_mod_log_set_root_pointer(struct btrfs_root *root,
- struct extent_buffer *new_root_node)
+ struct extent_buffer *new_root_node, int free_old)
{
int ret;
ret = tree_mod_log_insert_root(root->fs_info, root->node,
- new_root_node, GFP_NOFS);
+ new_root_node, GFP_NOFS, free_old);
BUG_ON(ret < 0);
}
@@ -1029,7 +1031,7 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
parent_start = 0;
extent_buffer_get(cow);
- tree_mod_log_set_root_pointer(root, cow);
+ tree_mod_log_set_root_pointer(root, cow, 1);
rcu_assign_pointer(root->node, cow);
btrfs_free_tree_block(trans, root, buf, parent_start,
@@ -1725,7 +1727,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
goto enospc;
}
- tree_mod_log_set_root_pointer(root, child);
+ tree_mod_log_set_root_pointer(root, child, 1);
rcu_assign_pointer(root->node, child);
add_root_to_dirty_list(root);
@@ -3107,7 +3109,7 @@ static noinline int insert_new_root(struct btrfs_trans_handle *trans,
btrfs_mark_buffer_dirty(c);
old = root->node;
- tree_mod_log_set_root_pointer(root, c);
+ tree_mod_log_set_root_pointer(root, c, 0);
rcu_assign_pointer(root->node, c);
/* the super has an extra ref to root->node */
--
1.7.7.6
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
