Re: [PATCH 1/5] btrfs: drop log root for dropped roots

[Nikolay Borisov <nborisov@suse.com>]

On 10.12.19 г. 22:05 ч., Josef Bacik wrote:
> On 12/6/19 10:03 AM, Nikolay Borisov wrote:
>>
>>
>> On 6.12.19 г. 16:37 ч., Josef Bacik wrote:
>>> If we fsync on a subvolume and create a log root for that volume, and
>>> then later delete that subvolume we'll never clean up its log root.  Fix
>>> this by making switch_commit_roots free the log for any dropped roots we
>>> encounter.
>>>
>>> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>>> ---
>>>   fs/btrfs/transaction.c | 22 ++++++++++++----------
>>>   1 file changed, 12 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
>>> index cfc08ef9b876..55d8fd68775a 100644
>>> --- a/fs/btrfs/transaction.c
>>> +++ b/fs/btrfs/transaction.c
>>> @@ -147,13 +147,14 @@ void btrfs_put_transaction(struct
>>> btrfs_transaction *transaction)
>>>       }
>>>   }
>>>   -static noinline void switch_commit_roots(struct btrfs_transaction
>>> *trans)
>>> +static noinline void switch_commit_roots(struct btrfs_trans_handle
>>> *trans)
>>>   {
>>> +    struct btrfs_transaction *cur_trans = trans->transaction;
>>>       struct btrfs_fs_info *fs_info = trans->fs_info;
>>>       struct btrfs_root *root, *tmp;
>>>         down_write(&fs_info->commit_root_sem);
>>> -    list_for_each_entry_safe(root, tmp, &trans->switch_commits,
>>> +    list_for_each_entry_safe(root, tmp, &cur_trans->switch_commits,
>>>                    dirty_list) {
>>>           list_del_init(&root->dirty_list);
>>>           free_extent_buffer(root->commit_root);
>>> @@ -165,16 +166,17 @@ static noinline void switch_commit_roots(struct
>>> btrfs_transaction *trans)
>>>       }
>>>         /* We can free old roots now. */
>>> -    spin_lock(&trans->dropped_roots_lock);
>>> -    while (!list_empty(&trans->dropped_roots)) {
>>> -        root = list_first_entry(&trans->dropped_roots,
>>> +    spin_lock(&cur_trans->dropped_roots_lock);
>>> +    while (!list_empty(&cur_trans->dropped_roots)) {
>>> +        root = list_first_entry(&cur_trans->dropped_roots,
>>>                       struct btrfs_root, root_list);
>>>           list_del_init(&root->root_list);
>>> -        spin_unlock(&trans->dropped_roots_lock);
>>> +        spin_unlock(&cur_trans->dropped_roots_lock);
>>> +        btrfs_free_log(trans, root);
>>
>> THis patch should really have been this line and converting
>> switch_commit_roots to taking a trans handle another patch. Otherwise
>> this is lost in the mechanical refactoring.
>>
> 
> We need the trans handle to even call btrfs_free_log, we're just fixing
> it so the trans handle can be passed in, making its separate is just
> superfluous.  Thanks,

Actually no because callees handle the case when trans is not passed
(i.e. walk_log_tree and walk_(up|down)_log_tree. If passing valid
trances changes the call logic then this needs to be explained in the
changelog. And there is currently one caller calling that function
without a trans - btrfs_drop_and_free_fs_root in BTRFS_FS_STATE_ERROR case.

> 
> Josef