> On Tue, 5 Aug 2008 00:51:34 +0100 "Duane Griffin" <duaneg@dghda.com> wrote:
>
>> The __log_wait_for_space function sits in a loop checkpointing transactions
>> until there is sufficient space free in the journal. However, if there are
>> no transactions to be processed (e.g. because the free space calculation is
>> wrong due to a corrupted filesystem) it will never progress.
>>
>> Check for space being required when no transactions are outstanding and
>> abort the journal instead of endlessly looping.
>>
>> This patch fixes the bug reported by Sami Liedes at:
>>
http://bugzilla.kernel.org/show_bug.cgi?id=10976
>>
>> Signed-off-by: Duane Griffin <duaneg@dghda.com>
>> Tested-by: Sami Liedes <sliedes@cc.hut.fi>
>> ---
>> diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
>> index a5432bb..9fac177 100644
>> --- a/fs/jbd/checkpoint.c
>> +++ b/fs/jbd/checkpoint.c
>> @@ -126,14 +126,29 @@ void __log_wait_for_space(journal_t *journal)
>>
>> /*
>> * Test again, another process may have checkpointed while we
>> - * were waiting for the checkpoint lock
>> + * were waiting for the checkpoint lock. If there are no
>> + * outstanding transactions there is nothing to checkpoint and
>> + * we can't make progress. Abort the journal in this case.
>> */
>> spin_lock(&journal->j_state_lock);
>> + spin_lock(&journal->j_list_lock);
>> nblocks = jbd_space_needed(journal);
>> if (__log_space_left(journal) < nblocks) {
>> + int chkpt = journal->j_checkpoint_transactions != NULL;
>> +
>> + spin_unlock(&journal->j_list_lock);
>> spin_unlock(&journal->j_state_lock);
>> - log_do_checkpoint(journal);
>> + if (chkpt) {
>> + log_do_checkpoint(journal);
>> + } else {
>> + printk(KERN_ERR "%s: no transactions\n",
>> + __func__);
>> + journal_abort(journal, 0);
>> + }
>> +
>> spin_lock(&journal->j_state_lock);
>> + } else {
>> + spin_unlock(&journal->j_list_lock);
>> }
>> mutex_unlock(&journal->j_checkpoint_mutex);
>> }
>
> I don't expect that the additional taking of j_list_lock in here does
> anything useful.
>
> Plus.. after j_list_lock has been dropped, new transactions could
> theoretically appear at journal->j_checkpoint_transactions, so we
> _could_ reclaim more journal space. But a) that probably couldn't
> happen due to ->j_state_lock and lots of other things and b) it's
> hopelessly theoretical even if it _could_ happen, methinks. Just
> sayin'..
