On Tue 18-12-12 21:08:51, Eric Sandeen wrote: > On 12/18/12 8:05 PM, Jan Kara wrote: > > On Wed 19-12-12 02:27:10, Jan Kara wrote: > >>> With a u8 tid_t, the "else" clause from commit d9b0193 fires > >>> frequently; I really think the underlying problem is that tid_geq() > >>> etc does not properly handle wraparounds - if, say, target is 255 > >>> and j_commit_request is 0, we don't know if j_commit_request > >>> is 255 tids behind, or 1 tid ahead. I have to think about that > >>> some more, unless it's obvious to someone else. > >> Well, there's no way to handle wraps better AFAICT. Tids eventually wrap > >> and if someone has stored away tid of a transaction he wants committed and > >> keeps it for a long time before using it, it can end up being anywhere > >> before / after current j_commit_request. The hope was that it takes long > >> enough to wrap around 32-bit tids. If this happens often in practice we may > >> have to switch to 64-bit tids (in memory, on disk 32-bit tids are enough > >> because of limited journal size). > > I was wondering if, since the tid_g*() functions only work if the > distance is half the unsigned int space, we can force a commit at some > point if j_transaction_sequence has gotten too far ahead? I'm not sure > where or if that could be done... I don't quiete understand. If someone stores tid = transaction->t_tid and in two weeks calls log_start_commit(tid), I don't see how any forcing of commits could solve that tid may now look ahead of the log... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
