On 12/19/12 2:13 AM, Jan Kara wrote: > 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... I'm probably missing something, but I was thinking we could compare j_commit_sequence to j_transaction_sequence and force a commit up to at least j_commit_sequence if it's too "stale" - but I'm only handwaving. :) -Eric > Honza > -- 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
